add dialogs for failed save/load

- failed validation doesn't prevent save/load,
  but the user is now warned about it.
- there is now a warning dialog if fromJSON fails,
  rather than the usual silent failure.

IPython/html/services/contents/filemanager.py

@@ -1,536 +1,545 b''
 """A contents manager that uses the local file system for storage."""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import base64
 import io
 import os
 import glob
 import shutil
 
 from tornado import web
 
 from .manager import ContentsManager
 from IPython.nbformat import current
 from IPython.utils.io import atomic_writing
 from IPython.utils.path import ensure_dir_exists
 from IPython.utils.traitlets import Unicode, Bool, TraitError
 from IPython.utils.py3compat import getcwd
 from IPython.utils import tz
 from IPython.html.utils import is_hidden, to_os_path, url_path_join
 
 
 class FileContentsManager(ContentsManager):
 
     root_dir = Unicode(getcwd(), config=True)
 
     save_script = Bool(False, config=True, help='DEPRECATED, IGNORED')
     def _save_script_changed(self):
         self.log.warn("""
         Automatically saving notebooks as scripts has been removed.
         Use `ipython nbconvert --to python [notebook]` instead.
         """)
 
     def _root_dir_changed(self, name, old, new):
         """Do a bit of validation of the root_dir."""
         if not os.path.isabs(new):
             # If we receive a non-absolute path, make it absolute.
             self.root_dir = os.path.abspath(new)
             return
         if not os.path.isdir(new):
             raise TraitError("%r is not a directory" % new)
 
     checkpoint_dir = Unicode('.ipynb_checkpoints', config=True,
         help="""The directory name in which to keep file checkpoints
 
         This is a path relative to the file's own directory.
 
         By default, it is .ipynb_checkpoints
         """
     )
 
     def _copy(self, src, dest):
         """copy src to dest
 
         like shutil.copy2, but log errors in copystat
         """
         shutil.copyfile(src, dest)
         try:
             shutil.copystat(src, dest)
         except OSError as e:
             self.log.debug("copystat on %s failed", dest, exc_info=True)
 
     def _get_os_path(self, name=None, path=''):
         """Given a filename and API path, return its file system
         path.
 
         Parameters
         ----------
         name : string
             A filename
         path : string
             The relative API path to the named file.
 
         Returns
         -------
         path : string
             API path to be evaluated relative to root_dir.
         """
         if name is not None:
             path = url_path_join(path, name)
         return to_os_path(path, self.root_dir)
 
     def path_exists(self, path):
         """Does the API-style path refer to an extant directory?
 
         API-style wrapper for os.path.isdir
 
         Parameters
         ----------
         path : string
             The path to check. This is an API path (`/` separated,
             relative to root_dir).
 
         Returns
         -------
         exists : bool
             Whether the path is indeed a directory.
         """
         path = path.strip('/')
         os_path = self._get_os_path(path=path)
         return os.path.isdir(os_path)
 
     def is_hidden(self, path):
         """Does the API style path correspond to a hidden directory or file?
 
         Parameters
         ----------
         path : string
             The path to check. This is an API path (`/` separated,
             relative to root_dir).
 
         Returns
         -------
         exists : bool
             Whether the path is hidden.
 
         """
         path = path.strip('/')
         os_path = self._get_os_path(path=path)
         return is_hidden(os_path, self.root_dir)
 
     def file_exists(self, name, path=''):
         """Returns True if the file exists, else returns False.
 
         API-style wrapper for os.path.isfile
 
         Parameters
         ----------
         name : string
             The name of the file you are checking.
         path : string
             The relative path to the file's directory (with '/' as separator)
 
         Returns
         -------
         exists : bool
             Whether the file exists.
         """
         path = path.strip('/')
         nbpath = self._get_os_path(name, path=path)
         return os.path.isfile(nbpath)
 
     def exists(self, name=None, path=''):
         """Returns True if the path [and name] exists, else returns False.
 
         API-style wrapper for os.path.exists
 
         Parameters
         ----------
         name : string
             The name of the file you are checking.
         path : string
             The relative path to the file's directory (with '/' as separator)
 
         Returns
         -------
         exists : bool
             Whether the target exists.
         """
         path = path.strip('/')
         os_path = self._get_os_path(name, path=path)
         return os.path.exists(os_path)
 
     def _base_model(self, name, path=''):
         """Build the common base of a contents model"""
         os_path = self._get_os_path(name, path)
         info = os.stat(os_path)
         last_modified = tz.utcfromtimestamp(info.st_mtime)
         created = tz.utcfromtimestamp(info.st_ctime)
         # Create the base model.
         model = {}
         model['name'] = name
         model['path'] = path
         model['last_modified'] = last_modified
         model['created'] = created
         model['content'] = None
         model['format'] = None
+        model['message'] = None
         return model
 
     def _dir_model(self, name, path='', content=True):
         """Build a model for a directory
 
         if content is requested, will include a listing of the directory
         """
         os_path = self._get_os_path(name, path)
 
         four_o_four = u'directory does not exist: %r' % os_path
 
         if not os.path.isdir(os_path):
             raise web.HTTPError(404, four_o_four)
         elif is_hidden(os_path, self.root_dir):
             self.log.info("Refusing to serve hidden directory %r, via 404 Error",
                 os_path
             )
             raise web.HTTPError(404, four_o_four)
 
         if name is None:
             if '/' in path:
                 path, name = path.rsplit('/', 1)
             else:
                 name = ''
         model = self._base_model(name, path)
         model['type'] = 'directory'
         dir_path = u'{}/{}'.format(path, name)
         if content:
             model['content'] = contents = []
             for os_path in glob.glob(self._get_os_path('*', dir_path)):
                 name = os.path.basename(os_path)
                 # skip over broken symlinks in listing
                 if not os.path.exists(os_path):
                     self.log.warn("%s doesn't exist", os_path)
                     continue
                 if self.should_list(name) and not is_hidden(os_path, self.root_dir):
                     contents.append(self.get_model(name=name, path=dir_path, content=False))
 
             model['format'] = 'json'
 
         return model
 
     def _file_model(self, name, path='', content=True):
         """Build a model for a file
 
         if content is requested, include the file contents.
         UTF-8 text files will be unicode, binary files will be base64-encoded.
         """
         model = self._base_model(name, path)
         model['type'] = 'file'
         if content:
             os_path = self._get_os_path(name, path)
             with io.open(os_path, 'rb') as f:
                 bcontent = f.read()
             try:
                 model['content'] = bcontent.decode('utf8')
             except UnicodeError as e:
                 model['content'] = base64.encodestring(bcontent).decode('ascii')
                 model['format'] = 'base64'
             else:
                 model['format'] = 'text'
         return model
 
 
     def _notebook_model(self, name, path='', content=True):
         """Build a notebook model
 
         if content is requested, the notebook content will be populated
         as a JSON structure (not double-serialized)
         """
         model = self._base_model(name, path)
         model['type'] = 'notebook'
         if content:
             os_path = self._get_os_path(name, path)
             with io.open(os_path, 'r', encoding='utf-8') as f:
                 try:
                     nb = current.read(f, u'json')
                 except Exception as e:
                     raise web.HTTPError(400, u"Unreadable Notebook: %s %s" % (os_path, e))
             self.mark_trusted_cells(nb, name, path)
             model['content'] = nb
             model['format'] = 'json'
+            self.validate_notebook_model(model)
         return model
 
     def get_model(self, name, path='', content=True):
         """ Takes a path and name for an entity and returns its model
 
         Parameters
         ----------
         name : str
             the name of the target
         path : str
             the API path that describes the relative path for the target
 
         Returns
         -------
         model : dict
             the contents model. If content=True, returns the contents
             of the file or directory as well.
         """
         path = path.strip('/')
 
         if not self.exists(name=name, path=path):
             raise web.HTTPError(404, u'No such file or directory: %s/%s' % (path, name))
 
         os_path = self._get_os_path(name, path)
         if os.path.isdir(os_path):
             model = self._dir_model(name, path, content)
         elif name.endswith('.ipynb'):
             model = self._notebook_model(name, path, content)
         else:
             model = self._file_model(name, path, content)
         return model
 
     def _save_notebook(self, os_path, model, name='', path=''):
         """save a notebook file"""
         # Save the notebook file
         nb = current.to_notebook_json(model['content'])
 
         self.check_and_sign(nb, name, path)
 
         if 'name' in nb['metadata']:
             nb['metadata']['name'] = u''
 
         with atomic_writing(os_path, encoding='utf-8') as f:
             current.write(nb, f, u'json')
 
     def _save_file(self, os_path, model, name='', path=''):
         """save a non-notebook file"""
         fmt = model.get('format', None)
         if fmt not in {'text', 'base64'}:
             raise web.HTTPError(400, "Must specify format of file contents as 'text' or 'base64'")
         try:
             content = model['content']
             if fmt == 'text':
                 bcontent = content.encode('utf8')
             else:
                 b64_bytes = content.encode('ascii')
                 bcontent = base64.decodestring(b64_bytes)
         except Exception as e:
             raise web.HTTPError(400, u'Encoding error saving %s: %s' % (os_path, e))
         with atomic_writing(os_path, text=False) as f:
             f.write(bcontent)
 
     def _save_directory(self, os_path, model, name='', path=''):
         """create a directory"""
         if is_hidden(os_path, self.root_dir):
             raise web.HTTPError(400, u'Cannot create hidden directory %r' % os_path)
         if not os.path.exists(os_path):
             os.mkdir(os_path)
         elif not os.path.isdir(os_path):
             raise web.HTTPError(400, u'Not a directory: %s' % (os_path))
         else:
             self.log.debug("Directory %r already exists", os_path)
 
     def save(self, model, name='', path=''):
         """Save the file model and return the model with no content."""
         path = path.strip('/')
 
         if 'type' not in model:
             raise web.HTTPError(400, u'No file type provided')
         if 'content' not in model and model['type'] != 'directory':
             raise web.HTTPError(400, u'No file content provided')
 
         # One checkpoint should always exist
         if self.file_exists(name, path) and not self.list_checkpoints(name, path):
             self.create_checkpoint(name, path)
 
         new_path = model.get('path', path).strip('/')
         new_name = model.get('name', name)
 
         if path != new_path or name != new_name:
             self.rename(name, path, new_name, new_path)
 
         os_path = self._get_os_path(new_name, new_path)
         self.log.debug("Saving %s", os_path)
         try:
             if model['type'] == 'notebook':
                 self._save_notebook(os_path, model, new_name, new_path)
             elif model['type'] == 'file':
                 self._save_file(os_path, model, new_name, new_path)
             elif model['type'] == 'directory':
                 self._save_directory(os_path, model, new_name, new_path)
             else:
                 raise web.HTTPError(400, "Unhandled contents type: %s" % model['type'])
         except web.HTTPError:
             raise
         except Exception as e:
             raise web.HTTPError(400, u'Unexpected error while saving file: %s %s' % (os_path, e))
 
+        validation_message = None
+        if model['type'] == 'notebook':
+            self.validate_notebook_model(model)
+            validation_message = model.get('message', None)
+
         model = self.get_model(new_name, new_path, content=False)
+        if validation_message:
+            model['message'] = validation_message
         return model
 
     def update(self, model, name, path=''):
         """Update the file's path and/or name
 
         For use in PATCH requests, to enable renaming a file without
         re-uploading its contents. Only used for renaming at the moment.
         """
         path = path.strip('/')
         new_name = model.get('name', name)
         new_path = model.get('path', path).strip('/')
         if path != new_path or name != new_name:
             self.rename(name, path, new_name, new_path)
         model = self.get_model(new_name, new_path, content=False)
         return model
 
     def delete(self, name, path=''):
         """Delete file by name and path."""
         path = path.strip('/')
         os_path = self._get_os_path(name, path)
         rm = os.unlink
         if os.path.isdir(os_path):
             listing = os.listdir(os_path)
             # don't delete non-empty directories (checkpoints dir doesn't count)
             if listing and listing != [self.checkpoint_dir]:
                 raise web.HTTPError(400, u'Directory %s not empty' % os_path)
         elif not os.path.isfile(os_path):
             raise web.HTTPError(404, u'File does not exist: %s' % os_path)
 
         # clear checkpoints
         for checkpoint in self.list_checkpoints(name, path):
             checkpoint_id = checkpoint['id']
             cp_path = self.get_checkpoint_path(checkpoint_id, name, path)
             if os.path.isfile(cp_path):
                 self.log.debug("Unlinking checkpoint %s", cp_path)
                 os.unlink(cp_path)
 
         if os.path.isdir(os_path):
             self.log.debug("Removing directory %s", os_path)
             shutil.rmtree(os_path)
         else:
             self.log.debug("Unlinking file %s", os_path)
             rm(os_path)
 
     def rename(self, old_name, old_path, new_name, new_path):
         """Rename a file."""
         old_path = old_path.strip('/')
         new_path = new_path.strip('/')
         if new_name == old_name and new_path == old_path:
             return
 
         new_os_path = self._get_os_path(new_name, new_path)
         old_os_path = self._get_os_path(old_name, old_path)
 
         # Should we proceed with the move?
         if os.path.isfile(new_os_path):
             raise web.HTTPError(409, u'File with name already exists: %s' % new_os_path)
 
         # Move the file
         try:
             shutil.move(old_os_path, new_os_path)
         except Exception as e:
             raise web.HTTPError(500, u'Unknown error renaming file: %s %s' % (old_os_path, e))
 
         # Move the checkpoints
         old_checkpoints = self.list_checkpoints(old_name, old_path)
         for cp in old_checkpoints:
             checkpoint_id = cp['id']
             old_cp_path = self.get_checkpoint_path(checkpoint_id, old_name, old_path)
             new_cp_path = self.get_checkpoint_path(checkpoint_id, new_name, new_path)
             if os.path.isfile(old_cp_path):
                 self.log.debug("Renaming checkpoint %s -> %s", old_cp_path, new_cp_path)
                 shutil.move(old_cp_path, new_cp_path)
 
     # Checkpoint-related utilities
 
     def get_checkpoint_path(self, checkpoint_id, name, path=''):
         """find the path to a checkpoint"""
         path = path.strip('/')
         basename, ext = os.path.splitext(name)
         filename = u"{name}-{checkpoint_id}{ext}".format(
             name=basename,
             checkpoint_id=checkpoint_id,
             ext=ext,
         )
         os_path = self._get_os_path(path=path)
         cp_dir = os.path.join(os_path, self.checkpoint_dir)
         ensure_dir_exists(cp_dir)
         cp_path = os.path.join(cp_dir, filename)
         return cp_path
 
     def get_checkpoint_model(self, checkpoint_id, name, path=''):
         """construct the info dict for a given checkpoint"""
         path = path.strip('/')
         cp_path = self.get_checkpoint_path(checkpoint_id, name, path)
         stats = os.stat(cp_path)
         last_modified = tz.utcfromtimestamp(stats.st_mtime)
         info = dict(
             id = checkpoint_id,
             last_modified = last_modified,
         )
         return info
 
     # public checkpoint API
 
     def create_checkpoint(self, name, path=''):
         """Create a checkpoint from the current state of a file"""
         path = path.strip('/')
         src_path = self._get_os_path(name, path)
         # only the one checkpoint ID:
         checkpoint_id = u"checkpoint"
         cp_path = self.get_checkpoint_path(checkpoint_id, name, path)
         self.log.debug("creating checkpoint for %s", name)
         self._copy(src_path, cp_path)
 
         # return the checkpoint info
         return self.get_checkpoint_model(checkpoint_id, name, path)
 
     def list_checkpoints(self, name, path=''):
         """list the checkpoints for a given file
 
         This contents manager currently only supports one checkpoint per file.
         """
         path = path.strip('/')
         checkpoint_id = "checkpoint"
         os_path = self.get_checkpoint_path(checkpoint_id, name, path)
         if not os.path.exists(os_path):
             return []
         else:
             return [self.get_checkpoint_model(checkpoint_id, name, path)]
 
 
     def restore_checkpoint(self, checkpoint_id, name, path=''):
         """restore a file to a checkpointed state"""
         path = path.strip('/')
         self.log.info("restoring %s from checkpoint %s", name, checkpoint_id)
         nb_path = self._get_os_path(name, path)
         cp_path = self.get_checkpoint_path(checkpoint_id, name, path)
         if not os.path.isfile(cp_path):
             self.log.debug("checkpoint file does not exist: %s", cp_path)
             raise web.HTTPError(404,
                 u'checkpoint does not exist: %s-%s' % (name, checkpoint_id)
             )
         # ensure notebook is readable (never restore from an unreadable notebook)
         if cp_path.endswith('.ipynb'):
             with io.open(cp_path, 'r', encoding='utf-8') as f:
                 current.read(f, u'json')
         self._copy(cp_path, nb_path)
         self.log.debug("copying %s -> %s", cp_path, nb_path)
 
     def delete_checkpoint(self, checkpoint_id, name, path=''):
         """delete a file's checkpoint"""
         path = path.strip('/')
         cp_path = self.get_checkpoint_path(checkpoint_id, name, path)
         if not os.path.isfile(cp_path):
             raise web.HTTPError(404,
                 u'Checkpoint does not exist: %s%s-%s' % (path, name, checkpoint_id)
             )
         self.log.debug("unlinking %s", cp_path)
         os.unlink(cp_path)
 
     def info_string(self):
         return "Serving notebooks from local directory: %s" % self.root_dir
 
     def get_kernel_path(self, name, path='', model=None):
         """Return the initial working dir a kernel associated with a given notebook"""
         return os.path.join(self.root_dir, path)

IPython/html/services/contents/manager.py

@@ -1,333 +1,344 b''
 """A base class for contents managers."""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 from fnmatch import fnmatch
 import itertools
+import json
 import os
 
 from tornado.web import HTTPError
 
 from IPython.config.configurable import LoggingConfigurable
 from IPython.nbformat import current, sign
 from IPython.utils.traitlets import Instance, Unicode, List
 
 
 class ContentsManager(LoggingConfigurable):
     """Base class for serving files and directories.
 
     This serves any text or binary file,
     as well as directories,
     with special handling for JSON notebook documents.
 
     Most APIs take a path argument,
     which is always an API-style unicode path,
     and always refers to a directory.
 
     - unicode, not url-escaped
     - '/'-separated
     - leading and trailing '/' will be stripped
     - if unspecified, path defaults to '',
       indicating the root path.
 
     name is also unicode, and refers to a specfic target:
 
     - unicode, not url-escaped
     - must not contain '/'
     - It refers to an individual filename
     - It may refer to a directory name,
       in the case of listing or creating directories.
 
     """
 
     notary = Instance(sign.NotebookNotary)
     def _notary_default(self):
         return sign.NotebookNotary(parent=self)
 
     hide_globs = List(Unicode, [
             u'__pycache__', '*.pyc', '*.pyo',
             '.DS_Store', '*.so', '*.dylib', '*~',
         ], config=True, help="""
         Glob patterns to hide in file and directory listings.
     """)
 
     untitled_notebook = Unicode("Untitled", config=True,
         help="The base name used when creating untitled notebooks."
     )
 
     untitled_file = Unicode("untitled", config=True,
         help="The base name used when creating untitled files."
     )
 
     untitled_directory = Unicode("Untitled Folder", config=True,
         help="The base name used when creating untitled directories."
     )
 
     # ContentsManager API part 1: methods that must be
     # implemented in subclasses.
 
     def path_exists(self, path):
         """Does the API-style path (directory) actually exist?
 
         Like os.path.isdir
 
         Override this method in subclasses.
 
         Parameters
         ----------
         path : string
             The path to check
 
         Returns
         -------
         exists : bool
             Whether the path does indeed exist.
         """
         raise NotImplementedError
 
     def is_hidden(self, path):
         """Does the API style path correspond to a hidden directory or file?
 
         Parameters
         ----------
         path : string
             The path to check. This is an API path (`/` separated,
             relative to root dir).
 
         Returns
         -------
         hidden : bool
             Whether the path is hidden.
 
         """
         raise NotImplementedError
 
     def file_exists(self, name, path=''):
         """Does a file exist at the given name and path?
 
         Like os.path.isfile
 
         Override this method in subclasses.
 
         Parameters
         ----------
         name : string
             The name of the file you are checking.
         path : string
             The relative path to the file's directory (with '/' as separator)
 
         Returns
         -------
         exists : bool
             Whether the file exists.
         """
         raise NotImplementedError('must be implemented in a subclass')
 
     def exists(self, name, path=''):
         """Does a file or directory exist at the given name and path?
 
         Like os.path.exists
 
         Parameters
         ----------
         name : string
             The name of the file you are checking.
         path : string
             The relative path to the file's directory (with '/' as separator)
 
         Returns
         -------
         exists : bool
             Whether the target exists.
         """
         return self.file_exists(name, path) or self.path_exists("%s/%s" % (path, name))
 
     def get_model(self, name, path='', content=True):
         """Get the model of a file or directory with or without content."""
         raise NotImplementedError('must be implemented in a subclass')
 
     def save(self, model, name, path=''):
         """Save the file or directory and return the model with no content."""
         raise NotImplementedError('must be implemented in a subclass')
 
     def update(self, model, name, path=''):
         """Update the file or directory and return the model with no content.
 
         For use in PATCH requests, to enable renaming a file without
         re-uploading its contents. Only used for renaming at the moment.
         """
         raise NotImplementedError('must be implemented in a subclass')
 
     def delete(self, name, path=''):
         """Delete file or directory by name and path."""
         raise NotImplementedError('must be implemented in a subclass')
 
     def create_checkpoint(self, name, path=''):
         """Create a checkpoint of the current state of a file
 
         Returns a checkpoint_id for the new checkpoint.
         """
         raise NotImplementedError("must be implemented in a subclass")
 
     def list_checkpoints(self, name, path=''):
         """Return a list of checkpoints for a given file"""
         return []
 
     def restore_checkpoint(self, checkpoint_id, name, path=''):
         """Restore a file from one of its checkpoints"""
         raise NotImplementedError("must be implemented in a subclass")
 
     def delete_checkpoint(self, checkpoint_id, name, path=''):
         """delete a checkpoint for a file"""
         raise NotImplementedError("must be implemented in a subclass")
 
     # ContentsManager API part 2: methods that have useable default
     # implementations, but can be overridden in subclasses.
 
     def info_string(self):
         return "Serving contents"
 
     def get_kernel_path(self, name, path='', model=None):
         """ Return the path to start kernel in """
         return path
 
     def increment_filename(self, filename, path=''):
         """Increment a filename until it is unique.
 
         Parameters
         ----------
         filename : unicode
             The name of a file, including extension
         path : unicode
             The API path of the target's directory
 
         Returns
         -------
         name : unicode
             A filename that is unique, based on the input filename.
         """
         path = path.strip('/')
         basename, ext = os.path.splitext(filename)
         for i in itertools.count():
             name = u'{basename}{i}{ext}'.format(basename=basename, i=i,
                                                 ext=ext)
             if not self.file_exists(name, path):
                 break
         return name
 
+    def validate_notebook_model(self, model):
+        """Add failed-validation message to model"""
+        try:
+            current.validate(model['content'])
+        except current.ValidationError as e:
+            model['message'] = 'Notebook Validation failed: {}:\n{}'.format(
+                e.message, json.dumps(e.instance, indent=1, default=lambda obj: '<UNKNOWN>'),
+            )
+        return model
+
     def create_file(self, model=None, path='', ext='.ipynb'):
         """Create a new file or directory and return its model with no content."""
         path = path.strip('/')
         if model is None:
             model = {}
         if 'content' not in model and model.get('type', None) != 'directory':
             if ext == '.ipynb':
                 metadata = current.new_metadata(name=u'')
                 model['content'] = current.new_notebook(metadata=metadata)
                 model['type'] = 'notebook'
                 model['format'] = 'json'
             else:
                 model['content'] = ''
                 model['type'] = 'file'
                 model['format'] = 'text'
         if 'name' not in model:
             if model['type'] == 'directory':
                 untitled = self.untitled_directory
             elif model['type'] == 'notebook':
                 untitled = self.untitled_notebook
             elif model['type'] == 'file':
                 untitled = self.untitled_file
             else:
                 raise HTTPError(400, "Unexpected model type: %r" % model['type'])
             model['name'] = self.increment_filename(untitled + ext, path)
 
         model['path'] = path
         model = self.save(model, model['name'], model['path'])
         return model
 
     def copy(self, from_name, to_name=None, path=''):
         """Copy an existing file and return its new model.
 
         If to_name not specified, increment `from_name-Copy#.ext`.
 
         copy_from can be a full path to a file,
         or just a base name. If a base name, `path` is used.
         """
         path = path.strip('/')
         if '/' in from_name:
             from_path, from_name = from_name.rsplit('/', 1)
         else:
             from_path = path
         model = self.get_model(from_name, from_path)
         if model['type'] == 'directory':
             raise HTTPError(400, "Can't copy directories")
         if not to_name:
             base, ext = os.path.splitext(from_name)
             copy_name = u'{0}-Copy{1}'.format(base, ext)
             to_name = self.increment_filename(copy_name, path)
         model['name'] = to_name
         model['path'] = path
         model = self.save(model, to_name, path)
         return model
 
     def log_info(self):
         self.log.info(self.info_string())
 
     def trust_notebook(self, name, path=''):
         """Explicitly trust a notebook
 
         Parameters
         ----------
         name : string
             The filename of the notebook
         path : string
             The notebook's directory
         """
         model = self.get_model(name, path)
         nb = model['content']
         self.log.warn("Trusting notebook %s/%s", path, name)
         self.notary.mark_cells(nb, True)
         self.save(model, name, path)
 
     def check_and_sign(self, nb, name='', path=''):
         """Check for trusted cells, and sign the notebook.
 
         Called as a part of saving notebooks.
 
         Parameters
         ----------
         nb : dict
             The notebook object (in nbformat.current format)
         name : string
             The filename of the notebook (for logging)
         path : string
             The notebook's directory (for logging)
         """
         if self.notary.check_cells(nb):
             self.notary.sign(nb)
         else:
             self.log.warn("Saving untrusted notebook %s/%s", path, name)
 
     def mark_trusted_cells(self, nb, name='', path=''):
         """Mark cells as trusted if the notebook signature matches.
 
         Called as a part of loading notebooks.
 
         Parameters
         ----------
         nb : dict
             The notebook object (in nbformat.current format)
         name : string
             The filename of the notebook (for logging)
         path : string
             The notebook's directory (for logging)
         """
         trusted = self.notary.check_signature(nb)
         if not trusted:
             self.log.warn("Notebook %s/%s is not trusted", path, name)
         self.notary.mark_cells(nb, trusted)
 
     def should_list(self, name):
         """Should this file/directory name be displayed in a listing?"""
         return not any(fnmatch(name, glob) for glob in self.hide_globs)

IPython/html/static/notebook/js/notebook.js

@@ -1,2658 +1,2734 b''
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     'base/js/namespace',
     'jquery',
     'base/js/utils',
     'base/js/dialog',
     'notebook/js/textcell',
     'notebook/js/codecell',
     'services/sessions/js/session',
     'notebook/js/celltoolbar',
     'components/marked/lib/marked',
     'highlight',
     'notebook/js/mathjaxutils',
     'base/js/keyboard',
     'notebook/js/tooltip',
     'notebook/js/celltoolbarpresets/default',
     'notebook/js/celltoolbarpresets/rawcell',
     'notebook/js/celltoolbarpresets/slideshow',
     'notebook/js/scrollmanager'
 ], function (
     IPython, 
     $, 
     utils, 
     dialog, 
     textcell, 
     codecell, 
     session, 
     celltoolbar, 
     marked,
     hljs,
     mathjaxutils,
     keyboard,
     tooltip,
     default_celltoolbar,
     rawcell_celltoolbar,
     slideshow_celltoolbar,
     scrollmanager
     ) {
 
     var Notebook = function (selector, options) {
         // Constructor
         //
         // A notebook contains and manages cells.
         //
         // Parameters:
         //  selector: string
         //  options: dictionary
         //      Dictionary of keyword arguments.
         //          events: $(Events) instance
         //          keyboard_manager: KeyboardManager instance
         //          save_widget: SaveWidget instance
         //          config: dictionary
         //          base_url : string
         //          notebook_path : string
         //          notebook_name : string
         this.config = utils.mergeopt(Notebook, options.config);
         this.base_url = options.base_url;
         this.notebook_path = options.notebook_path;
         this.notebook_name = options.notebook_name;
         this.events = options.events;
         this.keyboard_manager = options.keyboard_manager;
         this.save_widget = options.save_widget;
         this.tooltip = new tooltip.Tooltip(this.events);
         this.ws_url = options.ws_url;
         this._session_starting = false;
         this.default_cell_type = this.config.default_cell_type || 'code';
 
         //  Create default scroll manager.
         this.scroll_manager = new scrollmanager.ScrollManager(this);
 
         // TODO: This code smells (and the other `= this` line a couple lines down)
         // We need a better way to deal with circular instance references.
         this.keyboard_manager.notebook = this;
         this.save_widget.notebook = this;
         
         mathjaxutils.init();
 
         if (marked) {
             marked.setOptions({
                 gfm : true,
                 tables: true,
                 langPrefix: "language-",
                 highlight: function(code, lang) {
                     if (!lang) {
                         // no language, no highlight
                         return code;
                     }
                     var highlighted;
                     try {
                         highlighted = hljs.highlight(lang, code, false);
                     } catch(err) {
                         highlighted = hljs.highlightAuto(code);
                     }
                     return highlighted.value;
                 }
             });
         }
 
         this.element = $(selector);
         this.element.scroll();
         this.element.data("notebook", this);
         this.next_prompt_number = 1;
         this.session = null;
         this.kernel = null;
         this.clipboard = null;
         this.undelete_backup = null;
         this.undelete_index = null;
         this.undelete_below = false;
         this.paste_enabled = false;
         // It is important to start out in command mode to match the intial mode
         // of the KeyboardManager.
         this.mode = 'command';
         this.set_dirty(false);
         this.metadata = {};
         this._checkpoint_after_save = false;
         this.last_checkpoint = null;
         this.checkpoints = [];
         this.autosave_interval = 0;
         this.autosave_timer = null;
         // autosave *at most* every two minutes
         this.minimum_autosave_interval = 120000;
         // single worksheet for now
         this.worksheet_metadata = {};
         this.notebook_name_blacklist_re = /[\/\\:]/;
         this.nbformat = 3; // Increment this when changing the nbformat
         this.nbformat_minor = 0; // Increment this when changing the nbformat
         this.codemirror_mode = 'ipython';
         this.create_elements();
         this.bind_events();
         this.save_notebook = function() { // don't allow save until notebook_loaded
             this.save_notebook_error(null, null, "Load failed, save is disabled");
         };
 
         // Trigger cell toolbar registration.
         default_celltoolbar.register(this);
         rawcell_celltoolbar.register(this);
         slideshow_celltoolbar.register(this);
     };
 
     Notebook.options_default = {
         // can be any cell type, or the special values of
         // 'above', 'below', or 'selected' to get the value from another cell.
         Notebook: {
             default_cell_type: 'code',
         }
     };
 
 
     /**
      * Create an HTML and CSS representation of the notebook.
      * 
      * @method create_elements
      */
     Notebook.prototype.create_elements = function () {
         var that = this;
         this.element.attr('tabindex','-1');
         this.container = $("<div/>").addClass("container").attr("id", "notebook-container");
         // We add this end_space div to the end of the notebook div to:
         // i) provide a margin between the last cell and the end of the notebook
         // ii) to prevent the div from scrolling up when the last cell is being
         // edited, but is too low on the page, which browsers will do automatically.
         var end_space = $('<div/>').addClass('end_space');
         end_space.dblclick(function (e) {
             var ncells = that.ncells();
             that.insert_cell_below('code',ncells-1);
         });
         this.element.append(this.container);
         this.container.append(end_space);
     };
 
     /**
      * Bind JavaScript events: key presses and custom IPython events.
      * 
      * @method bind_events
      */
     Notebook.prototype.bind_events = function () {
         var that = this;
 
         this.events.on('set_next_input.Notebook', function (event, data) {
             var index = that.find_cell_index(data.cell);
             var new_cell = that.insert_cell_below('code',index);
             new_cell.set_text(data.text);
             that.dirty = true;
         });
 
         this.events.on('set_dirty.Notebook', function (event, data) {
             that.dirty = data.value;
         });
 
         this.events.on('trust_changed.Notebook', function (event, data) {
             that.trusted = data.value;
         });
 
         this.events.on('select.Cell', function (event, data) {
             var index = that.find_cell_index(data.cell);
             that.select(index);
         });
 
         this.events.on('edit_mode.Cell', function (event, data) {
             that.handle_edit_mode(data.cell);
         });
 
         this.events.on('command_mode.Cell', function (event, data) {
             that.handle_command_mode(data.cell);
         });
 
         this.events.on('status_autorestarting.Kernel', function () {
             dialog.modal({
                 notebook: that,
                 keyboard_manager: that.keyboard_manager,
                 title: "Kernel Restarting",
                 body: "The kernel appears to have died. It will restart automatically.",
                 buttons: {
                     OK : {
                         class : "btn-primary"
                     }
                 }
             });
         });
         
         this.events.on('spec_changed.Kernel', function(event, data) {
             that.set_kernelspec_metadata(data);
             if (data.codemirror_mode) {
                 that.set_codemirror_mode(data.codemirror_mode);
             }
         });
 
         var collapse_time = function (time) {
             var app_height = $('#ipython-main-app').height(); // content height
             var splitter_height = $('div#pager_splitter').outerHeight(true);
             var new_height = app_height - splitter_height;
             that.element.animate({height : new_height + 'px'}, time);
         };
 
         this.element.bind('collapse_pager', function (event, extrap) {
             var time = (extrap !== undefined) ? ((extrap.duration !== undefined ) ? extrap.duration : 'fast') : 'fast';
             collapse_time(time);
         });
 
         var expand_time = function (time) {
             var app_height = $('#ipython-main-app').height(); // content height
             var splitter_height = $('div#pager_splitter').outerHeight(true);
             var pager_height = $('div#pager').outerHeight(true);
             var new_height = app_height - pager_height - splitter_height;
             that.element.animate({height : new_height + 'px'}, time);
         };
 
         this.element.bind('expand_pager', function (event, extrap) {
             var time = (extrap !== undefined) ? ((extrap.duration !== undefined ) ? extrap.duration : 'fast') : 'fast';
             expand_time(time);
         });
         
         // Firefox 22 broke $(window).on("beforeunload")
         // I'm not sure why or how.
         window.onbeforeunload = function (e) {
             // TODO: Make killing the kernel configurable.
             var kill_kernel = false;
             if (kill_kernel) {
                 that.session.kill_kernel();
             }
             // if we are autosaving, trigger an autosave on nav-away.
             // still warn, because if we don't the autosave may fail.
             if (that.dirty) {
                 if ( that.autosave_interval ) {
                     // schedule autosave in a timeout
                     // this gives you a chance to forcefully discard changes
                     // by reloading the page if you *really* want to.
                     // the timer doesn't start until you *dismiss* the dialog.
                     setTimeout(function () {
                         if (that.dirty) {
                             that.save_notebook();
                         }
                     }, 1000);
                     return "Autosave in progress, latest changes may be lost.";
                 } else {
                     return "Unsaved changes will be lost.";
                 }
             }
             // Null is the *only* return value that will make the browser not
             // pop up the "don't leave" dialog.
             return null;
         };
     };
 
     /**
      * Set the dirty flag, and trigger the set_dirty.Notebook event
      * 
      * @method set_dirty
      */
     Notebook.prototype.set_dirty = function (value) {
         if (value === undefined) {
             value = true;
         }
         if (this.dirty == value) {
             return;
         }
         this.events.trigger('set_dirty.Notebook', {value: value});
     };
 
     /**
      * Scroll the top of the page to a given cell.
      * 
      * @method scroll_to_cell
      * @param {Number} cell_number An index of the cell to view
      * @param {Number} time Animation time in milliseconds
      * @return {Number} Pixel offset from the top of the container
      */
     Notebook.prototype.scroll_to_cell = function (cell_number, time) {
         var cells = this.get_cells();
         time = time || 0;
         cell_number = Math.min(cells.length-1,cell_number);
         cell_number = Math.max(0             ,cell_number);
         var scroll_value = cells[cell_number].element.position().top-cells[0].element.position().top ;
         this.element.animate({scrollTop:scroll_value}, time);
         return scroll_value;
     };
 
     /**
      * Scroll to the bottom of the page.
      * 
      * @method scroll_to_bottom
      */
     Notebook.prototype.scroll_to_bottom = function () {
         this.element.animate({scrollTop:this.element.get(0).scrollHeight}, 0);
     };
 
     /**
      * Scroll to the top of the page.
      * 
      * @method scroll_to_top
      */
     Notebook.prototype.scroll_to_top = function () {
         this.element.animate({scrollTop:0}, 0);
     };
 
     // Edit Notebook metadata
 
     Notebook.prototype.edit_metadata = function () {
         var that = this;
         dialog.edit_metadata({
             md: this.metadata, 
             callback: function (md) {
                 that.metadata = md;
             }, 
             name: 'Notebook',
             notebook: this,
             keyboard_manager: this.keyboard_manager});
     };
     
     Notebook.prototype.set_kernelspec_metadata = function(ks) {
         var tostore = {};
         $.map(ks, function(value, field) {
             if (field !== 'argv' && field !== 'env') {
                 tostore[field] = value;
             }
         });
         this.metadata.kernelspec = tostore;
     }
 
     // Cell indexing, retrieval, etc.
 
     /**
      * Get all cell elements in the notebook.
      * 
      * @method get_cell_elements
      * @return {jQuery} A selector of all cell elements
      */
     Notebook.prototype.get_cell_elements = function () {
         return this.container.children("div.cell");
     };
 
     /**
      * Get a particular cell element.
      * 
      * @method get_cell_element
      * @param {Number} index An index of a cell to select
      * @return {jQuery} A selector of the given cell.
      */
     Notebook.prototype.get_cell_element = function (index) {
         var result = null;
         var e = this.get_cell_elements().eq(index);
         if (e.length !== 0) {
             result = e;
         }
         return result;
     };
 
     /**
      * Try to get a particular cell by msg_id.
      * 
      * @method get_msg_cell
      * @param {String} msg_id A message UUID
      * @return {Cell} Cell or null if no cell was found.
      */
     Notebook.prototype.get_msg_cell = function (msg_id) {
         return codecell.CodeCell.msg_cells[msg_id] || null;
     };
 
     /**
      * Count the cells in this notebook.
      * 
      * @method ncells
      * @return {Number} The number of cells in this notebook
      */
     Notebook.prototype.ncells = function () {
         return this.get_cell_elements().length;
     };
 
     /**
      * Get all Cell objects in this notebook.
      * 
      * @method get_cells
      * @return {Array} This notebook's Cell objects
      */
     // TODO: we are often calling cells as cells()[i], which we should optimize
     // to cells(i) or a new method.
     Notebook.prototype.get_cells = function () {
         return this.get_cell_elements().toArray().map(function (e) {
             return $(e).data("cell");
         });
     };
 
     /**
      * Get a Cell object from this notebook.
      * 
      * @method get_cell
      * @param {Number} index An index of a cell to retrieve
      * @return {Cell} Cell or null if no cell was found.
      */
     Notebook.prototype.get_cell = function (index) {
         var result = null;
         var ce = this.get_cell_element(index);
         if (ce !== null) {
             result = ce.data('cell');
         }
         return result;
     };
 
     /**
      * Get the cell below a given cell.
      * 
      * @method get_next_cell
      * @param {Cell} cell The provided cell
      * @return {Cell} the next cell or null if no cell was found.
      */
     Notebook.prototype.get_next_cell = function (cell) {
         var result = null;
         var index = this.find_cell_index(cell);
         if (this.is_valid_cell_index(index+1)) {
             result = this.get_cell(index+1);
         }
         return result;
     };
 
     /**
      * Get the cell above a given cell.
      * 
      * @method get_prev_cell
      * @param {Cell} cell The provided cell
      * @return {Cell} The previous cell or null if no cell was found.
      */
     Notebook.prototype.get_prev_cell = function (cell) {
         var result = null;
         var index = this.find_cell_index(cell);
         if (index !== null && index > 0) {
             result = this.get_cell(index-1);
         }
         return result;
     };
     
     /**
      * Get the numeric index of a given cell.
      * 
      * @method find_cell_index
      * @param {Cell} cell The provided cell
      * @return {Number} The cell's numeric index or null if no cell was found.
      */
     Notebook.prototype.find_cell_index = function (cell) {
         var result = null;
         this.get_cell_elements().filter(function (index) {
             if ($(this).data("cell") === cell) {
                 result = index;
             }
         });
         return result;
     };
 
     /**
      * Get a given index , or the selected index if none is provided.
      * 
      * @method index_or_selected
      * @param {Number} index A cell's index
      * @return {Number} The given index, or selected index if none is provided.
      */
     Notebook.prototype.index_or_selected = function (index) {
         var i;
         if (index === undefined || index === null) {
             i = this.get_selected_index();
             if (i === null) {
                 i = 0;
             }
         } else {
             i = index;
         }
         return i;
     };
 
     /**
      * Get the currently selected cell.
      * @method get_selected_cell
      * @return {Cell} The selected cell
      */
     Notebook.prototype.get_selected_cell = function () {
         var index = this.get_selected_index();
         return this.get_cell(index);
     };
 
     /**
      * Check whether a cell index is valid.
      * 
      * @method is_valid_cell_index
      * @param {Number} index A cell index
      * @return True if the index is valid, false otherwise
      */
     Notebook.prototype.is_valid_cell_index = function (index) {
         if (index !== null && index >= 0 && index < this.ncells()) {
             return true;
         } else {
             return false;
         }
     };
 
     /**
      * Get the index of the currently selected cell.
      
      * @method get_selected_index
      * @return {Number} The selected cell's numeric index
      */
     Notebook.prototype.get_selected_index = function () {
         var result = null;
         this.get_cell_elements().filter(function (index) {
             if ($(this).data("cell").selected === true) {
                 result = index;
             }
         });
         return result;
     };
 
 
     // Cell selection.
 
     /**
      * Programmatically select a cell.
      * 
      * @method select
      * @param {Number} index A cell's index
      * @return {Notebook} This notebook
      */
     Notebook.prototype.select = function (index) {
         if (this.is_valid_cell_index(index)) {
             var sindex = this.get_selected_index();
             if (sindex !== null && index !== sindex) {
                 // If we are about to select a different cell, make sure we are
                 // first in command mode.
                 if (this.mode !== 'command') {
                     this.command_mode();
                 }
                 this.get_cell(sindex).unselect();
             }
             var cell = this.get_cell(index);
             cell.select();
             if (cell.cell_type === 'heading') {
                 this.events.trigger('selected_cell_type_changed.Notebook',
                     {'cell_type':cell.cell_type,level:cell.level}
                 );
             } else {
                 this.events.trigger('selected_cell_type_changed.Notebook',
                     {'cell_type':cell.cell_type}
                 );
             }
         }
         return this;
     };
 
     /**
      * Programmatically select the next cell.
      *
      * @method select_next
      * @return {Notebook} This notebook
      */
     Notebook.prototype.select_next = function () {
         var index = this.get_selected_index();
         this.select(index+1);
         return this;
     };
 
     /**
      * Programmatically select the previous cell.
      *
      * @method select_prev
      * @return {Notebook} This notebook
      */
     Notebook.prototype.select_prev = function () {
         var index = this.get_selected_index();
         this.select(index-1);
         return this;
     };
 
 
     // Edit/Command mode
 
     /**
      * Gets the index of the cell that is in edit mode.
      *
      * @method get_edit_index
      *
      * @return index {int}
      **/
     Notebook.prototype.get_edit_index = function () {
         var result = null;
         this.get_cell_elements().filter(function (index) {
             if ($(this).data("cell").mode === 'edit') {
                 result = index;
             }
         });
         return result;
     };
 
     /**
      * Handle when a a cell blurs and the notebook should enter command mode.
      *
      * @method handle_command_mode
      * @param [cell] {Cell} Cell to enter command mode on.
      **/
     Notebook.prototype.handle_command_mode = function (cell) {
         if (this.mode !== 'command') {
             cell.command_mode();
             this.mode = 'command';
             this.events.trigger('command_mode.Notebook');
             this.keyboard_manager.command_mode();
         }
     };
 
     /**
      * Make the notebook enter command mode.
      *
      * @method command_mode
      **/
     Notebook.prototype.command_mode = function () {
         var cell = this.get_cell(this.get_edit_index());
         if (cell && this.mode !== 'command') {
             // We don't call cell.command_mode, but rather call cell.focus_cell()
             // which will blur and CM editor and trigger the call to
             // handle_command_mode.
             cell.focus_cell();
         }
     };
 
     /**
      * Handle when a cell fires it's edit_mode event.
      *
      * @method handle_edit_mode
      * @param [cell] {Cell} Cell to enter edit mode on.
      **/
     Notebook.prototype.handle_edit_mode = function (cell) {
         if (cell && this.mode !== 'edit') {
             cell.edit_mode();
             this.mode = 'edit';
             this.events.trigger('edit_mode.Notebook');
             this.keyboard_manager.edit_mode();
         }
     };
 
     /**
      * Make a cell enter edit mode.
      *
      * @method edit_mode
      **/
     Notebook.prototype.edit_mode = function () {
         var cell = this.get_selected_cell();
         if (cell && this.mode !== 'edit') {
             cell.unrender();
             cell.focus_editor();
         }
     };
 
     /**
      * Focus the currently selected cell.
      *
      * @method focus_cell
      **/
     Notebook.prototype.focus_cell = function () {
         var cell = this.get_selected_cell();
         if (cell === null) {return;}  // No cell is selected
         cell.focus_cell();
     };
 
     // Cell movement
 
     /**
      * Move given (or selected) cell up and select it.
      * 
      * @method move_cell_up
      * @param [index] {integer} cell index
      * @return {Notebook} This notebook
      **/
     Notebook.prototype.move_cell_up = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i) && i > 0) {
             var pivot = this.get_cell_element(i-1);
             var tomove = this.get_cell_element(i);
             if (pivot !== null && tomove !== null) {
                 tomove.detach();
                 pivot.before(tomove);
                 this.select(i-1);
                 var cell = this.get_selected_cell();
                 cell.focus_cell();
             }
             this.set_dirty(true);
         }
         return this;
     };
 
 
     /**
      * Move given (or selected) cell down and select it
      * 
      * @method move_cell_down
      * @param [index] {integer} cell index
      * @return {Notebook} This notebook
      **/
     Notebook.prototype.move_cell_down = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i) && this.is_valid_cell_index(i+1)) {
             var pivot = this.get_cell_element(i+1);
             var tomove = this.get_cell_element(i);
             if (pivot !== null && tomove !== null) {
                 tomove.detach();
                 pivot.after(tomove);
                 this.select(i+1);
                 var cell = this.get_selected_cell();
                 cell.focus_cell();
             }
         }
         this.set_dirty();
         return this;
     };
 
 
     // Insertion, deletion.
 
     /**
      * Delete a cell from the notebook.
      * 
      * @method delete_cell
      * @param [index] A cell's numeric index
      * @return {Notebook} This notebook
      */
     Notebook.prototype.delete_cell = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (!cell.is_deletable()) {
             return this;
         }
 
         this.undelete_backup = cell.toJSON();
         $('#undelete_cell').removeClass('disabled');
         if (this.is_valid_cell_index(i)) {
             var old_ncells = this.ncells();
             var ce = this.get_cell_element(i);
             ce.remove();
             if (i === 0) {
                 // Always make sure we have at least one cell.
                 if (old_ncells === 1) {
                     this.insert_cell_below('code');
                 }
                 this.select(0);
                 this.undelete_index = 0;
                 this.undelete_below = false;
             } else if (i === old_ncells-1 && i !== 0) {
                 this.select(i-1);
                 this.undelete_index = i - 1;
                 this.undelete_below = true;
             } else {
                 this.select(i);
                 this.undelete_index = i;
                 this.undelete_below = false;
             }
             this.events.trigger('delete.Cell', {'cell': cell, 'index': i});
             this.set_dirty(true);
         }
         return this;
     };
 
     /**
      * Restore the most recently deleted cell.
      * 
      * @method undelete
      */
     Notebook.prototype.undelete_cell = function() {
         if (this.undelete_backup !== null && this.undelete_index !== null) {
             var current_index = this.get_selected_index();
             if (this.undelete_index < current_index) {
                 current_index = current_index + 1;
             }
             if (this.undelete_index >= this.ncells()) {
                 this.select(this.ncells() - 1);
             }
             else {
                 this.select(this.undelete_index);
             }
             var cell_data = this.undelete_backup;
             var new_cell = null;
             if (this.undelete_below) {
                 new_cell = this.insert_cell_below(cell_data.cell_type);
             } else {
                 new_cell = this.insert_cell_above(cell_data.cell_type);
             }
             new_cell.fromJSON(cell_data);
             if (this.undelete_below) {
                 this.select(current_index+1);
             } else {
                 this.select(current_index);
             }
             this.undelete_backup = null;
             this.undelete_index = null;
         }
         $('#undelete_cell').addClass('disabled');
     };
 
     /**
      * Insert a cell so that after insertion the cell is at given index.
      *
      * If cell type is not provided, it will default to the type of the
      * currently active cell.
      *
      * Similar to insert_above, but index parameter is mandatory
      *
      * Index will be brought back into the accessible range [0,n]
      *
      * @method insert_cell_at_index
      * @param [type] {string} in ['code','markdown','heading'], defaults to 'code'
      * @param [index] {int} a valid index where to insert cell
      *
      * @return cell {cell|null} created cell or null
      **/
     Notebook.prototype.insert_cell_at_index = function(type, index){
 
         var ncells = this.ncells();
         index = Math.min(index, ncells);
         index = Math.max(index, 0);
         var cell = null;
         type = type || this.default_cell_type;
         if (type === 'above') {
             if (index > 0) {
                 type = this.get_cell(index-1).cell_type;
             } else {
                 type = 'code';
             }
         } else if (type === 'below') {
             if (index < ncells) {
                 type = this.get_cell(index).cell_type;
             } else {
                 type = 'code';
             }
         } else if (type === 'selected') {
             type = this.get_selected_cell().cell_type;
         }
 
         if (ncells === 0 || this.is_valid_cell_index(index) || index === ncells) {
             var cell_options = {
                 events: this.events, 
                 config: this.config, 
                 keyboard_manager: this.keyboard_manager, 
                 notebook: this,
                 tooltip: this.tooltip,
             };
             if (type === 'code') {
                 cell = new codecell.CodeCell(this.kernel, cell_options);
                 cell.set_input_prompt();
             } else if (type === 'markdown') {
                 cell = new textcell.MarkdownCell(cell_options);
             } else if (type === 'raw') {
                 cell = new textcell.RawCell(cell_options);
             } else if (type === 'heading') {
                 cell = new textcell.HeadingCell(cell_options);
             }
 
             if(this._insert_element_at_index(cell.element,index)) {
                 cell.render();
                 this.events.trigger('create.Cell', {'cell': cell, 'index': index});
                 cell.refresh();
                 // We used to select the cell after we refresh it, but there
                 // are now cases were this method is called where select is
                 // not appropriate. The selection logic should be handled by the
                 // caller of the the top level insert_cell methods.
                 this.set_dirty(true);
             }
         }
         return cell;
 
     };
 
     /**
      * Insert an element at given cell index.
      *
      * @method _insert_element_at_index
      * @param element {dom element} a cell element
      * @param [index] {int} a valid index where to inser cell
      * @private
      *
      * return true if everything whent fine.
      **/
     Notebook.prototype._insert_element_at_index = function(element, index){
         if (element === undefined){
             return false;
         }
 
         var ncells = this.ncells();
 
         if (ncells === 0) {
             // special case append if empty
             this.element.find('div.end_space').before(element);
         } else if ( ncells === index ) {
             // special case append it the end, but not empty
             this.get_cell_element(index-1).after(element);
         } else if (this.is_valid_cell_index(index)) {
             // otherwise always somewhere to append to
             this.get_cell_element(index).before(element);
         } else {
             return false;
         }
 
         if (this.undelete_index !== null && index <= this.undelete_index) {
             this.undelete_index = this.undelete_index + 1;
             this.set_dirty(true);
         }
         return true;
     };
 
     /**
      * Insert a cell of given type above given index, or at top
      * of notebook if index smaller than 0.
      *
      * default index value is the one of currently selected cell
      *
      * @method insert_cell_above
      * @param [type] {string} cell type
      * @param [index] {integer}
      *
      * @return handle to created cell or null
      **/
     Notebook.prototype.insert_cell_above = function (type, index) {
         index = this.index_or_selected(index);
         return this.insert_cell_at_index(type, index);
     };
 
     /**
      * Insert a cell of given type below given index, or at bottom
      * of notebook if index greater than number of cells
      *
      * default index value is the one of currently selected cell
      *
      * @method insert_cell_below
      * @param [type] {string} cell type
      * @param [index] {integer}
      *
      * @return handle to created cell or null
      *
      **/
     Notebook.prototype.insert_cell_below = function (type, index) {
         index = this.index_or_selected(index);
         return this.insert_cell_at_index(type, index+1);
     };
 
 
     /**
      * Insert cell at end of notebook
      *
      * @method insert_cell_at_bottom
      * @param {String} type cell type
      *
      * @return the added cell; or null
      **/
     Notebook.prototype.insert_cell_at_bottom = function (type){
         var len = this.ncells();
         return this.insert_cell_below(type,len-1);
     };
 
     /**
      * Turn a cell into a code cell.
      * 
      * @method to_code
      * @param {Number} [index] A cell's index
      */
     Notebook.prototype.to_code = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var source_cell = this.get_cell(i);
             if (!(source_cell instanceof codecell.CodeCell)) {
                 var target_cell = this.insert_cell_below('code',i);
                 var text = source_cell.get_text();
                 if (text === source_cell.placeholder) {
                     text = '';
                 }
                 //metadata
                 target_cell.metadata = source_cell.metadata;
 
                 target_cell.set_text(text);
                 // make this value the starting point, so that we can only undo
                 // to this state, instead of a blank cell
                 target_cell.code_mirror.clearHistory();
                 source_cell.element.remove();
                 this.select(i);
                 var cursor = source_cell.code_mirror.getCursor();
                 target_cell.code_mirror.setCursor(cursor);
                 this.set_dirty(true);
             }
         }
     };
 
     /**
      * Turn a cell into a Markdown cell.
      * 
      * @method to_markdown
      * @param {Number} [index] A cell's index
      */
     Notebook.prototype.to_markdown = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var source_cell = this.get_cell(i);
 
             if (!(source_cell instanceof textcell.MarkdownCell)) {
                 var target_cell = this.insert_cell_below('markdown',i);
                 var text = source_cell.get_text();
 
                 if (text === source_cell.placeholder) {
                     text = '';
                 }
                 // metadata
                 target_cell.metadata = source_cell.metadata
                 // We must show the editor before setting its contents
                 target_cell.unrender();
                 target_cell.set_text(text);
                 // make this value the starting point, so that we can only undo
                 // to this state, instead of a blank cell
                 target_cell.code_mirror.clearHistory();
                 source_cell.element.remove();
                 this.select(i);
                 if ((source_cell instanceof textcell.TextCell) && source_cell.rendered) {
                     target_cell.render();
                 }
                 var cursor = source_cell.code_mirror.getCursor();
                 target_cell.code_mirror.setCursor(cursor);
                 this.set_dirty(true);
             }
         }
     };
 
     /**
      * Turn a cell into a raw text cell.
      * 
      * @method to_raw
      * @param {Number} [index] A cell's index
      */
     Notebook.prototype.to_raw = function (index) {
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var target_cell = null;
             var source_cell = this.get_cell(i);
 
             if (!(source_cell instanceof textcell.RawCell)) {
                 target_cell = this.insert_cell_below('raw',i);
                 var text = source_cell.get_text();
                 if (text === source_cell.placeholder) {
                     text = '';
                 }
                 //metadata
                 target_cell.metadata = source_cell.metadata;
                 // We must show the editor before setting its contents
                 target_cell.unrender();
                 target_cell.set_text(text);
                 // make this value the starting point, so that we can only undo
                 // to this state, instead of a blank cell
                 target_cell.code_mirror.clearHistory();
                 source_cell.element.remove();
                 this.select(i);
                 var cursor = source_cell.code_mirror.getCursor();
                 target_cell.code_mirror.setCursor(cursor);
                 this.set_dirty(true);
             }
         }
     };
 
     /**
      * Turn a cell into a heading cell.
      * 
      * @method to_heading
      * @param {Number} [index] A cell's index
      * @param {Number} [level] A heading level (e.g., 1 becomes &lt;h1&gt;)
      */
     Notebook.prototype.to_heading = function (index, level) {
         level = level || 1;
         var i = this.index_or_selected(index);
         if (this.is_valid_cell_index(i)) {
             var source_cell = this.get_cell(i);
             var target_cell = null;
             if (source_cell instanceof textcell.HeadingCell) {
                 source_cell.set_level(level);
             } else {
                 target_cell = this.insert_cell_below('heading',i);
                 var text = source_cell.get_text();
                 if (text === source_cell.placeholder) {
                     text = '';
                 }
                 //metadata
                 target_cell.metadata = source_cell.metadata;
                 // We must show the editor before setting its contents
                 target_cell.set_level(level);
                 target_cell.unrender();
                 target_cell.set_text(text);
                 // make this value the starting point, so that we can only undo
                 // to this state, instead of a blank cell
                 target_cell.code_mirror.clearHistory();
                 source_cell.element.remove();
                 this.select(i);
                 var cursor = source_cell.code_mirror.getCursor();
                 target_cell.code_mirror.setCursor(cursor);
                 if ((source_cell instanceof textcell.TextCell) && source_cell.rendered) {
                     target_cell.render();
                 }
             }
             this.set_dirty(true);
             this.events.trigger('selected_cell_type_changed.Notebook',
                 {'cell_type':'heading',level:level}
             );
         }
     };
 
 
     // Cut/Copy/Paste
 
     /**
      * Enable UI elements for pasting cells.
      * 
      * @method enable_paste
      */
     Notebook.prototype.enable_paste = function () {
         var that = this;
         if (!this.paste_enabled) {
             $('#paste_cell_replace').removeClass('disabled')
                 .on('click', function () {that.paste_cell_replace();});
             $('#paste_cell_above').removeClass('disabled')
                 .on('click', function () {that.paste_cell_above();});
             $('#paste_cell_below').removeClass('disabled')
                 .on('click', function () {that.paste_cell_below();});
             this.paste_enabled = true;
         }
     };
 
     /**
      * Disable UI elements for pasting cells.
      * 
      * @method disable_paste
      */
     Notebook.prototype.disable_paste = function () {
         if (this.paste_enabled) {
             $('#paste_cell_replace').addClass('disabled').off('click');
             $('#paste_cell_above').addClass('disabled').off('click');
             $('#paste_cell_below').addClass('disabled').off('click');
             this.paste_enabled = false;
         }
     };
 
     /**
      * Cut a cell.
      * 
      * @method cut_cell
      */
     Notebook.prototype.cut_cell = function () {
         this.copy_cell();
         this.delete_cell();
     };
 
     /**
      * Copy a cell.
      * 
      * @method copy_cell
      */
     Notebook.prototype.copy_cell = function () {
         var cell = this.get_selected_cell();
         this.clipboard = cell.toJSON();
         // remove undeletable status from the copied cell
         if (this.clipboard.metadata.deletable !== undefined) {
             delete this.clipboard.metadata.deletable;
         }
         this.enable_paste();
     };
 
     /**
      * Replace the selected cell with a cell in the clipboard.
      * 
      * @method paste_cell_replace
      */
     Notebook.prototype.paste_cell_replace = function () {
         if (this.clipboard !== null && this.paste_enabled) {
             var cell_data = this.clipboard;
             var new_cell = this.insert_cell_above(cell_data.cell_type);
             new_cell.fromJSON(cell_data);
             var old_cell = this.get_next_cell(new_cell);
             this.delete_cell(this.find_cell_index(old_cell));
             this.select(this.find_cell_index(new_cell));
         }
     };
 
     /**
      * Paste a cell from the clipboard above the selected cell.
      * 
      * @method paste_cell_above
      */
     Notebook.prototype.paste_cell_above = function () {
         if (this.clipboard !== null && this.paste_enabled) {
             var cell_data = this.clipboard;
             var new_cell = this.insert_cell_above(cell_data.cell_type);
             new_cell.fromJSON(cell_data);
             new_cell.focus_cell();
         }
     };
 
     /**
      * Paste a cell from the clipboard below the selected cell.
      * 
      * @method paste_cell_below
      */
     Notebook.prototype.paste_cell_below = function () {
         if (this.clipboard !== null && this.paste_enabled) {
             var cell_data = this.clipboard;
             var new_cell = this.insert_cell_below(cell_data.cell_type);
             new_cell.fromJSON(cell_data);
             new_cell.focus_cell();
         }
     };
 
     // Split/merge
 
     /**
      * Split the selected cell into two, at the cursor.
      * 
      * @method split_cell
      */
     Notebook.prototype.split_cell = function () {
         var mdc = textcell.MarkdownCell;
         var rc = textcell.RawCell;
         var cell = this.get_selected_cell();
         if (cell.is_splittable()) {
             var texta = cell.get_pre_cursor();
             var textb = cell.get_post_cursor();
             cell.set_text(textb);
             var new_cell = this.insert_cell_above(cell.cell_type);
             // Unrender the new cell so we can call set_text.
             new_cell.unrender();
             new_cell.set_text(texta);
         }
     };
 
     /**
      * Combine the selected cell into the cell above it.
      * 
      * @method merge_cell_above
      */
     Notebook.prototype.merge_cell_above = function () {
         var mdc = textcell.MarkdownCell;
         var rc = textcell.RawCell;
         var index = this.get_selected_index();
         var cell = this.get_cell(index);
         var render = cell.rendered;
         if (!cell.is_mergeable()) {
             return;
         }
         if (index > 0) {
             var upper_cell = this.get_cell(index-1);
             if (!upper_cell.is_mergeable()) {
                 return;
             }
             var upper_text = upper_cell.get_text();
             var text = cell.get_text();
             if (cell instanceof codecell.CodeCell) {
                 cell.set_text(upper_text+'\n'+text);
             } else {
                 cell.unrender(); // Must unrender before we set_text.
                 cell.set_text(upper_text+'\n\n'+text);
                 if (render) {
                     // The rendered state of the final cell should match
                     // that of the original selected cell;
                     cell.render();
                 }
             }
             this.delete_cell(index-1);
             this.select(this.find_cell_index(cell));
         }
     };
 
     /**
      * Combine the selected cell into the cell below it.
      * 
      * @method merge_cell_below
      */
     Notebook.prototype.merge_cell_below = function () {
         var mdc = textcell.MarkdownCell;
         var rc = textcell.RawCell;
         var index = this.get_selected_index();
         var cell = this.get_cell(index);
         var render = cell.rendered;
         if (!cell.is_mergeable()) {
             return;
         }
         if (index < this.ncells()-1) {
             var lower_cell = this.get_cell(index+1);
             if (!lower_cell.is_mergeable()) {
                 return;
             }
             var lower_text = lower_cell.get_text();
             var text = cell.get_text();
             if (cell instanceof codecell.CodeCell) {
                 cell.set_text(text+'\n'+lower_text);
             } else {
                 cell.unrender(); // Must unrender before we set_text.
                 cell.set_text(text+'\n\n'+lower_text);
                 if (render) {
                     // The rendered state of the final cell should match
                     // that of the original selected cell;
                     cell.render();
                 }
             }
             this.delete_cell(index+1);
             this.select(this.find_cell_index(cell));
         }
     };
 
 
     // Cell collapsing and output clearing
 
     /**
      * Hide a cell's output.
      * 
      * @method collapse_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.collapse_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof codecell.CodeCell)) {
             cell.collapse_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Hide each code cell's output area.
      * 
      * @method collapse_all_output
      */
     Notebook.prototype.collapse_all_output = function () {
         $.map(this.get_cells(), function (cell, i) {
             if (cell instanceof codecell.CodeCell) {
                 cell.collapse_output();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     /**
      * Show a cell's output.
      * 
      * @method expand_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.expand_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof codecell.CodeCell)) {
             cell.expand_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Expand each code cell's output area, and remove scrollbars.
      * 
      * @method expand_all_output
      */
     Notebook.prototype.expand_all_output = function () {
         $.map(this.get_cells(), function (cell, i) {
             if (cell instanceof codecell.CodeCell) {
                 cell.expand_output();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     /**
      * Clear the selected CodeCell's output area.
      * 
      * @method clear_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.clear_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof codecell.CodeCell)) {
             cell.clear_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Clear each code cell's output area.
      * 
      * @method clear_all_output
      */
     Notebook.prototype.clear_all_output = function () {
         $.map(this.get_cells(), function (cell, i) {
             if (cell instanceof codecell.CodeCell) {
                 cell.clear_output();
             }
         });
         this.set_dirty(true);
     };
 
     /**
      * Scroll the selected CodeCell's output area.
      * 
      * @method scroll_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.scroll_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof codecell.CodeCell)) {
             cell.scroll_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Expand each code cell's output area, and add a scrollbar for long output.
      * 
      * @method scroll_all_output
      */
     Notebook.prototype.scroll_all_output = function () {
         $.map(this.get_cells(), function (cell, i) {
             if (cell instanceof codecell.CodeCell) {
                 cell.scroll_output();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     /** Toggle whether a cell's output is collapsed or expanded.
      * 
      * @method toggle_output
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.toggle_output = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof codecell.CodeCell)) {
             cell.toggle_output();
             this.set_dirty(true);
         }
     };
 
     /**
      * Hide/show the output of all cells.
      * 
      * @method toggle_all_output
      */
     Notebook.prototype.toggle_all_output = function () {
         $.map(this.get_cells(), function (cell, i) {
             if (cell instanceof codecell.CodeCell) {
                 cell.toggle_output();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     /**
      * Toggle a scrollbar for long cell outputs.
      * 
      * @method toggle_output_scroll
      * @param {Number} index A cell's numeric index
      */
     Notebook.prototype.toggle_output_scroll = function (index) {
         var i = this.index_or_selected(index);
         var cell = this.get_cell(i);
         if (cell !== null && (cell instanceof codecell.CodeCell)) {
             cell.toggle_output_scroll();
             this.set_dirty(true);
         }
     };
 
     /**
      * Toggle the scrolling of long output on all cells.
      * 
      * @method toggle_all_output_scrolling
      */
     Notebook.prototype.toggle_all_output_scroll = function () {
         $.map(this.get_cells(), function (cell, i) {
             if (cell instanceof codecell.CodeCell) {
                 cell.toggle_output_scroll();
             }
         });
         // this should not be set if the `collapse` key is removed from nbformat
         this.set_dirty(true);
     };
 
     // Other cell functions: line numbers, ...
 
     /**
      * Toggle line numbers in the selected cell's input area.
      * 
      * @method cell_toggle_line_numbers
      */
     Notebook.prototype.cell_toggle_line_numbers = function() {
         this.get_selected_cell().toggle_line_numbers();
     };
     
     /**
      * Set the codemirror mode for all code cells, including the default for
      * new code cells.
      * 
      * @method set_codemirror_mode
      */
     Notebook.prototype.set_codemirror_mode = function(newmode){
         if (newmode === this.codemirror_mode) {
             return;
         }
         this.codemirror_mode = newmode;
         codecell.CodeCell.options_default.cm_config.mode = newmode;
         modename = newmode.name || newmode
 
         that = this;
         CodeMirror.requireMode(modename, function(){
             $.map(that.get_cells(), function(cell, i) {
                 if (cell.cell_type === 'code'){
                     cell.code_mirror.setOption('mode', newmode);
                     // This is currently redundant, because cm_config ends up as
                     // codemirror's own .options object, but I don't want to
                     // rely on that.
                     cell.cm_config.mode = newmode;
                 }
             });
         })
     };
 
     // Session related things
 
     /**
      * Start a new session and set it on each code cell.
      * 
      * @method start_session
      */
     Notebook.prototype.start_session = function (kernel_name) {
         var that = this;
         if (this._session_starting) {
             throw new session.SessionAlreadyStarting();
         }
         this._session_starting = true;
         
         if (this.session !== null) {
             var s = this.session;
             this.session = null;
             // need to start the new session in a callback after delete,
             // because javascript does not guarantee the ordering of AJAX requests (?!)
             s.delete(function () {
                     // on successful delete, start new session
                     that._session_starting = false;
                     that.start_session(kernel_name);
                 }, function (jqXHR, status, error) {
                     // log the failed delete, but still create a new session
                     // 404 just means it was already deleted by someone else,
                     // but other errors are possible.
                     utils.log_ajax_error(jqXHR, status, error);
                     that._session_starting = false;
                     that.start_session(kernel_name);
                 }
             );
             return;
         }
         
         
     
         this.session = new session.Session({
             base_url: this.base_url,
             ws_url: this.ws_url,
             notebook_path: this.notebook_path,
             notebook_name: this.notebook_name,
             // For now, create all sessions with the 'python' kernel, which is the
             // default. Later, the user will be able to select kernels. This is
             // overridden if KernelManager.kernel_cmd is specified for the server.
             kernel_name: kernel_name,
             notebook: this});
 
         this.session.start(
             $.proxy(this._session_started, this),
             $.proxy(this._session_start_failed, this)
         );
     };
 
 
     /**
      * Once a session is started, link the code cells to the kernel and pass the 
      * comm manager to the widget manager
      *
      */
     Notebook.prototype._session_started = function (){
         this._session_starting = false;
         this.kernel = this.session.kernel;
         var ncells = this.ncells();
         for (var i=0; i<ncells; i++) {
             var cell = this.get_cell(i);
             if (cell instanceof codecell.CodeCell) {
                 cell.set_kernel(this.session.kernel);
             }
         }
     };
     Notebook.prototype._session_start_failed = function (jqxhr, status, error){
         this._session_starting = false;
         utils.log_ajax_error(jqxhr, status, error);
     };
     
     /**
      * Prompt the user to restart the IPython kernel.
      * 
      * @method restart_kernel
      */
     Notebook.prototype.restart_kernel = function () {
         var that = this;
         dialog.modal({
             notebook: this,
             keyboard_manager: this.keyboard_manager,
             title : "Restart kernel or continue running?",
             body : $("<p/>").text(
                 'Do you want to restart the current kernel?  You will lose all variables defined in it.'
             ),
             buttons : {
                 "Continue running" : {},
                 "Restart" : {
                     "class" : "btn-danger",
                     "click" : function() {
                         that.session.restart_kernel();
                     }
                 }
             }
         });
     };
     
     /**
      * Execute or render cell outputs and go into command mode.
      * 
      * @method execute_cell
      */
     Notebook.prototype.execute_cell = function () {
         // mode = shift, ctrl, alt
         var cell = this.get_selected_cell();
         var cell_index = this.find_cell_index(cell);
         
         cell.execute();
         this.command_mode();
         this.set_dirty(true);
     };
 
     /**
      * Execute or render cell outputs and insert a new cell below.
      * 
      * @method execute_cell_and_insert_below
      */
     Notebook.prototype.execute_cell_and_insert_below = function () {
         var cell = this.get_selected_cell();
         var cell_index = this.find_cell_index(cell);
         
         cell.execute();
 
         // If we are at the end always insert a new cell and return
         if (cell_index === (this.ncells()-1)) {
             this.command_mode();
             this.insert_cell_below();
             this.select(cell_index+1);
             this.edit_mode();
             this.scroll_to_bottom();
             this.set_dirty(true);
             return;
         }
 
         this.command_mode();
         this.insert_cell_below();
         this.select(cell_index+1);
         this.edit_mode();
         this.set_dirty(true);
     };
 
     /**
      * Execute or render cell outputs and select the next cell.
      * 
      * @method execute_cell_and_select_below
      */
     Notebook.prototype.execute_cell_and_select_below = function () {
 
         var cell = this.get_selected_cell();
         var cell_index = this.find_cell_index(cell);
         
         cell.execute();
 
         // If we are at the end always insert a new cell and return
         if (cell_index === (this.ncells()-1)) {
             this.command_mode();
             this.insert_cell_below();
             this.select(cell_index+1);
             this.edit_mode();
             this.scroll_to_bottom();
             this.set_dirty(true);
             return;
         }
 
         this.command_mode();
         this.select(cell_index+1);
         this.focus_cell();
         this.set_dirty(true);
     };
 
     /**
      * Execute all cells below the selected cell.
      * 
      * @method execute_cells_below
      */
     Notebook.prototype.execute_cells_below = function () {
         this.execute_cell_range(this.get_selected_index(), this.ncells());
         this.scroll_to_bottom();
     };
 
     /**
      * Execute all cells above the selected cell.
      * 
      * @method execute_cells_above
      */
     Notebook.prototype.execute_cells_above = function () {
         this.execute_cell_range(0, this.get_selected_index());
     };
 
     /**
      * Execute all cells.
      * 
      * @method execute_all_cells
      */
     Notebook.prototype.execute_all_cells = function () {
         this.execute_cell_range(0, this.ncells());
         this.scroll_to_bottom();
     };
 
     /**
      * Execute a contiguous range of cells.
      * 
      * @method execute_cell_range
      * @param {Number} start Index of the first cell to execute (inclusive)
      * @param {Number} end Index of the last cell to execute (exclusive)
      */
     Notebook.prototype.execute_cell_range = function (start, end) {
         this.command_mode();
         for (var i=start; i<end; i++) {
             this.select(i);
             this.execute_cell();
         }
     };
 
     // Persistance and loading
 
     /**
      * Getter method for this notebook's name.
      * 
      * @method get_notebook_name
      * @return {String} This notebook's name (excluding file extension)
      */
     Notebook.prototype.get_notebook_name = function () {
         var nbname = this.notebook_name.substring(0,this.notebook_name.length-6);
         return nbname;
     };
 
     /**
      * Setter method for this notebook's name.
      *
      * @method set_notebook_name
      * @param {String} name A new name for this notebook
      */
     Notebook.prototype.set_notebook_name = function (name) {
         this.notebook_name = name;
     };
 
     /**
      * Check that a notebook's name is valid.
      * 
      * @method test_notebook_name
      * @param {String} nbname A name for this notebook
      * @return {Boolean} True if the name is valid, false if invalid
      */
     Notebook.prototype.test_notebook_name = function (nbname) {
         nbname = nbname || '';
         if (nbname.length>0 && !this.notebook_name_blacklist_re.test(nbname)) {
             return true;
         } else {
             return false;
         }
     };
 
     /**
      * Load a notebook from JSON (.ipynb).
      * 
      * This currently handles one worksheet: others are deleted.
      * 
      * @method fromJSON
      * @param {Object} data JSON representation of a notebook
      */
     Notebook.prototype.fromJSON = function (data) {
+
         var content = data.content;
         var ncells = this.ncells();
         var i;
         for (i=0; i<ncells; i++) {
             // Always delete cell 0 as they get renumbered as they are deleted.
             this.delete_cell(0);
         }
         // Save the metadata and name.
         this.metadata = content.metadata;
         this.notebook_name = data.name;
         var trusted = true;
         
         // Trigger an event changing the kernel spec - this will set the default
         // codemirror mode
         if (this.metadata.kernelspec !== undefined) {
             this.events.trigger('spec_changed.Kernel', this.metadata.kernelspec);
         }
         
         // Only handle 1 worksheet for now.
         var worksheet = content.worksheets[0];
         if (worksheet !== undefined) {
             if (worksheet.metadata) {
                 this.worksheet_metadata = worksheet.metadata;
             }
             var new_cells = worksheet.cells;
             ncells = new_cells.length;
             var cell_data = null;
             var new_cell = null;
             for (i=0; i<ncells; i++) {
                 cell_data = new_cells[i];
                 // VERSIONHACK: plaintext -> raw
                 // handle never-released plaintext name for raw cells
                 if (cell_data.cell_type === 'plaintext'){
                     cell_data.cell_type = 'raw';
                 }
 
                 new_cell = this.insert_cell_at_index(cell_data.cell_type, i);
                 new_cell.fromJSON(cell_data);
                 if (new_cell.cell_type == 'code' && !new_cell.output_area.trusted) {
                     trusted = false;
                 }
             }
         }
         if (trusted !== this.trusted) {
             this.trusted = trusted;
             this.events.trigger("trust_changed.Notebook", {value: trusted});
         }
         if (content.worksheets.length > 1) {
             dialog.modal({
                 notebook: this,
                 keyboard_manager: this.keyboard_manager,
                 title : "Multiple worksheets",
                 body : "This notebook has " + data.worksheets.length + " worksheets, " +
                     "but this version of IPython can only handle the first.  " +
                     "If you save this notebook, worksheets after the first will be lost.",
                 buttons : {
                     OK : {
                         class : "btn-danger"
                     }
                 }
             });
         }
     };
 
     /**
      * Dump this notebook into a JSON-friendly object.
      * 
      * @method toJSON
      * @return {Object} A JSON-friendly representation of this notebook.
      */
     Notebook.prototype.toJSON = function () {
         var cells = this.get_cells();
         var ncells = cells.length;
         var cell_array = new Array(ncells);
         var trusted = true;
         for (var i=0; i<ncells; i++) {
             var cell = cells[i];
             if (cell.cell_type == 'code' && !cell.output_area.trusted) {
                 trusted = false;
             }
             cell_array[i] = cell.toJSON();
         }
         var data = {
             // Only handle 1 worksheet for now.
             worksheets : [{
                 cells: cell_array,
                 metadata: this.worksheet_metadata
             }],
             metadata : this.metadata
         };
         if (trusted != this.trusted) {
             this.trusted = trusted;
             this.events.trigger("trust_changed.Notebook", trusted);
         }
         return data;
     };
 
     /**
      * Start an autosave timer, for periodically saving the notebook.
      * 
      * @method set_autosave_interval
      * @param {Integer} interval the autosave interval in milliseconds
      */
     Notebook.prototype.set_autosave_interval = function (interval) {
         var that = this;
         // clear previous interval, so we don't get simultaneous timers
         if (this.autosave_timer) {
             clearInterval(this.autosave_timer);
         }
         
         this.autosave_interval = this.minimum_autosave_interval = interval;
         if (interval) {
             this.autosave_timer = setInterval(function() {
                 if (that.dirty) {
                     that.save_notebook();
                 }
             }, interval);
             this.events.trigger("autosave_enabled.Notebook", interval);
         } else {
             this.autosave_timer = null;
             this.events.trigger("autosave_disabled.Notebook");
         }
     };
     
     /**
      * Save this notebook on the server. This becomes a notebook instance's
      * .save_notebook method *after* the entire notebook has been loaded.
      * 
      * @method save_notebook
      */
     Notebook.prototype.save_notebook = function (extra_settings) {
         // Create a JSON model to be sent to the server.
         var model = {};
         model.name = this.notebook_name;
         model.path = this.notebook_path;
         model.type = 'notebook';
         model.format = 'json';
         model.content = this.toJSON();
         model.content.nbformat = this.nbformat;
         model.content.nbformat_minor = this.nbformat_minor;
         // time the ajax call for autosave tuning purposes.
         var start =  new Date().getTime();
         // We do the call with settings so we can set cache to false.
         var settings = {
             processData : false,
             cache : false,
             type : "PUT",
             data : JSON.stringify(model),
             headers : {'Content-Type': 'application/json'},
+            dataType : "json",
             success : $.proxy(this.save_notebook_success, this, start),
             error : $.proxy(this.save_notebook_error, this)
         };
         if (extra_settings) {
             for (var key in extra_settings) {
                 settings[key] = extra_settings[key];
             }
         }
         this.events.trigger('notebook_saving.Notebook');
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name
         );
         $.ajax(url, settings);
     };
     
     /**
      * Success callback for saving a notebook.
      * 
      * @method save_notebook_success
      * @param {Integer} start the time when the save request started
      * @param {Object} data JSON representation of a notebook
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.save_notebook_success = function (start, data, status, xhr) {
         this.set_dirty(false);
+        if (data.message) {
+            // save succeeded, but validation failed.
+            var body = $("<div>");
+            var title = "Notebook validation failed";
+
+            body.append($("<p>").text(
+                "The save operation succeeded," +
+                " but the notebook does not appear to be valid." +
+                " The validation error was:"
+            )).append($("<div>").addClass("validation-error").append(
+                $("<pre>").text(data.message)
+            ));
+            dialog.modal({
+                notebook: this,
+                keyboard_manager: this.keyboard_manager,
+                title: title,
+                body: body,
+                buttons : {
+                    OK : {
+                        "class" : "btn-primary"
+                    }
+                }
+            });
+        }
         this.events.trigger('notebook_saved.Notebook');
         this._update_autosave_interval(start);
         if (this._checkpoint_after_save) {
             this.create_checkpoint();
             this._checkpoint_after_save = false;
         }
     };
     
     /**
      * update the autosave interval based on how long the last save took
      * 
      * @method _update_autosave_interval
      * @param {Integer} timestamp when the save request started
      */
     Notebook.prototype._update_autosave_interval = function (start) {
         var duration = (new Date().getTime() - start);
         if (this.autosave_interval) {
             // new save interval: higher of 10x save duration or parameter (default 30 seconds)
             var interval = Math.max(10 * duration, this.minimum_autosave_interval);
             // round to 10 seconds, otherwise we will be setting a new interval too often
             interval = 10000 * Math.round(interval / 10000);
             // set new interval, if it's changed
             if (interval != this.autosave_interval) {
                 this.set_autosave_interval(interval);
             }
         }
     };
     
     /**
      * Failure callback for saving a notebook.
      * 
      * @method save_notebook_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error HTTP error message
      */
     Notebook.prototype.save_notebook_error = function (xhr, status, error) {
         this.events.trigger('notebook_save_failed.Notebook', [xhr, status, error]);
     };
 
     /**
      * Explicitly trust the output of this notebook.
      *
      * @method trust_notebook
      */
     Notebook.prototype.trust_notebook = function (extra_settings) {
         var body = $("<div>").append($("<p>")
             .text("A trusted IPython notebook may execute hidden malicious code ")
             .append($("<strong>")
                 .append(
                     $("<em>").text("when you open it")
                 )
             ).append(".").append(
                 " Selecting trust will immediately reload this notebook in a trusted state."
             ).append(
                 " For more information, see the "
             ).append($("<a>").attr("href", "http://ipython.org/ipython-doc/2/notebook/security.html")
                 .text("IPython security documentation")
             ).append(".")
         );
 
         var nb = this;
         dialog.modal({
             notebook: this,
             keyboard_manager: this.keyboard_manager,
             title: "Trust this notebook?",
             body: body,
 
             buttons: {
                 Cancel : {},
                 Trust : {
                     class : "btn-danger",
                     click : function () {
                         var cells = nb.get_cells();
                         for (var i = 0; i < cells.length; i++) {
                             var cell = cells[i];
                             if (cell.cell_type == 'code') {
                                 cell.output_area.trusted = true;
                             }
                         }
                         nb.events.on('notebook_saved.Notebook', function () {
                             window.location.reload();
                         });
                         nb.save_notebook();
                     }
                 }
             }
         });
     };
 
     Notebook.prototype.new_notebook = function(){
         var path = this.notebook_path;
         var base_url = this.base_url;
         var settings = {
             processData : false,
             cache : false,
             type : "POST",
             dataType : "json",
             async : false,
             success : function (data, status, xhr){
                 var notebook_name = data.name;
                 window.open(
                     utils.url_join_encode(
                         base_url,
                         'notebooks',
                         path,
                         notebook_name
                     ),
                     '_blank'
                 );
             },
             error : utils.log_ajax_error,
         };
         var url = utils.url_join_encode(
             base_url,
             'api/contents',
             path
         );
         $.ajax(url,settings);
     };
 
 
     Notebook.prototype.copy_notebook = function(){
         var path = this.notebook_path;
         var base_url = this.base_url;
         var settings = {
             processData : false,
             cache : false,
             type : "POST",
             dataType : "json",
             data : JSON.stringify({copy_from : this.notebook_name}),
             async : false,
             success : function (data, status, xhr) {
                 window.open(utils.url_join_encode(
                     base_url,
                     'notebooks',
                     data.path,
                     data.name
                 ), '_blank');
             },
             error : utils.log_ajax_error,
         };
         var url = utils.url_join_encode(
             base_url,
             'api/contents',
             path
         );
         $.ajax(url,settings);
     };
 
     Notebook.prototype.rename = function (nbname) {
         var that = this;
         if (!nbname.match(/\.ipynb$/)) {
             nbname = nbname + ".ipynb";
         }
         var data = {name: nbname};
         var settings = {
             processData : false,
             cache : false,
             type : "PATCH",
             data : JSON.stringify(data),
             dataType: "json",
             headers : {'Content-Type': 'application/json'},
             success : $.proxy(that.rename_success, this),
             error : $.proxy(that.rename_error, this)
         };
         this.events.trigger('rename_notebook.Notebook', data);
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name
         );
         $.ajax(url, settings);
     };
 
     Notebook.prototype.delete = function () {
         var that = this;
         var settings = {
             processData : false,
             cache : false,
             type : "DELETE",
             dataType: "json",
             error : utils.log_ajax_error,
         };
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name
         );
         $.ajax(url, settings);
     };
 
     
     Notebook.prototype.rename_success = function (json, status, xhr) {
         var name = this.notebook_name = json.name;
         var path = json.path;
         this.session.rename_notebook(name, path);
         this.events.trigger('notebook_renamed.Notebook', json);
     };
 
     Notebook.prototype.rename_error = function (xhr, status, error) {
         var that = this;
         var dialog_body = $('<div/>').append(
             $("<p/>").text('This notebook name already exists.')
         );
         this.events.trigger('notebook_rename_failed.Notebook', [xhr, status, error]);
         dialog.modal({
             notebook: this,
             keyboard_manager: this.keyboard_manager,
             title: "Notebook Rename Error!",
             body: dialog_body,
             buttons : {
                 "Cancel": {},
                 "OK": {
                     class: "btn-primary",
                     click: function () {
                         this.save_widget.rename_notebook({notebook:that});
                 }}
                 },
             open : function (event, ui) {
                 var that = $(this);
                 // Upon ENTER, click the OK button.
                 that.find('input[type="text"]').keydown(function (event, ui) {
                     if (event.which === this.keyboard.keycodes.enter) {
                         that.find('.btn-primary').first().click();
                     }
                 });
                 that.find('input[type="text"]').focus();
             }
         });
     };
 
     /**
      * Request a notebook's data from the server.
      * 
      * @method load_notebook
      * @param {String} notebook_name and path A notebook to load
      */
     Notebook.prototype.load_notebook = function (notebook_name, notebook_path) {
         var that = this;
         this.notebook_name = notebook_name;
         this.notebook_path = notebook_path;
         // We do the call with settings so we can set cache to false.
         var settings = {
             processData : false,
             cache : false,
             type : "GET",
             dataType : "json",
             success : $.proxy(this.load_notebook_success,this),
             error : $.proxy(this.load_notebook_error,this),
         };
         this.events.trigger('notebook_loading.Notebook');
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name
         );
         $.ajax(url, settings);
     };
 
     /**
      * Success callback for loading a notebook from the server.
      * 
      * Load notebook data from the JSON response.
      * 
      * @method load_notebook_success
      * @param {Object} data JSON representation of a notebook
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.load_notebook_success = function (data, status, xhr) {
-        this.fromJSON(data);
+        var failed;
+        try {
+            this.fromJSON(data);
+        } catch (e) {
+            failed = e;
+            console.log("Notebook failed to load from JSON:", e);
+        }
+        if (failed || data.message) {
+            // *either* fromJSON failed or validation failed
+            var body = $("<div>");
+            var title;
+            if (failed) {
+                title = "Notebook failed to load";
+                body.append($("<p>").text(
+                    "The error was: "
+                )).append($("<div>").addClass("js-error").text(
+                    failed.toString()
+                )).append($("<p>").text(
+                    "See the error console for details."
+                ));
+            } else {
+                title = "Notebook validation failed";
+            }
+
+            if (data.message) {
+                var msg;
+                if (failed) {
+                    msg = "The notebook also failed validation:"
+                } else {
+                    msg = "An invalid notebook may not function properly." +
+                    " The validation error was:"
+                }
+                body.append($("<p>").text(
+                    msg
+                )).append($("<div>").addClass("validation-error").append(
+                    $("<pre>").text(data.message)
+                ));
+            }
+
+            dialog.modal({
+                notebook: this,
+                keyboard_manager: this.keyboard_manager,
+                title: title,
+                body: body,
+                buttons : {
+                    OK : {
+                        "class" : "btn-primary"
+                    }
+                }
+            });
+        }
         if (this.ncells() === 0) {
             this.insert_cell_below('code');
             this.edit_mode(0);
         } else {
             this.select(0);
             this.handle_command_mode(this.get_cell(0));
         }
         this.set_dirty(false);
         this.scroll_to_top();
         if (data.orig_nbformat !== undefined && data.nbformat !== data.orig_nbformat) {
             var msg = "This notebook has been converted from an older " +
             "notebook format (v"+data.orig_nbformat+") to the current notebook " +
             "format (v"+data.nbformat+"). The next time you save this notebook, the " +
             "newer notebook format will be used and older versions of IPython " +
             "may not be able to read it. To keep the older version, close the " +
             "notebook without saving it.";
             dialog.modal({
                 notebook: this,
                 keyboard_manager: this.keyboard_manager,
                 title : "Notebook converted",
                 body : msg,
                 buttons : {
                     OK : {
                         class : "btn-primary"
                     }
                 }
             });
         } else if (data.orig_nbformat_minor !== undefined && data.nbformat_minor !== data.orig_nbformat_minor) {
             var that = this;
             var orig_vs = 'v' + data.nbformat + '.' + data.orig_nbformat_minor;
             var this_vs = 'v' + data.nbformat + '.' + this.nbformat_minor;
             var msg = "This notebook is version " + orig_vs + ", but we only fully support up to " +
             this_vs + ".  You can still work with this notebook, but some features " +
             "introduced in later notebook versions may not be available.";
 
             dialog.modal({
                 notebook: this,
                 keyboard_manager: this.keyboard_manager,
                 title : "Newer Notebook",
                 body : msg,
                 buttons : {
                     OK : {
                         class : "btn-danger"
                     }
                 }
             });
 
         }
         
         // Create the session after the notebook is completely loaded to prevent
         // code execution upon loading, which is a security risk.
         if (this.session === null) {
             var kernelspec = this.metadata.kernelspec || {};
             var kernel_name = kernelspec.name;
 
             this.start_session(kernel_name);
         }
         // load our checkpoint list
         this.list_checkpoints();
         
         // load toolbar state
         if (this.metadata.celltoolbar) {
             celltoolbar.CellToolbar.global_show();
             celltoolbar.CellToolbar.activate_preset(this.metadata.celltoolbar);
         } else {
             celltoolbar.CellToolbar.global_hide();
         }
 
         // now that we're fully loaded, it is safe to restore save functionality
         delete(this.save_notebook);
         this.events.trigger('notebook_loaded.Notebook');
     };
 
     /**
      * Failure callback for loading a notebook from the server.
      * 
      * @method load_notebook_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error HTTP error message
      */
     Notebook.prototype.load_notebook_error = function (xhr, status, error) {
         this.events.trigger('notebook_load_failed.Notebook', [xhr, status, error]);
         utils.log_ajax_error(xhr, status, error);
         var msg;
         if (xhr.status === 400) {
             msg = escape(utils.ajax_error_msg(xhr));
         } else if (xhr.status === 500) {
             msg = "An unknown error occurred while loading this notebook. " +
             "This version can load notebook formats " +
             "v" + this.nbformat + " or earlier. See the server log for details.";
         }
         dialog.modal({
             notebook: this,
             keyboard_manager: this.keyboard_manager,
             title: "Error loading notebook",
             body : msg,
             buttons : {
                 "OK": {}
             }
         });
     };
 
     /*********************  checkpoint-related  *********************/
     
     /**
      * Save the notebook then immediately create a checkpoint.
      * 
      * @method save_checkpoint
      */
     Notebook.prototype.save_checkpoint = function () {
         this._checkpoint_after_save = true;
         this.save_notebook();
     };
     
     /**
      * Add a checkpoint for this notebook.
      * for use as a callback from checkpoint creation.
      * 
      * @method add_checkpoint
      */
     Notebook.prototype.add_checkpoint = function (checkpoint) {
         var found = false;
         for (var i = 0; i < this.checkpoints.length; i++) {
             var existing = this.checkpoints[i];
             if (existing.id == checkpoint.id) {
                 found = true;
                 this.checkpoints[i] = checkpoint;
                 break;
             }
         }
         if (!found) {
             this.checkpoints.push(checkpoint);
         }
         this.last_checkpoint = this.checkpoints[this.checkpoints.length - 1];
     };
     
     /**
      * List checkpoints for this notebook.
      * 
      * @method list_checkpoints
      */
     Notebook.prototype.list_checkpoints = function () {
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name,
             'checkpoints'
         );
         $.get(url).done(
             $.proxy(this.list_checkpoints_success, this)
         ).fail(
             $.proxy(this.list_checkpoints_error, this)
         );
     };
 
     /**
      * Success callback for listing checkpoints.
      * 
      * @method list_checkpoint_success
      * @param {Object} data JSON representation of a checkpoint
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.list_checkpoints_success = function (data, status, xhr) {
         data = $.parseJSON(data);
         this.checkpoints = data;
         if (data.length) {
             this.last_checkpoint = data[data.length - 1];
         } else {
             this.last_checkpoint = null;
         }
         this.events.trigger('checkpoints_listed.Notebook', [data]);
     };
 
     /**
      * Failure callback for listing a checkpoint.
      * 
      * @method list_checkpoint_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error_msg HTTP error message
      */
     Notebook.prototype.list_checkpoints_error = function (xhr, status, error_msg) {
         this.events.trigger('list_checkpoints_failed.Notebook');
     };
     
     /**
      * Create a checkpoint of this notebook on the server from the most recent save.
      * 
      * @method create_checkpoint
      */
     Notebook.prototype.create_checkpoint = function () {
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name,
             'checkpoints'
         );
         $.post(url).done(
             $.proxy(this.create_checkpoint_success, this)
         ).fail(
             $.proxy(this.create_checkpoint_error, this)
         );
     };
 
     /**
      * Success callback for creating a checkpoint.
      * 
      * @method create_checkpoint_success
      * @param {Object} data JSON representation of a checkpoint
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.create_checkpoint_success = function (data, status, xhr) {
         data = $.parseJSON(data);
         this.add_checkpoint(data);
         this.events.trigger('checkpoint_created.Notebook', data);
     };
 
     /**
      * Failure callback for creating a checkpoint.
      * 
      * @method create_checkpoint_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error_msg HTTP error message
      */
     Notebook.prototype.create_checkpoint_error = function (xhr, status, error_msg) {
         this.events.trigger('checkpoint_failed.Notebook');
     };
     
     Notebook.prototype.restore_checkpoint_dialog = function (checkpoint) {
         var that = this;
         checkpoint = checkpoint || this.last_checkpoint;
         if ( ! checkpoint ) {
             console.log("restore dialog, but no checkpoint to restore to!");
             return;
         }
         var body = $('<div/>').append(
             $('<p/>').addClass("p-space").text(
                 "Are you sure you want to revert the notebook to " +
                 "the latest checkpoint?"
             ).append(
                 $("<strong/>").text(
                     " This cannot be undone."
                 )
             )
         ).append(
             $('<p/>').addClass("p-space").text("The checkpoint was last updated at:")
         ).append(
             $('<p/>').addClass("p-space").text(
                 Date(checkpoint.last_modified)
             ).css("text-align", "center")
         );
         
         dialog.modal({
             notebook: this,
             keyboard_manager: this.keyboard_manager,
             title : "Revert notebook to checkpoint",
             body : body,
             buttons : {
                 Revert : {
                     class : "btn-danger",
                     click : function () {
                         that.restore_checkpoint(checkpoint.id);
                     }
                 },
                 Cancel : {}
                 }
         });
     };
     
     /**
      * Restore the notebook to a checkpoint state.
      * 
      * @method restore_checkpoint
      * @param {String} checkpoint ID
      */
     Notebook.prototype.restore_checkpoint = function (checkpoint) {
         this.events.trigger('notebook_restoring.Notebook', checkpoint);
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name,
             'checkpoints',
             checkpoint
         );
         $.post(url).done(
             $.proxy(this.restore_checkpoint_success, this)
         ).fail(
             $.proxy(this.restore_checkpoint_error, this)
         );
     };
     
     /**
      * Success callback for restoring a notebook to a checkpoint.
      * 
      * @method restore_checkpoint_success
      * @param {Object} data (ignored, should be empty)
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.restore_checkpoint_success = function (data, status, xhr) {
         this.events.trigger('checkpoint_restored.Notebook');
         this.load_notebook(this.notebook_name, this.notebook_path);
     };
 
     /**
      * Failure callback for restoring a notebook to a checkpoint.
      * 
      * @method restore_checkpoint_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error_msg HTTP error message
      */
     Notebook.prototype.restore_checkpoint_error = function (xhr, status, error_msg) {
         this.events.trigger('checkpoint_restore_failed.Notebook');
     };
     
     /**
      * Delete a notebook checkpoint.
      * 
      * @method delete_checkpoint
      * @param {String} checkpoint ID
      */
     Notebook.prototype.delete_checkpoint = function (checkpoint) {
         this.events.trigger('notebook_restoring.Notebook', checkpoint);
         var url = utils.url_join_encode(
             this.base_url,
             'api/contents',
             this.notebook_path,
             this.notebook_name,
             'checkpoints',
             checkpoint
         );
         $.ajax(url, {
             type: 'DELETE',
             success: $.proxy(this.delete_checkpoint_success, this),
             error: $.proxy(this.delete_checkpoint_error, this)
         });
     };
     
     /**
      * Success callback for deleting a notebook checkpoint
      * 
      * @method delete_checkpoint_success
      * @param {Object} data (ignored, should be empty)
      * @param {String} status Description of response status
      * @param {jqXHR} xhr jQuery Ajax object
      */
     Notebook.prototype.delete_checkpoint_success = function (data, status, xhr) {
         this.events.trigger('checkpoint_deleted.Notebook', data);
         this.load_notebook(this.notebook_name, this.notebook_path);
     };
 
     /**
      * Failure callback for deleting a notebook checkpoint.
      * 
      * @method delete_checkpoint_error
      * @param {jqXHR} xhr jQuery Ajax object
      * @param {String} status Description of response status
      * @param {String} error HTTP error message
      */
     Notebook.prototype.delete_checkpoint_error = function (xhr, status, error) {
         this.events.trigger('checkpoint_delete_failed.Notebook', [xhr, status, error]);
     };
 
 
     // For backwards compatability.
     IPython.Notebook = Notebook;
 
     return {'Notebook': Notebook};
 });