IPython/core/history.py

""" History related magics and functionality """
#-----------------------------------------------------------------------------
#  Copyright (C) 2010 The IPython Development Team.
#
#  Distributed under the terms of the BSD License.
#
#  The full license is in the file COPYING.txt, distributed with this software.
#-----------------------------------------------------------------------------

#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------
from __future__ import print_function

# Stdlib imports
import atexit
import datetime
import os
import re
import sqlite3
import threading

# Our own packages
from IPython.config.configurable import Configurable

from IPython.testing.skipdoctest import skip_doctest
from IPython.utils import io
from IPython.utils.path import locate_profile
from IPython.utils.traitlets import Bool, Dict, Instance, Int, CInt, List, Unicode
from IPython.utils.warn import warn

#-----------------------------------------------------------------------------
# Classes and functions
#-----------------------------------------------------------------------------

class HistoryAccessor(Configurable):
    """Access the history database without adding to it.
    
    This is intended for use by standalone history tools. IPython shells use
    HistoryManager, below, which is a subclass of this."""
    # String holding the path to the history file
    hist_file = Unicode(config=True)

    # The SQLite database
    db = Instance(sqlite3.Connection)
    
    def __init__(self, profile='default', hist_file=u'', shell=None, config=None, **traits):
        """Create a new history accessor.
        
        Parameters
        ----------
        profile : str
          The name of the profile from which to open history.
        hist_file : str
          Path to an SQLite history database stored by IPython. If specified,
          hist_file overrides profile.
        shell :
          InteractiveShell object, for use by HistoryManager subclass
        config :
          Config object. hist_file can also be set through this.
        """
        # We need a pointer back to the shell for various tasks.
        super(HistoryAccessor, self).__init__(shell=shell, config=config,
                                              hist_file=hist_file, **traits)

        if self.hist_file == u'':
            # No one has set the hist_file, yet.
            self.hist_file = self._get_hist_file_name(profile)

        try:
            self.init_db()
        except sqlite3.DatabaseError:
            if os.path.isfile(self.hist_file):
                # Try to move the file out of the way.
                newpath = os.path.join(self.shell.profile_dir.location, "hist-corrupt.sqlite")
                os.rename(self.hist_file, newpath)
                print("ERROR! History file wasn't a valid SQLite database.",
                "It was moved to %s" % newpath, "and a new file created.")
                self.init_db()
            else:
                # The hist_file is probably :memory: or something else.
                raise
    
    def _get_hist_file_name(self, profile='default'):
        """Find the history file for the given profile name.
        
        This is overridden by the HistoryManager subclass, to use the shell's
        active profile.
        
        Parameters
        ----------
        profile : str
          The name of a profile which has a history file.
        """
        return os.path.join(locate_profile(profile), 'history.sqlite')
    
    def init_db(self):
        """Connect to the database, and create tables if necessary."""
        # use detect_types so that timestamps return datetime objects
        self.db = sqlite3.connect(self.hist_file, detect_types=sqlite3.PARSE_DECLTYPES|sqlite3.PARSE_COLNAMES)
        self.db.execute("""CREATE TABLE IF NOT EXISTS sessions (session integer
                        primary key autoincrement, start timestamp,
                        end timestamp, num_cmds integer, remark text)""")
        self.db.execute("""CREATE TABLE IF NOT EXISTS history
                (session integer, line integer, source text, source_raw text,
                PRIMARY KEY (session, line))""")
        # Output history is optional, but ensure the table's there so it can be
        # enabled later.
        self.db.execute("""CREATE TABLE IF NOT EXISTS output_history
                        (session integer, line integer, output text,
                        PRIMARY KEY (session, line))""")
        self.db.commit()

    def writeout_cache(self):
        """Overridden by HistoryManager to dump the cache before certain
        database lookups."""
        pass

    ## -------------------------------
    ## Methods for retrieving history:
    ## -------------------------------
    def _run_sql(self, sql, params, raw=True, output=False):
        """Prepares and runs an SQL query for the history database.

        Parameters
        ----------
        sql : str
          Any filtering expressions to go after SELECT ... FROM ...
        params : tuple
          Parameters passed to the SQL query (to replace "?")
        raw, output : bool
          See :meth:`get_range`

        Returns
        -------
        Tuples as :meth:`get_range`
        """
        toget = 'source_raw' if raw else 'source'
        sqlfrom = "history"
        if output:
            sqlfrom = "history LEFT JOIN output_history USING (session, line)"
            toget = "history.%s, output_history.output" % toget
        cur = self.db.execute("SELECT session, line, %s FROM %s " %\
                                (toget, sqlfrom) + sql, params)
        if output:    # Regroup into 3-tuples, and parse JSON
            return ((ses, lin, (inp, out)) for ses, lin, inp, out in cur)
        return cur

    def get_session_info(self, session=0):
        """get info about a session

        Parameters
        ----------

        session : int
            Session number to retrieve. The current session is 0, and negative
            numbers count back from current session, so -1 is previous session.

        Returns
        -------

        (session_id [int], start [datetime], end [datetime], num_cmds [int], remark [unicode])

        Sessions that are running or did not exit cleanly will have `end=None`
        and `num_cmds=None`.

        """

        if session <= 0:
            session += self.session_number

        query = "SELECT * from sessions where session == ?"
        return self.db.execute(query, (session,)).fetchone()

    def get_tail(self, n=10, raw=True, output=False, include_latest=False):
        """Get the last n lines from the history database.

        Parameters
        ----------
        n : int
          The number of lines to get
        raw, output : bool
          See :meth:`get_range`
        include_latest : bool
          If False (default), n+1 lines are fetched, and the latest one
          is discarded. This is intended to be used where the function
          is called by a user command, which it should not return.

        Returns
        -------
        Tuples as :meth:`get_range`
        """
        self.writeout_cache()
        if not include_latest:
            n += 1
        cur = self._run_sql("ORDER BY session DESC, line DESC LIMIT ?",
                                (n,), raw=raw, output=output)
        if not include_latest:
            return reversed(list(cur)[1:])
        return reversed(list(cur))

    def search(self, pattern="*", raw=True, search_raw=True,
                                                        output=False):
        """Search the database using unix glob-style matching (wildcards
        * and ?).

        Parameters
        ----------
        pattern : str
          The wildcarded pattern to match when searching
        search_raw : bool
          If True, search the raw input, otherwise, the parsed input
        raw, output : bool
          See :meth:`get_range`

        Returns
        -------
        Tuples as :meth:`get_range`
        """
        tosearch = "source_raw" if search_raw else "source"
        if output:
            tosearch = "history." + tosearch
        self.writeout_cache()
        return self._run_sql("WHERE %s GLOB ?" % tosearch, (pattern,),
                                    raw=raw, output=output)
    
    def get_range(self, session, start=1, stop=None, raw=True,output=False):
        """Retrieve input by session.

        Parameters
        ----------
        session : int
            Session number to retrieve.
        start : int
            First line to retrieve.
        stop : int
            End of line range (excluded from output itself). If None, retrieve
            to the end of the session.
        raw : bool
            If True, return untranslated input
        output : bool
            If True, attempt to include output. This will be 'real' Python
            objects for the current session, or text reprs from previous
            sessions if db_log_output was enabled at the time. Where no output
            is found, None is used.

        Returns
        -------
        An iterator over the desired lines. Each line is a 3-tuple, either
        (session, line, input) if output is False, or
        (session, line, (input, output)) if output is True.
        """
        if stop:
            lineclause = "line >= ? AND line < ?"
            params = (session, start, stop)
        else:
            lineclause = "line>=?"
            params = (session, start)

        return self._run_sql("WHERE session==? AND %s""" % lineclause,
                                    params, raw=raw, output=output)

    def get_range_by_str(self, rangestr, raw=True, output=False):
        """Get lines of history from a string of ranges, as used by magic
        commands %hist, %save, %macro, etc.

        Parameters
        ----------
        rangestr : str
          A string specifying ranges, e.g. "5 ~2/1-4". See
          :func:`magic_history` for full details.
        raw, output : bool
          As :meth:`get_range`

        Returns
        -------
        Tuples as :meth:`get_range`
        """
        for sess, s, e in extract_hist_ranges(rangestr):
            for line in self.get_range(sess, s, e, raw=raw, output=output):
                yield line


class HistoryManager(HistoryAccessor):
    """A class to organize all history-related functionality in one place.
    """
    # Public interface

    # An instance of the IPython shell we are attached to
    shell = Instance('IPython.core.interactiveshell.InteractiveShellABC')
    # Lists to hold processed and raw history. These start with a blank entry
    # so that we can index them starting from 1
    input_hist_parsed = List([""])
    input_hist_raw = List([""])
    # A list of directories visited during session
    dir_hist = List()
    def _dir_hist_default(self):
        try:
            return [os.getcwdu()]
        except OSError:
            return []

    # A dict of output history, keyed with ints from the shell's
    # execution count.
    output_hist = Dict()
    # The text/plain repr of outputs.
    output_hist_reprs = Dict()

    # The number of the current session in the history database
    session_number = CInt()
    # Should we log output to the database? (default no)
    db_log_output = Bool(False, config=True)
    # Write to database every x commands (higher values save disk access & power)
    #  Values of 1 or less effectively disable caching. 
    db_cache_size = Int(0, config=True)
    # The input and output caches
    db_input_cache = List()
    db_output_cache = List()
    
    # History saving in separate thread
    save_thread = Instance('IPython.core.history.HistorySavingThread')
    try:               # Event is a function returning an instance of _Event...
        save_flag = Instance(threading._Event)
    except AttributeError:         # ...until Python 3.3, when it's a class.
        save_flag = Instance(threading.Event)
    
    # Private interface
    # Variables used to store the three last inputs from the user.  On each new
    # history update, we populate the user's namespace with these, shifted as
    # necessary.
    _i00 = Unicode(u'')
    _i = Unicode(u'')
    _ii = Unicode(u'')
    _iii = Unicode(u'')

    # A regex matching all forms of the exit command, so that we don't store
    # them in the history (it's annoying to rewind the first entry and land on
    # an exit call).
    _exit_re = re.compile(r"(exit|quit)(\s*\(.*\))?$")

    def __init__(self, shell=None, config=None, **traits):
        """Create a new history manager associated with a shell instance.
        """
        # We need a pointer back to the shell for various tasks.
        super(HistoryManager, self).__init__(shell=shell, config=config,
            **traits)
        self.save_flag = threading.Event()
        self.db_input_cache_lock = threading.Lock()
        self.db_output_cache_lock = threading.Lock()
        self.save_thread = HistorySavingThread(self)
        self.save_thread.start()

        self.new_session()
    
    def _get_hist_file_name(self, profile=None):
        """Get default history file name based on the Shell's profile.
        
        The profile parameter is ignored, but must exist for compatibility with
        the parent class."""
        profile_dir = self.shell.profile_dir.location
        return os.path.join(profile_dir, 'history.sqlite')
    
    def new_session(self, conn=None):
        """Get a new session number."""
        if conn is None:
            conn = self.db
        
        with conn:
            cur = conn.execute("""INSERT INTO sessions VALUES (NULL, ?, NULL,
                            NULL, "") """, (datetime.datetime.now(),))
            self.session_number = cur.lastrowid
            
    def end_session(self):
        """Close the database session, filling in the end time and line count."""
        self.writeout_cache()
        with self.db:
            self.db.execute("""UPDATE sessions SET end=?, num_cmds=? WHERE
                            session==?""", (datetime.datetime.now(),
                            len(self.input_hist_parsed)-1, self.session_number))
        self.session_number = 0
                            
    def name_session(self, name):
        """Give the current session a name in the history database."""
        with self.db:
            self.db.execute("UPDATE sessions SET remark=? WHERE session==?",
                            (name, self.session_number))
                            
    def reset(self, new_session=True):
        """Clear the session history, releasing all object references, and
        optionally open a new session."""
        self.output_hist.clear()
        # The directory history can't be completely empty
        self.dir_hist[:] = [os.getcwdu()]
        
        if new_session:
            if self.session_number:
                self.end_session()
            self.input_hist_parsed[:] = [""]
            self.input_hist_raw[:] = [""]
            self.new_session()
    
    # ------------------------------
    # Methods for retrieving history
    # ------------------------------
    def _get_range_session(self, start=1, stop=None, raw=True, output=False):
        """Get input and output history from the current session. Called by
        get_range, and takes similar parameters."""
        input_hist = self.input_hist_raw if raw else self.input_hist_parsed
            
        n = len(input_hist)
        if start < 0:
            start += n
        if not stop or (stop > n):
            stop = n
        elif stop < 0:
            stop += n
        
        for i in range(start, stop):
            if output:
                line = (input_hist[i], self.output_hist_reprs.get(i))
            else:
                line = input_hist[i]
            yield (0, i, line)
    
    def get_range(self, session=0, start=1, stop=None, raw=True,output=False):
        """Retrieve input by session.
        
        Parameters
        ----------
        session : int
            Session number to retrieve. The current session is 0, and negative
            numbers count back from current session, so -1 is previous session.
        start : int
            First line to retrieve.
        stop : int
            End of line range (excluded from output itself). If None, retrieve
            to the end of the session.
        raw : bool
            If True, return untranslated input
        output : bool
            If True, attempt to include output. This will be 'real' Python
            objects for the current session, or text reprs from previous
            sessions if db_log_output was enabled at the time. Where no output
            is found, None is used.
            
        Returns
        -------
        An iterator over the desired lines. Each line is a 3-tuple, either
        (session, line, input) if output is False, or
        (session, line, (input, output)) if output is True.
        """
        if session <= 0:
            session += self.session_number
        if session==self.session_number:          # Current session
            return self._get_range_session(start, stop, raw, output)
        return super(HistoryManager, self).get_range(session, start, stop, raw, output)

    ## ----------------------------
    ## Methods for storing history:
    ## ----------------------------
    def store_inputs(self, line_num, source, source_raw=None):
        """Store source and raw input in history and create input cache
        variables _i*.

        Parameters
        ----------
        line_num : int
          The prompt number of this input.

        source : str
          Python input.

        source_raw : str, optional
          If given, this is the raw input without any IPython transformations
          applied to it.  If not given, ``source`` is used.
        """
        if source_raw is None:
            source_raw = source
        source = source.rstrip('\n')
        source_raw = source_raw.rstrip('\n')

        # do not store exit/quit commands
        if self._exit_re.match(source_raw.strip()):
            return

        self.input_hist_parsed.append(source)
        self.input_hist_raw.append(source_raw)

        with self.db_input_cache_lock:
            self.db_input_cache.append((line_num, source, source_raw))
            # Trigger to flush cache and write to DB.
            if len(self.db_input_cache) >= self.db_cache_size:
                self.save_flag.set()

        # update the auto _i variables
        self._iii = self._ii
        self._ii = self._i
        self._i = self._i00
        self._i00 = source_raw

        # hackish access to user namespace to create _i1,_i2... dynamically
        new_i = '_i%s' % line_num
        to_main = {'_i': self._i,
                   '_ii': self._ii,
                   '_iii': self._iii,
                   new_i : self._i00 }
        self.shell.user_ns.update(to_main)

    def store_output(self, line_num):
        """If database output logging is enabled, this saves all the
        outputs from the indicated prompt number to the database. It's
        called by run_cell after code has been executed.

        Parameters
        ----------
        line_num : int
          The line number from which to save outputs
        """
        if (not self.db_log_output) or (line_num not in self.output_hist_reprs):
            return
        output = self.output_hist_reprs[line_num]

        with self.db_output_cache_lock:
            self.db_output_cache.append((line_num, output))
        if self.db_cache_size <= 1:
            self.save_flag.set()

    def _writeout_input_cache(self, conn):
        with conn:
            for line in self.db_input_cache:
                conn.execute("INSERT INTO history VALUES (?, ?, ?, ?)",
                                (self.session_number,)+line)

    def _writeout_output_cache(self, conn):
        with conn:
            for line in self.db_output_cache:
                conn.execute("INSERT INTO output_history VALUES (?, ?, ?)",
                                (self.session_number,)+line)

    def writeout_cache(self, conn=None):
        """Write any entries in the cache to the database."""
        if conn is None:
            conn = self.db

        with self.db_input_cache_lock:
            try:
                self._writeout_input_cache(conn)
            except sqlite3.IntegrityError:
                self.new_session(conn)
                print("ERROR! Session/line number was not unique in",
                      "database. History logging moved to new session",
                                                self.session_number)
                try: # Try writing to the new session. If this fails, don't recurse
                    self._writeout_input_cache(conn)
                except sqlite3.IntegrityError:
                    pass
            finally:
                self.db_input_cache = []

        with self.db_output_cache_lock:
            try:
                self._writeout_output_cache(conn)
            except sqlite3.IntegrityError:
                print("!! Session/line number for output was not unique",
                      "in database. Output will not be stored.")
            finally:
                self.db_output_cache = []


class HistorySavingThread(threading.Thread):
    """This thread takes care of writing history to the database, so that
    the UI isn't held up while that happens.

    It waits for the HistoryManager's save_flag to be set, then writes out
    the history cache. The main thread is responsible for setting the flag when
    the cache size reaches a defined threshold."""
    daemon = True
    stop_now = False
    def __init__(self, history_manager):
        super(HistorySavingThread, self).__init__()
        self.history_manager = history_manager
        atexit.register(self.stop)

    def run(self):
        # We need a separate db connection per thread:
        try:
            self.db = sqlite3.connect(self.history_manager.hist_file)
            while True:
                self.history_manager.save_flag.wait()
                if self.stop_now:
                    return
                self.history_manager.save_flag.clear()
                self.history_manager.writeout_cache(self.db)
        except Exception as e:
            print(("The history saving thread hit an unexpected error (%s)."
                   "History will not be written to the database.") % repr(e))

    def stop(self):
        """This can be called from the main thread to safely stop this thread.

        Note that it does not attempt to write out remaining history before
        exiting. That should be done by calling the HistoryManager's
        end_session method."""
        self.stop_now = True
        self.history_manager.save_flag.set()
        self.join()


# To match, e.g. ~5/8-~2/3
range_re = re.compile(r"""
((?P<startsess>~?\d+)/)?
(?P<start>\d+)                    # Only the start line num is compulsory
((?P<sep>[\-:])
 ((?P<endsess>~?\d+)/)?
 (?P<end>\d+))?
$""", re.VERBOSE)

def extract_hist_ranges(ranges_str):
    """Turn a string of history ranges into 3-tuples of (session, start, stop).

    Examples
    --------
    list(extract_input_ranges("~8/5-~7/4 2"))
    [(-8, 5, None), (-7, 1, 4), (0, 2, 3)]
    """
    for range_str in ranges_str.split():
        rmatch = range_re.match(range_str)
        if not rmatch:
            continue
        start = int(rmatch.group("start"))
        end = rmatch.group("end")
        end = int(end) if end else start+1   # If no end specified, get (a, a+1)
        if rmatch.group("sep") == "-":       # 1-3 == 1:4 --> [1, 2, 3]
            end += 1
        startsess = rmatch.group("startsess") or "0"
        endsess = rmatch.group("endsess") or startsess
        startsess = int(startsess.replace("~","-"))
        endsess = int(endsess.replace("~","-"))
        assert endsess >= startsess

        if endsess == startsess:
            yield (startsess, start, end)
            continue
        # Multiple sessions in one range:
        yield (startsess, start, None)
        for sess in range(startsess+1, endsess):
            yield (sess, 1, None)
        yield (endsess, 1, end)

def _format_lineno(session, line):
    """Helper function to format line numbers properly."""
    if session == 0:
        return str(line)
    return "%s#%s" % (session, line)

@skip_doctest
def magic_history(self, parameter_s = ''):
    """Print input history (_i<n> variables), with most recent last.

    %history       -> print at most 40 inputs (some may be multi-line)\\
    %history n     -> print at most n inputs\\
    %history n1 n2 -> print inputs between n1 and n2 (n2 not included)\\

    By default, input history is printed without line numbers so it can be
    directly pasted into an editor. Use -n to show them.

    Ranges of history can be indicated using the syntax:
    4      : Line 4, current session
    4-6    : Lines 4-6, current session
    243/1-5: Lines 1-5, session 243
    ~2/7   : Line 7, session 2 before current
    ~8/1-~6/5 : From the first line of 8 sessions ago, to the fifth line
                of 6 sessions ago.
    Multiple ranges can be entered, separated by spaces

    The same syntax is used by %macro, %save, %edit, %rerun

    Options:

      -n: print line numbers for each input.
      This feature is only available if numbered prompts are in use.

      -o: also print outputs for each input.

      -p: print classic '>>>' python prompts before each input.  This is useful
       for making documentation, and in conjunction with -o, for producing
       doctest-ready output.

      -r: (default) print the 'raw' history, i.e. the actual commands you typed.

      -t: print the 'translated' history, as IPython understands it.  IPython
      filters your input and converts it all into valid Python source before
      executing it (things like magics or aliases are turned into function
      calls, for example). With this option, you'll see the native history
      instead of the user-entered version: '%cd /' will be seen as
      'get_ipython().magic("%cd /")' instead of '%cd /'.

      -g: treat the arg as a pattern to grep for in (full) history.
      This includes the saved history (almost all commands ever written).
      Use '%hist -g' to show full saved history (may be very long).

      -l: get the last n lines from all sessions. Specify n as a single arg, or
      the default is the last 10 lines.

      -f FILENAME: instead of printing the output to the screen, redirect it to
       the given file.  The file is always overwritten, though IPython asks for
       confirmation first if it already exists.

    Examples
    --------
    ::

      In [6]: %hist -n 4 6
      4:a = 12
      5:print a**2

    """

    if not self.shell.displayhook.do_full_cache:
        print('This feature is only available if numbered prompts are in use.')
        return
    opts,args = self.parse_options(parameter_s,'noprtglf:',mode='string')

    # For brevity
    history_manager = self.shell.history_manager

    def _format_lineno(session, line):
        """Helper function to format line numbers properly."""
        if session in (0, history_manager.session_number):
            return str(line)
        return "%s/%s" % (session, line)

    # Check if output to specific file was requested.
    try:
        outfname = opts['f']
    except KeyError:
        outfile = io.stdout  # default
        # We don't want to close stdout at the end!
        close_at_end = False
    else:
        if os.path.exists(outfname):
            if not io.ask_yes_no("File %r exists. Overwrite?" % outfname):
                print('Aborting.')
                return

        outfile = open(outfname,'w')
        close_at_end = True

    print_nums = 'n' in opts
    get_output = 'o' in opts
    pyprompts = 'p' in opts
    # Raw history is the default
    raw = not('t' in opts)

    default_length = 40
    pattern = None

    if 'g' in opts:         # Glob search
        pattern = "*" + args + "*" if args else "*"
        hist = history_manager.search(pattern, raw=raw, output=get_output)
        print_nums = True
    elif 'l' in opts:       # Get 'tail'
        try:
            n = int(args)
        except ValueError, IndexError:
            n = 10
        hist = history_manager.get_tail(n, raw=raw, output=get_output)
    else:
        if args:            # Get history by ranges
            hist = history_manager.get_range_by_str(args, raw, get_output)
        else:               # Just get history for the current session
            hist = history_manager.get_range(raw=raw, output=get_output)

    # We could be displaying the entire history, so let's not try to pull it
    # into a list in memory. Anything that needs more space will just misalign.
    width = 4

    for session, lineno, inline in hist:
        # Print user history with tabs expanded to 4 spaces.  The GUI clients
        # use hard tabs for easier usability in auto-indented code, but we want
        # to produce PEP-8 compliant history for safe pasting into an editor.
        if get_output:
            inline, output = inline
        inline = inline.expandtabs(4).rstrip()

        multiline = "\n" in inline
        line_sep = '\n' if multiline else ' '
        if print_nums:
            print('%s:%s' % (_format_lineno(session, lineno).rjust(width),
                    line_sep),  file=outfile, end='')
        if pyprompts:
            print(">>> ", end="", file=outfile)
            if multiline:
                inline = "\n... ".join(inline.splitlines()) + "\n..."
        print(inline, file=outfile)
        if get_output and output:
            print(output, file=outfile)

    if close_at_end:
        outfile.close()


def magic_rep(self, arg):
    r"""Repeat a command, or get command to input line for editing. %recall and
    %rep are equivalent.

    - %recall (no arguments):

    Place a string version of last computation result (stored in the special '_'
    variable) to the next input prompt. Allows you to create elaborate command
    lines without using copy-paste::

         In[1]: l = ["hei", "vaan"]
         In[2]: "".join(l)
        Out[2]: heivaan
         In[3]: %rep
         In[4]: heivaan_ <== cursor blinking

    %recall 45

    Place history line 45 on the next input prompt. Use %hist to find
    out the number.

    %recall 1-4

    Combine the specified lines into one cell, and place it on the next
    input prompt. See %history for the slice syntax.

    %recall foo+bar

    If foo+bar can be evaluated in the user namespace, the result is
    placed at the next input prompt. Otherwise, the history is searched
    for lines which contain that substring, and the most recent one is
    placed at the next input prompt.
    """
    if not arg:                 # Last output
        self.set_next_input(str(self.shell.user_ns["_"]))
        return
                                # Get history range
    histlines = self.history_manager.get_range_by_str(arg)
    cmd = "\n".join(x[2] for x in histlines)
    if cmd:
        self.set_next_input(cmd.rstrip())
        return

    try:                        # Variable in user namespace
        cmd = str(eval(arg, self.shell.user_ns))
    except Exception:           # Search for term in history
        histlines = self.history_manager.search("*"+arg+"*")
        for h in reversed([x[2] for x in histlines]):
            if 'rep' in h:
                continue
            self.set_next_input(h.rstrip())
            return
    else:
        self.set_next_input(cmd.rstrip())
    print("Couldn't evaluate or find in history:", arg)

def magic_rerun(self, parameter_s=''):
    """Re-run previous input

    By default, you can specify ranges of input history to be repeated
    (as with %history). With no arguments, it will repeat the last line.

    Options:

      -l <n> : Repeat the last n lines of input, not including the
      current command.

      -g foo : Repeat the most recent line which contains foo
    """
    opts, args = self.parse_options(parameter_s, 'l:g:', mode='string')
    if "l" in opts:         # Last n lines
        n = int(opts['l'])
        hist = self.history_manager.get_tail(n)
    elif "g" in opts:       # Search
        p = "*"+opts['g']+"*"
        hist = list(self.history_manager.search(p))
        for l in reversed(hist):
            if "rerun" not in l[2]:
                hist = [l]     # The last match which isn't a %rerun
                break
        else:
            hist = []          # No matches except %rerun
    elif args:              # Specify history ranges
        hist = self.history_manager.get_range_by_str(args)
    else:                   # Last line
        hist = self.history_manager.get_tail(1)
    hist = [x[2] for x in hist]
    if not hist:
        print("No lines in history match specification")
        return
    histlines = "\n".join(hist)
    print("=== Executing: ===")
    print(histlines)
    print("=== Output: ===")
    self.run_cell("\n".join(hist), store_history=False)


def init_ipython(ip):
    ip.define_magic("rep", magic_rep)
    ip.define_magic("recall", magic_rep)
    ip.define_magic("rerun", magic_rerun)
    ip.define_magic("hist",magic_history)    # Alternative name
    ip.define_magic("history",magic_history)

    # XXX - ipy_completers are in quarantine, need to be updated to new apis
    #import ipy_completers
    #ipy_completers.quick_completer('%hist' ,'-g -t -r -n')