# Copyright (c) IPython Development Team.
# Distributed under the terms of the Modified BSD License.

import errno
import os.path

from IPython.config.application import Application
from IPython.core.application import BaseIPythonApplication, base_flags
from IPython.utils.traitlets import Instance, Dict, Unicode, Bool

from .kernelspec import KernelSpecManager

def _pythonfirst(s):
    "Sort key function that will put strings starting with 'python' first."
    if s.startswith('python'):
        return ''
    return s

class ListKernelSpecs(BaseIPythonApplication):
    description = """List installed kernel specifications."""
    kernel_spec_manager = Instance(KernelSpecManager)

    def _kernel_spec_manager_default(self):
        return KernelSpecManager(ipython_dir=self.ipython_dir)

    def start(self):
        print("Available kernels:")
        for kernelname in sorted(self.kernel_spec_manager.find_kernel_specs(),
                                 key=_pythonfirst):
            print("  %s" % kernelname)


class InstallKernelSpec(BaseIPythonApplication):
    description = """Install a kernel specification directory."""
    kernel_spec_manager = Instance(KernelSpecManager)

    def _kernel_spec_manager_default(self):
        return KernelSpecManager(ipython_dir=self.ipython_dir)

    sourcedir = Unicode()
    kernel_name = Unicode("", config=True,
        help="Install the kernel spec with this name"
    )
    def _kernel_name_default(self):
        return os.path.basename(self.sourcedir)

    system = Bool(False, config=True,
        help="""
        Try to install the kernel spec to the systemwide directory instead of
        the per-user directory.
        """
    )
    replace = Bool(False, config=True,
        help="Replace any existing kernel spec with this name."
    )

    aliases = {'name': 'InstallKernelSpec.kernel_name'}

    flags = {'system': ({'InstallKernelSpec': {'system': True}},
                "Install to the systemwide kernel registry"),
             'replace': ({'InstallKernelSpec': {'replace': True}},
                "Replace any existing kernel spec with this name."),
            }
    flags.update(base_flags)

    def parse_command_line(self, argv):
        super(InstallKernelSpec, self).parse_command_line(argv)
        # accept positional arg as profile name
        if self.extra_args:
            self.sourcedir = self.extra_args[0]
        else:
            print("No source directory specified.")
            self.exit(1)

    def start(self):
        try:
            self.kernel_spec_manager.install_kernel_spec(self.sourcedir,
                                                 kernel_name=self.kernel_name,
                                                 system=self.system,
                                                 replace=self.replace,
                                                )
        except OSError as e:
            if e.errno == errno.EACCES:
                print("Permission denied")
                self.exit(1)
            elif e.errno == errno.EEXIST:
                print("A kernel spec named %r is already present" % self.kernel_name)
                self.exit(1)
            raise

class KernelSpecApp(Application):
    name = "ipython-kernelspec"
    description = """Manage IPython kernel specifications."""

    subcommands = Dict(dict(
        list = (ListKernelSpecs, ListKernelSpecs.description.splitlines()[0]),
        install = (InstallKernelSpec, InstallKernelSpec.description.splitlines()[0])
    ))

    def start(self):
        if self.subapp is None:
            print("No subcommand specified. Must specify one of: %s"% list(self.subcommands))
            print()
            self.print_description()
            self.print_subcommands()
            self.exit(1)
        else:
            return self.subapp.start()