"""Python virtual environment manager for xonsh."""

import sys
import textwrap
import xontrib.voxapi as voxapi
import xonsh.lazyasd as lazyasd

__all__ = ()


class VoxHandler:
    """Vox is a virtual environment manager for xonsh."""

    def parser():
        from argparse import ArgumentParser

        parser = ArgumentParser(prog="vox", description=__doc__)
        subparsers = parser.add_subparsers(dest="command")

        create = subparsers.add_parser(
            "new",
            aliases=["create"],
            help="Create a new virtual environment in $VIRTUALENV_HOME",
        )
        create.add_argument("name", metavar="ENV", help="The environments to create")

        create.add_argument(
            "--system-site-packages",
            default=False,
            action="store_true",
            dest="system_site_packages",
            help="Give the virtual environment access to the "
            "system site-packages dir.",
        )

        create.add_argument(
            "-p",
            "--interpreter",
            default=None,
            help=textwrap.dedent(
                """
                The Python interpreter used to create the virtual environment.
                Can be configured via the $VOX_DEFAULT_INTERPRETER environment variable.
                """
            ).strip(),
        )

        from xonsh.platform import ON_WINDOWS

        group = create.add_mutually_exclusive_group()
        group.add_argument(
            "--symlinks",
            default=not ON_WINDOWS,
            action="store_true",
            dest="symlinks",
            help="Try to use symlinks rather than copies, "
            "when symlinks are not the default for "
            "the platform.",
        )
        group.add_argument(
            "--copies",
            default=ON_WINDOWS,
            action="store_false",
            dest="symlinks",
            help="Try to use copies rather than symlinks, "
            "even when symlinks are the default for "
            "the platform.",
        )
        create.add_argument(
            "--without-pip",
            dest="with_pip",
            default=True,
            action="store_false",
            help="Skips installing or upgrading pip in the "
            "virtual environment (pip is bootstrapped "
            "by default)",
        )

        activate = subparsers.add_parser(
            "activate", aliases=["workon", "enter"], help="Activate virtual environment"
        )
        activate.add_argument(
            "name",
            metavar="ENV",
            help=(
                "The environment to activate. ENV can be "
                "either a name from the venvs shown by vox"
                "list or the path to an arbitrary venv"
            ),
        )
        subparsers.add_parser(
            "deactivate",
            aliases=["exit"],
            help="Deactivate current virtual environment",
        )
        subparsers.add_parser(
            "list",
            aliases=["ls"],
            help=("List environments available in " "$VIRTUALENV_HOME"),
        )
        remove = subparsers.add_parser(
            "remove", aliases=["rm", "delete", "del"], help="Remove virtual environment"
        )
        remove.add_argument(
            "names",
            metavar="ENV",
            nargs="+",
            help=(
                "The environments to remove. ENV can be "
                "either a name from the venvs shown by vox"
                "list or the path to an arbitrary venv"
            ),
        )
        subparsers.add_parser("help", help="Show this help message")
        return parser

    parser = lazyasd.LazyObject(parser, locals(), "parser")

    aliases = {
        "create": "new",
        "workon": "activate",
        "enter": "activate",
        "exit": "deactivate",
        "ls": "list",
        "rm": "remove",
        "delete": "remove",
        "del": "remove",
    }

    def __init__(self):
        self.vox = voxapi.Vox()

    def __call__(self, args, stdin=None):
        """Call the right handler method for a given command."""

        args = self.parser.parse_args(args)
        cmd = self.aliases.get(args.command, args.command)
        if cmd is None:
            self.parser.print_usage()
        else:
            getattr(self, "cmd_" + cmd)(args, stdin)

    def cmd_new(self, args, stdin=None):
        """Create a virtual environment in $VIRTUALENV_HOME with python3's ``venv``.
        """
        print("Creating environment...")
        self.vox.create(
            args.name,
            system_site_packages=args.system_site_packages,
            symlinks=args.symlinks,
            with_pip=args.with_pip,
            interpreter=args.interpreter,
        )
        msg = 'Environment {0!r} created. Activate it with "vox activate {0}".\n'
        print(msg.format(args.name))

    def cmd_activate(self, args, stdin=None):
        """Activate a virtual environment.
        """

        try:
            self.vox.activate(args.name)
        except KeyError:
            print(
                'This environment doesn\'t exist. Create it with "vox new %s".\n'
                % args.name,
                file=sys.stderr,
            )
            return None
        else:
            print('Activated "%s".\n' % args.name)

    def cmd_deactivate(self, args, stdin=None):
        """Deactivate the active virtual environment."""

        if self.vox.active() is None:
            print(
                'No environment currently active. Activate one with "vox activate".\n',
                file=sys.stderr,
            )
            return None
        env_name = self.vox.deactivate()
        print('Deactivated "%s".\n' % env_name)

    def cmd_list(self, args, stdin=None):
        """List available virtual environments."""

        try:
            envs = sorted(self.vox.keys())
        except PermissionError:
            print("No permissions on VIRTUALENV_HOME")
            return None

        if not envs:
            print(
                'No environments available. Create one with "vox new".\n',
                file=sys.stderr,
            )
            return None

        print("Available environments:")
        print("\n".join(envs))

    def cmd_remove(self, args, stdin=None):
        """Remove virtual environments.
        """
        for name in args.names:
            try:
                del self.vox[name]
            except voxapi.EnvironmentInUse:
                print(
                    'The "%s" environment is currently active. In order to remove it, deactivate it first with "vox deactivate %s".\n'
                    % (name, name),
                    file=sys.stderr,
                )
                return
            else:
                print('Environment "%s" removed.' % name)
        print()

    def cmd_help(self, args, stdin=None):
        self.parser.print_help()

    @classmethod
    def handle(cls, args, stdin=None):
        """Runs Vox environment manager."""
        vox = cls()
        return vox(args, stdin=stdin)


aliases["vox"] = VoxHandler.handle
