from __future__ import unicode_literals

import collections
from importlib import import_module
import os
import pkgutil
import sys

import django
from django.apps import apps
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.core.management.base import (BaseCommand, CommandError,
    CommandParser, handle_default_options)
from django.core.management.color import color_style
from django.utils import lru_cache, six
from django.utils._os import npath, upath


def find_commands(management_dir):
    """
    Given a path to a management directory, returns a list of all the command
    names that are available.

    Returns an empty list if no commands are defined.
    """
    command_dir = os.path.join(management_dir, 'commands')
    return [name for _, name, is_pkg in pkgutil.iter_modules([npath(command_dir)])
            if not is_pkg and not name.startswith('_')]


def load_command_class(app_name, name):
    """
    Given a command name and an application name, returns the Command
    class instance. All errors raised by the import process
    (ImportError, AttributeError) are allowed to propagate.
    """
    module = import_module('%s.management.commands.%s' % (app_name, name))
    return module.Command()


@lru_cache.lru_cache(maxsize=None)
def get_commands():
    """
    Returns a dictionary mapping command names to their callback applications.

    This works by looking for a management.commands package in django.core, and
    in each installed application -- if a commands package exists, all commands
    in that package are registered.

    Core commands are always included. If a settings module has been
    specified, user-defined commands will also be included.

    The dictionary is in the format {command_name: app_name}. Key-value
    pairs from this dictionary can then be used in calls to
    load_command_class(app_name, command_name)

    If a specific version of a command must be loaded (e.g., with the
    startapp command), the instantiated module can be placed in the
    dictionary in place of the application name.

    The dictionary is cached on the first call and reused on subsequent
    calls.
    """
    commands = {name: 'django.core' for name in find_commands(upath(__path__[0]))}

    if not settings.configured:
        return commands

    for app_config in reversed(list(apps.get_app_configs())):
        path = os.path.join(app_config.path, 'management')
        commands.update({name: app_config.name for name in find_commands(path)})

    return commands


def call_command(name, *args, **options):
    """
    Calls the given command, with the given options and args/kwargs.

    This is the primary API you should use for calling specific commands.

    Some examples:
        call_command('migrate')
        call_command('shell', plain=True)
        call_command('sqlmigrate', 'myapp')
    """
    # Load the command object.
    try:
        app_name = get_commands()[name]
    except KeyError:
        raise CommandError("Unknown command: %r" % name)

    if isinstance(app_name, BaseCommand):
        # If the command is already loaded, use it directly.
        command = app_name
    else:
        command = load_command_class(app_name, name)

    # Simulate argument parsing to get the option defaults (see #10080 for details).
    parser = command.create_parser('', name)
    if command.use_argparse:
        # Use the `dest` option name from the parser option
        opt_mapping = {sorted(s_opt.option_strings)[0].lstrip('-').replace('-', '_'): s_opt.dest
                       for s_opt in parser._actions if s_opt.option_strings}
        arg_options = {opt_mapping.get(key, key): value for key, value in options.items()}
        defaults = parser.parse_args(args=args)
        defaults = dict(defaults._get_kwargs(), **arg_options)
        # Move positional args out of options to mimic legacy optparse
        args = defaults.pop('args', ())
    else:
        # Legacy optparse method
        defaults, _ = parser.parse_args(args=[])
        defaults = dict(defaults.__dict__, **options)
    if 'skip_checks' not in options:
        defaults['skip_checks'] = True

    return command.execute(*args, **defaults)


class ManagementUtility(object):
    """
    Encapsulates the logic of the django-admin and manage.py utilities.

    A ManagementUtility has a number of commands, which can be manipulated
    by editing the self.commands dictionary.
    """
    def __init__(self, argv=None):
        self.argv = argv or sys.argv[:]
        self.prog_name = os.path.basename(self.argv[0])
        self.settings_exception = None

    def main_help_text(self, commands_only=False):
        """
        Returns the script's main help text, as a string.
        """
        if commands_only:
            usage = sorted(get_commands().keys())
        else:
            usage = [
                "",
                "Type '%s help <subcommand>' for help on a specific subcommand." % self.prog_name,
                "",
                "Available subcommands:",
            ]
            commands_dict = collections.defaultdict(lambda: [])
            for name, app in six.iteritems(get_commands()):
                if app == 'django.core':
                    app = 'django'
                else:
                    app = app.rpartition('.')[-1]
                commands_dict[app].append(name)
            style = color_style()
            for app in sorted(commands_dict.keys()):
                usage.append("")
                usage.append(style.NOTICE("[%s]" % app))
                for name in sorted(commands_dict[app]):
                    usage.append("    %s" % name)
            # Output an extra note if settings are not properly configured
            if self.settings_exception is not None:
                usage.append(style.NOTICE(
                    "Note that only Django core commands are listed "
                    "as settings are not properly configured (error: %s)."
                    % self.settings_exception))

        return '\n'.join(usage)

    def fetch_command(self, subcommand):
        """
        Tries to fetch the given subcommand, printing a message with the
        appropriate command called from the command line (usually
        "django-admin" or "manage.py") if it can't be found.
        """
        # Get commands outside of try block to prevent swallowing exceptions
        commands = get_commands()
        try:
            app_name = commands[subcommand]
        except KeyError:
            # This might trigger ImproperlyConfigured (masked in get_commands)
            settings.INSTALLED_APPS
            sys.stderr.write("Unknown command: %r\nType '%s help' for usage.\n" %
                (subcommand, self.prog_name))
            sys.exit(1)
        if isinstance(app_name, BaseCommand):
            # If the command is already loaded, use it directly.
            klass = app_name
        else:
            klass = load_command_class(app_name, subcommand)
        return klass

    def autocomplete(self):
        """
        Output completion suggestions for BASH.

        The output of this function is passed to BASH's `COMREPLY` variable and
        treated as completion suggestions. `COMREPLY` expects a space
        separated string as the result.

        The `COMP_WORDS` and `COMP_CWORD` BASH environment variables are used
        to get information about the cli input. Please refer to the BASH
        man-page for more information about this variables.

        Subcommand options are saved as pairs. A pair consists of
        the long option string (e.g. '--exclude') and a boolean
        value indicating if the option requires arguments. When printing to
        stdout, an equal sign is appended to options which require arguments.

        Note: If debugging this function, it is recommended to write the debug
        output in a separate file. Otherwise the debug output will be treated
        and formatted as potential completion suggestions.
        """
        # Don't complete if user hasn't sourced bash_completion file.
        if 'DJANGO_AUTO_COMPLETE' not in os.environ:
            return

        cwords = os.environ['COMP_WORDS'].split()[1:]
        cword = int(os.environ['COMP_CWORD'])

        try:
            curr = cwords[cword - 1]
        except IndexError:
            curr = ''

        subcommands = list(get_commands()) + ['help']
        options = [('--help', False)]

        # subcommand
        if cword == 1:
            print(' '.join(sorted(filter(lambda x: x.startswith(curr), subcommands))))
        # subcommand options
        # special case: the 'help' subcommand has no options
        elif cwords[0] in subcommands and cwords[0] != 'help':
            subcommand_cls = self.fetch_command(cwords[0])
            # special case: add the names of installed apps to options
            if cwords[0] in ('dumpdata', 'sqlmigrate', 'sqlsequencereset', 'test'):
                try:
                    app_configs = apps.get_app_configs()
                    # Get the last part of the dotted path as the app name.
                    options.extend((app_config.label, 0) for app_config in app_configs)
                except ImportError:
                    # Fail silently if DJANGO_SETTINGS_MODULE isn't set. The
                    # user will find out once they execute the command.
                    pass
            parser = subcommand_cls.create_parser('', cwords[0])
            if subcommand_cls.use_argparse:
                options.extend((sorted(s_opt.option_strings)[0], s_opt.nargs != 0) for s_opt in
                               parser._actions if s_opt.option_strings)
            else:
                options.extend((s_opt.get_opt_string(), s_opt.nargs) for s_opt in
                               parser.option_list)
            # filter out previously specified options from available options
            prev_opts = [x.split('=')[0] for x in cwords[1:cword - 1]]
            options = [opt for opt in options if opt[0] not in prev_opts]

            # filter options by current input
            options = sorted((k, v) for k, v in options if k.startswith(curr))
            for option in options:
                opt_label = option[0]
                # append '=' to options which require args
                if option[1]:
                    opt_label += '='
                print(opt_label)
        sys.exit(1)

    def execute(self):
        """
        Given the command-line arguments, this figures out which subcommand is
        being run, creates a parser appropriate to that command, and runs it.
        """
        try:
            subcommand = self.argv[1]
        except IndexError:
            subcommand = 'help'  # Display help if no arguments were given.

        # Preprocess options to extract --settings and --pythonpath.
        # These options could affect the commands that are available, so they
        # must be processed early.
        parser = CommandParser(None, usage="%(prog)s subcommand [options] [args]", add_help=False)
        parser.add_argument('--settings')
        parser.add_argument('--pythonpath')
        parser.add_argument('args', nargs='*')  # catch-all
        try:
            options, args = parser.parse_known_args(self.argv[2:])
            handle_default_options(options)
        except CommandError:
            pass  # Ignore any option errors at this point.

        no_settings_commands = [
            'help', 'version', '--help', '--version', '-h',
            'compilemessages', 'makemessages',
            'startapp', 'startproject',
        ]

        try:
            settings.INSTALLED_APPS
        except ImproperlyConfigured as exc:
            self.settings_exception = exc
            # A handful of built-in management commands work without settings.
            # Load the default settings -- where INSTALLED_APPS is empty.
            if subcommand in no_settings_commands:
                settings.configure()

        if settings.configured:
            django.setup()

        self.autocomplete()

        if subcommand == 'help':
            if '--commands' in args:
                sys.stdout.write(self.main_help_text(commands_only=True) + '\n')
            elif len(options.args) < 1:
                sys.stdout.write(self.main_help_text() + '\n')
            else:
                self.fetch_command(options.args[0]).print_help(self.prog_name, options.args[0])
        # Special-cases: We want 'django-admin --version' and
        # 'django-admin --help' to work, for backwards compatibility.
        elif subcommand == 'version' or self.argv[1:] == ['--version']:
            sys.stdout.write(django.get_version() + '\n')
        elif self.argv[1:] in (['--help'], ['-h']):
            sys.stdout.write(self.main_help_text() + '\n')
        else:
            self.fetch_command(subcommand).run_from_argv(self.argv)


def execute_from_command_line(argv=None):
    """
    A simple method that runs a ManagementUtility.
    """
    utility = ManagementUtility(argv)
    utility.execute()