"""
Base classes for writing management commands (named commands which can
be executed through ``django-admin`` or ``manage.py``).
"""
import os
import sys
from argparse import ArgumentParser, HelpFormatter
from io import TextIOBase

import django
from django.core import checks
from django.core.exceptions import ImproperlyConfigured
from django.core.management.color import color_style, no_style
from django.db import DEFAULT_DB_ALIAS, connections


class CommandError(Exception):
    """
    Exception class indicating a problem while executing a management
    command.

    If this exception is raised during the execution of a management
    command, it will be caught and turned into a nicely-printed error
    message to the appropriate output stream (i.e., stderr); as a
    result, raising this exception (with a sensible description of the
    error) is the preferred way to indicate that something has gone
    wrong in the execution of a command.
    """
    pass


class SystemCheckError(CommandError):
    """
    The system check framework detected unrecoverable errors.
    """
    pass


class CommandParser(ArgumentParser):
    """
    Customized ArgumentParser class to improve some error messages and prevent
    SystemExit in several occasions, as SystemExit is unacceptable when a
    command is called programmatically.
    """
    def __init__(self, *, missing_args_message=None, called_from_command_line=None, **kwargs):
        self.missing_args_message = missing_args_message
        self.called_from_command_line = called_from_command_line
        super().__init__(**kwargs)

    def parse_args(self, args=None, namespace=None):
        # Catch missing argument for a better error message
        if (self.missing_args_message and
                not (args or any(not arg.startswith('-') for arg in args))):
            self.error(self.missing_args_message)
        return super().parse_args(args, namespace)

    def error(self, message):
        if self.called_from_command_line:
            super().error(message)
        else:
            raise CommandError("Error: %s" % message)


def handle_default_options(options):
    """
    Include any default options that all commands should accept here
    so that ManagementUtility can handle them before searching for
    user commands.
    """
    if options.settings:
        os.environ['DJANGO_SETTINGS_MODULE'] = options.settings
    if options.pythonpath:
        sys.path.insert(0, options.pythonpath)


def no_translations(handle_func):
    """Decorator that forces a command to run with translations deactivated."""
    def wrapped(*args, **kwargs):
        from django.utils import translation
        saved_locale = translation.get_language()
        translation.deactivate_all()
        try:
            res = handle_func(*args, **kwargs)
        finally:
            if saved_locale is not None:
                translation.activate(saved_locale)
        return res
    return wrapped


class DjangoHelpFormatter(HelpFormatter):
    """
    Customized formatter so that command-specific arguments appear in the
    --help output before arguments common to all commands.
    """
    show_last = {
        '--version', '--verbosity', '--traceback', '--settings', '--pythonpath',
        '--no-color', '--force-color', '--skip-checks',
    }

    def _reordered_actions(self, actions):
        return sorted(
            actions,
            key=lambda a: set(a.option_strings) & self.show_last != set()
        )

    def add_usage(self, usage, actions, *args, **kwargs):
        super().add_usage(usage, self._reordered_actions(actions), *args, **kwargs)

    def add_arguments(self, actions):
        super().add_arguments(self._reordered_actions(actions))


class OutputWrapper(TextIOBase):
    """
    Wrapper around stdout/stderr
    """
    @property
    def style_func(self):
        return self._style_func

    @style_func.setter
    def style_func(self, style_func):
        if style_func and self.isatty():
            self._style_func = style_func
        else:
            self._style_func = lambda x: x

    def __init__(self, out, ending='\n'):
        self._out = out
        self.style_func = None
        self.ending = ending

    def __getattr__(self, name):
        return getattr(self._out, name)

    def isatty(self):
        return hasattr(self._out, 'isatty') and self._out.isatty()

    def write(self, msg, style_func=None, ending=None):
        ending = self.ending if ending is None else ending
        if ending and not msg.endswith(ending):
            msg += ending
        style_func = style_func or self.style_func
        self._out.write(style_func(msg))


class BaseCommand:
    """
    The base class from which all management commands ultimately
    derive.

    Use this class if you want access to all of the mechanisms which
    parse the command-line arguments and work out what code to call in
    response; if you don't need to change any of that behavior,
    consider using one of the subclasses defined in this file.

    If you are interested in overriding/customizing various aspects of
    the command-parsing and -execution behavior, the normal flow works
    as follows:

    1. ``django-admin`` or ``manage.py`` loads the command class
       and calls its ``run_from_argv()`` method.

    2. The ``run_from_argv()`` method calls ``create_parser()`` to get
       an ``ArgumentParser`` for the arguments, parses them, performs
       any environment changes requested by options like
       ``pythonpath``, and then calls the ``execute()`` method,
       passing the parsed arguments.

    3. The ``execute()`` method attempts to carry out the command by
       calling the ``handle()`` method with the parsed arguments; any
       output produced by ``handle()`` will be printed to standard
       output and, if the command is intended to produce a block of
       SQL statements, will be wrapped in ``BEGIN`` and ``COMMIT``.

    4. If ``handle()`` or ``execute()`` raised any exception (e.g.
       ``CommandError``), ``run_from_argv()`` will  instead print an error
       message to ``stderr``.

    Thus, the ``handle()`` method is typically the starting point for
    subclasses; many built-in commands and command types either place
    all of their logic in ``handle()``, or perform some additional
    parsing work in ``handle()`` and then delegate from it to more
    specialized methods as needed.

    Several attributes affect behavior at various steps along the way:

    ``help``
        A short description of the command, which will be printed in
        help messages.

    ``output_transaction``
        A boolean indicating whether the command outputs SQL
        statements; if ``True``, the output will automatically be
        wrapped with ``BEGIN;`` and ``COMMIT;``. Default value is
        ``False``.

    ``requires_migrations_checks``
        A boolean; if ``True``, the command prints a warning if the set of
        migrations on disk don't match the migrations in the database.

    ``requires_system_checks``
        A boolean; if ``True``, entire Django project will be checked for errors
        prior to executing the command. Default value is ``True``.
        To validate an individual application's models
        rather than all applications' models, call
        ``self.check(app_configs)`` from ``handle()``, where ``app_configs``
        is the list of application's configuration provided by the
        app registry.

    ``stealth_options``
        A tuple of any options the command uses which aren't defined by the
        argument parser.
    """
    # Metadata about this command.
    help = ''

    # Configuration shortcuts that alter various logic.
    _called_from_command_line = False
    output_transaction = False  # Whether to wrap the output in a "BEGIN; COMMIT;"
    requires_migrations_checks = False
    requires_system_checks = True
    # Arguments, common to all commands, which aren't defined by the argument
    # parser.
    base_stealth_options = ('stderr', 'stdout')
    # Command-specific options not defined by the argument parser.
    stealth_options = ()

    def __init__(self, stdout=None, stderr=None, no_color=False, force_color=False):
        self.stdout = OutputWrapper(stdout or sys.stdout)
        self.stderr = OutputWrapper(stderr or sys.stderr)
        if no_color and force_color:
            raise CommandError("'no_color' and 'force_color' can't be used together.")
        if no_color:
            self.style = no_style()
        else:
            self.style = color_style(force_color)
            self.stderr.style_func = self.style.ERROR

    def get_version(self):
        """
        Return the Django version, which should be correct for all built-in
        Django commands. User-supplied commands can override this method to
        return their own version.
        """
        return django.get_version()

    def create_parser(self, prog_name, subcommand, **kwargs):
        """
        Create and return the ``ArgumentParser`` which will be used to
        parse the arguments to this command.
        """
        parser = CommandParser(
            prog='%s %s' % (os.path.basename(prog_name), subcommand),
            description=self.help or None,
            formatter_class=DjangoHelpFormatter,
            missing_args_message=getattr(self, 'missing_args_message', None),
            called_from_command_line=getattr(self, '_called_from_command_line', None),
            **kwargs
        )
        parser.add_argument('--version', action='version', version=self.get_version())
        parser.add_argument(
            '-v', '--verbosity', default=1,
            type=int, choices=[0, 1, 2, 3],
            help='Verbosity level; 0=minimal output, 1=normal output, 2=verbose output, 3=very verbose output',
        )
        parser.add_argument(
            '--settings',
            help=(
                'The Python path to a settings module, e.g. '
                '"myproject.settings.main". If this isn\'t provided, the '
                'DJANGO_SETTINGS_MODULE environment variable will be used.'
            ),
        )
        parser.add_argument(
            '--pythonpath',
            help='A directory to add to the Python path, e.g. "/home/djangoprojects/myproject".',
        )
        parser.add_argument('--traceback', action='store_true', help='Raise on CommandError exceptions')
        parser.add_argument(
            '--no-color', action='store_true',
            help="Don't colorize the command output.",
        )
        parser.add_argument(
            '--force-color', action='store_true',
            help='Force colorization of the command output.',
        )
        if self.requires_system_checks:
            parser.add_argument(
                '--skip-checks', action='store_true',
                help='Skip system checks.',
            )
        self.add_arguments(parser)
        return parser

    def add_arguments(self, parser):
        """
        Entry point for subclassed commands to add custom arguments.
        """
        pass

    def print_help(self, prog_name, subcommand):
        """
        Print the help message for this command, derived from
        ``self.usage()``.
        """
        parser = self.create_parser(prog_name, subcommand)
        parser.print_help()

    def run_from_argv(self, argv):
        """
        Set up any environment changes requested (e.g., Python path
        and Django settings), then run this command. If the
        command raises a ``CommandError``, intercept it and print it sensibly
        to stderr. If the ``--traceback`` option is present or the raised
        ``Exception`` is not ``CommandError``, raise it.
        """
        self._called_from_command_line = True
        parser = self.create_parser(argv[0], argv[1])

        options = parser.parse_args(argv[2:])
        cmd_options = vars(options)
        # Move positional args out of options to mimic legacy optparse
        args = cmd_options.pop('args', ())
        handle_default_options(options)
        try:
            self.execute(*args, **cmd_options)
        except Exception as e:
            if options.traceback or not isinstance(e, CommandError):
                raise

            # SystemCheckError takes care of its own formatting.
            if isinstance(e, SystemCheckError):
                self.stderr.write(str(e), lambda x: x)
            else:
                self.stderr.write('%s: %s' % (e.__class__.__name__, e))
            sys.exit(1)
        finally:
            try:
                connections.close_all()
            except ImproperlyConfigured:
                # Ignore if connections aren't setup at this point (e.g. no
                # configured settings).
                pass

    def execute(self, *args, **options):
        """
        Try to execute this command, performing system checks if needed (as
        controlled by the ``requires_system_checks`` attribute, except if
        force-skipped).
        """
        if options['force_color'] and options['no_color']:
            raise CommandError("The --no-color and --force-color options can't be used together.")
        if options['force_color']:
            self.style = color_style(force_color=True)
        elif options['no_color']:
            self.style = no_style()
            self.stderr.style_func = None
        if options.get('stdout'):
            self.stdout = OutputWrapper(options['stdout'])
        if options.get('stderr'):
            self.stderr = OutputWrapper(options['stderr'])

        if self.requires_system_checks and not options['skip_checks']:
            self.check()
        if self.requires_migrations_checks:
            self.check_migrations()
        output = self.handle(*args, **options)
        if output:
            if self.output_transaction:
                connection = connections[options.get('database', DEFAULT_DB_ALIAS)]
                output = '%s\n%s\n%s' % (
                    self.style.SQL_KEYWORD(connection.ops.start_transaction_sql()),
                    output,
                    self.style.SQL_KEYWORD(connection.ops.end_transaction_sql()),
                )
            self.stdout.write(output)
        return output

    def _run_checks(self, **kwargs):
        return checks.run_checks(**kwargs)

    def check(self, app_configs=None, tags=None, display_num_errors=False,
              include_deployment_checks=False, fail_level=checks.ERROR):
        """
        Use the system check framework to validate entire Django project.
        Raise CommandError for any serious message (error or critical errors).
        If there are only light messages (like warnings), print them to stderr
        and don't raise an exception.
        """
        all_issues = self._run_checks(
            app_configs=app_configs,
            tags=tags,
            include_deployment_checks=include_deployment_checks,
        )

        header, body, footer = "", "", ""
        visible_issue_count = 0  # excludes silenced warnings

        if all_issues:
            debugs = [e for e in all_issues if e.level < checks.INFO and not e.is_silenced()]
            infos = [e for e in all_issues if checks.INFO <= e.level < checks.WARNING and not e.is_silenced()]
            warnings = [e for e in all_issues if checks.WARNING <= e.level < checks.ERROR and not e.is_silenced()]
            errors = [e for e in all_issues if checks.ERROR <= e.level < checks.CRITICAL and not e.is_silenced()]
            criticals = [e for e in all_issues if checks.CRITICAL <= e.level and not e.is_silenced()]
            sorted_issues = [
                (criticals, 'CRITICALS'),
                (errors, 'ERRORS'),
                (warnings, 'WARNINGS'),
                (infos, 'INFOS'),
                (debugs, 'DEBUGS'),
            ]

            for issues, group_name in sorted_issues:
                if issues:
                    visible_issue_count += len(issues)
                    formatted = (
                        self.style.ERROR(str(e))
                        if e.is_serious()
                        else self.style.WARNING(str(e))
                        for e in issues)
                    formatted = "\n".join(sorted(formatted))
                    body += '\n%s:\n%s\n' % (group_name, formatted)

        if visible_issue_count:
            header = "System check identified some issues:\n"

        if display_num_errors:
            if visible_issue_count:
                footer += '\n'
            footer += "System check identified %s (%s silenced)." % (
                "no issues" if visible_issue_count == 0 else
                "1 issue" if visible_issue_count == 1 else
                "%s issues" % visible_issue_count,
                len(all_issues) - visible_issue_count,
            )

        if any(e.is_serious(fail_level) and not e.is_silenced() for e in all_issues):
            msg = self.style.ERROR("SystemCheckError: %s" % header) + body + footer
            raise SystemCheckError(msg)
        else:
            msg = header + body + footer

        if msg:
            if visible_issue_count:
                self.stderr.write(msg, lambda x: x)
            else:
                self.stdout.write(msg)

    def check_migrations(self):
        """
        Print a warning if the set of migrations on disk don't match the
        migrations in the database.
        """
        from django.db.migrations.executor import MigrationExecutor
        try:
            executor = MigrationExecutor(connections[DEFAULT_DB_ALIAS])
        except ImproperlyConfigured:
            # No databases are configured (or the dummy one)
            return

        plan = executor.migration_plan(executor.loader.graph.leaf_nodes())
        if plan:
            apps_waiting_migration = sorted({migration.app_label for migration, backwards in plan})
            self.stdout.write(
                self.style.NOTICE(
                    "\nYou have %(unpplied_migration_count)s unapplied migration(s). "
                    "Your project may not work properly until you apply the "
                    "migrations for app(s): %(apps_waiting_migration)s." % {
                        "unpplied_migration_count": len(plan),
                        "apps_waiting_migration": ", ".join(apps_waiting_migration),
                    }
                )
            )
            self.stdout.write(self.style.NOTICE("Run 'python manage.py migrate' to apply them.\n"))

    def handle(self, *args, **options):
        """
        The actual logic of the command. Subclasses must implement
        this method.
        """
        raise NotImplementedError('subclasses of BaseCommand must provide a handle() method')


class AppCommand(BaseCommand):
    """
    A management command which takes one or more installed application labels
    as arguments, and does something with each of them.

    Rather than implementing ``handle()``, subclasses must implement
    ``handle_app_config()``, which will be called once for each application.
    """
    missing_args_message = "Enter at least one application label."

    def add_arguments(self, parser):
        parser.add_argument('args', metavar='app_label', nargs='+', help='One or more application label.')

    def handle(self, *app_labels, **options):
        from django.apps import apps
        try:
            app_configs = [apps.get_app_config(app_label) for app_label in app_labels]
        except (LookupError, ImportError) as e:
            raise CommandError("%s. Are you sure your INSTALLED_APPS setting is correct?" % e)
        output = []
        for app_config in app_configs:
            app_output = self.handle_app_config(app_config, **options)
            if app_output:
                output.append(app_output)
        return '\n'.join(output)

    def handle_app_config(self, app_config, **options):
        """
        Perform the command's actions for app_config, an AppConfig instance
        corresponding to an application label given on the command line.
        """
        raise NotImplementedError(
            "Subclasses of AppCommand must provide"
            "a handle_app_config() method.")


class LabelCommand(BaseCommand):
    """
    A management command which takes one or more arbitrary arguments
    (labels) on the command line, and does something with each of
    them.

    Rather than implementing ``handle()``, subclasses must implement
    ``handle_label()``, which will be called once for each label.

    If the arguments should be names of installed applications, use
    ``AppCommand`` instead.
    """
    label = 'label'
    missing_args_message = "Enter at least one %s." % label

    def add_arguments(self, parser):
        parser.add_argument('args', metavar=self.label, nargs='+')

    def handle(self, *labels, **options):
        output = []
        for label in labels:
            label_output = self.handle_label(label, **options)
            if label_output:
                output.append(label_output)
        return '\n'.join(output)

    def handle_label(self, label, **options):
        """
        Perform the command's actions for ``label``, which will be the
        string as given on the command line.
        """
        raise NotImplementedError('subclasses of LabelCommand must provide a handle_label() method')
