"""Module containing shims around Flake8 2.x behaviour.

Previously, users would import :func:`get_style_guide` from ``flake8.engine``.
In 3.0 we no longer have an "engine" module but we maintain the API from it.
"""
import argparse
import logging
import os.path
from typing import Any
from typing import List
from typing import Optional
from typing import Type

import flake8
from flake8.discover_files import expand_paths
from flake8.formatting import base as formatter
from flake8.main import application as app
from flake8.options import config

LOG = logging.getLogger(__name__)


__all__ = ("get_style_guide",)


class Report:
    """Public facing object that mimic's Flake8 2.0's API.

    .. note::

        There are important changes in how this object behaves compared to
        the object provided in Flake8 2.x.

    .. warning::

        This should not be instantiated by users.

    .. versionchanged:: 3.0.0
    """

    def __init__(self, application: app.Application) -> None:
        """Initialize the Report for the user.

        .. warning:: This should not be instantiated by users.
        """
        assert application.guide is not None
        self._application = application
        self._style_guide = application.guide
        self._stats = self._style_guide.stats

    @property
    def total_errors(self) -> int:
        """Return the total number of errors."""
        return self._application.result_count

    def get_statistics(self, violation: str) -> List[str]:
        """Get the list of occurrences of a violation.

        :returns:
            List of occurrences of a violation formatted as:
            {Count} {Error Code} {Message}, e.g.,
            ``8 E531 Some error message about the error``
        """
        return [
            f"{s.count} {s.error_code} {s.message}"
            for s in self._stats.statistics_for(violation)
        ]


class StyleGuide:
    """Public facing object that mimic's Flake8 2.0's StyleGuide.

    .. note::

        There are important changes in how this object behaves compared to
        the StyleGuide object provided in Flake8 2.x.

    .. warning::

        This object should not be instantiated directly by users.

    .. versionchanged:: 3.0.0
    """

    def __init__(self, application: app.Application) -> None:
        """Initialize our StyleGuide."""
        self._application = application
        self._file_checker_manager = application.file_checker_manager

    @property
    def options(self) -> argparse.Namespace:
        """Return application's options.

        An instance of :class:`argparse.Namespace` containing parsed options.
        """
        assert self._application.options is not None
        return self._application.options

    @property
    def paths(self) -> List[str]:
        """Return the extra arguments passed as paths."""
        assert self._application.options is not None
        return self._application.options.filenames

    def check_files(self, paths: Optional[List[str]] = None) -> Report:
        """Run collected checks on the files provided.

        This will check the files passed in and return a :class:`Report`
        instance.

        :param paths:
            List of filenames (or paths) to check.
        :returns:
            Object that mimic's Flake8 2.0's Reporter class.
        """
        assert self._application.options is not None
        self._application.options.filenames = paths
        self._application.run_checks()
        self._application.report_errors()
        return Report(self._application)

    def excluded(self, filename: str, parent: Optional[str] = None) -> bool:
        """Determine if a file is excluded.

        :param filename:
            Path to the file to check if it is excluded.
        :param parent:
            Name of the parent directory containing the file.
        :returns:
            True if the filename is excluded, False otherwise.
        """

        def excluded(path: str) -> bool:
            paths = tuple(
                expand_paths(
                    paths=[path],
                    stdin_display_name=self.options.stdin_display_name,
                    filename_patterns=self.options.filename,
                    exclude=self.options.exclude,
                    is_running_from_diff=self.options.diff,
                )
            )
            return not paths

        return excluded(filename) or (
            parent is not None and excluded(os.path.join(parent, filename))
        )

    def init_report(
        self,
        reporter: Optional[Type[formatter.BaseFormatter]] = None,
    ) -> None:
        """Set up a formatter for this run of Flake8."""
        if reporter is None:
            return
        if not issubclass(reporter, formatter.BaseFormatter):
            raise ValueError(
                "Report should be subclass of "
                "flake8.formatter.BaseFormatter."
            )
        self._application.formatter = reporter(self.options)
        self._application.guide = None
        # NOTE(sigmavirus24): This isn't the intended use of
        # Application#make_guide but it works pretty well.
        # Stop cringing... I know it's gross.
        self._application.make_guide()
        self._application.file_checker_manager = None
        self._application.make_file_checker_manager()

    def input_file(
        self,
        filename: str,
        lines: Optional[Any] = None,
        expected: Optional[Any] = None,
        line_offset: Optional[Any] = 0,
    ) -> Report:
        """Run collected checks on a single file.

        This will check the file passed in and return a :class:`Report`
        instance.

        :param filename:
            The path to the file to check.
        :param lines:
            Ignored since Flake8 3.0.
        :param expected:
            Ignored since Flake8 3.0.
        :param line_offset:
            Ignored since Flake8 3.0.
        :returns:
            Object that mimic's Flake8 2.0's Reporter class.
        """
        return self.check_files([filename])


def get_style_guide(**kwargs: Any) -> StyleGuide:
    r"""Provision a StyleGuide for use.

    :param \*\*kwargs:
        Keyword arguments that provide some options for the StyleGuide.
    :returns:
        An initialized StyleGuide
    """
    application = app.Application()
    prelim_opts, remaining_args = application.parse_preliminary_options([])
    flake8.configure_logging(prelim_opts.verbose, prelim_opts.output_file)

    cfg, cfg_dir = config.load_config(
        config=prelim_opts.config,
        extra=prelim_opts.append_config,
        isolated=prelim_opts.isolated,
    )

    application.find_plugins(
        cfg,
        cfg_dir,
        enable_extensions=prelim_opts.enable_extensions,
        require_plugins=prelim_opts.require_plugins,
    )
    application.register_plugin_options()
    application.parse_configuration_and_cli(cfg, cfg_dir, remaining_args)
    # We basically want application.initialize to be called but with these
    # options set instead before we make our formatter, notifier, internal
    # style guide and file checker manager.
    options = application.options
    for key, value in kwargs.items():
        try:
            getattr(options, key)
            setattr(options, key, value)
        except AttributeError:
            LOG.error('Could not update option "%s"', key)
    application.make_formatter()
    application.make_guide()
    application.make_file_checker_manager()
    return StyleGuide(application)