from __future__ import absolute_import, unicode_literals
import io
import os
import sys

import warnings
import functools
from collections import defaultdict
from functools import partial
from functools import wraps
from importlib import import_module

from distutils.errors import DistutilsOptionError, DistutilsFileError
from setuptools.extern.packaging.version import LegacyVersion, parse
from setuptools.extern.six import string_types, PY3


__metaclass__ = type


def read_configuration(
        filepath, find_others=False, ignore_option_errors=False):
    """Read given configuration file and returns options from it as a dict.

    :param str|unicode filepath: Path to configuration file
        to get options from.

    :param bool find_others: Whether to search for other configuration files
        which could be on in various places.

    :param bool ignore_option_errors: Whether to silently ignore
        options, values of which could not be resolved (e.g. due to exceptions
        in directives such as file:, attr:, etc.).
        If False exceptions are propagated as expected.

    :rtype: dict
    """
    from setuptools.dist import Distribution, _Distribution

    filepath = os.path.abspath(filepath)

    if not os.path.isfile(filepath):
        raise DistutilsFileError(
            'Configuration file %s does not exist.' % filepath)

    current_directory = os.getcwd()
    os.chdir(os.path.dirname(filepath))

    try:
        dist = Distribution()

        filenames = dist.find_config_files() if find_others else []
        if filepath not in filenames:
            filenames.append(filepath)

        _Distribution.parse_config_files(dist, filenames=filenames)

        handlers = parse_configuration(
            dist, dist.command_options,
            ignore_option_errors=ignore_option_errors)

    finally:
        os.chdir(current_directory)

    return configuration_to_dict(handlers)


def _get_option(target_obj, key):
    """
    Given a target object and option key, get that option from
    the target object, either through a get_{key} method or
    from an attribute directly.
    """
    getter_name = 'get_{key}'.format(**locals())
    by_attribute = functools.partial(getattr, target_obj, key)
    getter = getattr(target_obj, getter_name, by_attribute)
    return getter()


def configuration_to_dict(handlers):
    """Returns configuration data gathered by given handlers as a dict.

    :param list[ConfigHandler] handlers: Handlers list,
        usually from parse_configuration()

    :rtype: dict
    """
    config_dict = defaultdict(dict)

    for handler in handlers:
        for option in handler.set_options:
            value = _get_option(handler.target_obj, option)
            config_dict[handler.section_prefix][option] = value

    return config_dict


def parse_configuration(
        distribution, command_options, ignore_option_errors=False):
    """Performs additional parsing of configuration options
    for a distribution.

    Returns a list of used option handlers.

    :param Distribution distribution:
    :param dict command_options:
    :param bool ignore_option_errors: Whether to silently ignore
        options, values of which could not be resolved (e.g. due to exceptions
        in directives such as file:, attr:, etc.).
        If False exceptions are propagated as expected.
    :rtype: list
    """
    options = ConfigOptionsHandler(
        distribution, command_options, ignore_option_errors)
    options.parse()

    meta = ConfigMetadataHandler(
        distribution.metadata, command_options, ignore_option_errors,
        distribution.package_dir)
    meta.parse()

    return meta, options


class ConfigHandler:
    """Handles metadata supplied in configuration files."""

    section_prefix = None
    """Prefix for config sections handled by this handler.
    Must be provided by class heirs.

    """

    aliases = {}
    """Options aliases.
    For compatibility with various packages. E.g.: d2to1 and pbr.
    Note: `-` in keys is replaced with `_` by config parser.

    """

    def __init__(self, target_obj, options, ignore_option_errors=False):
        sections = {}

        section_prefix = self.section_prefix
        for section_name, section_options in options.items():
            if not section_name.startswith(section_prefix):
                continue

            section_name = section_name.replace(section_prefix, '').strip('.')
            sections[section_name] = section_options

        self.ignore_option_errors = ignore_option_errors
        self.target_obj = target_obj
        self.sections = sections
        self.set_options = []

    @property
    def parsers(self):
        """Metadata item name to parser function mapping."""
        raise NotImplementedError(
            '%s must provide .parsers property' % self.__class__.__name__)

    def __setitem__(self, option_name, value):
        unknown = tuple()
        target_obj = self.target_obj

        # Translate alias into real name.
        option_name = self.aliases.get(option_name, option_name)

        current_value = getattr(target_obj, option_name, unknown)

        if current_value is unknown:
            raise KeyError(option_name)

        if current_value:
            # Already inhabited. Skipping.
            return

        skip_option = False
        parser = self.parsers.get(option_name)
        if parser:
            try:
                value = parser(value)

            except Exception:
                skip_option = True
                if not self.ignore_option_errors:
                    raise

        if skip_option:
            return

        setter = getattr(target_obj, 'set_%s' % option_name, None)
        if setter is None:
            setattr(target_obj, option_name, value)
        else:
            setter(value)

        self.set_options.append(option_name)

    @classmethod
    def _parse_list(cls, value, separator=','):
        """Represents value as a list.

        Value is split either by separator (defaults to comma) or by lines.

        :param value:
        :param separator: List items separator character.
        :rtype: list
        """
        if isinstance(value, list):  # _get_parser_compound case
            return value

        if '\n' in value:
            value = value.splitlines()
        else:
            value = value.split(separator)

        return [chunk.strip() for chunk in value if chunk.strip()]

    @classmethod
    def _parse_dict(cls, value):
        """Represents value as a dict.

        :param value:
        :rtype: dict
        """
        separator = '='
        result = {}
        for line in cls._parse_list(value):
            key, sep, val = line.partition(separator)
            if sep != separator:
                raise DistutilsOptionError(
                    'Unable to parse option value to dict: %s' % value)
            result[key.strip()] = val.strip()

        return result

    @classmethod
    def _parse_bool(cls, value):
        """Represents value as boolean.

        :param value:
        :rtype: bool
        """
        value = value.lower()
        return value in ('1', 'true', 'yes')

    @classmethod
    def _parse_file(cls, value):
        """Represents value as a string, allowing including text
        from nearest files using `file:` directive.

        Directive is sandboxed and won't reach anything outside
        directory with setup.py.

        Examples:
            file: LICENSE
            file: README.rst, CHANGELOG.md, src/file.txt

        :param str value:
        :rtype: str
        """
        include_directive = 'file:'

        if not isinstance(value, string_types):
            return value

        if not value.startswith(include_directive):
            return value

        spec = value[len(include_directive):]
        filepaths = (os.path.abspath(path.strip()) for path in spec.split(','))
        return '\n'.join(
            cls._read_file(path)
            for path in filepaths
            if (cls._assert_local(path) or True)
            and os.path.isfile(path)
        )

    @staticmethod
    def _assert_local(filepath):
        if not filepath.startswith(os.getcwd()):
            raise DistutilsOptionError(
                '`file:` directive can not access %s' % filepath)

    @staticmethod
    def _read_file(filepath):
        with io.open(filepath, encoding='utf-8') as f:
            return f.read()

    @classmethod
    def _parse_attr(cls, value, package_dir=None):
        """Represents value as a module attribute.

        Examples:
            attr: package.attr
            attr: package.module.attr

        :param str value:
        :rtype: str
        """
        attr_directive = 'attr:'
        if not value.startswith(attr_directive):
            return value

        attrs_path = value.replace(attr_directive, '').strip().split('.')
        attr_name = attrs_path.pop()

        module_name = '.'.join(attrs_path)
        module_name = module_name or '__init__'

        parent_path = os.getcwd()
        if package_dir:
            if attrs_path[0] in package_dir:
                # A custom path was specified for the module we want to import
                custom_path = package_dir[attrs_path[0]]
                parts = custom_path.rsplit('/', 1)
                if len(parts) > 1:
                    parent_path = os.path.join(os.getcwd(), parts[0])
                    module_name = parts[1]
                else:
                    module_name = custom_path
            elif '' in package_dir:
                # A custom parent directory was specified for all root modules
                parent_path = os.path.join(os.getcwd(), package_dir[''])
        sys.path.insert(0, parent_path)
        try:
            module = import_module(module_name)
            value = getattr(module, attr_name)

        finally:
            sys.path = sys.path[1:]

        return value

    @classmethod
    def _get_parser_compound(cls, *parse_methods):
        """Returns parser function to represents value as a list.

        Parses a value applying given methods one after another.

        :param parse_methods:
        :rtype: callable
        """