"""Configuration management setup

Some terminology:
- name
  As written in config files.
- value
  Value associated with a name
- key
  Name combined with it's section (section.name)
- variant
  A single word describing where the configuration key-value pair came from
"""

import configparser
import locale
import logging
import os
import sys
from typing import Any, Dict, Iterable, List, NewType, Optional, Tuple

from pip._internal.exceptions import (
    ConfigurationError,
    ConfigurationFileCouldNotBeLoaded,
)
from pip._internal.utils import appdirs
from pip._internal.utils.compat import WINDOWS
from pip._internal.utils.misc import ensure_dir, enum

RawConfigParser = configparser.RawConfigParser  # Shorthand
Kind = NewType("Kind", str)

CONFIG_BASENAME = 'pip.ini' if WINDOWS else 'pip.conf'
ENV_NAMES_IGNORED = "version", "help"

# The kinds of configurations there are.
kinds = enum(
    USER="user",        # User Specific
    GLOBAL="global",    # System Wide
    SITE="site",        # [Virtual] Environment Specific
    ENV="env",          # from PIP_CONFIG_FILE
    ENV_VAR="env-var",  # from Environment Variables
)
OVERRIDE_ORDER = kinds.GLOBAL, kinds.USER, kinds.SITE, kinds.ENV, kinds.ENV_VAR
VALID_LOAD_ONLY = kinds.USER, kinds.GLOBAL, kinds.SITE

logger = logging.getLogger(__name__)


# NOTE: Maybe use the optionx attribute to normalize keynames.
def _normalize_name(name):
    # type: (str) -> str
    """Make a name consistent regardless of source (environment or file)
    """
    name = name.lower().replace('_', '-')
    if name.startswith('--'):
        name = name[2:]  # only prefer long opts
    return name


def _disassemble_key(name):
    # type: (str) -> List[str]
    if "." not in name:
        error_message = (
            "Key does not contain dot separated section and key. "
            "Perhaps you wanted to use 'global.{}' instead?"
        ).format(name)
        raise ConfigurationError(error_message)
    return name.split(".", 1)


def get_configuration_files():
    # type: () -> Dict[Kind, List[str]]
    global_config_files = [
        os.path.join(path, CONFIG_BASENAME)
        for path in appdirs.site_config_dirs('pip')
    ]

    site_config_file = os.path.join(sys.prefix, CONFIG_BASENAME)
    legacy_config_file = os.path.join(
        os.path.expanduser('~'),
        'pip' if WINDOWS else '.pip',
        CONFIG_BASENAME,
    )
    new_config_file = os.path.join(
        appdirs.user_config_dir("pip"), CONFIG_BASENAME
    )
    return {
        kinds.GLOBAL: global_config_files,
        kinds.SITE: [site_config_file],
        kinds.USER: [legacy_config_file, new_config_file],
    }


class Configuration:
    """Handles management of configuration.

    Provides an interface to accessing and managing configuration files.

    This class converts provides an API that takes "section.key-name" style
    keys and stores the value associated with it as "key-name" under the
    section "section".

    This allows for a clean interface wherein the both the section and the
    key-name are preserved in an easy to manage form in the configuration files
    and the data stored is also nice.
    """

    def __init__(self, isolated, load_only=None):
        # type: (bool, Optional[Kind]) -> None
        super().__init__()

        if load_only is not None and load_only not in VALID_LOAD_ONLY:
            raise ConfigurationError(
                "Got invalid value for load_only - should be one of {}".format(
                    ", ".join(map(repr, VALID_LOAD_ONLY))
                )
            )
        self.isolated = isolated
        self.load_only = load_only

        # Because we keep track of where we got the data from
        self._parsers = {
            variant: [] for variant in OVERRIDE_ORDER
        }  # type: Dict[Kind, List[Tuple[str, RawConfigParser]]]
        self._config = {
            variant: {} for variant in OVERRIDE_ORDER
        }  # type: Dict[Kind, Dict[str, Any]]
        self._modified_parsers = []  # type: List[Tuple[str, RawConfigParser]]

    def load(self):
        # type: () -> None
        """Loads configuration from configuration files and environment
        """
        self._load_config_files()
        if not self.isolated:
            self._load_environment_vars()

    def get_file_to_edit(self):
        # type: () -> Optional[str]
        """Returns the file with highest priority in configuration
        """
        assert self.load_only is not None, \
            "Need to be specified a file to be editing"

        try:
            return self._get_parser_to_modify()[0]
        except IndexError:
            return None

    def items(self):
        # type: () -> Iterable[Tuple[str, Any]]
        """Returns key-value pairs like dict.items() representing the loaded
        configuration
        """
        return self._dictionary.items()

    def get_value(self, key):
        # type: (str) -> Any
        """Get a value from the configuration.
        """
        try:
            return self._dictionary[key]
        except KeyError:
            raise ConfigurationError(f"No such key - {key}")

    def set_value(self, key, value):
        # type: (str, Any) -> None
        """Modify a value in the configuration.
        """
        self._ensure_have_load_only()

        assert self.load_only
        fname, parser = self._get_parser_to_modify()

        if parser is not None:
            section, name = _disassemble_key(key)

            # Modify the parser and the configuration
            if not parser.has_section(section):
                parser.add_section(section)
            parser.set(section, name, value)

        self._config[self.load_only][key] = value
        self._mark_as_modified(fname, parser)

    def unset_value(self, key):
        # type: (str) -> None
        """Unset a value in the configuration."""
        self._ensure_have_load_only()

        assert self.load_only
        if key not in self._config[self.load_only]:
            raise ConfigurationError(f"No such key - {key}")

        fname, parser = self._get_parser_to_modify()

        if parser is not None:
            section, name = _disassemble_key(key)
            if not (parser.has_section(section)
                    and parser.remove_option(section, name)):
                # The option was not removed.
                raise ConfigurationError(
                    "Fatal Internal error [id=1]. Please report as a bug."
                )

            # The section may be empty after the option was removed.
            if not parser.items(section):
                parser.remove_section(section)
            self._mark_as_modified(fname, parser)

        del self._config[self.load_only][key]

    def save(self):
        # type: () -> None
        """Save the current in-memory state.
        """
        self._ensure_have_load_only()

        for fname, parser in self._modified_parsers:
            logger.info("Writing to %s", fname)

            # Ensure directory exists.
            ensure_dir(os.path.dirname(fname))

            with open(fname, "w") as f:
                parser.write(f)

    #
    # Private routines
    #

    def _ensure_have_load_only(self):
        # type: () -> None
        if self.load_only is None:
            raise ConfigurationError("Needed a specific file to be modifying.")
        logger.debug("Will be working with %s variant only", self.load_only)

    @property
    def _dictionary(self):
        # type: () -> Dict[str, Any]
        """A dictionary representing the loaded configuration.
        """
        # NOTE: Dictionaries are not populated if not loaded. So, conditionals
        #       are not needed here.
        retval = {}

        for variant in OVERRIDE_ORDER:
            retval.update(self._config[variant])

        return retval

    def _load_config_files(self):
        # type: () -> None
        """Loads configuration from configuration files
        """
        config_files = dict(self.iter_config_files())
        if config_files[kinds.ENV][0:1] == [os.devnull]:
            logger.debug(
                "Skipping loading configuration files due to "
                "environment's PIP_CONFIG_FILE being os.devnull"
            )
            return

        for variant, files in config_files.items():
            for fname in files:
                # If there's specific variant set in `load_only`, load only
                # that variant, not the others.
                if self.load_only is not None and variant != self.load_only:
                    logger.debug(
                        "Skipping file '%s' (variant: %s)", fname, variant
                    )
                    continue

                parser = self._load_file(variant, fname)

                # Keeping track of the parsers used
                self._parsers[variant].append((fname, parser))

    def _load_file(self, variant, fname):
        # type: (Kind, str) -> RawConfigParser
        logger.debug("For variant '%s', will try loading '%s'", variant, fname)
        parser = self._construct_parser(fname)

        for section in parser.sections():
            items = parser.items(section)
            self._config[variant].update(self._normalized_keys(section, items))