from __future__ import annotations

import json
import os
import string
from configparser import RawConfigParser
from itertools import chain
from typing import IO
from typing import Any
from typing import Generator

from .. import PROJECT_HOME
from .. import exceptions
from ..utils import cached_property
from ..utils import expand_path
from ..vobject import Item
from .fetchparams import expand_fetch_params
from .utils import storage_class_from_config

GENERAL_ALL = frozenset(["status_path"])
GENERAL_REQUIRED = frozenset(["status_path"])
SECTION_NAME_CHARS = frozenset(chain(string.ascii_letters, string.digits, "_"))


def validate_section_name(name, section_type):
    invalid = set(name) - SECTION_NAME_CHARS
    if invalid:
        chars_display = "".join(sorted(SECTION_NAME_CHARS))
        raise exceptions.UserError(
            f'The {section_type}-section "{name}" contains invalid characters. Only '
            "the following characters are allowed for storage and "
            f"pair names:\n{chars_display}"
        )


def _validate_general_section(general_config: dict[str, str]):
    invalid = set(general_config) - GENERAL_ALL
    missing = GENERAL_REQUIRED - set(general_config)
    problems: list[str] = []

    if invalid:
        problems.append(
            "general section doesn't take the parameters: {}".format(", ".join(invalid))
        )

    if missing:
        problems.append(
            "general section is missing the parameters: {}".format(", ".join(missing))
        )

    if problems:
        raise exceptions.UserError(
            "Invalid general section. Copy the example "
            f"config from the repository and edit it: {PROJECT_HOME}",
            problems=problems,
        )


def _validate_collections_param(collections):
    if collections is None:
        return

    if not isinstance(collections, list):
        raise ValueError("`collections` parameter must be a list or `null`.")

    collection_names = set()

    for i, collection in enumerate(collections):
        try:
            if isinstance(collection, (str, bytes)):
                collection_name = collection
            elif isinstance(collection, list):
                e = ValueError(
                    "Expected list of format "
                    '["config_name", "storage_a_name", "storage_b_name"]'
                )
                if len(collection) != 3:
                    raise e

                if not isinstance(collection[0], (str, bytes)):
                    raise e

                for x in collection[1:]:
                    if x is not None and not isinstance(x, (str, bytes)):
                        raise e

                collection_name = collection[0]
            else:
                raise ValueError("Expected string or list of three strings.")

            if collection_name in collection_names:
                raise ValueError("Duplicate value.")
            collection_names.add(collection_name)
        except ValueError as e:
            raise ValueError(f"`collections` parameter, position {i}: {str(e)}")


class _ConfigReader:
    def __init__(self, f: IO[Any]):
        self._file: IO[Any] = f
        self._parser = c = RawConfigParser()
        c.read_file(f)
        self._seen_names: set = set()

        self._general: dict[str, str] = {}
        self._pairs: dict[str, dict[str, str]] = {}
        self._storages: dict[str, dict[str, str]] = {}

    def _parse_section(
        self, section_type: str, name: str, options: dict[str, Any]
    ) -> None:
        validate_section_name(name, section_type)
        if name in self._seen_names:
            raise ValueError(f'Name "{name}" already used.')
        self._seen_names.add(name)

        if section_type == "general":
            if self._general:
                raise ValueError("More than one general section.")
            self._general = options
        elif section_type == "storage":
            self._storages[name] = options
        elif section_type == "pair":
            self._pairs[name] = options
        else:
            raise ValueError("Unknown section type.")

    def parse(
        self,
    ) -> tuple[dict[str, str], dict[str, dict[str, str]], dict[str, dict[str, str]]]:
        for section in self._parser.sections():
            if " " in section:
                section_type, name = section.split(" ", 1)
            else:
                section_type = name = section

            try:
                self._parse_section(
                    section_type,
                    name,
                    dict(_parse_options(self._parser.items(section), section=section)),
                )
            except ValueError as e:
                raise exceptions.UserError(f'Section "{section}": {str(e)}')

        _validate_general_section(self._general)
        if getattr(self._file, "name", None):
            self._general["status_path"] = os.path.join(
                os.path.dirname(self._file.name),
                expand_path(self._general["status_path"]),
            )

        return self._general, self._pairs, self._storages


def _parse_options(
    items: list[tuple[str, str]], section: str | None = None
) -> Generator[tuple[str, dict[str, str]], None, None]:
    for key, value in items:
        try:
            yield key, json.loads(value)
        except ValueError as e:
            raise ValueError(f'Section "{section}", option "{key}": {e}')


class Config:
    def __init__(
        self,
        general: dict[str, str],
        pairs: dict[str, dict[str, str]],
        storages: dict[str, dict[str, str]],
    ) -> None:
        self.general = general
        self.storages = storages
        for name, options in storages.items():
            options["instance_name"] = name

        self.pairs: dict[str, PairConfig] = {}
        for name, options in pairs.items():
            try:
                self.pairs[name] = PairConfig(self, name, options)
            except ValueError as e:
                raise exceptions.UserError(f"Pair {name}: {e}")

    @classmethod
    def from_fileobject(cls, f: IO[Any]):
        reader = _ConfigReader(f)
        return cls(*reader.parse())

    @classmethod
    def from_filename_or_environment(cls, fname: str | None = None):
        if fname is None:
            fname = os.environ.get("VDIRSYNCER_CONFIG", None)
        if fname is None:
            fname = expand_path("~/.vdirsyncer/config")
            if not os.path.exists(fname):
                xdg_config_dir = os.environ.get(
                    "XDG_CONFIG_HOME", expand_path("~/.config/")
                )
                fname = os.path.join(xdg_config_dir, "vdirsyncer/config")

        try:
            with open(fname) as f:
                return cls.from_fileobject(f)
        except Exception as e:
            raise exceptions.UserError(f"Error during reading config {fname}: {e}")

    def get_storage_args(self, storage_name: str):
        try:
            args = self.storages[storage_name]
        except KeyError:
            raise exceptions.UserError(
                f"Storage {storage_name!r} not found. "
                f"These are the configured storages: {list(self.storages)}"
            )
        else:
            return expand_fetch_params(args)

    def get_pair(self, pair_name: str) -> PairConfig:
        try:
            return self.pairs[pair_name]
        except KeyError as e:
            raise exceptions.PairNotFound(e, pair_name=pair_name)


class PairConfig:
    def __init__(self, full_config: Config, name: str, options: dict[str, str]):
        self._config: Config = full_config
        self.name: str = name
        self.name_a: str = options.pop("a")
        self.name_b: str = options.pop("b")

        self._partial_sync: str | None = options.pop("partial_sync", None)
        self.metadata = options.pop("metadata", None) or ()

        self.conflict_resolution = self._process_conflict_resolution_param(
            options.pop("conflict_resolution", None)
        )

        try:
            self.collections = options.pop("collections")
        except KeyError:
            raise ValueError(
                "collections parameter missing.\n\n"
                "As of 0.9.0 this parameter has no default anymore. "
                "Set `collections = null` explicitly in your pair config."
            )
        else:
            _validate_collections_param(self.collections)

        if options:
            raise ValueError("Unknown options: {}".format(", ".join(options)))

    def _process_conflict_resolution_param(
        self, conflict_resolution: str | list[str] | None
    ):
        if conflict_resolution in (None, "a wins", "b wins"):
            return conflict_resolution
        elif (
            isinstance(conflict_resolution, list)
            and len(conflict_resolution) > 1
            and conflict_resolution[0] == "command"
        ):

            def resolve(a, b):
                a_name = self.config_a["instance_name"]
                b_name = self.config_b["instance_name"]
                command = conflict_resolution[1:]

                return _resolve_conflict_via_command(a, b, command, a_name, b_name)

            return resolve
        else:
            raise ValueError("Invalid value for `conflict_resolution`.")

    # The following parameters are lazily evaluated because evaluating
    # self.config_a would expand all `x.fetch` parameters. This is costly and
    # unnecessary if the pair is not actually synced.

    @cached_property
    def config_a(self):
        return self._config.get_storage_args(self.name_a)

    @cached_property
    def config_b(self):
        return self._config.get_storage_args(self.name_b)

    @cached_property
    def partial_sync(self):
        partial_sync = self._partial_sync
        # We need to use UserError here because ValueError is not
        # caught at the time this is expanded.

        if partial_sync is not None:
            cls_a, _ = storage_class_from_config(self.config_a)
            cls_b, _ = storage_class_from_config(self.config_b)

            if (
                not cls_a.read_only
                and not self.config_a.get("read_only", False)
                and not cls_b.read_only
                and not self.config_b.get("read_only", False)
            ):
                raise exceptions.UserError(
                    "`partial_sync` is only effective if one storage is "
                    "read-only. Use `read_only = true` in exactly one storage "
                    "section."
                )

        if partial_sync is None:
            partial_sync = "revert"

        if partial_sync not in ("ignore", "revert", "error"):
            raise exceptions.UserError("Invalid value for `partial_sync`.")

        return partial_sync


class CollectionConfig:
    def __init__(self, pair, name: str, config_a, config_b):
        self.pair = pair
        self._config = pair._config
        self.name: str = name
        self.config_a = config_a
        self.config_b = config_b


#: Public API. Khal's config wizard depends on this function.
load_config = Config.from_filename_or_environment


def _resolve_conflict_via_command(
    a, b, command, a_name, b_name, _check_call=None
) -> Item:
    import shutil
    import tempfile

    if _check_call is None:
        from subprocess import check_call as _check_call

    from ..vobject import Item

    dir = tempfile.mkdtemp(prefix="vdirsyncer-conflict.")
    try:
        a_tmp = os.path.join(dir, a_name)
        b_tmp = os.path.join(dir, b_name)

        with open(a_tmp, "w") as f:
            f.write(a.raw)
        with open(b_tmp, "w") as f:
            f.write(b.raw)

        command[0] = expand_path(command[0])
        _check_call(command + [a_tmp, b_tmp])

        with open(a_tmp) as f:
            new_a = f.read()
        with open(b_tmp) as f:
            new_b = f.read()

        if new_a != new_b:
            raise exceptions.UserError("The two files are not completely " "equal.")
        return Item(new_a)
    finally:
        shutil.rmtree(dir)
