# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at https://mozilla.org/MPL/2.0/.

import json
import re
from functools import wraps
from hashlib import md5

from django.conf import settings
from django.core.cache import caches
from django.utils.encoding import force_bytes
from django.utils.functional import cached_property, lazy

from fluent.runtime import FluentLocalization, FluentResource
from fluent.syntax.ast import GroupComment, Message

from lib.l10n_utils import translation

__all__ = [
    "fluent_l10n",
    "ftl",
    "ftl_file_is_active",
    "ftl_has_messages",
    "ftl_lazy",
    "get_metadata_file_path",
    "has_messages",
    "translate",
]
cache = caches["fluent"]
REQUIRED_RE = re.compile(r"^required\b", re.MULTILINE | re.IGNORECASE)
TERM_RE = re.compile(r"\{\s*-[a-z-]+\s*\}")


class FluentL10n(FluentLocalization):
    def _localized_bundles(self):
        for bundle in self._bundles():
            if bundle.locales[0] == self.locales[0]:
                yield bundle

    @cached_property
    def _message_ids(self):
        messages = set()
        for bundle in self._bundles():
            messages.update(bundle._messages.keys())

        return list(messages)

    @cached_property
    def _localized_message_ids(self):
        messages = set()
        for bundle in self._localized_bundles():
            messages.update(bundle._messages.keys())

        return list(messages)

    @cached_property
    def required_message_ids(self):
        """
        Look in the "en" file for message IDs grouped by a comment that starts with "Required"

        :return: list of message IDs
        """
        messages = set()
        for resources in self.resource_loader.resources("en", self.resource_ids):
            for resource in resources:
                in_required = False
                for item in resource.body:
                    if isinstance(item, GroupComment):
                        in_required = REQUIRED_RE.search(item.content)
                        continue

                    if isinstance(item, Message) and in_required:
                        messages.add(item.id.name)

        return list(messages)

    @cached_property
    def has_required_messages(self):
        return all(self.has_message(m) for m in self.required_message_ids)

    @cached_property
    def active_locales(self):
        # first resource is the one to check for activation
        return get_active_locales(self.resource_ids[0])

    @cached_property
    def percent_translated(self):
        if not self._message_ids:
            return 0

        return (float(len(self._localized_message_ids)) / float(len(self._message_ids))) * 100

    def has_message(self, message_id):
        # assume English locales have the message
        if self.locales[0].startswith("en-"):
            return True

        return message_id in self._localized_message_ids


class FluentResourceLoader:
    """A resource loader that will add english brand terms to every bundle"""

    @staticmethod
    def resources(locale, resource_ids):
        for root in settings.FLUENT_PATHS:
            resources = load_fluent_resources(root, locale, resource_ids)
            if resources:
                yield resources


def _cache_key(*args, **kwargs):
    key = f"fluent:{args}:{kwargs}"
    return md5(force_bytes(key)).hexdigest()


def memoize(f):
    """Decorator to cache the results of expensive functions"""

    @wraps(f)
    def inner(*args, **kwargs):
        key = _cache_key(f.__name__, *args, **kwargs)
        value = cache.get(key)
        if value is None:
            value = f(*args, **kwargs)
            cache.set(key, value)

        return value

    return inner


def l10nize(f):
    """Decorator to create and pass in the l10n object"""

    @wraps(f)
    def inner(*args, **kwargs):
        ftl_files = kwargs.get("ftl_files", [])
        if isinstance(ftl_files, str):
            ftl_files = [ftl_files]
        elif isinstance(ftl_files, tuple):
            ftl_files = list(ftl_files)

        # can not use += here because that mutates the original list
        ftl_files = ftl_files + settings.FLUENT_DEFAULT_FILES
        locale = kwargs.get("locale") or translation.get_language()
        locales = [locale]
        if locale != "en":
            locales.append("en")
        l10n = fluent_l10n(locales, ftl_files)
        return f(l10n, *args, **kwargs)

    return inner


@memoize
def load_fluent_resources(root, locale, resource_ids):
    resources = []
    for resource_id in resource_ids:
        path = root.joinpath(locale, resource_id)
        if not path.is_file():
            continue

        resources.append(load_fluent_file(path))
    if resources:
        if locale != "en":
            path = settings.FLUENT_LOCAL_PATH.joinpath("en", "brands.ftl")
            resources.append(load_fluent_file(path))
    return resources


@memoize
def load_fluent_file(path):
    with path.open(encoding="utf-8") as ftl_file:
        return FluentResource(ftl_file.read())


def get_metadata_file_path(ftl_file):
    return settings.FLUENT_REPO_PATH.joinpath("metadata", ftl_file).with_suffix(".json")


def get_metadata(ftl_file):
    path = get_metadata_file_path(ftl_file)
    try:
        with path.open() as mdf:
            return json.load(mdf)
    except (OSError, ValueError):
        return {}


def write_metadata(ftl_file, data):
    metadata_path = get_metadata_file_path(ftl_file)
    if not metadata_path.exists():
        metadata_path.parent.mkdir(parents=True, exist_ok=True)

    with metadata_path.open("w") as mdf:
        json.dump(data, mdf, indent=2, sort_keys=True)


@memoize
def get_active_locales(ftl_files, force=False):
    """Return the list of active locales for a Fluent file.

    If `settings.DEV` is `True` it will just return the full list of
    available languages. You can pass `force=True` to override this
    behavior.
    """
    if settings.DEV and not force:
        return settings.DEV_LANGUAGES

    if isinstance(ftl_files, str):
        ftl_files = [ftl_files]

    locales = {settings.LANGUAGE_CODE}
    for ftl_file in ftl_files:
        file_locales = set()
        metadata = get_metadata(ftl_file)
        if metadata and "active_locales" in metadata:
            file_locales.update(metadata["active_locales"])
            i_locales = metadata.get("inactive_locales")
            if i_locales:
                file_locales.difference_update(i_locales)

        locales.update(file_locales)

    return sorted(locales)


def ftl_file_is_active(ftl_file, locale=None):
    """Return True if the given FTL file is active in the given locale."""
    locale = locale or translation.get_language()
    return locale in get_active_locales(ftl_file)


def fluent_l10n(locales, files):
    if isinstance(locales, str):
        locales = [locales]

    # file IDs may not have file extension
    files = [f"{f}.ftl" if not f.endswith(".ftl") else f for f in files]
    return FluentL10n(locales, files, FluentResourceLoader)


def ftl_has_messages(l10n, *message_ids, require_all=True):
    test = all if require_all else any
    return test([l10n.has_message(mid) for mid in message_ids])


def translate(l10n, message_id, fallback=None, **kwargs):
    # check the `locale` bundle for the message if we have a fallback defined
    if fallback and l10n.has_message(fallback) and not l10n.has_message(message_id):
        message_id = fallback

    return l10n.format_value(message_id, kwargs)


# View Utils

# for use in python views
has_messages = l10nize(ftl_has_messages)
ftl = l10nize(translate)

# for use in python outside of a view
ftl_lazy = lazy(ftl, str)