# Copyright (C) 2015-2024 RhodeCode GmbH
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License, version 3
# (only), as published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
# This program is dual-licensed. If you wish to learn more about the
# RhodeCode Enterprise Edition, including its added features, Support services,
# and proprietary license terms, please see https://rhodecode.com/licenses/

import errno
import fcntl
import functools
import logging
import os
import pickle
import time

import gevent
import msgpack
import redis

flock_org = fcntl.flock
from typing import Union

from dogpile.cache.api import Deserializer, Serializer
from dogpile.cache.backends import file as file_backend
from dogpile.cache.backends import memory as memory_backend
from dogpile.cache.backends import redis as redis_backend
from dogpile.cache.backends.file import FileLock
from dogpile.cache.util import memoized_property

from ...lib.memory_lru_dict import LRUDict, LRUDictDebug
from ...lib.str_utils import safe_bytes, safe_str
from ...lib.type_utils import str2bool

_default_max_size = 1024

log = logging.getLogger(__name__)


class LRUMemoryBackend(memory_backend.MemoryBackend):
    key_prefix = 'lru_mem_backend'
    pickle_values = False

    def __init__(self, arguments):
        self.max_size = arguments.pop('max_size', _default_max_size)

        LRUDictClass = LRUDict
        if arguments.pop('log_key_count', None):
            LRUDictClass = LRUDictDebug

        arguments['cache_dict'] = LRUDictClass(self.max_size)
        super().__init__(arguments)

    def __repr__(self):
        return f'{self.__class__}(maxsize=`{self.max_size}`)'

    def __str__(self):
        return self.__repr__()

    def delete(self, key):
        try:
            del self._cache[key]
        except KeyError:
            # we don't care if key isn't there at deletion
            pass

    def list_keys(self, prefix):
        return list(self._cache.keys())

    def delete_multi(self, keys):
        for key in keys:
            self.delete(key)

    def delete_multi_by_prefix(self, prefix):
        cache_keys = self.list_keys(prefix=prefix)
        num_affected_keys = len(cache_keys)
        if num_affected_keys:
            self.delete_multi(cache_keys)
        return num_affected_keys


class PickleSerializer:
    serializer: None | Serializer = staticmethod(  # type: ignore
        functools.partial(pickle.dumps, protocol=pickle.HIGHEST_PROTOCOL)
    )
    deserializer: None | Deserializer = staticmethod(  # type: ignore
        functools.partial(pickle.loads)
    )


class MsgPackSerializer:
    serializer: None | Serializer = staticmethod(  # type: ignore
        msgpack.packb
    )
    deserializer: None | Deserializer = staticmethod(  # type: ignore
        functools.partial(msgpack.unpackb, use_list=False)
    )


class CustomLockFactory(FileLock):

    @memoized_property
    def _module(self):

        def gevent_flock(fd, operation):
            """
            Gevent compatible flock
            """
            # set non-blocking, this will cause an exception if we cannot acquire a lock
            operation |= fcntl.LOCK_NB
            start_lock_time = time.time()
            timeout = 60 * 15  # 15min
            while True:
                try:
                    flock_org(fd, operation)
                    # lock has been acquired
                    break
                except (OSError, IOError) as e:
                    # raise on other errors than Resource temporarily unavailable
                    if e.errno != errno.EAGAIN:
                        raise
                    elif (time.time() - start_lock_time) > timeout:
                        # waited to much time on a lock, better fail than loop for ever
                        log.error('Failed to acquire lock on `%s` after waiting %ss',
                                  self.filename, timeout)
                        raise
                    wait_timeout = 0.03
                    log.debug('Failed to acquire lock on `%s`, retry in %ss',
                              self.filename, wait_timeout)
                    gevent.sleep(wait_timeout)

        fcntl.flock = gevent_flock
        return fcntl


class FileNamespaceBackend(PickleSerializer, file_backend.DBMBackend):
    key_prefix = 'file_backend'

    def __init__(self, arguments):
        arguments['lock_factory'] = CustomLockFactory
        db_file = arguments.get('filename')

        log.debug('initialing cache-backend=%s db in %s', self.__class__.__name__, db_file)
        db_file_dir = os.path.dirname(db_file)
        if not os.path.isdir(db_file_dir):
            os.makedirs(db_file_dir)

        try:
            super().__init__(arguments)
        except Exception:
            log.exception('Failed to initialize db at: %s', db_file)
            raise

    def __repr__(self):
        return f'{self.__class__}(file=`{self.filename}`)'

    def __str__(self):
        return self.__repr__()

    def _get_keys_pattern(self, prefix: bytes = b''):
        return b'%b:%b' % (safe_bytes(self.key_prefix), safe_bytes(prefix))

    def list_keys(self, prefix: bytes = b''):
        prefix = self._get_keys_pattern(prefix)

        def cond(dbm_key: bytes):
            if not prefix:
                return True

            if dbm_key.startswith(prefix):
                return True
            return False

        with self._dbm_file(True) as dbm:
            try:
                return list(filter(cond, dbm.keys()))
            except Exception:
                log.error('Failed to fetch DBM keys from DB: %s', self.get_store())
                raise

    def delete_multi_by_prefix(self, prefix):
        cache_keys = self.list_keys(prefix=prefix)
        num_affected_keys = len(cache_keys)
        if num_affected_keys:
            self.delete_multi(cache_keys)
        return num_affected_keys

    def get_store(self):
        return self.filename

    def cleanup_store(self):
        for ext in ("db", "dat", "pag", "dir"):
            final_filename = self.filename + os.extsep + ext
            if os.path.exists(final_filename):
                os.remove(final_filename)
                log.warning('Removed dbm file %s', final_filename)


class BaseRedisBackend(redis_backend.RedisBackend):
    key_prefix = ''

    def __init__(self, arguments):
        self.db_conn = arguments.get('host', '') or arguments.get('url', '') or 'redis-host'
        super().__init__(arguments)

        self._lock_timeout = self.lock_timeout
        self._lock_auto_renewal = str2bool(arguments.pop("lock_auto_renewal", True))

        self._store_key_prefix = arguments.pop('key_prefix', '')
        self.key_prefix = f'{self._store_key_prefix}{self.key_prefix}'

        if self._lock_auto_renewal and not self._lock_timeout:
            # set default timeout for auto_renewal
            self._lock_timeout = 30

    def __repr__(self):
        return f'{self.__class__}(conn=`{self.db_conn}`)'

    def __str__(self):
        return self.__repr__()

    def _create_client(self):
        args = {}

        if self.url is not None:
            args.update(url=self.url)

        else:
            args.update(
                host=self.host, password=self.password,
                port=self.port, db=self.db
            )

        connection_pool = redis.ConnectionPool(**args)
        self.writer_client = redis.StrictRedis(
            connection_pool=connection_pool
        )
        self.reader_client = self.writer_client

    def _get_keys_pattern(self, prefix: bytes = b''):
        return b'%b:%b*' % (safe_bytes(self.key_prefix), safe_bytes(prefix))

    def list_keys(self, prefix: bytes = b''):
        prefix = self._get_keys_pattern(prefix)
        return self.reader_client.keys(prefix)

    def delete_multi_by_prefix(self, prefix, use_lua=False):
        if use_lua:
            # high efficient LUA script to delete ALL keys by prefix...
            lua = """local keys = redis.call('keys', ARGV[1])
                     for i=1,#keys,5000 do
                     redis.call('del', unpack(keys, i, math.min(i+(5000-1), #keys)))
                     end
                     return #keys"""
            num_affected_keys = self.writer_client.eval(
                lua,
                0,
                f"{prefix}*")
        else:
            cache_keys = self.list_keys(prefix=prefix)
            num_affected_keys = len(cache_keys)
            if num_affected_keys:
                self.delete_multi(cache_keys)
        return num_affected_keys

    def get_store(self):
        return self.reader_client.connection_pool

    def get_mutex(self, key):
        if self.distributed_lock:
            lock_key = f'{self._store_key_prefix}_lock_{safe_str(key)}'
            return get_mutex_lock(
                self.writer_client, lock_key,
                self._lock_timeout,
                auto_renewal=self._lock_auto_renewal
            )
        else:
            return None


class RedisPickleBackend(PickleSerializer, BaseRedisBackend):
    key_prefix = 'redis_pickle_backend'
    pass


class RedisMsgPackBackend(MsgPackSerializer, BaseRedisBackend):
    key_prefix = 'redis_msgpack_backend'
    pass


def get_mutex_lock(client, lock_key, lock_timeout, auto_renewal=False):
    from ...lib._vendor import redis_lock

    class _RedisLockWrapper:
        """LockWrapper for redis_lock"""

        @classmethod
        def get_lock(cls):
            return redis_lock.Lock(
                redis_client=client,
                name=lock_key,
                expire=lock_timeout,
                auto_renewal=auto_renewal,
                strict=True,
            )

        def __repr__(self):
            return f"{self.__class__.__name__}:{lock_key}"

        def __str__(self):
            return f"{self.__class__.__name__}:{lock_key}"

        def __init__(self):
            self.lock = self.get_lock()
            self.lock_key = lock_key

        def acquire(self, wait=True):
            log.debug('Trying to acquire Redis lock for key %s', self.lock_key)
            try:
                acquired = self.lock.acquire(wait)
                log.debug('Got lock for key %s, %s', self.lock_key, acquired)
                return acquired
            except redis_lock.AlreadyAcquired:
                return False
            except redis_lock.AlreadyStarted:
                # refresh thread exists, but it also means we acquired the lock
                return True

        def release(self):
            try:
                self.lock.release()
            except redis_lock.NotAcquired:
                pass

    return _RedisLockWrapper()