# 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 os
import functools
import logging
import typing
import time
import zlib

from ...ext_json import json
from ..utils import StatsDB, NOT_GIVEN, ShardFileReader, EVICTION_POLICY, format_size
from ..lock import GenerationLock

log = logging.getLogger(__name__)


class BaseShard:
    storage_type: str = ''
    fs = None

    @classmethod
    def hash(cls, key):
        """Compute portable hash for `key`.

        :param key: key to hash
        :return: hash value

        """
        mask = 0xFFFFFFFF
        return zlib.adler32(key.encode('utf-8')) & mask  # noqa

    def _write_file(self, full_path, read_iterator, mode):
        raise NotImplementedError

    def _get_keyfile(self, key):
        raise NotImplementedError

    def random_filename(self):
        raise NotImplementedError

    def store(self, *args, **kwargs):
        raise NotImplementedError

    def _store(self, key, value_reader, metadata, mode):
        (filename,  # hash-name
         full_path  # full-path/hash-name
         ) = self.random_filename()

        key_file, key_file_path = self._get_keyfile(key)

        # STORE METADATA
        _metadata = {
            "version": "v1",

            "key_file": key_file,  # this is the .key.json file storing meta
            "key_file_path": key_file_path,  # full path to key_file
            "archive_key": key,  # original name we stored archive under, e.g my-archive.zip
            "archive_filename": filename,  # the actual filename we stored that file under
            "archive_full_path": full_path,

            "store_time": time.time(),
            "access_count": 0,
            "access_time": 0,

            "size": 0
        }
        if metadata:
            _metadata.update(metadata)

        read_iterator = iter(functools.partial(value_reader.read, 2**22), b'')
        size, sha256 = self._write_file(full_path, read_iterator, mode)
        _metadata['size'] = size
        _metadata['sha256'] = sha256

        # after archive is finished, we create a key to save the presence of the binary file
        with self.fs.open(key_file_path, 'wb') as f:
            f.write(json.dumps(_metadata))

        return key, filename, size, _metadata

    def fetch(self, *args, **kwargs):
        raise NotImplementedError

    def _fetch(self,  key, retry, retry_attempts, retry_backoff,
               presigned_url_expires: int = 0) -> tuple[ShardFileReader, dict]:
        if retry is NOT_GIVEN:
            retry = False
        if retry_attempts is NOT_GIVEN:
            retry_attempts = 0

        if retry and retry_attempts > 0:
            for attempt in range(1, retry_attempts + 1):
                if key in self:
                    break
                # we didn't find the key, wait retry_backoff N seconds, and re-check
                time.sleep(retry_backoff)

        if key not in self:
            log.exception(f'requested key={key} not found in {self} retry={retry}, attempts={retry_attempts}')
            raise KeyError(key)

        key_file, key_file_path = self._get_keyfile(key)
        with self.fs.open(key_file_path, 'rb') as f:
            metadata = json.loads(f.read())

        archive_path = metadata['archive_full_path']
        if presigned_url_expires and presigned_url_expires > 0:
            metadata['url'] = self.fs.url(archive_path, expires=presigned_url_expires)

        try:
            return ShardFileReader(self.fs.open(archive_path, 'rb')), metadata
        finally:
            # update usage stats, count and accessed
            metadata["access_count"] = metadata.get("access_count", 0) + 1
            metadata["access_time"] = time.time()
            log.debug('Updated %s with access snapshot, access_count=%s access_time=%s',
                      key_file, metadata['access_count'], metadata['access_time'])
            with self.fs.open(key_file_path, 'wb') as f:
                f.write(json.dumps(metadata))

    def remove(self, *args, **kwargs):
        raise NotImplementedError

    def _remove(self, key):
        if key not in self:
            log.exception(f'requested key={key} not found in {self}')
            raise KeyError(key)

        key_file, key_file_path = self._get_keyfile(key)
        with self.fs.open(key_file_path, 'rb') as f:
            metadata = json.loads(f.read())

        archive_path = metadata['archive_full_path']
        self.fs.rm(archive_path)
        self.fs.rm(key_file_path)
        return 1

    @property
    def storage_medium(self):
        return getattr(self, self.storage_type)

    @property
    def key_suffix(self):
        return 'key.json'

    def __contains__(self, key):
        """Return `True` if `key` matching item is found in cache.

        :param key: key matching item
        :return: True if key matching item

        """
        key_file, key_file_path = self._get_keyfile(key)
        return self.fs.exists(key_file_path)


class BaseCache:
    _locking_url: str = ''
    _storage_path: str = ''
    _config: dict = {}
    retry = False
    retry_attempts: int = 0
    retry_backoff: int | float = 1
    _shards = tuple()
    shard_cls = BaseShard
    # define the presigned url expiration, 0 == disabled
    presigned_url_expires: int = 0

    def __contains__(self, key):
        """Return `True` if `key` matching item is found in cache.

        :param key: key matching item
        :return: True if key matching item

        """
        return self.has_key(key)

    def __repr__(self):
        return f'<{self.__class__.__name__}(storage={self._storage_path})>'

    @classmethod
    def gb_to_bytes(cls, gb):
        return gb * (1024 ** 3)

    @property
    def storage_path(self):
        return self._storage_path

    @classmethod
    def get_stats_db(cls):
        return StatsDB()

    def get_conf(self, key, pop=False):
        if key not in self._config:
            raise ValueError(f"No configuration key '{key}', please make sure it exists in archive_cache config")
        val = self._config[key]
        if pop:
            del self._config[key]
        return val

    def _get_shard(self, key) -> shard_cls:
        index = self._hash(key) % self._shard_count
        shard = self._shards[index]
        return shard

    def _get_size(self, shard, archive_path):
        raise NotImplementedError

    def store(self, key, value_reader, metadata=None):
        shard = self._get_shard(key)
        return shard.store(key, value_reader, metadata)

    def fetch(self, key, retry=NOT_GIVEN, retry_attempts=NOT_GIVEN) -> tuple[typing.BinaryIO, dict]:
        """
        Return file handle corresponding to `key` from specific shard cache.
        """
        if retry is NOT_GIVEN:
            retry = self.retry
        if retry_attempts is NOT_GIVEN:
            retry_attempts = self.retry_attempts
        retry_backoff = self.retry_backoff
        presigned_url_expires = self.presigned_url_expires

        shard = self._get_shard(key)
        return shard.fetch(key, retry=retry,
                           retry_attempts=retry_attempts,
                           retry_backoff=retry_backoff,
                           presigned_url_expires=presigned_url_expires)

    def remove(self, key):
        shard = self._get_shard(key)
        return shard.remove(key)

    def has_key(self, archive_key):
        """Return `True` if `key` matching item is found in cache.

        :param archive_key: key for item, this is a unique archive name we want to store data under. e.g my-archive-svn.zip
        :return: True if key is found

        """
        shard = self._get_shard(archive_key)
        return archive_key in shard

    def iter_keys(self):
        for shard in self._shards:
            if shard.fs.exists(shard.storage_medium):
                for path, _dirs, _files in shard.fs.walk(shard.storage_medium):
                    for key_file_path in _files:
                        if key_file_path.endswith(shard.key_suffix):
                            yield shard, key_file_path

    def get_lock(self, lock_key):
        return GenerationLock(lock_key, self._locking_url)

    def evict(self, policy=None, size_limit=None) -> dict:
        """
        Remove old items based on the conditions


        explanation of this algo:
        iterate over each shard, then for each shard iterate over the .key files
        read the key files metadata stored. This gives us a full list of keys, cached_archived, their size and
        access data, time creation, and access counts.

        Store that into a memory DB in order we can run different sorting strategies easily.
        Summing the size is a sum sql query.

        Then we run a sorting strategy based on eviction policy.
        We iterate over sorted keys, and remove each checking if we hit the overall limit.
        """
        removal_info = {
            "removed_items": 0,
            "removed_size": 0
        }
        policy = policy or self._eviction_policy
        size_limit = size_limit or self._cache_size_limit

        select_policy = EVICTION_POLICY[policy]['evict']

        log.debug('Running eviction policy \'%s\', and checking for size limit: %s',
                  policy, format_size(size_limit))

        if select_policy is None:
            return removal_info

        db = self.get_stats_db()

        data = []
        cnt = 1

        for shard, key_file in self.iter_keys():
            with shard.fs.open(os.path.join(shard.storage_medium, key_file), 'rb') as f:
                metadata = json.loads(f.read())

            key_file_path = os.path.join(shard.storage_medium, key_file)

            archive_key = metadata['archive_key']
            archive_path = metadata['archive_full_path']

            size = metadata.get('size')
            if not size:
                # in case we don't have size re-calc it...
                size = self._get_size(shard, archive_path)

            data.append([
                cnt,
                key_file,
                key_file_path,
                archive_key,
                archive_path,
                metadata.get('store_time', 0),
                metadata.get('access_time', 0),
                metadata.get('access_count', 0),
                size,
            ])
            cnt += 1

        # Insert bulk data using executemany
        db.bulk_insert(data)

        total_size = db.get_total_size()
        log.debug('Analyzed %s keys, occupying: %s, running eviction to match %s',
                  len(data), format_size(total_size), format_size(size_limit))

        removed_items = 0
        removed_size = 0
        for key_file, archive_key, size in db.get_sorted_keys(select_policy):
            # simulate removal impact BEFORE removal
            total_size -= size

            if total_size <= size_limit:
                # we obtained what we wanted...
                break

            self.remove(archive_key)
            removed_items += 1
            removed_size += size
        removal_info['removed_items'] = removed_items
        removal_info['removed_size'] = removed_size
        log.debug('Removed %s cache archives, and reduced size by: %s',
                  removed_items, format_size(removed_size))
        return removal_info

    def get_statistics(self):
        total_files = 0
        total_size = 0
        meta = {}

        for shard, key_file in self.iter_keys():
            json_key = f"{shard.storage_medium}/{key_file}"
            with shard.fs.open(json_key, 'rb') as f:
                total_files += 1
                metadata = json.loads(f.read())
                total_size += metadata['size']

        return total_files, total_size, meta