# 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 functools
import logging
import os
import threading
import time

import decorator
from dogpile.cache import CacheRegion

import rhodecode
from rhodecode.lib.hash_utils import sha1
from rhodecode.lib.str_utils import safe_bytes
from rhodecode.lib.type_utils import str2bool # noqa :required by imports from .utils

from . import region_meta

log = logging.getLogger(__name__)


def isCython(func):
    """
    Private helper that checks if a function is a cython function.
    """
    return func.__class__.__name__ == 'cython_function_or_method'


class RhodeCodeCacheRegion(CacheRegion):

    def __repr__(self):
        return f'`{self.__class__.__name__}(name={self.name}, backend={self.backend.__class__})`'

    def conditional_cache_on_arguments(
            self, namespace=None,
            expiration_time=None,
            should_cache_fn=None,
            to_str=str,
            function_key_generator=None,
            condition=True):
        """
        Custom conditional decorator, that will not touch any dogpile internals if
        condition isn't meet. This works a bit different from should_cache_fn
        And it's faster in cases we don't ever want to compute cached values
        """
        expiration_time_is_callable = callable(expiration_time)
        if not namespace:
            namespace = getattr(self, '_default_namespace', None)

        if function_key_generator is None:
            function_key_generator = self.function_key_generator

        def get_or_create_for_user_func(func_key_generator, user_func, *arg, **kw):

            if not condition:
                log.debug('Calling un-cached method:%s', user_func.__name__)
                start = time.time()
                result = user_func(*arg, **kw)
                total = time.time() - start
                log.debug('un-cached method:%s took %.4fs', user_func.__name__, total)
                return result

            key = func_key_generator(*arg, **kw)

            timeout = expiration_time() if expiration_time_is_callable \
                else expiration_time

            log.debug('Calling cached method:`%s`', user_func.__name__)
            return self.get_or_create(key, user_func, timeout, should_cache_fn, (arg, kw))

        def cache_decorator(user_func):
            if to_str is str:
                # backwards compatible
                key_generator = function_key_generator(namespace, user_func)
            else:
                key_generator = function_key_generator(namespace, user_func, to_str=to_str)

            def refresh(*arg, **kw):
                """
                Like invalidate, but regenerates the value instead
                """
                key = key_generator(*arg, **kw)
                value = user_func(*arg, **kw)
                self.set(key, value)
                return value

            def invalidate(*arg, **kw):
                key = key_generator(*arg, **kw)
                self.delete(key)

            def set_(value, *arg, **kw):
                key = key_generator(*arg, **kw)
                self.set(key, value)

            def get(*arg, **kw):
                key = key_generator(*arg, **kw)
                return self.get(key)

            user_func.set = set_
            user_func.invalidate = invalidate
            user_func.get = get
            user_func.refresh = refresh
            user_func.key_generator = key_generator
            user_func.original = user_func

            # Use `decorate` to preserve the signature of :param:`user_func`.
            return decorator.decorate(user_func, functools.partial(
                get_or_create_for_user_func, key_generator))

        return cache_decorator


def make_region(*arg, **kw):
    return RhodeCodeCacheRegion(*arg, **kw)


def get_default_cache_settings(settings, prefixes=None):
    prefixes = prefixes or []
    cache_settings = {}
    for key in settings.keys():
        for prefix in prefixes:
            if key.startswith(prefix):
                name = key.split(prefix)[1].strip()
                val = settings[key]
                if isinstance(val, str):
                    val = val.strip()
                cache_settings[name] = val
    return cache_settings


def compute_key_from_params(*args):
    """
    Helper to compute key from given params to be used in cache manager
    """
    return sha1(safe_bytes("_".join(map(str, args))))


def custom_key_generator(backend, namespace, fn):
    func_name = fn.__name__

    def generate_key(*args):
        backend_pref = getattr(backend, 'key_prefix', None) or 'backend_prefix'
        namespace_pref = namespace or 'default_namespace'
        arg_key = compute_key_from_params(*args)
        final_key = f"{backend_pref}:{namespace_pref}:{func_name}_{arg_key}"

        return final_key

    return generate_key


def backend_key_generator(backend):
    """
    Special wrapper that also sends over the backend to the key generator
    """
    def wrapper(namespace, fn):
        return custom_key_generator(backend, namespace, fn)
    return wrapper


def get_or_create_region(region_name, region_namespace: str = None, use_async_runner=False):
    from .backends import FileNamespaceBackend
    from . import async_creation_runner

    region_obj = region_meta.dogpile_cache_regions.get(region_name)
    if not region_obj:
        reg_keys = list(region_meta.dogpile_cache_regions.keys())
        raise OSError(f'Region `{region_name}` not in configured: {reg_keys}.')

    region_uid_name = f'{region_name}:{region_namespace}'

    # Special case for ONLY the FileNamespaceBackend backend. We register one-file-per-region
    if isinstance(region_obj.actual_backend, FileNamespaceBackend):
        if not region_namespace:
            raise ValueError(f'{FileNamespaceBackend} used requires to specify region_namespace param')

        region_exist = region_meta.dogpile_cache_regions.get(region_namespace)
        if region_exist:
            log.debug('Using already configured region: %s', region_namespace)
            return region_exist

        expiration_time = region_obj.expiration_time

        cache_dir = region_meta.dogpile_config_defaults['cache_dir']
        namespace_cache_dir = cache_dir

        # we default the namespace_cache_dir to our default cache dir.
        # however, if this backend is configured with filename= param, we prioritize that
        # so all caches within that particular region, even those namespaced end up in the same path
        if region_obj.actual_backend.filename:
            namespace_cache_dir = os.path.dirname(region_obj.actual_backend.filename)

        if not os.path.isdir(namespace_cache_dir):
            os.makedirs(namespace_cache_dir)
        new_region = make_region(
            name=region_uid_name,
            function_key_generator=backend_key_generator(region_obj.actual_backend)
        )

        namespace_filename = os.path.join(
            namespace_cache_dir, f"{region_name}_{region_namespace}.cache_db")
        # special type that allows 1db per namespace
        new_region.configure(
            backend='dogpile.cache.rc.file_namespace',
            expiration_time=expiration_time,
            arguments={"filename": namespace_filename}
        )

        # create and save in region caches
        log.debug('configuring new region: %s', region_uid_name)
        region_obj = region_meta.dogpile_cache_regions[region_namespace] = new_region

    region_obj._default_namespace = region_namespace
    if use_async_runner:
        region_obj.async_creation_runner = async_creation_runner
    return region_obj


def clear_cache_namespace(cache_region: str | RhodeCodeCacheRegion, cache_namespace_uid: str, method: str) -> int:
    from . import CLEAR_DELETE, CLEAR_INVALIDATE

    if not isinstance(cache_region, RhodeCodeCacheRegion):
        cache_region = get_or_create_region(cache_region, cache_namespace_uid)
    log.debug('clearing cache region: %s [prefix:%s] with method=%s',
              cache_region, cache_namespace_uid, method)

    num_affected_keys = 0

    if method == CLEAR_INVALIDATE:
        # NOTE: The CacheRegion.invalidate() method’s default mode of
        # operation is to set a timestamp local to this CacheRegion in this Python process only.
        # It does not impact other Python processes or regions as the timestamp is only stored locally in memory.
        cache_region.invalidate(hard=True)

    if method == CLEAR_DELETE:
        num_affected_keys = cache_region.backend.delete_multi_by_prefix(prefix=cache_namespace_uid)
    return num_affected_keys


class ActiveRegionCache(object):
    def __init__(self, context, cache_data: dict):
        self.context = context
        self.cache_data = cache_data

    @property
    def state_uid(self) -> str:
        return self.cache_data['cache_state_uid']


class InvalidationContext(object):
    """
    usage::

        from rhodecode.lib import rc_cache

        repo_namespace_key = 'some-cache-for-repo-id-100'
        inv_context_manager = rc_cache.InvalidationContext(key=repo_namespace_key)

        def cache_generator(_state_uid):

            @region.conditional_cache_on_arguments(namespace='some-common-namespace-100')
            def _dummy_func(*args):
                # compute heavy function
                return _state_uid, 'result'

            return _dummy_func

        with inv_context_manager as invalidation_context:
            cache_state_uid = invalidation_context.state_uid
            cache_func = cache_generator(cache_state_uid)
            previous_state_uid, result = cache_func(*call_args)

            should_invalidate = previous_state_uid != cache_state_uid
            if should_invalidate:
                _, result = cache_func.refresh(*call_args)

        # To send global invalidation signal, simply run
        CacheKey.set_invalidate(repo_namespace_key)

    """

    def __repr__(self):
        return f'<InvalidationContext:{self.cache_key}>'

    def __init__(self, key, raise_exception=False, thread_scoped=None):
        self.cache_key = key

        self.raise_exception = raise_exception
        self.proc_id = rhodecode.ConfigGet().get_str('instance_id') or 'DEFAULT'
        self.thread_id = 'global'

        if thread_scoped is None:
            # if we set "default" we can override this via .ini settings
            thread_scoped = rhodecode.ConfigGet().get_bool('cache_thread_scoped')

        # Append the thread id to the cache key if this invalidation context
        # should be scoped to the current thread.
        if thread_scoped is True:
            self.thread_id = threading.current_thread().ident

        self.proc_key = f'proc:{self.proc_id}|thread:{self.thread_id}|key:{self.cache_key}'
        self.compute_time = 0

    def get_or_create_cache_obj(self):
        from rhodecode.model.db import CacheKey, Session, IntegrityError

        cache_obj = CacheKey.get_active_cache(self.cache_key)
        log.debug('Fetched cache obj %s using %s cache key.', cache_obj, self.cache_key)

        if not cache_obj:
            # generate new UID for non-existing cache object
            cache_state_uid = CacheKey.generate_new_state_uid()
            cache_obj = CacheKey(self.cache_key, cache_args=f'repo_state:{self._start_time}',
                                 cache_state_uid=cache_state_uid, cache_active=True)
            try:
                Session().add(cache_obj)
                Session().commit()
            except IntegrityError:
                # if we catch integrity error, it means we inserted this object
                # assumption is that's really an edge race-condition case and
                # it's safe is to skip it
                Session().rollback()
            except Exception:
                log.exception('Failed to commit on cache key update')
                Session().rollback()
                if self.raise_exception:
                    raise
        return cache_obj

    def __enter__(self):
        log.debug('Entering cache invalidation check context: %s', self)
        self._start_time = time.time()

        self.cache_obj = self.get_or_create_cache_obj()
        cache_data = self.cache_obj.get_dict()

        return ActiveRegionCache(context=self, cache_data=cache_data)

    def __exit__(self, exc_type, exc_val, exc_tb):
        # save compute time
        self.compute_time = time.time() - self._start_time