# -*- coding: utf-8 -*-
# Copyright 2015, 2016 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from twisted.internet import defer

import baserules

import logging
import simplejson as json
import re

from synapse.types import UserID
from synapse.util.caches.lrucache import LruCache

logger = logging.getLogger(__name__)


GLOB_REGEX = re.compile(r'\\\[(\\\!|)(.*)\\\]')
IS_GLOB = re.compile(r'[\?\*\[\]]')
INEQUALITY_EXPR = re.compile("^([=<>]*)([0-9]*)$")


@defer.inlineCallbacks
def evaluator_for_user_id_and_profile_tag(user_id, profile_tag, room_id, store):
    rawrules = yield store.get_push_rules_for_user(user_id)
    enabled_map = yield store.get_push_rules_enabled_for_user(user_id)
    our_member_event = yield store.get_current_state(
        room_id=room_id,
        event_type='m.room.member',
        state_key=user_id,
    )

    defer.returnValue(PushRuleEvaluator(
        user_id, profile_tag, rawrules, enabled_map,
        room_id, our_member_event, store
    ))


def _room_member_count(ev, condition, room_member_count):
    if 'is' not in condition:
        return False
    m = INEQUALITY_EXPR.match(condition['is'])
    if not m:
        return False
    ineq = m.group(1)
    rhs = m.group(2)
    if not rhs.isdigit():
        return False
    rhs = int(rhs)

    if ineq == '' or ineq == '==':
        return room_member_count == rhs
    elif ineq == '<':
        return room_member_count < rhs
    elif ineq == '>':
        return room_member_count > rhs
    elif ineq == '>=':
        return room_member_count >= rhs
    elif ineq == '<=':
        return room_member_count <= rhs
    else:
        return False


class PushRuleEvaluator:
    DEFAULT_ACTIONS = []

    def __init__(self, user_id, profile_tag, raw_rules, enabled_map, room_id,
                 our_member_event, store):
        self.user_id = user_id
        self.profile_tag = profile_tag
        self.room_id = room_id
        self.our_member_event = our_member_event
        self.store = store

        rules = []
        for raw_rule in raw_rules:
            rule = dict(raw_rule)
            rule['conditions'] = json.loads(raw_rule['conditions'])
            rule['actions'] = json.loads(raw_rule['actions'])
            rules.append(rule)

        self.rules = baserules.list_with_base_rules(rules)

        self.enabled_map = enabled_map

    @staticmethod
    def tweaks_for_actions(actions):
        tweaks = {}
        for a in actions:
            if not isinstance(a, dict):
                continue
            if 'set_tweak' in a and 'value' in a:
                tweaks[a['set_tweak']] = a['value']
        return tweaks

    @defer.inlineCallbacks
    def actions_for_event(self, ev):
        """
        This should take into account notification settings that the user
        has configured both globally and per-room when we have the ability
        to do such things.
        """
        if ev['user_id'] == self.user_id:
            # let's assume you probably know about messages you sent yourself
            defer.returnValue([])

        room_id = ev['room_id']

        # get *our* member event for display name matching
        my_display_name = None

        if self.our_member_event:
            my_display_name = self.our_member_event[0].content.get("displayname")

        room_members = yield self.store.get_users_in_room(room_id)
        room_member_count = len(room_members)

        evaluator = PushRuleEvaluatorForEvent(ev, room_member_count)

        for r in self.rules:
            enabled = self.enabled_map.get(r['rule_id'], None)
            if enabled is not None and not enabled:
                continue

            if not r.get("enabled", True):
                continue

            conditions = r['conditions']
            actions = r['actions']

            # ignore rules with no actions (we have an explict 'dont_notify')
            if len(actions) == 0:
                logger.warn(
                    "Ignoring rule id %s with no actions for user %s",
                    r['rule_id'], self.user_id
                )
                continue

            matches = True
            for c in conditions:
                matches = evaluator.matches(
                    c, self.user_id, my_display_name, self.profile_tag
                )
                if not matches:
                    break

            logger.debug(
                "Rule %s %s",
                r['rule_id'], "matches" if matches else "doesn't match"
            )

            if matches:
                logger.debug(
                    "%s matches for user %s, event %s",
                    r['rule_id'], self.user_id, ev['event_id']
                )

                # filter out dont_notify as we treat an empty actions list
                # as dont_notify, and this doesn't take up a row in our database
                actions = [x for x in actions if x != 'dont_notify']

                defer.returnValue(actions)

        logger.debug(
            "No rules match for user %s, event %s",
            self.user_id, ev['event_id']
        )
        defer.returnValue(PushRuleEvaluator.DEFAULT_ACTIONS)


class PushRuleEvaluatorForEvent(object):
    def __init__(self, event, room_member_count):
        self._event = event
        self._room_member_count = room_member_count

        # Maps strings of e.g. 'content.body' -> event["content"]["body"]
        self._value_cache = _flatten_dict(event)

    def matches(self, condition, user_id, display_name, profile_tag):
        if condition['kind'] == 'event_match':
            return self._event_match(condition, user_id)
        elif condition['kind'] == 'device':
            if 'profile_tag' not in condition:
                return True
            return condition['profile_tag'] == profile_tag
        elif condition['kind'] == 'contains_display_name':
            return self._contains_display_name(display_name)
        elif condition['kind'] == 'room_member_count':
            return _room_member_count(
                self._event, condition, self._room_member_count
            )
        else:
            return True

    def _event_match(self, condition, user_id):
        pattern = condition.get('pattern', None)

        if not pattern:
            pattern_type = condition.get('pattern_type', None)
            if pattern_type == "user_id":
                pattern = user_id
            elif pattern_type == "user_localpart":
                pattern = UserID.from_string(user_id).localpart

        if not pattern:
            logger.warn("event_match condition with no pattern")
            return False

        # XXX: optimisation: cache our pattern regexps
        if condition['key'] == 'content.body':
            body = self._event["content"].get("body", None)
            if not body:
                return False

            return _glob_matches(pattern, body, word_boundary=True)
        else:
            haystack = self._get_value(condition['key'])
            if haystack is None:
                return False

            return _glob_matches(pattern, haystack)

    def _contains_display_name(self, display_name):
        if not display_name:
            return False

        body = self._event["content"].get("body", None)
        if not body:
            return False

        return _glob_matches(display_name, body, word_boundary=True)

    def _get_value(self, dotted_key):
        return self._value_cache.get(dotted_key, None)


def _glob_matches(glob, value, word_boundary=False):
    """Tests if value matches glob.

    Args:
        glob (string)
        value (string): String to test against glob.
        word_boundary (bool): Whether to match against word boundaries or entire
            string. Defaults to False.

    Returns:
        bool
    """
    try:
        if IS_GLOB.search(glob):
            r = re.escape(glob)

            r = r.replace(r'\*', '.*?')
            r = r.replace(r'\?', '.')

            # handle [abc], [a-z] and [!a-z] style ranges.
            r = GLOB_REGEX.sub(
                lambda x: (
                    '[%s%s]' % (
                        x.group(1) and '^' or '',
                        x.group(2).replace(r'\\\-', '-')
                    )
                ),
                r,
            )
            if word_boundary:
                r = r"\b%s\b" % (r,)
                r = _compile_regex(r)

                return r.search(value)
            else:
                r = r + "$"
                r = _compile_regex(r)

                return r.match(value)
        elif word_boundary:
            r = re.escape(glob)
            r = r"\b%s\b" % (r,)
            r = _compile_regex(r)

            return r.search(value)
        else:
            return value.lower() == glob.lower()
    except re.error:
        logger.warn("Failed to parse glob to regex: %r", glob)
        return False


def _flatten_dict(d, prefix=[], result={}):
    for key, value in d.items():
        if isinstance(value, basestring):
            result[".".join(prefix + [key])] = value.lower()
        elif hasattr(value, "items"):
            _flatten_dict(value, prefix=(prefix+[key]), result=result)

    return result


regex_cache = LruCache(5000, 1)


def _compile_regex(regex_str):
    r = regex_cache.get((regex_str,), None)
    if r:
        return r

    r = re.compile(regex_str, flags=re.IGNORECASE)
    regex_cache[(regex_str,)] = r
    return r