# -*- coding: utf-8 -*-
# Copyright 2014 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

from synapse.api.errors import SynapseError, Codes, UnrecognizedRequestError, NotFoundError
from base import RestServlet, client_path_pattern
from synapse.storage.push_rule import InconsistentRuleException, RuleNotFoundException

import json


class PushRuleRestServlet(RestServlet):
    PATTERN = client_path_pattern("/pushrules/.*$")
    PRIORITY_CLASS_MAP = {
        'underride': 0,
        'sender': 1,
        'room': 2,
        'content': 3,
        'override': 4
    }
    PRIORITY_CLASS_INVERSE_MAP = {v: k for k,v in PRIORITY_CLASS_MAP.items()}
    SLIGHTLY_PEDANTIC_TRAILING_SLASH_ERROR =\
        "Unrecognised request: You probably wanted a trailing slash"

    def rule_spec_from_path(self, path):
        if len(path) < 2:
            raise UnrecognizedRequestError()
        if path[0] != 'pushrules':
            raise UnrecognizedRequestError()

        scope = path[1]
        path = path[2:]
        if scope not in ['global', 'device']:
            raise UnrecognizedRequestError()

        device = None
        if scope == 'device':
            if len(path) == 0:
                raise UnrecognizedRequestError()
            device = path[0]
            path = path[1:]

        if len(path) == 0:
            raise UnrecognizedRequestError()

        template = path[0]
        path = path[1:]

        if len(path) == 0:
            raise UnrecognizedRequestError()

        rule_id = path[0]

        spec = {
            'scope' : scope,
            'template': template,
            'rule_id': rule_id
        }
        if device:
            spec['device'] = device
        return spec

    def rule_tuple_from_request_object(self, rule_template, rule_id, req_obj):
        if rule_template in ['override', 'underride']:
            if 'conditions' not in req_obj:
                raise InvalidRuleException("Missing 'conditions'")
            conditions = req_obj['conditions']
            for c in conditions:
                if 'kind' not in c:
                    raise InvalidRuleException("Condition without 'kind'")
        elif rule_template == 'room':
            conditions = [{
                'kind': 'event_match',
                'key': 'room_id',
                'pattern': rule_id
            }]
        elif rule_template == 'sender':
            conditions = [{
                'kind': 'event_match',
                'key': 'user_id',
                'pattern': rule_id
            }]
        elif rule_template == 'content':
            if 'pattern' not in req_obj:
                raise InvalidRuleException("Content rule missing 'pattern'")
            conditions = [{
                'kind': 'event_match',
                'key': 'content.body',
                'pattern': req_obj['pattern']
            }]
        else:
            raise InvalidRuleException("Unknown rule template: %s" % (rule_template))

        if 'actions' not in req_obj:
            raise InvalidRuleException("No actions found")
        actions = req_obj['actions']

        for a in actions:
            if a in ['notify', 'dont-notify', 'coalesce']:
                pass
            elif isinstance(a, dict) and 'set_sound' in a:
                pass
            else:
                raise InvalidRuleException("Unrecognised action")

        return (conditions, actions)

    def priority_class_from_spec(self, spec):
        if spec['template'] not in PushRuleRestServlet.PRIORITY_CLASS_MAP.keys():
            raise InvalidRuleException("Unknown template: %s" % (spec['kind']))
        pc = PushRuleRestServlet.PRIORITY_CLASS_MAP[spec['template']]

        if spec['scope'] == 'device':
            pc += 5

        return pc

    @defer.inlineCallbacks
    def on_PUT(self, request):
        spec = self.rule_spec_from_path(request.postpath)
        try:
            priority_class = self.priority_class_from_spec(spec)
        except InvalidRuleException as e:
            raise SynapseError(400, e.message)

        user = yield self.auth.get_user_by_req(request)

        content = _parse_json(request)

        try:
            (conditions, actions) = self.rule_tuple_from_request_object(
                spec['template'],
                spec['rule_id'],
                content
            )
        except InvalidRuleException as e:
            raise SynapseError(400, e.message)

        before = request.args.get("before", None)
        if before and len(before):
            before = before[0]
        after = request.args.get("after", None)
        if after and len(after):
            after = after[0]

        try:
            yield self.hs.get_datastore().add_push_rule(
                user_name=user.to_string(),
                rule_id=spec['rule_id'],
                priority_class=priority_class,
                conditions=conditions,
                actions=actions,
                before=before,
                after=after
            )
        except InconsistentRuleException as e:
            raise SynapseError(400, e.message)
        except RuleNotFoundException as e:
            raise SynapseError(400, e.message)

        defer.returnValue((200, {}))

    @defer.inlineCallbacks
    def on_GET(self, request):
        user = yield self.auth.get_user_by_req(request)

        # we build up the full structure and then decide which bits of it
        # to send which means doing unnecessary work sometimes but is
        # is probably not going to make a whole lot of difference
        rawrules = yield self.hs.get_datastore().get_push_rules_for_user_name(user.to_string())

        rules = {'global': {}, 'device': {}}

        rules['global'] = _add_empty_priority_class_arrays(rules['global'])

        for r in rawrules:
            rulearray = None

            r["conditions"] = json.loads(r["conditions"])
            r["actions"] = json.loads(r["actions"])

            template_name = _priority_class_to_template_name(r['priority_class'])

            if r['priority_class'] > PushRuleRestServlet.PRIORITY_CLASS_MAP['override']:
                # per-device rule
                instance_handle = _instance_handle_from_conditions(r["conditions"])
                if not instance_handle:
                    continue
                if instance_handle not in rules['device']:
                    rules['device'][instance_handle] = []
                    rules['device'][instance_handle] = \
                        _add_empty_priority_class_arrays(rules['device'][instance_handle])

                rulearray = rules['device'][instance_handle]
            else:
                rulearray = rules['global'][template_name]

            template_rule = _rule_to_template(r)
            if template_rule:
                rulearray.append(template_rule)

        path = request.postpath[1:]

        if path == []:
            # we're a reference impl: pedantry is our job.
            raise UnrecognizedRequestError(PushRuleRestServlet.SLIGHTLY_PEDANTIC_TRAILING_SLASH_ERROR)

        if path[0] == '':
            defer.returnValue((200, rules))
        elif path[0] == 'global':
            path = path[1:]
            result = _filter_ruleset_with_path(rules['global'], path)
            defer.returnValue((200, result))
        elif path[0] == 'device':
            path = path[1:]
            if path == []:
                raise UnrecognizedRequestError
            instance_handle = path[0]
            if instance_handle not in rules['device']:
                ret = {}
                ret = _add_empty_priority_class_arrays(ret)
                defer.returnValue((200, ret))
            ruleset = rules['device'][instance_handle]
            result = _filter_ruleset_with_path(ruleset, path)
            defer.returnValue((200, result))
        else:
            raise UnrecognizedRequestError()


    def on_OPTIONS(self, _):
        return 200, {}


def _add_empty_priority_class_arrays(d):
    for pc in PushRuleRestServlet.PRIORITY_CLASS_MAP.keys():
        d[pc] = []
    return d

def _instance_handle_from_conditions(conditions):
    """
    Given a list of conditions, return the instance handle of the
    device rule if there is one
    """
    for c in conditions:
        if c['kind'] == 'device':
            return c['instance_handle']
    return None

def _filter_ruleset_with_path(ruleset, path):
    if path == []:
        raise UnrecognizedRequestError(PushRuleRestServlet.SLIGHTLY_PEDANTIC_TRAILING_SLASH_ERROR)

    if path[0] == '':
        return ruleset
    template_kind = path[0]
    if template_kind not in ruleset:
        raise UnrecognizedRequestError()
    path = path[1:]
    if path == []:
        raise UnrecognizedRequestError(PushRuleRestServlet.SLIGHTLY_PEDANTIC_TRAILING_SLASH_ERROR)
    if path[0] == '':
        return ruleset[template_kind]
    rule_id = path[0]
    for r in ruleset[template_kind]:
        if r['rule_id'] == rule_id:
            return r
    raise NotFoundError

def _priority_class_to_template_name(pc):
    if pc > PushRuleRestServlet.PRIORITY_CLASS_MAP['override']:
        # per-device
        prio_class_index = pc - PushRuleRestServlet.PRIORITY_CLASS_MAP['override']
        return PushRuleRestServlet.PRIORITY_CLASS_INVERSE_MAP[prio_class_index]
    else:
        return PushRuleRestServlet.PRIORITY_CLASS_INVERSE_MAP[pc]

def _rule_to_template(rule):
    template_name = _priority_class_to_template_name(rule['priority_class'])
    if template_name in ['override', 'underride']:
        return {k:rule[k] for k in ["rule_id", "conditions", "actions"]}
    elif template_name in ["sender", "room"]:
        return {k:rule[k] for k in ["rule_id", "actions"]}
    elif template_name == 'content':
        if len(rule["conditions"]) != 1:
            return None
        thecond = rule["conditions"][0]
        if "pattern" not in thecond:
            return None
        ret = {k:rule[k] for k in ["rule_id", "actions"]}
        ret["pattern"] = thecond["pattern"]
        return ret


class InvalidRuleException(Exception):
    pass


# XXX: C+ped from rest/room.py - surely this should be common?
def _parse_json(request):
    try:
        content = json.loads(request.content.read())
        if type(content) != dict:
            raise SynapseError(400, "Content must be a JSON object.",
                               errcode=Codes.NOT_JSON)
        return content
    except ValueError:
        raise SynapseError(400, "Content not JSON.", errcode=Codes.NOT_JSON)


def register_servlets(hs, http_server):
    PushRuleRestServlet(hs).register(http_server)