# -*- coding: utf-8 -*-
# Copyright 2014, Ian Gulliver
#
# 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.

import json
import logging

from google.appengine.api import channel
from google.appengine.ext import db

import utils


# Profile
# ↳ Client
# ↳ StateEntry
#
# Subject
# ↳ Subscription (⤴︎ Client)


class Profile(db.Model):
  google_user = db.UserProperty()

  @classmethod
  def FromGoogleUser(cls, google_user):
    if not google_user:
      profile = Profile()
      profile.put()
      return profile

    profiles = Profile.all().filter('google_user =', google_user).fetch(1)
    if profiles:
      return profiles[0]
    else:
      # TODO(flamingcow): Fetch-then-store uniqueness is a race.
      profile = Profile(google_user=google_user)
      profile.put()
      return profile

  @db.transactional(xg=True)
  def MergeFrom(self, source_profile):
    # Merge from another profile into this one, using last_set time as the
    # arbiter.
    my_states = {}
    for state_entry in self.GetStateEntries():
      my_states[state_entry.entry_key] = state_entry

    for state_entry in (StateEntry.all()
                        .ancestor(source_profile)
                        .run()):
      my_state_entry = my_states.get(state_entry.entry_key, None)
      if my_state_entry:
        if state_entry.last_set > my_state_entry.last_set:
          # newer, merge in
          my_state_entry.entry_value = state_entry.entry_value
          my_state_entry.put()
      else:
        # entirely new, add
        StateEntry(parent=self,
            entry_key=state_entry.entry_key,
            entry_value=state_entry.entry_value
            ).put()

  @db.transactional()
  def GetStateEntries(self):
    return StateEntry.all().ancestor(self)


class Client(db.Model):
  # parent=Profile

  first_seen = db.DateTimeProperty(required=True, auto_now_add=True)
  channel_active = db.BooleanProperty(required=True, default=False)

  @classmethod
  def FromProfile(cls, profile):
    client = cls(parent=profile)
    client.put()
    return client

  @classmethod
  def FromGoogleUser(cls, google_user):
    profile = Profile.FromGoogleUser(google_user)
    return cls.FromProfile(profile)

  def SendMessage(self, msg):
    self.SendByKey(self.key(), msg)

  @staticmethod
  def SendByKey(key, msg):
    channel.send_message(str(key), json.dumps(msg, default=utils.EncodeJSON))


class StateEntry(db.Model):
  # parent=Profile

  last_set = db.DateTimeProperty(required=True, auto_now=True)
  entry_key = db.StringProperty(required=True)
  entry_value = db.StringProperty()
  public = db.BooleanProperty(required=True, default=False)

  def ToEvent(self):
    return {
      'event_type':   'state',
      'key':          self.entry_key,
      'value':        self.entry_value,
      'last_set':     self.last_set,
      'public':       self.public,
    }


class Subject(db.Model):
  # key_name=name

  @classmethod
  def FindOrCreate(cls, name):
    subject = cls.get_by_key_name(name)
    if subject:
      return subject
    return cls(key_name=name).put()

  @db.transactional()
  def RecentMessages(self, num_messages):
    query = (
        Message.all()
        .ancestor(self)
        .order('-created'))
    if num_messages <= 0:
      num_messages = None
    return query.run(limit=num_messages)

  @db.transactional()
  def SendMessage(self, message, sender):
    obj = Message(parent=self, message=message, sender=sender)
    obj.put()

    event = obj.ToEvent()

    for subscription in Subscription.all().ancestor(self):
      Client.SendByKey(Subscription.client.get_value_for_datastore(subscription), event)


class Subscription(db.Model):
  # parent=Subject

  client = db.ReferenceProperty(reference_class=Client)

  @classmethod
  @db.transactional()
  def FindOrCreate(cls, subject, client, messages):
    subscriptions = (
        cls.all(keys_only=True)
        .ancestor(subject)
        .filter('client =', client)
        .fetch(1))
    if not subscriptions:
      cls(parent=subject, client=client).put()
    if messages == 0:
      return []
    return [m.ToEvent() for m in subject.RecentMessages(messages)]

  @classmethod
  @db.transactional()
  def Remove(cls, subject, client):
    subscriptions = (
        cls.all()
        .ancestor(subject)
        .filter('client =', client))
    for subscription in subscriptions:
      subscription.delete()


class Message(db.Model):
  # parent=Subject

  created = db.DateTimeProperty(required=True, auto_now_add=True)
  message = db.TextProperty(required=True)
  sender = db.ReferenceProperty(required=True, reference_class=Profile)

  def ToEvent(self):
    return {
      'event_type':   'message',
      'id':           self.key().id(),
      'sender':       str(Message.sender.get_value_for_datastore(self)),
      'subject':      self.parent_key().name(),
      'created':      self.created,
      'message':      self.message,
    }