# Copyright 2019 miruka
# This file is part of harmonyqml, licensed under GPLv3.

from threading import Lock
from typing import Any, Deque, Dict, List, Optional

from PyQt5.QtCore import QDateTime, QObject, pyqtBoundSignal

import nio

from .backend import Backend
from .client import Client
from .model.items import Room, RoomEvent, User


class SignalManager(QObject):
    _event_handling_lock: Lock = Lock()

    def __init__(self, backend: Backend) -> None:
        super().__init__(parent=backend)
        self.backend = backend

        self.last_room_events: Deque[str] = Deque(maxlen=1000)
        self._events_in_transfer:     int        = 0

        cm = self.backend.clientManager
        cm.clientAdded.connect(self.onClientAdded)
        cm.clientDeleted.connect(self.onClientDeleted)


    def onClientAdded(self, client: Client) -> None:
        self.connectClient(client)
        self.backend.models.accounts.append(User(
            user_id      = client.userID,
            display_name = client.userID.lstrip("@").split(":")[0],
        ))


    def onClientDeleted(self, user_id: str) -> None:
        accs = self.backend.models.accounts
        del accs[accs.indexWhere("user_id", user_id)]


    def connectClient(self, client: Client) -> None:
        for name in dir(client):
            attr = getattr(client, name)

            if isinstance(attr, pyqtBoundSignal):
                def onSignal(*args, name=name) -> None:
                    func = getattr(self, f"on{name[0].upper()}{name[1:]}")
                    func(client, *args)

                attr.connect(onSignal)


    def onRoomInvited(self, client: Client, room_id: str) -> None:
        pass  # TODO


    def onRoomJoined(self, client: Client, room_id: str) -> None:
        model = self.backend.models.rooms[client.userID]
        room  = client.nio.rooms[room_id]

        def group_name() -> Optional[str]:
            name = room.group_name()
            return None if name == "Empty room?" else name

        item = Room(
            room_id      = room_id,
            display_name = room.name or room.canonical_alias or group_name(),
            description  = getattr(room, "topic", ""),  # FIXME: outside init
        )

        try:
            index = model.indexWhere("room_id", room_id)
        except ValueError:
            model.append(item)
        else:
            model[index] = item


    def onRoomLeft(self, client: Client, room_id: str) -> None:
        rooms = self.backend.models.rooms[client.userID]
        del rooms[rooms.indexWhere("room_id", room_id)]


    def onRoomSyncPrevBatchTokenReceived(
            self, _: Client, room_id: str, token: str
        ) -> None:

        if room_id not in self.backend.past_tokens:
            self.backend.past_tokens[room_id] = token


    def onRoomPastPrevBatchTokenReceived(
            self, _: Client, room_id: str, token: str
        ) -> None:

        if self.backend.past_tokens[room_id] == token:
            self.backend.fully_loaded_rooms.add(room_id)

        self.backend.past_tokens[room_id] = token


    def onRoomEventReceived(
            self, _: Client, room_id: str, etype: str, edict: Dict[str, Any]
        ) -> None:

        with self._event_handling_lock:
            # Prevent duplicate events in models due to multiple accounts
            if edict["event_id"] in self.last_room_events:
                return

            self.last_room_events.appendleft(edict["event_id"])

            model     = self.backend.models.roomEvents[room_id]
            date_time = QDateTime\
                        .fromMSecsSinceEpoch(edict["server_timestamp"])
            new_event = RoomEvent(type=etype, date_time=date_time, dict=edict)

            if self._events_in_transfer:
                local_echoes_met: int           = 0
                replace_at:       Optional[int] = None

                # Find if any locally echoed event corresponds to new_event
                for i, event in enumerate(model):
                    if not event.is_local_echo:
                        continue

                    sb     = (event.dict["sender"], event.dict["body"])
                    new_sb = (new_event.dict["sender"], new_event.dict["body"])

                    if sb == new_sb:
                        # The oldest matching local echo shall be replaced
                        replace_at = max(replace_at or 0, i)

                    local_echoes_met += 1
                    if local_echoes_met >= self._events_in_transfer:
                        break

                if replace_at is not None:
                    model[replace_at] = new_event
                    self._events_in_transfer -= 1
                    return

            for i, event in enumerate(model):
                if event.is_local_echo:
                    continue

                # Model is sorted from newest to oldest message
                if new_event.date_time > event.date_time:
                    model.insert(i, new_event)
                    return

            model.append(new_event)


    def onRoomTypingUsersUpdated(
            self, client: Client, room_id: str, users: List[str]
        ) -> None:

        rooms = self.backend.models.rooms[client.userID]
        rooms[rooms.indexWhere("room_id", room_id)].typing_users = users


    def onMessageAboutToBeSent(
            self, client: Client, room_id: str, content: Dict[str, str]
        ) -> None:
        with self._event_handling_lock:
            timestamp = QDateTime.currentMSecsSinceEpoch()
            model     = self.backend.models.roomEvents[room_id]
            nio_event = nio.events.RoomMessage.parse_event({
                "event_id":         "",
                "sender":           client.userID,
                "origin_server_ts": timestamp,
                "content":          content,
            })
            event = RoomEvent(
                type          = type(nio_event).__name__,
                date_time     = QDateTime.fromMSecsSinceEpoch(timestamp),
                dict          = nio_event.__dict__,
                is_local_echo = True,
            )
            model.insert(0, event)
            self._events_in_transfer += 1