# mautrix-telegram - A Matrix-Telegram puppeting bridge
# Copyright (C) 2021 Tulir Asokan
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# 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 Affero 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 <https://www.gnu.org/licenses/>.
from typing import Awaitable, Callable, Dict, List, Optional, Tuple
import logging

from telethon.errors import ChannelInvalidError, ChannelPrivateError
from telethon.tl.functions.channels import GetChannelsRequest, GetParticipantRequest
from telethon.tl.functions.messages import GetChatsRequest, GetFullChatRequest
from telethon.tl.patched import Message, MessageService
from telethon.tl.types import (
    ChannelParticipantAdmin,
    ChannelParticipantCreator,
    ChatForbidden,
    ChatParticipantAdmin,
    ChatParticipantCreator,
    InputChannel,
    InputUser,
    MessageActionChatAddUser,
    MessageActionChatDeleteUser,
    MessageActionChatMigrateTo,
    MessageEntityBotCommand,
    PeerChannel,
    PeerChat,
    PeerUser,
    TypePeer,
    UpdateNewChannelMessage,
    UpdateNewMessage,
    User,
)

from mautrix.types import UserID

from . import portal as po, puppet as pu, user as u
from .abstract_user import AbstractUser
from .db import BotChat
from .types import TelegramID

ReplyFunc = Callable[[str], Awaitable[Message]]


class Bot(AbstractUser):
    log: logging.Logger = logging.getLogger("mau.user.bot")

    token: str
    chats: Dict[int, str]
    tg_whitelist: List[int]
    whitelist_group_admins: bool
    _me_info: Optional[User]
    _me_mxid: Optional[UserID]

    def __init__(self, token: str) -> None:
        super().__init__()
        self.token = token
        self.tgid = None
        self.mxid = None
        self.puppet_whitelisted = True
        self.whitelisted = True
        self.relaybot_whitelisted = True
        self.tg_username = None
        self.is_relaybot = True
        self.is_bot = True
        self.chats = {}
        self.tg_whitelist = []
        self.whitelist_group_admins = (
            self.config["bridge.relaybot.whitelist_group_admins"] or False
        )
        self._me_info = None
        self._me_mxid = None

    async def get_me(self, use_cache: bool = True) -> Tuple[User, UserID]:
        if not use_cache or not self._me_mxid:
            self._me_info = await self.client.get_me()
            self._me_mxid = pu.Puppet.get_mxid_from_id(TelegramID(self._me_info.id))
        return self._me_info, self._me_mxid

    async def init_permissions(self) -> None:
        whitelist = self.config["bridge.relaybot.whitelist"] or []
        for user_id in whitelist:
            if isinstance(user_id, str):
                entity = await self.client.get_input_entity(user_id)
                if isinstance(entity, InputUser):
                    user_id = entity.user_id
                else:
                    user_id = None
            if isinstance(user_id, int):
                self.tg_whitelist.append(user_id)

    async def start(self, delete_unless_authenticated: bool = False) -> "Bot":
        self.chats = {chat.id: chat.type for chat in await BotChat.all()}
        await super().start(delete_unless_authenticated)
        if not await self.is_logged_in():
            await self.client.sign_in(bot_token=self.token)
        await self.post_login()
        return self

    async def post_login(self) -> None:
        await self.init_permissions()
        info = await self.client.get_me()
        self.tgid = TelegramID(info.id)
        self.tg_username = info.username
        self.mxid = pu.Puppet.get_mxid_from_id(self.tgid)

        chat_ids = [chat_id for chat_id, chat_type in self.chats.items() if chat_type == "chat"]
        response = await self.client(GetChatsRequest(chat_ids))
        for chat in response.chats:
            if isinstance(chat, ChatForbidden) or chat.left or chat.deactivated:
                await self.remove_chat(TelegramID(chat.id))

        channel_ids = [
            InputChannel(chat_id, 0)
            for chat_id, chat_type in self.chats.items()
            if chat_type == "channel"
        ]
        for channel_id in channel_ids:
            try:
                await self.client(GetChannelsRequest([channel_id]))
            except (ChannelPrivateError, ChannelInvalidError):
                await self.remove_chat(TelegramID(channel_id.channel_id))

    async def register_portal(self, portal: po.Portal) -> None:
        await self.add_chat(portal.tgid, portal.peer_type)

    async def unregister_portal(self, tgid: TelegramID, tg_receiver: TelegramID) -> None:
        await self.remove_chat(tgid)

    async def add_chat(self, chat_id: TelegramID, chat_type: str) -> None:
        if chat_id not in self.chats:
            self.chats[chat_id] = chat_type
            await BotChat(id=chat_id, type=chat_type).insert()

    async def remove_chat(self, chat_id: TelegramID) -> None:
        try:
            del self.chats[chat_id]
        except KeyError:
            pass
        await BotChat.delete_by_id(chat_id)

    async def _can_use_commands(self, chat: TypePeer, tgid: TelegramID) -> bool:
        if tgid in self.tg_whitelist:
            return True

        user = await u.User.get_by_tgid(tgid)
        if user and user.is_admin:
            self.tg_whitelist.append(user.tgid)
            return True

        if self.whitelist_group_admins:
            if isinstance(chat, PeerChannel):
                p = await self.client(GetParticipantRequest(chat, tgid))
                return isinstance(
                    p.participant, (ChannelParticipantCreator, ChannelParticipantAdmin)
                )
            elif isinstance(chat, PeerChat):
                chat = await self.client(GetFullChatRequest(chat.chat_id))
                participants = chat.full_chat.participants.participants
                for p in participants:
                    if p.user_id == tgid:
                        return isinstance(p, (ChatParticipantCreator, ChatParticipantAdmin))
        return False

    async def check_can_use_commands(self, event: Message, reply: ReplyFunc) -> bool:
        # FIXME event.from_id is not int
        if not await self._can_use_commands(event.to_id, TelegramID(event.from_id)):
            await reply("You do not have the permission to use that command.")
            return False
        return True

    async def handle_command_portal(self, portal: po.Portal, reply: ReplyFunc) -> Message:
        if not self.config["bridge.relaybot.authless_portals"]:
            return await reply("This bridge doesn't allow portal creation from Telegram.")

        if not portal.allow_bridging:
            return await reply("This bridge doesn't allow bridging this chat.")

        await portal.create_matrix_room(self)
        if portal.mxid:
            if portal.username:
                return await reply(
                    f"Portal is public: [{portal.alias}](https://matrix.to/#/{portal.alias})"
                )
            else:
                return await reply("Portal is not public. Use `/invite <mxid>` to get an invite.")

    async def handle_command_invite(
        self, portal: po.Portal, reply: ReplyFunc, mxid_input: UserID
    ) -> Message:
        if len(mxid_input) == 0:
            return await reply("Usage: `/invite <mxid>`")
        elif not portal.mxid:
            return await reply("Portal does not have Matrix room. Create one with /portal first.")
        if mxid_input[0] != "@" or mxid_input.find(":") < 2:
            return await reply("That doesn't look like a Matrix ID.")
        user = await u.User.get_and_start_by_mxid(mxid_input)
        if not user.relaybot_whitelisted:
            return await reply("That user is not whitelisted to use the bridge.")
        elif await user.is_logged_in():
            displayname = f"@{user.tg_username}" if user.tg_username else user.displayname
            return await reply(
                "That user seems to be logged in. "
                f"Just invite [{displayname}](tg://user?id={user.tgid})"
            )
        else:
            await portal.invite_to_matrix(user.mxid)
            return await reply(f"Invited `{user.mxid}` to the portal.")

    @staticmethod
    def handle_command_id(message: Message, reply: ReplyFunc) -> Awaitable[Message]:
        # Provide the prefixed ID to the user so that the user wouldn't need to specify whether the
        # chat is a normal group or a supergroup/channel when using the ID.
        if isinstance(message.to_id, PeerChannel):
            return reply(f"-100{message.to_id.channel_id}")
        elif isinstance(message.to_id, PeerChat):
            return reply(str(-message.to_id.chat_id))
        elif isinstance(message.to_id, PeerUser):
            return reply(f"Your user ID is {message.to_id.user_id}.")
        else:
            return reply("Failed to find chat ID.")

    def match_command(self, text: str, command: str) -> bool:
        text = text.lower()
        command = f"/{command.lower()}"
        command_targeted = f"{command}@{self.tg_username.lower()}"

        is_plain_command = text == command or text == command_targeted
        if is_plain_command:
            return True

        is_arg_command = text.startswith(command + " ") or text.startswith(command_targeted + " ")
        if is_arg_command:
            return True

        return False

    async def handle_command(self, message: Message) -> None:
        def reply(reply_text: str) -> Awaitable[Message]:
            return self.client.send_message(message.chat_id, reply_text, reply_to=message.id)

        text = message.message

        if self.match_command(text, "start"):
            pcm = self.config["bridge.relaybot.private_chat.message"]
            if pcm:
                await reply(pcm)
            return
        elif self.match_command(text, "id"):
            await self.handle_command_id(message, reply)
            return
        elif message.is_private:
            return

        portal = await po.Portal.get_by_entity(message.to_id)

        is_portal_cmd = self.match_command(text, "portal")
        is_invite_cmd = self.match_command(text, "invite")
        if is_portal_cmd or is_invite_cmd:
            if not await self.check_can_use_commands(message, reply):
                return
            if is_portal_cmd:
                await self.handle_command_portal(portal, reply)
            elif is_invite_cmd:
                try:
                    mxid = text[text.index(" ") + 1 :]
                except ValueError:
                    mxid = ""
                await self.handle_command_invite(portal, reply, mxid_input=UserID(mxid))

    async def handle_service_message(self, message: MessageService) -> None:
        to_peer = message.to_id
        if isinstance(to_peer, PeerChannel):
            to_id = TelegramID(to_peer.channel_id)
            chat_type = "channel"
        elif isinstance(to_peer, PeerChat):
            to_id = TelegramID(to_peer.chat_id)
            chat_type = "chat"
        else:
            return

        action = message.action
        if isinstance(action, MessageActionChatAddUser) and self.tgid in action.users:
            await self.add_chat(to_id, chat_type)
        elif isinstance(action, MessageActionChatDeleteUser) and action.user_id == self.tgid:
            await self.remove_chat(to_id)
        elif isinstance(action, MessageActionChatMigrateTo):
            await self.remove_chat(to_id)
            await self.add_chat(TelegramID(action.channel_id), "channel")

    async def update(self, update) -> bool:
        if not isinstance(update, (UpdateNewMessage, UpdateNewChannelMessage)):
            return False
        if isinstance(update.message, MessageService):
            await self.handle_service_message(update.message)
            return False

        is_command = (
            isinstance(update.message, Message)
            and update.message.entities
            and len(update.message.entities) > 0
            and isinstance(update.message.entities[0], MessageEntityBotCommand)
            and update.message.entities[0].offset == 0
        )
        if is_command:
            await self.handle_command(update.message)
        return False

    def is_in_chat(self, peer_id) -> bool:
        return peer_id in self.chats

    @property
    def name(self) -> str:
        return "bot"