# mautrix-telegram - A Matrix-Telegram puppeting bridge
# Copyright (C) 2022 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 __future__ import annotations

from typing import TYPE_CHECKING, Awaitable, Callable, Literal
import logging
import time

from telethon.errors import (
    AuthKeyError,
    ChannelInvalidError,
    ChannelPrivateError,
    UnauthorizedError,
)
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,
    ChatParticipantsForbidden,
    InputChannel,
    InputUser,
    MessageActionChatAddUser,
    MessageActionChatDeleteUser,
    MessageActionChatMigrateTo,
    MessageEntityBotCommand,
    PeerChannel,
    PeerChat,
    PeerUser,
    TypeChannelParticipant,
    TypeChatParticipant,
    TypeInputPeer,
    TypePeer,
    UpdateNewChannelMessage,
    UpdateNewMessage,
    User,
)
from telethon.utils import add_surrogate, del_surrogate

from mautrix.errors import MBadState, MForbidden
from mautrix.types import RoomID, UserID

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

if TYPE_CHECKING:
    from asyncio import Future

ReplyFunc = Callable[[str], Awaitable[Message]]
BanFunc = Callable[[RoomID, UserID, str], Awaitable[None]]
TelegramAdminPermission = Literal[
    "change_info",
    "post_messages",
    "edit_messages",
    "delete_messages",
    "ban_users",
    "invite_users",
    "pin_messages",
    "add_admins",
    "anonymous",
    "manage_call",
    "other",
]


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: User | None
    _me_mxid: UserID | None
    _admin_cache: dict[
        tuple[int, int],
        tuple[ChatParticipantAdmin | ChatParticipantCreator | None, float],
    ]
    _login_wait_fut: Future | None
    required_permissions: dict[str, TelegramAdminPermission] = {
        "portal": None,
        "invite": "invite_users",
        "mxban": "ban_users",
        "mxkick": "ban_users",
    }

    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._admin_cache = {}
        self.tg_whitelist = []
        self.whitelist_group_admins = (
            self.config["bridge.relaybot.whitelist_group_admins"] or False
        )
        self._me_info = None
        self._me_mxid = None
        self._login_wait_fut = self.loop.create_future()

    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 on_signed_out(self, err: UnauthorizedError | AuthKeyError) -> None:
        self.log.fatal("Relay bot got signed out, crashing bridge", exc_info=err)
        self.bridge.manual_stop(51)

    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)
        if self._login_wait_fut:
            self._login_wait_fut.set_result(None)
            self._login_wait_fut = None

        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 _get_admin_participant(
        self, chat: TypePeer | TypeInputPeer, tgid: TelegramID
    ) -> TypeChatParticipant | TypeChannelParticipant | None:
        chan_id = chat.channel_id if isinstance(chat, PeerChannel) else chat.chat_id
        try:
            cached, created = self._admin_cache[chan_id, tgid]
            if created + 60 < time.time():
                return cached
        except KeyError:
            pass
        if isinstance(chat, PeerChannel):
            p = await self.client(GetParticipantRequest(chat, tgid))
            pcp = p.participant
            self._admin_cache[chat.channel_id, tgid] = (pcp, time.time())
            return pcp
        elif isinstance(chat, PeerChat):
            chat = await self.client(GetFullChatRequest(chat.chat_id))
            if isinstance(chat.full_chat.participants, ChatParticipantsForbidden):
                return None
            participants = chat.full_chat.participants.participants
            for p in participants:
                self._admin_cache[chat.channel_id, tgid] = (p, time.time())
                if p.user_id == tgid:
                    return p
        return None

    @staticmethod
    def _has_participant_permission(
        pcp: TypeChatParticipant | TypeChannelParticipant | None,
        permission: TelegramAdminPermission | None,
    ) -> bool:
        if isinstance(pcp, (ChannelParticipantCreator, ChannelParticipantAdmin)):
            return permission is None or getattr(pcp.admin_rights, permission, False)
        elif isinstance(pcp, (ChatParticipantCreator, ChatParticipantAdmin)):
            return True
        return False

    async def _can_use_commands(
        self, chat: TypePeer, tgid: TelegramID, permission: TelegramAdminPermission | None = None
    ) -> 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:
            pcp = await self._get_admin_participant(chat, tgid)
            return self._has_participant_permission(pcp, permission)
        return False

    async def check_can_use_command(self, event: Message, reply: ReplyFunc, command: str) -> bool:
        if command not in self.required_permissions:
            # Unknown command
            return False
        elif not isinstance(event.from_id, PeerUser):
            await reply("Channels can't use commands")
            return False
        elif not await self._can_use_commands(
            event.to_id, TelegramID(event.from_id.user_id), self.required_permissions[command]
        ):
            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.")
        else:
            return await reply("Couldn't create portal room")

    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:
            try:
                await portal.invite_to_matrix(user.mxid)
            except MBadState:
                try:
                    await portal.main_intent.unban_user(
                        portal.mxid, user.mxid, reason="Invited from Telegram"
                    )
                except Exception:
                    return await reply(f"Failed to unban `{user.mxid}` from the portal.")
                await portal.invite_to_matrix(user.mxid)
                return await reply(f"Unbanned and invited `{user.mxid}` to the portal.")
            return await reply(f"Invited `{user.mxid}` to the portal.")

    async def handle_command_ban(
        self,
        message: Message,
        portal: po.Portal,
        reply: ReplyFunc,
        reason: str,
        action: Literal["kick", "ban"] = "ban",
    ) -> Message:
        if not message.reply_to:
            return await reply("You must reply to a relaybot message when using that command")
        reply_to_id = TelegramID(message.reply_to.reply_to_msg_id)
        tg_space = portal.tgid if portal.peer_type == "channel" else self.tgid
        msg = await DBMessage.get_one_by_tgid(reply_to_id, tg_space)
        if not msg or msg.sender != self.tgid or not msg.sender_mxid:
            return await reply("Target message is not a relayed message")
        puppet = await pu.Puppet.get_by_peer(message.from_id)
        actioned = "Banned" if action == "ban" else "Kicked"
        try:
            intent = puppet.intent_for(portal)
            func: BanFunc = intent.ban_user if action == "ban" else intent.kick_user
            await func(portal.mxid, msg.sender_mxid, reason)
        except MForbidden as e:
            self.log.warning(
                f"Failed to {action} {msg.sender_mxid} from {portal.mxid} as {puppet.mxid}: {e}, "
                f"falling back to bridge bot"
            )
            reason_prefix = f"{actioned} by {puppet.displayname or puppet.tgid}"
            reason = f"{reason_prefix}: {reason}" if reason else reason_prefix
            try:
                func: BanFunc = (
                    self.az.intent.ban_user if action == "ban" else self.az.intent.kick_user
                )
                await func(portal.mxid, msg.sender_mxid, reason)
            except MForbidden as e:
                self.log.warning(
                    f"Failed to {action} {msg.sender_mxid} from {portal.mxid} as bridge bot: {e}"
                )
                return await reply(f"Failed to {action} `{msg.sender_mxid}`")
        return await reply(f"Successfully {actioned.lower()} `{msg.sender_mxid}`")

    @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}.\n\n"
                f"If you're trying to bridge a group chat to Matrix, you must run the command in "
                f"the group, not here. **The ID above will not work** with `!tg bridge`."
            )
        else:
            return reply("Failed to find chat ID.")

    def parse_command(self, message: Message) -> tuple[str | None, str | None]:
        if not message.entities or len(message.entities) < 1 or not message.message:
            return None, None
        cmd_entity = message.entities[0]
        if not isinstance(cmd_entity, MessageEntityBotCommand) or cmd_entity.offset != 0:
            return None, None
        surrogated_text = add_surrogate(message.message)
        command: str = del_surrogate(surrogated_text[: cmd_entity.length]).lower()
        rest_of_message: str = ""
        if len(surrogated_text) > cmd_entity.length + 1:
            rest_of_message: str = del_surrogate(surrogated_text[cmd_entity.length + 1 :])
        command, *target = command.split("@", 1)
        if not command.startswith("/"):
            return None, None
        elif target and target[0] != self.tg_username.lower():
            return None, None
        return command[1:], rest_of_message

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

        if command == "start" and message.is_private:
            pcm = self.config["bridge.relaybot.private_chat.message"]
            if pcm:
                await reply(pcm)
        elif command == "id":
            await self.handle_command_id(message, reply)
        elif not message.is_private:
            if not await self.check_can_use_command(message, reply, command):
                return
            portal = await po.Portal.get_by_entity(message.to_id)
            if command == "portal":
                await self.handle_command_portal(portal, reply)
            elif command == "invite":
                await self.handle_command_invite(portal, reply, mxid_input=UserID(args))
            elif command == "mxban":
                await self.handle_command_ban(message, portal, reply, reason=args)
            elif command == "mxkick":
                await self.handle_command_ban(message, portal, reply, reason=args, action="kick")

    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 self._login_wait_fut:
            await self._login_wait_fut
        if not isinstance(update, (UpdateNewMessage, UpdateNewChannelMessage)):
            return False
        if isinstance(update.message, MessageService):
            await self.handle_service_message(update.message)
            return False

        if isinstance(update.message, Message):
            command, args = self.parse_command(update.message)
            if command:
                await self.handle_command(update.message, command, args)
        return False

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

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