# mautrix-telegram - A Matrix-Telegram puppeting bridge
# Copyright (C) 2019 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 html import escape
import logging
import re

from telethon.tl.types import (MessageEntityMention, MessageEntityMentionName, MessageEntityUrl,
                               MessageEntityEmail, MessageEntityTextUrl, MessageEntityBold,
                               MessageEntityItalic, MessageEntityCode, MessageEntityPre,
                               MessageEntityBotCommand, MessageEntityHashtag, MessageEntityCashtag,
                               MessageEntityPhone, TypeMessageEntity, PeerChannel, PeerChat,
                               MessageEntityBlockquote, MessageEntityStrike, MessageFwdHeader,
                               MessageEntityUnderline, PeerUser)
from telethon.tl.custom import Message
from telethon.errors import RPCError
from telethon.helpers import add_surrogate, del_surrogate

from mautrix.appservice import IntentAPI
from mautrix.types import (TextMessageEventContent, RelatesTo, RelationType, Format, MessageType,
                           EventType)

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

log: logging.Logger = logging.getLogger("mau.fmt.tg")


async def telegram_reply_to_matrix(evt: Message, source: au.AbstractUser) -> RelatesTo | None:
    if evt.reply_to:
        space = (evt.peer_id.channel_id
                 if isinstance(evt, Message) and isinstance(evt.peer_id, PeerChannel)
                 else source.tgid)
        msg = await DBMessage.get_one_by_tgid(TelegramID(evt.reply_to.reply_to_msg_id), space)
        if msg:
            return RelatesTo(rel_type=RelationType.REPLY, event_id=msg.mxid)
    return None


async def _add_forward_header(source: au.AbstractUser, content: TextMessageEventContent,
                              fwd_from: MessageFwdHeader) -> None:
    if not content.formatted_body or content.format != Format.HTML:
        content.format = Format.HTML
        content.formatted_body = escape(content.body)
    fwd_from_html, fwd_from_text = None, None
    if isinstance(fwd_from.from_id, PeerUser):
        user = await u.User.get_by_tgid(TelegramID(fwd_from.from_id.user_id))
        if user:
            fwd_from_text = user.displayname or user.mxid
            fwd_from_html = (f"<a href='https://matrix.to/#/{user.mxid}'>"
                             f"{escape(fwd_from_text)}</a>")

        if not fwd_from_text:
            puppet = await pu.Puppet.get_by_tgid(
                TelegramID(fwd_from.from_id.user_id), create=False
            )
            if puppet and puppet.displayname:
                fwd_from_text = puppet.displayname or puppet.mxid
                fwd_from_html = (f"<a href='https://matrix.to/#/{puppet.mxid}'>"
                                 f"{escape(fwd_from_text)}</a>")

        if not fwd_from_text:
            try:
                user = await source.client.get_entity(fwd_from.from_id)
                if user:
                    fwd_from_text, _ = pu.Puppet.get_displayname(user, False)
                    fwd_from_html = f"<b>{escape(fwd_from_text)}</b>"
            except (ValueError, RPCError):
                fwd_from_text = fwd_from_html = "unknown user"
    elif isinstance(fwd_from.from_id, (PeerChannel, PeerChat)):
        from_id = (fwd_from.from_id.chat_id if isinstance(fwd_from.from_id, PeerChat)
                   else fwd_from.from_id.channel_id)
        portal = await po.Portal.get_by_tgid(TelegramID(from_id))
        if portal and portal.title:
            fwd_from_text = portal.title
            if portal.alias:
                fwd_from_html = (f"<a href='https://matrix.to/#/{portal.alias}'>"
                                 f"{escape(fwd_from_text)}</a>")
            else:
                fwd_from_html = f"channel <b>{escape(fwd_from_text)}</b>"
        else:
            try:
                channel = await source.client.get_entity(fwd_from.from_id)
                if channel:
                    fwd_from_text = f"channel {channel.title}"
                    fwd_from_html = f"channel <b>{escape(channel.title)}</b>"
            except (ValueError, RPCError):
                fwd_from_text = fwd_from_html = "unknown channel"
    elif fwd_from.from_name:
        fwd_from_text = fwd_from.from_name
        fwd_from_html = f"<b>{escape(fwd_from.from_name)}</b>"
    else:
        fwd_from_text = "unknown source"
        fwd_from_html = f"unknown source"

    content.body = "\n".join([f"> {line}" for line in content.body.split("\n")])
    content.body = f"Forwarded from {fwd_from_text}:\n{content.body}"
    content.formatted_body = (
        f"Forwarded message from {fwd_from_html}<br/>"
        f"<tg-forward><blockquote>{content.formatted_body}</blockquote></tg-forward>")


async def _add_reply_header(source: au.AbstractUser, content: TextMessageEventContent,
                            evt: Message, main_intent: IntentAPI) -> None:
    space = (evt.peer_id.channel_id
             if isinstance(evt, Message) and isinstance(evt.peer_id, PeerChannel)
             else source.tgid)

    msg = await DBMessage.get_one_by_tgid(TelegramID(evt.reply_to.reply_to_msg_id), space)
    if not msg:
        return

    content.relates_to = RelatesTo(rel_type=RelationType.REPLY, event_id=msg.mxid)

    try:
        event = await main_intent.get_event(msg.mx_room, msg.mxid)
        if event.type == EventType.ROOM_ENCRYPTED and source.bridge.matrix.e2ee:
            event = await source.bridge.matrix.e2ee.decrypt(event)
        if isinstance(event.content, TextMessageEventContent):
            event.content.trim_reply_fallback()
        puppet = await pu.Puppet.get_by_mxid(event.sender, create=False)
        content.set_reply(event, displayname=puppet.displayname if puppet else event.sender)
    except Exception:
        log.exception("Failed to get event to add reply fallback")


async def telegram_to_matrix(evt: Message, source: au.AbstractUser,
                             main_intent: IntentAPI | None = None,
                             prefix_text: str | None = None, prefix_html: str | None = None,
                             override_text: str = None,
                             override_entities: list[TypeMessageEntity] = None,
                             no_reply_fallback: bool = False) -> TextMessageEventContent:
    content = TextMessageEventContent(
        msgtype=MessageType.TEXT,
        body=add_surrogate(override_text or evt.message),
    )
    entities = override_entities or evt.entities
    if entities:
        content.format = Format.HTML
        content.formatted_body = await _telegram_entities_to_matrix_catch(content.body, entities)

    if prefix_html:
        if not content.formatted_body:
            content.format = Format.HTML
            content.formatted_body = escape(content.body)
        content.formatted_body = prefix_html + content.formatted_body
    if prefix_text:
        content.body = prefix_text + content.body

    if evt.fwd_from:
        await _add_forward_header(source, content, evt.fwd_from)

    if evt.reply_to and not no_reply_fallback:
        await _add_reply_header(source, content, evt, main_intent)

    if isinstance(evt, Message) and evt.post and evt.post_author:
        if not content.formatted_body:
            content.formatted_body = escape(content.body)
        content.body += f"\n- {evt.post_author}"
        content.formatted_body += f"<br/><i>- <u>{evt.post_author}</u></i>"

    content.body = del_surrogate(content.body)

    if content.formatted_body:
        content.formatted_body = del_surrogate(content.formatted_body.replace("\n", "<br/>"))

    return content


async def _telegram_entities_to_matrix_catch(text: str, entities: list[TypeMessageEntity]) -> str:
    try:
        return await _telegram_entities_to_matrix(text, entities)
    except Exception:
        log.exception("Failed to convert Telegram format:\n"
                      "message=%s\n"
                      "entities=%s",
                      text, entities)
    return "[failed conversion in _telegram_entities_to_matrix]"


async def _telegram_entities_to_matrix(text: str, entities: list[TypeMessageEntity],
                                       offset: int = 0, length: int = None) -> str:
    if not entities:
        return escape(text)
    if length is None:
        length = len(text)
    html = []
    last_offset = 0
    for i, entity in enumerate(entities):
        if entity.offset > offset + length:
            break
        relative_offset = entity.offset - offset
        if relative_offset > last_offset:
            html.append(escape(text[last_offset:relative_offset]))
        elif relative_offset < last_offset:
            continue

        skip_entity = False
        entity_text = await _telegram_entities_to_matrix(
            text=text[relative_offset:relative_offset + entity.length],
            entities=entities[i + 1:], offset=entity.offset, length=entity.length)
        entity_type = type(entity)

        if entity_type == MessageEntityBold:
            html.append(f"<strong>{entity_text}</strong>")
        elif entity_type == MessageEntityItalic:
            html.append(f"<em>{entity_text}</em>")
        elif entity_type == MessageEntityUnderline:
            html.append(f"<u>{entity_text}</u>")
        elif entity_type == MessageEntityStrike:
            html.append(f"<del>{entity_text}</del>")
        elif entity_type == MessageEntityBlockquote:
            html.append(f"<blockquote>{entity_text}</blockquote>")
        elif entity_type == MessageEntityCode:
            html.append(f"<pre><code>{entity_text}</code></pre>"
                        if "\n" in entity_text
                        else f"<code>{entity_text}</code>")
        elif entity_type == MessageEntityPre:
            skip_entity = _parse_pre(html, entity_text, entity.language)
        elif entity_type == MessageEntityMention:
            skip_entity = await _parse_mention(html, entity_text)
        elif entity_type == MessageEntityMentionName:
            skip_entity = await _parse_name_mention(html, entity_text, TelegramID(entity.user_id))
        elif entity_type == MessageEntityEmail:
            html.append(f"<a href='mailto:{entity_text}'>{entity_text}</a>")
        elif entity_type in (MessageEntityTextUrl, MessageEntityUrl):
            skip_entity = await _parse_url(
                html, entity_text, entity.url if entity_type == MessageEntityTextUrl else None
            )
        elif entity_type == MessageEntityBotCommand:
            html.append(f"<font color='blue'>{entity_text}</font>")
        elif entity_type in (MessageEntityHashtag, MessageEntityCashtag, MessageEntityPhone):
            html.append(f"<font color='blue'>{entity_text}</font>")
        else:
            skip_entity = True
        last_offset = relative_offset + (0 if skip_entity else entity.length)
    html.append(escape(text[last_offset:]))

    return "".join(html)


def _parse_pre(html: list[str], entity_text: str, language: str) -> bool:
    if language:
        html.append(f"<pre><code class='language-{language}'>{entity_text}</code></pre>")
    else:
        html.append(f"<pre><code>{entity_text}</code></pre>")
    return False


async def _parse_mention(html: list[str], entity_text: str) -> bool:
    username = entity_text[1:]

    user = await u.User.find_by_username(username) or await pu.Puppet.find_by_username(username)
    if user:
        mxid = user.mxid
    else:
        portal = await po.Portal.find_by_username(username)
        mxid = portal.alias or portal.mxid if portal else None

    if mxid:
        html.append(f"<a href='https://matrix.to/#/{mxid}'>{entity_text}</a>")
    else:
        return True
    return False


async def _parse_name_mention(html: list[str], entity_text: str, user_id: TelegramID) -> bool:
    user = await u.User.get_by_tgid(user_id)
    if user:
        mxid = user.mxid
    else:
        puppet = await pu.Puppet.get_by_tgid(user_id, create=False)
        mxid = puppet.mxid if puppet else None
    if mxid:
        html.append(f"<a href='https://matrix.to/#/{mxid}'>{entity_text}</a>")
    else:
        return True
    return False


message_link_regex = re.compile(r"https?://t(?:elegram)?\.(?:me|dog)/"
                                r"([A-Za-z][A-Za-z0-9_]{3,}[A-Za-z0-9])/([0-9]{1,50})")


async def _parse_url(html: list[str], entity_text: str, url: str) -> bool:
    url = escape(url) if url else entity_text
    if not url.startswith(("https://", "http://", "ftp://", "magnet://")):
        url = "http://" + url

    message_link_match = message_link_regex.match(url)
    if message_link_match:
        group, msgid_str = message_link_match.groups()
        msgid = int(msgid_str)

        portal = await po.Portal.find_by_username(group)
        if portal:
            message = await DBMessage.get_one_by_tgid(TelegramID(msgid), portal.tgid)
            if message:
                url = f"https://matrix.to/#/{portal.mxid}/{message.mxid}"

    html.append(f"<a href='{url}'>{entity_text}</a>")
    return False