'''
VK data (exported by [[https://github.com/Totktonada/vk_messages_backup][Totktonada/vk_messages_backup]])
'''
# note: could reuse the original repo, but little point I guess since VK closed their API
from datetime import datetime
from dataclasses import dataclass
import json
from typing import Dict, Iterator

import pytz

from my.core import stat, Stats, Json, Res, datetime_aware, get_files
from my.core.common import unique_everseen

from my.config import vk_messages_backup as config


# I think vk_messages_backup used this tz?
# not sure if vk actually used to return this tz in api?
TZ = pytz.timezone('Europe/Moscow')


Uid = int

@dataclass(frozen=True)
class User:
    id: Uid
    first_name: str
    last_name: str


@dataclass(frozen=True)
class Chat:
    chat_id: str
    title: str


@dataclass(frozen=True)
class Message:
    dt: datetime_aware
    chat: Chat
    id: str  # todo not sure it's unique?
    user: User
    body: str


Users = Dict[Uid, User]
def users() -> Users:
    files = list(sorted(config.storage_path.glob('user_*.json')))
    res = {}
    for f in files:
        j = json.loads(f.read_text())
        uid = j['id']
        res[uid] = User(
            id=uid,
            first_name=j['first_name'],
            last_name=j['last_name'],
        )
    return res


GROUP_CHAT_MIN_ID = 2000000000
def _parse_chat(*, msg: Json, udict: Users) -> Chat:
    # exported with newer api, peer_id is a proper identifier both for users and chats
    peer_id = msg.get('peer_id')
    if peer_id is not None:
        chat_id = peer_id
    else:
        group_chat_id = msg.get('chat_id')
        if group_chat_id is not None:
            chat_id = GROUP_CHAT_MIN_ID + group_chat_id
        else:
            chat_id = msg['user_id']

    is_group_chat = chat_id >= GROUP_CHAT_MIN_ID
    if is_group_chat:
        title = msg['title']
    else:
        user_id = msg.get('user_id') or msg.get('from_id')
        assert user_id is not None
        user = udict[user_id]
        title = f'{user.first_name} {user.last_name}'
    return Chat(
        chat_id=chat_id,
        title=title,
    )


def _parse_msg(*, msg: Json, chat: Chat, udict: Users) -> Message:
    mid = msg['id']
    md  = msg['date']

    dt = datetime.fromtimestamp(md, tz=TZ)

    # todo attachments? e.g. url could be an attachment
    # todo might be forwarded?
    mb  = msg.get('body')
    if mb is None:
        mb = msg.get('text')
    assert mb is not None, msg

    out = msg['out'] == 1
    if out:
        user = udict[config.user_id]
    else:
        mu  = msg.get('user_id') or msg.get('from_id')
        assert mu is not None, msg
        user = udict[mu]
    return Message(
        dt=dt,
        chat=chat,
        id=mid,
        user=user,
        body=mb,
    )


def _messages() -> Iterator[Res[Message]]:
    udict = users()

    uchats = list(sorted(config.storage_path.glob('userchat_*.json' ))) + \
             list(sorted(config.storage_path.glob('groupchat_*.json')))
    for f in uchats:
        j = json.loads(f.read_text())
        # ugh. very annoying, sometimes not possible to extract title from last message
        # due to newer api...
        # so just do in defensively until we succeed...
        chat = None
        ex = None
        for m in reversed(j):
            try:
                chat = _parse_chat(msg=m, udict=udict)
            except Exception as e:
                ex = e
                continue
        if chat is None:
            assert ex is not None
            yield ex
            continue

        for msg in j:
            try:
                yield _parse_msg(msg=msg, chat=chat, udict=udict)
            except Exception as e:
                yield e


def messages() -> Iterator[Res[Message]]:
    # seems that during backup messages were sometimes duplicated..
    yield from unique_everseen(_messages)


def stats() -> Stats:
    return {
        **stat(users),
        **stat(messages),
    }