"""
Messenger data from Android app database (in =/data/data/com.facebook.orca/databases/threads_db2=)
"""
from __future__ import annotations

from dataclasses import dataclass
from datetime import datetime
from pathlib import Path
import sqlite3
from typing import Iterator, Sequence, Optional, Dict, Union

from more_itertools import unique_everseen

from my.core import get_files, Paths, datetime_naive, Res, assert_never, LazyLogger
from my.core.error import echain
from my.core.sqlite import sqlite_connection

from my.config import fbmessenger as user_config


logger = LazyLogger(__name__)


@dataclass
class config(user_config.android):
    # paths[s]/glob to the exported sqlite databases
    export_path: Paths


def inputs() -> Sequence[Path]:
    return get_files(config.export_path)


@dataclass(unsafe_hash=True)
class Sender:
    id: str
    name: str


@dataclass(unsafe_hash=True)
class Thread:
    id: str
    name: Optional[str]

# todo not sure about order of fields...
@dataclass
class _BaseMessage:
    id: str
    # checked against a message sent on 4 may 2022, and it does look naive
    dt: datetime_naive
    text: Optional[str]


@dataclass(unsafe_hash=True)
class _Message(_BaseMessage):
    thread_id: str
    sender_id: str
    reply_to_id: Optional[str]


# todo hmm, on the one hand would be kinda nice to inherit common.Message protocol here
# on the other, because the properties there are read only we can't construct the object anymore??
@dataclass(unsafe_hash=True)
class Message(_BaseMessage):
    thread: Thread
    sender: Sender
    reply_to: Optional[Message]


Entity = Union[Sender, Thread, _Message]
def _entities() -> Iterator[Res[Entity]]:
    dbs = inputs()
    for i, f in enumerate(dbs):
        logger.debug(f'processing {f} {i}/{len(dbs)}')
        with sqlite_connection(f, immutable=True, row_factory='row') as db:
            try:
                yield from _process_db(db)
            except Exception as e:
                yield echain(RuntimeError(f'While processing {f}'), cause=e)


def _normalise_user_id(ukey: str) -> str:
    # trying to match messages.author from fbchat
    prefix = 'FACEBOOK:'
    assert ukey.startswith(prefix), ukey
    return ukey[len(prefix):]


def _normalise_thread_id(key) -> str:
    # works both for GROUP:group_id and ONE_TO_ONE:other_user:your_user
    return key.split(':')[1]


def _process_db(db: sqlite3.Connection) -> Iterator[Res[Entity]]:

    for r in db.execute('SELECT * FROM threads'):
        yield Thread(
            id=_normalise_thread_id(r['thread_key']),
            name=r['name'],
        )
    
    for r in db.execute('''SELECT * FROM thread_users'''):
        # for messaging_actor_type == 'REDUCED_MESSAGING_ACTOR', name is None
        # but they are still referenced, so need to keep
        name = r['name'] or '<NAME UNAVAILABLE>'
        yield Sender(
            id=_normalise_user_id(r['user_key']),
            name=name,
        )

    for r in db.execute('''
    SELECT *, json_extract(sender, "$.user_key") AS user_key FROM messages 
    WHERE msg_type NOT IN (
        -1,  /* these don't have any data at all, likely immediately deleted or something? */
        2    /* these are 'left group' system messages, also a bit annoying since they might reference nonexistent users */
    )
    ORDER BY timestamp_ms /* they aren't in order in the database, so need to sort */
    '''):
        yield _Message(
            id=r['msg_id'],
            dt=datetime.fromtimestamp(r['timestamp_ms'] / 1000),
            # is_incoming=False, TODO??
            text=r['text'],
            thread_id=_normalise_thread_id(r['thread_key']),
            sender_id=_normalise_user_id(r['user_key']),
            reply_to_id=r['message_replied_to_id']
        )


def messages() -> Iterator[Res[Message]]:
    senders: Dict[str, Sender] = {}
    msgs: Dict[str, Message] = {}
    threads: Dict[str, Thread] = {}
    for x in unique_everseen(_entities()):
        if isinstance(x, Exception):
            yield x
            continue
        if isinstance(x, Sender):
            senders[x.id] = x
            continue
        if isinstance(x, Thread):
            threads[x.id] = x
            continue
        if isinstance(x, _Message):
            reply_to_id = x.reply_to_id
            # hmm, reply_to be missing due to the synthetic nature of export, so have to be defensive
            reply_to = None if reply_to_id is None else msgs.get(reply_to_id)
            # also would be interesting to merge together entities rather than resuling messages from different sources..
            # then the merging thing could be moved to common?
            try:
                sender = senders[x.sender_id]
                thread = threads[x.thread_id]
            except Exception as e:
                yield e
                continue
            m = Message(
                id=x.id,
                dt=x.dt,
                text=x.text,
                thread=thread,
                sender=sender,
                reply_to=reply_to,
            )
            msgs[m.id] = m
            yield m
            continue
        # NOTE: for some reason mypy coverage highlights it as red?
        # but it actually works as expected: i.e. if you omit one of the clauses above, mypy will complain
        assert_never(x)