"""The near-end checkpoint that finishes a Plex item.

- Exactly one scrobble per finish, even when two near-end checkpoints race (the 10 s tick and the
  debounced `seeked` flush arrive together): the transition is decided by a conditional write, not a
  read taken before it.
- The finish supersedes every resume push still in flight, so none can land at Plex after the
  scrobble and revive a resume point on a watched item.
"""

import threading
from datetime import datetime, timedelta, timezone

from sqlalchemy import select

from app.db import SessionLocal
from app.models import PlexItem, PlexLibrary, PlexState
from app.routes.plex import playback


def _item(db) -> PlexItem:
    lib = PlexLibrary(plex_key="1", title="Movies", kind="movie", enabled=True)
    db.add(lib)
    db.flush()
    item = PlexItem(rating_key="m1", library_id=lib.id, kind="movie", title="A Movie")
    db.add(item)
    db.commit()
    return item


def test_two_racing_finishes_flip_the_row_once(db, make_user):
    user = make_user()
    item = _item(db)
    db.add(PlexState(user_id=user.id, item_id=item.id, status="new", position_seconds=5000))
    db.commit()
    now = datetime.now(timezone.utc)

    first, second = SessionLocal(), SessionLocal()
    try:
        assert playback._mark_finished(first, user.id, item.id, now) is True  # holds the row lock
        out: list[bool] = []
        racer = threading.Thread(
            target=lambda: out.append(playback._mark_finished(second, user.id, item.id, now))
        )
        racer.start()
        racer.join(0.5)
        assert racer.is_alive(), "the second writer must wait on the first one's row lock"
        first.commit()
        racer.join(5)
        second.commit()
    finally:
        first.close()
        second.close()
    assert out == [False], "the second checkpoint saw the committed finish: no second scrobble"


def test_a_first_ever_finish_inserts_and_counts_once(db, make_user):
    user = make_user()
    item = _item(db)
    now = datetime.now(timezone.utc)
    assert playback._mark_finished(db, user.id, item.id, now) is True
    db.commit()
    assert playback._mark_finished(db, user.id, item.id, now + timedelta(seconds=10)) is False
    db.commit()
    st = db.execute(select(PlexState).where(PlexState.item_id == item.id)).scalars().one()
    assert (st.status, st.position_seconds) == ("watched", 0)


def test_the_finish_supersedes_a_resume_push_still_in_flight(db, as_user, make_user, monkeypatch):
    user = make_user()
    item = _item(db)
    monkeypatch.setattr(playback.plex_stream, "touch_session", lambda key: None)
    earlier = datetime.now(timezone.utc) - timedelta(seconds=5)
    # A resume push was scheduled a moment ago and has not reached Plex yet.
    assert playback._should_push_resume(user.id, item.id, earlier, final=True)

    r = as_user(user).post(
        "/api/plex/item/m1/progress", json={"position_seconds": 2995, "duration_seconds": 3000}
    )
    assert r.json() == {"status": "watched", "position_seconds": 0}
    assert playback._resume_push_superseded(user.id, item.id, earlier) is True