"""The log follower: chunked appends, partial lines, MTGA replacing the log, and no lingering handle."""

import os
import time
from pathlib import Path

import pytest
from PySide6.QtCore import QCoreApplication

from mtga_assistant.logtail import LogFollower

FIXTURE = Path(__file__).parent / "fixtures" / "bo3_match.log"


@pytest.fixture(scope="module")
def app():
    return QCoreApplication.instance() or QCoreApplication([])


def wait_for(app, cond, timeout=5.0):
    end = time.monotonic() + timeout
    while time.monotonic() < end:
        app.processEvents()
        if cond():
            return True
        time.sleep(0.02)
    return False


def open_handles_to(path: Path) -> int:
    """Number of this process's file descriptors pointing at path (Linux /proc)."""
    fd_dir = Path("/proc/self/fd")
    if not fd_dir.exists():
        pytest.skip("needs /proc")
    count = 0
    for fd in fd_dir.iterdir():
        try:
            if Path(os.readlink(fd)) == path:
                count += 1
        except OSError:
            pass
    return count


def test_follow_append_replace_and_no_open_handle(app, tmp_path):
    src = FIXTURE.read_bytes()
    log = tmp_path / "Player.log"
    log.write_bytes(b"")
    got, resets = [], []
    f = LogFollower(log)
    f.events.connect(lambda evs: got.extend(evs))
    f.reset.connect(lambda: resets.append(1))
    f.start()
    try:
        cut = len(src) * 3 // 4  # mid-line
        with open(log, "ab") as fh:
            fh.write(src[:cut])
        assert wait_for(app, lambda: len(got) >= 11)
        with open(log, "ab") as fh:
            fh.write(src[cut:])
        assert wait_for(app, lambda: len(got) == 22)

        # Between polls the follower must not keep Player.log open (Windows would then block
        # MTGA from renaming it).
        time.sleep(0.3)
        assert open_handles_to(log.resolve()) == 0

        # MTGA restarts: Player.log is replaced by a new file.
        new = tmp_path / "Player.new"
        new.write_bytes(src[:cut])
        os.replace(new, log)
        assert wait_for(app, lambda: resets and len(got) >= 33)
    finally:
        f.stop()
        f.wait(3000)