"""warm_cities.py's cross-process single-instance guard (LOCK_PATH + the
core/singleton.py flock it reuses) -- an overlapping deploy launching a second
copy while the first is still warming must stand down, not double-spend
archive-fetch quota."""
import fcntl
import os
import subprocess
import sys

import warm_cities


def test_lock_path_lives_under_data_dir():
    assert os.path.dirname(warm_cities.LOCK_PATH) == warm_cities.paths.DATA_DIR
    assert os.path.basename(warm_cities.LOCK_PATH) == "warm_cities.lock"


def test_second_instance_stands_down_and_exits_zero(tmp_path):
    """With the lock already held (simulating an overlapping deploy invocation), a
    second run of the script must log and exit 0 immediately -- never reaching
    main()'s network/parquet-write path."""
    lock = str(tmp_path / "warm_cities.lock")
    fd = os.open(lock, os.O_RDWR | os.O_CREAT, 0o644)
    fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
    try:
        env = dict(os.environ, THERMOGRAPH_DATA_DIR=str(tmp_path))
        # If the guard didn't work, this would try a real network fetch (or hang)
        # instead of returning almost instantly with exit code 0.
        result = subprocess.run(
            [sys.executable, warm_cities.__file__, "--limit", "0"],
            cwd=os.path.dirname(os.path.abspath(warm_cities.__file__)),
            env=env, capture_output=True, text=True, timeout=20,
        )
        assert result.returncode == 0
        assert "already running" in result.stdout
    finally:
        fcntl.flock(fd, fcntl.LOCK_UN)
        os.close(fd)