#!/usr/bin/env python3

import os
import sys
import tempfile

from posix_parity import compare_calls
from posix_parity import fail
from posix_parity import join
from posix_parity import touch


def main():
    if len(sys.argv) != 2:
        print("usage: TEST_posix_fsync_flush <mountpoint>", file=sys.stderr)
        return 1

    mount = sys.argv[1]

    with tempfile.TemporaryDirectory() as native:
        merge_file = join(mount, "posix-fsync/file")
        native_file = join(native, "posix-fsync/file")
        merge_dir = join(mount, "posix-fsync/dir")
        native_dir = join(native, "posix-fsync/dir")

        touch(merge_file, b"abc")
        touch(native_file, b"abc")
        os.makedirs(merge_dir, exist_ok=True)
        os.makedirs(native_dir, exist_ok=True)

        mfd = os.open(merge_file, os.O_RDWR)
        nfd = os.open(native_file, os.O_RDWR)
        try:
            os.lseek(mfd, 0, os.SEEK_END)
            os.lseek(nfd, 0, os.SEEK_END)
            os.write(mfd, b"-merge")
            os.write(nfd, b"-native")

            err = compare_calls("fsync file", lambda: os.fsync(mfd), lambda: os.fsync(nfd))
            if err:
                return fail(err)
        finally:
            os.close(mfd)
            os.close(nfd)

        mdirfd = os.open(merge_dir, os.O_RDONLY | os.O_DIRECTORY)
        ndirfd = os.open(native_dir, os.O_RDONLY | os.O_DIRECTORY)
        try:
            err = compare_calls("fsync dir", lambda: os.fsync(mdirfd), lambda: os.fsync(ndirfd))
            if err:
                return fail(err)
        finally:
            os.close(mdirfd)
            os.close(ndirfd)

        bad_m = os.open(merge_file, os.O_RDONLY)
        bad_n = os.open(native_file, os.O_RDONLY)
        os.close(bad_m)
        os.close(bad_n)
        err = compare_calls("fsync EBADF", lambda: os.fsync(bad_m), lambda: os.fsync(bad_n))
        if err:
            return fail(err)

        # Close-to-flush parity check: both paths should preserve appended payload.
        with open(merge_file, "rb") as mf, open(native_file, "rb") as nf:
            mdata = mf.read()
            ndata = nf.read()
        if not (mdata.startswith(b"abc") and ndata.startswith(b"abc")):
            return fail(f"flush content prefix mismatch mergerfs={mdata!r} native={ndata!r}")

        return 0


if __name__ == "__main__":
    raise SystemExit(main())