#!/usr/bin/env python3

import os
import sys
import tempfile

from posix_parity import cleanup_dir
from posix_parity import compare_calls
from posix_parity import fail
from posix_parity import join
from posix_parity import temp_dir
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_base = temp_dir(mount)
        try:
            native_base = join(native, os.path.basename(merge_base))
            os.makedirs(native_base, exist_ok=True)

            merge_file = join(merge_base, "file")
            native_file = join(native_base, "file")
            merge_dir = join(merge_base, "dir")
            native_dir = join(native_base, "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"-appended")
                os.write(nfd, b"-appended")

                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 mdata != ndata:
                return fail(f"flush content mismatch mergerfs={mdata!r} native={ndata!r}")

            return 0
        finally:
            cleanup_dir(merge_base)


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