#!/usr/bin/env python3

import array
import fcntl
import os
import termios
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 mergerfs_mount
from posix_parity import temp_dir
from posix_parity import touch


def fionread(fd):
    buf = array.array("i", [0])
    fcntl.ioctl(fd, termios.FIONREAD, buf, True)
    return buf[0]


def main():
    try:
        with mergerfs_mount() as (mount, _):
            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")
                    touch(merge_file, b"hello-world")
                    touch(native_file, b"hello-world")

                    mfd = os.open(merge_file, os.O_RDONLY)
                    nfd = os.open(native_file, os.O_RDONLY)
                    try:
                        err = compare_calls("ioctl FIONREAD", lambda: fionread(mfd), lambda: fionread(nfd), lambda a, b: a == b)
                        if err:
                            return fail(err)

                        os.lseek(mfd, 5, os.SEEK_SET)
                        os.lseek(nfd, 5, os.SEEK_SET)
                        err = compare_calls(
                            "ioctl FIONREAD after seek",
                            lambda: fionread(mfd),
                            lambda: fionread(nfd),
                            lambda a, b: a == b,
                        )
                        if err:
                            return fail(err)
                    finally:
                        os.close(mfd)
                        os.close(nfd)

                    return 0
                finally:
                    cleanup_dir(merge_base)
    except RuntimeError as exc:
        print(str(exc), end="")
        return 77


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