import os

const tfolder = os.join_path(os.vtmp_dir(), 'os_file_buffering_tests')

fn testsuite_begin() {
    os.rmdir_all(tfolder) or {}
    assert !os.is_dir(tfolder)
    os.mkdir_all(tfolder)!
    os.chdir(tfolder)!
    assert os.is_dir(tfolder)
}

fn testsuite_end() {
    os.rmdir_all(tfolder) or {}
}

fn test_set_buffer_line_buffered() {
    dump(@LOCATION)
    mut buf := []u8{len: 25}
    dump(buf)
    mut wfile := os.open_file('text.txt', 'wb', 0o666)!
    wfile.set_buffer(mut buf, .line_buffered)
    wfile.write_string('----------------------------------\n')!
    for line in ['hello\n', 'world\n', 'hi\n'] {
        wfile.write_string(line)!
        wfile.flush()
        dump(buf)
        print(buf.bytestr())
        // assert buf.bytestr().contains(line) // this works on GLIBC, but fails on MUSL.
        unsafe { buf.reset() }
    }
    wfile.close()

    content := os.read_lines('text.txt')!
    dump(content)
    assert content == ['----------------------------------', 'hello', 'world', 'hi']
}

fn test_set_buffer_fully_buffered() {
    dump(@LOCATION)
    mut buf := []u8{len: 30}
    dump(buf)
    mut wfile := os.open_file('text.txt', 'wb', 0o666)!
    wfile.set_buffer(mut buf, .fully_buffered)
    // Ubuntu GLIBC 2.31 seems to not use the buffer for the first write call, but it does write to the buffer first for the subsequent ones.
    // MUSL (detecting the MUSL version is deliberately made hard by its authors, because of course it is :-( ...), will skip the first 8 bytes
    // of the buffer, and write everything after those.
    wfile.write_string('S')!
    wfile.write_string('---\n')!
    dump(buf)
    for line in ['hello\n', 'world\n', 'hi\n'] {
        wfile.write_string(line)!
        dump(buf)
        // print(buf.bytestr())
    }
    wfile.close()
    dump(buf)
    // assert buf.bytestr().starts_with('---\nhello\nworld\nhi\n') // works on GLIBC, fails on MUSL
    assert buf.bytestr().contains('---\nhello\nworld\n')

    content := os.read_lines('text.txt')!
    dump(content)
    assert content == ['S---', 'hello', 'world', 'hi']
}

fn test_set_unbuffered() {
    dump(@LOCATION)
    mut buf := []u8{len: 30}
    dump(buf)
    mut wfile := os.open_file('text.txt', 'wb', 0o666)!
    wfile.set_buffer(mut buf, .not_buffered)
    wfile.write_string('S')!
    wfile.write_string('---\n')!
    dump(buf)
    for line in ['hello\n', 'world\n', 'hi\n'] {
        wfile.write_string(line)!
        dump(buf)
        // print(buf.bytestr())
    }
    wfile.close()
    // dump(buf.bytestr())
    assert buf.all(it == 0)

    content := os.read_lines('text.txt')!
    dump(content)
    assert content == ['S---', 'hello', 'world', 'hi']
}