import os
import time

const ready_marker = 'ready\n'

fn test_stdout_is_flushed_by_default() {
    $if windows {
        return
    }
    mut cap := os.stdio_capture()!
    println('ready')
    mut pending := false
    for _ in 0 .. 100 {
        if os.fd_is_pending(cap.stdout.read_fd) {
            pending = true
            break
        }
        time.sleep(10 * time.millisecond)
    }
    cap.stop()
    stdout := cap.stdout.slurp().join('')
    stderr := cap.stderr.slurp().join('')
    cap.close()
    assert pending
    assert stdout == ready_marker, stdout
    assert stderr == ''
}

fn redirected_stdout_bytes(snippet string) ![]u8 {
    stamp := time.now().unix_milli()
    source_path := os.join_path(os.vtmp_dir(), 'redirected_stdout_${stamp}.v')
    output_path := os.join_path(os.vtmp_dir(), 'redirected_stdout_${stamp}.bin')
    os.write_file(source_path, 'fn main() {\n\t${snippet}\n}\n')!
    defer {
        os.rm(source_path) or {}
        os.rm(output_path) or {}
    }
    cmd := '${os.quoted_path(@VEXE)} run ${os.quoted_path(source_path)} > ${os.quoted_path(output_path)}'
    res := os.execute(cmd)
    assert res.exit_code == 0, 'command failed: ${cmd}\noutput:\n${res.output}'
    return os.read_bytes(output_path)!
}

fn assert_redirected_stdout_bytes(snippet string, expected []u8) ! {
    bytes := redirected_stdout_bytes(snippet)!
    assert bytes == expected, 'expected ${expected}, got ${bytes}'
}

fn test_redirected_stdout_preserves_newline_bytes() ! {
    assert_redirected_stdout_bytes(r"print('\n')", [u8(`\n`)])!
    assert_redirected_stdout_bytes(r"print('\r\n')", [u8(`\r`), `\n`])!
}