/// ping but with rust, rust + ping -> ring
#[derive(Parser, Debug, Clone)] // Parser生成clap命令行解析方法
#[command(author, version, about, long_about = None)]
pub struct Args {
    /// Count of ping times
    #[arg(short, default_value_t = 4)] // short表示開啟短命名，默認為第一個字母，可以指定；default_value_t設置默認值
    count: u16,

    /// Ping packet size
    #[arg(short = 's', default_value_t = 64)]
    packet_size: usize,

    /// Ping ttl
    #[arg(short = 't', default_value_t = 64)]
    ttl: u32,

    /// Ping timeout seconds
    #[arg(short = 'w', default_value_t = 1)]
    timeout: u64,

    /// Ping interval duration milliseconds
    #[arg(short = 'i', default_value_t = 1000)]
    interval: u64,

    /// Ping destination, ip or domain
    #[arg(value_parser=Address::parse)] // 自定義解析
    destination: Address,
}

let mut buf = vec![0; self.config.packet_size];
let mut icmp = MutableEchoRequestPacket::new(&mut buf[..]).ok_or(RingError::InvalidBufferSize)?;
icmp.set_icmp_type(IcmpTypes::EchoRequest); // 設置為EchoRequest類型
icmp.set_icmp_code(IcmpCodes::NoCode);
icmp.set_sequence_number(self.config.sequence + seq_offset); // 序列號
icmp.set_identifier(self.config.id);
icmp.set_checksum(util::checksum(icmp.packet(), 1)); // 校驗函數

let socket = Socket::new(Domain::IPV4, Type::DGRAM, Some(Protocol::ICMPV4))?;
let src = SocketAddr::new(net::IpAddr::V4(Ipv4Addr::UNSPECIFIED), 0);
socket.bind(&src.into())?; // 綁定源地址
socket.set_ttl(config.ttl)?;
socket.set_read_timeout(Some(Duration::from_secs(config.timeout)))?; // 超時配置
socket.set_write_timeout(Some(Duration::from_secs(config.timeout)))?;

???????// 發送
socket.send_to(icmp.packet_mut(), &self.dest.into())?;

let mut mem_buf = unsafe { &mut *(buf.as_mut_slice() as *mut [u8] as *mut [std::mem::MaybeUninit<u8>]) };
let (size, _) = self.socket.recv_from(&mut mem_buf)?;

???????// 轉換成EchoReply
let reply = EchoReplyPacket::new(&buf).ok_or(RingError::InvalidPacket)?;

let send = Arc::new(AtomicU64::new(0)); // 統計發送次數
let _send = send.clone();
let this = Arc::new(self.clone());
let (sx, rx) = bounded(this.config.count as usize); // channel接受線程handler
thread::spawn(move || {
    for i in 0..this.config.count {
        let _this = this.clone();
        sx.send(thread::spawn(move || _this.ping(i))).unwrap(); // 線程中運行ping，并將handler發送到channel中

        _send.fetch_add(1, Ordering::SeqCst); // 發送一次，send加1

        if i < this.config.count - 1 {
            thread::sleep(Duration::from_millis(this.config.interval));
        }
    }
    drop(sx); // 發送完成關閉channel
});

let success = Arc::new(AtomicU64::new(0)); // 定義請求成功的請求
let _success = success.clone();
let (summary_s, summary_r) = bounded(1); // channel來判斷是否處理完成
thread::spawn(move || {
    for handle in rx.iter() {
        if let Some(res) = handle.join().ok() {
            if res.is_ok() {
                _success.fetch_add(1, Ordering::SeqCst); // 如果handler結果正常，success加1
            }
        }
    }
    summary_s.send(()).unwrap(); // 處理完成
});

let stop = signal_notify()?; // 監聽退出信號
select!(
    recv(stop) -> sig => {
        if let Some(s) = sig.ok() { // 收到退出信號
            println!("Receive signal {:?}", s);
        }
    },
    recv(summary_r) -> summary => { // 任務完成
        if let Some(e) = summary.err() {
            println!("Error on summary: {}", e);
        }
    },
);

fn signal_notify() -> std::io::Result<Receiver<i32>> {
    let (s, r) = bounded(1); // 定義channel，用來異步接受退出信號

    let mut signals = signal_hook::iterator::Signals::new(&[SIGINT, SIGTERM])?; // 創建信號

    thread::spawn(move || {
        for signal in signals.forever() { // 如果結果到信號發送到channel中
            s.send(signal).unwrap();
            break;
        }
    });

    Ok(r) // 返回接受channel
}