#[macro_use]
extern crate log;
extern crate env_logger;
extern crate getopts;
extern crate smoltcp;
extern crate byteorder;

mod utils;

use std::str::FromStr;
use std::collections::BTreeMap;
use std::cmp;
use std::os::unix::io::AsRawFd;
use smoltcp::time::{Duration, Instant};
use smoltcp::phy::Device;
use smoltcp::phy::wait as phy_wait;
use smoltcp::wire::{EthernetAddress, IpAddress, IpCidr,
                    Ipv4Address, Icmpv4Repr, Icmpv4Packet};
use smoltcp::iface::{NeighborCache, EthernetInterfaceBuilder};
use smoltcp::socket::{SocketSet, IcmpSocket, IcmpSocketBuffer, IcmpPacketMetadata, IcmpEndpoint};
use std::collections::HashMap;
use byteorder::{ByteOrder, NetworkEndian};

fn main() {
    utils::setup_logging("warn");

    let (mut opts, mut free) = utils::create_options();
    utils::add_tap_options(&mut opts, &mut free);
    utils::add_middleware_options(&mut opts, &mut free);
    opts.optopt("c", "count", "Amount of echo request packets to send (default: 4)", "COUNT");
    opts.optopt("i", "interval",
                "Interval between successive packets sent (seconds) (default: 1)", "INTERVAL");
    opts.optopt("", "timeout",
                "Maximum wait duration for an echo response packet (seconds) (default: 5)",
                "TIMEOUT");
    free.push("ADDRESS");

    let mut matches = utils::parse_options(&opts, free);
    let device = utils::parse_tap_options(&mut matches);
    let fd = device.as_raw_fd();
    let device = utils::parse_middleware_options(&mut matches, device, /*loopback=*/false);
    let device_caps = device.capabilities();
    let address  = Ipv4Address::from_str(&matches.free[0]).expect("invalid address format");
    let count    = matches.opt_str("count").map(|s| usize::from_str(&s).unwrap()).unwrap_or(4);
    let interval = matches.opt_str("interval")
        .map(|s| Duration::from_secs(u64::from_str(&s).unwrap()))
        .unwrap_or(Duration::from_secs(1));
    let timeout  = Duration::from_secs(
        matches.opt_str("timeout").map(|s| u64::from_str(&s).unwrap()).unwrap_or(5)
    );

    let neighbor_cache = NeighborCache::new(BTreeMap::new());

    let remote_addr = address;
    let local_addr  = Ipv4Address::new(192, 168, 69, 1);

    let icmp_rx_buffer = IcmpSocketBuffer::new(vec![IcmpPacketMetadata::EMPTY], vec![0; 256]);
    let icmp_tx_buffer = IcmpSocketBuffer::new(vec![IcmpPacketMetadata::EMPTY], vec![0; 256]);
    let icmp_socket = IcmpSocket::new(icmp_rx_buffer, icmp_tx_buffer);

    let ethernet_addr = EthernetAddress([0x02, 0x00, 0x00, 0x00, 0x00, 0x02]);
    let ip_addr = IpCidr::new(IpAddress::from(local_addr), 24);
    let default_v4_gw = Ipv4Address::new(192, 168, 69, 100);
    let mut iface = EthernetInterfaceBuilder::new(device)
            .ethernet_addr(ethernet_addr)
            .ip_addrs([ip_addr])
            .ipv4_gateway(default_v4_gw)
            .neighbor_cache(neighbor_cache)
            .finalize();

    let mut sockets = SocketSet::new(vec![]);
    let icmp_handle = sockets.add(icmp_socket);

    let mut send_at = Instant::from_millis(0);
    let mut seq_no = 0;
    let mut received = 0;
    let mut echo_payload = [0xffu8; 40];
    let mut waiting_queue = HashMap::new();
    let ident = 0x22b;
    let endpoint = IpAddress::Ipv4(remote_addr);

    loop {
        iface.poll(&mut sockets, Instant::now()).unwrap();

        {
            let timestamp = Instant::now();
            let mut socket = sockets.get::<IcmpSocket>(icmp_handle);
            if !socket.is_open() {
                socket.bind(IcmpEndpoint::Ident(ident)).unwrap();
                send_at = timestamp;
            }

            if socket.can_send() && seq_no < count as u16 &&
                    send_at <= timestamp {
                NetworkEndian::write_i64(&mut echo_payload, timestamp.total_millis());
                let icmp_repr = Icmpv4Repr::EchoRequest {
                    ident: ident,
                    seq_no,
                    data: &echo_payload,
                };

                let icmp_payload = socket
                    .send(icmp_repr.buffer_len(), endpoint)
                    .unwrap();

                let mut icmp_packet = Icmpv4Packet::new(icmp_payload);
                icmp_repr.emit(&mut icmp_packet, &device_caps.checksum);

                waiting_queue.insert(seq_no, timestamp);
                seq_no += 1;
                send_at += interval;
            }

            if socket.can_recv() {
                let (payload, _) = socket.recv().unwrap();
                let icmp_packet = Icmpv4Packet::new(&payload);
                let icmp_repr = Icmpv4Repr::parse(&icmp_packet, &device_caps.checksum).unwrap();

                if let Icmpv4Repr::EchoReply { seq_no, data, .. } = icmp_repr {
                    if let Some(_) = waiting_queue.get(&seq_no) {
                        let packet_timestamp_ms = NetworkEndian::read_i64(data);
                        println!("{} bytes from {}: icmp_seq={}, time={}ms",
                                 data.len(), remote_addr, seq_no,
                                 timestamp.total_millis() - packet_timestamp_ms);
                        waiting_queue.remove(&seq_no);
                        received += 1;
                    }
                }
            }

            waiting_queue.retain(|seq, from| {
                if timestamp - *from < timeout {
                    true
                } else {
                    println!("From {} icmp_seq={} timeout", remote_addr, seq);
                    false
                }
            });

            if seq_no == count as u16 && waiting_queue.is_empty() {
                break
            }
        }

        let timestamp = Instant::now();
        match iface.poll_at(&sockets, timestamp) {
            Some(poll_at) if timestamp < poll_at => {
                let resume_at = cmp::min(poll_at, send_at);
                phy_wait(fd, Some(resume_at - timestamp)).expect("wait error");
            },
            Some(_) => (),
            None => {
                phy_wait(fd, Some(send_at - timestamp)).expect("wait error");
            }
        }
    }

    println!("--- {} ping statistics ---", remote_addr);
    println!("{} packets transmitted, {} received, {:.0}% packet loss",
             seq_no, received, 100.0 * (seq_no - received) as f64 / seq_no as f64);
}