#include <stdio.h>
#include <string.h>
#include <winsock2.h>
#include <ws2tcpip.h>

#include "common.h"

#pragma comment(lib, "ws2_32.lib")

void send_with_stopwait(SOCKET sock,
                        struct sockaddr_in6 *peer,
                        struct packet *pkt)
{
    int len = sizeof(*peer);

    while (1) {
        sendto(sock, (char *)pkt, sizeof(*pkt), 0,
               (struct sockaddr *)peer, len);

        fd_set fds;
        FD_ZERO(&fds);
        FD_SET(sock, &fds);

        TIMEVAL tv;
        tv.tv_sec = TIMEOUT_SEC;
        tv.tv_usec = 0;

        int ret = select(0, &fds, NULL, NULL, &tv);
        if (ret > 0) {
            struct packet ack;
            recvfrom(sock, (char *)&ack, sizeof(ack), 0, NULL, NULL);
            if (ack.type == TYPE_ACK && ack.seq == pkt->seq) {
                return;
            }
        }
        printf("[timeout] retransmit\n");
    }
}

int main(int argc, char *argv[])
{
    if (argc != 2) {
        printf("用法: %s <对方IPv6地址>\n", argv[0]);
        return 1;
    }

    WSADATA wsa;
    WSAStartup(MAKEWORD(2, 2), &wsa);

    SOCKET sock = socket(AF_INET6, SOCK_DGRAM, 0);

    struct sockaddr_in6 local = {0};
    local.sin6_family = AF_INET6;
    local.sin6_addr = in6addr_any;
    local.sin6_port = htons(PORT);
    bind(sock, (struct sockaddr *)&local, sizeof(local));

    struct sockaddr_in6 peer = {0};
    peer.sin6_family = AF_INET6;
    peer.sin6_port = htons(PORT);
    inet_pton(AF_INET6, argv[1], &peer.sin6_addr);

    uint8_t send_seq = 0;
    uint8_t recv_seq = 0;
    struct packet pkt, rcv;

    printf("Windows UDP IPv6 Stop-Wait Chat\n");

    while (1) {
        fd_set fds;
        FD_ZERO(&fds);
        FD_SET(sock, &fds);
        TIMEVAL tv = {0, 100000};

        if (select(0, &fds, NULL, NULL, &tv) > 0) {
            recvfrom(sock, (char *)&rcv, sizeof(rcv), 0, NULL, NULL);
            if (rcv.type == TYPE_DATA) {
                if (rcv.seq == recv_seq) {
                    printf("\npeer: %s\n", rcv.payload);
                    recv_seq ^= 1;
                }
                rcv.type = TYPE_ACK;
                sendto(sock, (char *)&rcv, sizeof(rcv), 0,
                       (struct sockaddr *)&peer, sizeof(peer));
            }
        }

        printf(">> ");
        if (!fgets(pkt.payload, sizeof(pkt.payload), stdin))
            break;

        pkt.seq = send_seq;
        pkt.type = TYPE_DATA;

        send_with_stopwait(sock, &peer, &pkt);
        send_seq ^= 1;
    }

    closesocket(sock);
    WSACleanup();
    return 0;
}