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

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

#include "common.h"

#define LOCAL_PORT 9001
#define PEER_PORT  9000
#define TIMEOUT_MS 200

int main(int argc, char *argv[]) {
    if (argc != 2) {
        printf("Usage: %s <Ubuntu IPv6>\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_port = htons(LOCAL_PORT);
    local.sin6_addr = in6addr_any;
    bind(sock, (struct sockaddr*)&local, sizeof(local));

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

    int timeout = TIMEOUT_MS;
    setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO,
               (char*)&timeout, sizeof(timeout));

    uint8_t send_seq = 0;
    uint8_t waiting_ack = 0;
    packet_t last_pkt;

    while (1) {
        /*  尝试接收 */
        packet_t pkt;
        struct sockaddr_in6 from;
        int fromlen = sizeof(from);

        int n = recvfrom(sock, (char*)&pkt, sizeof(pkt), 0,
                         (struct sockaddr*)&from, &fromlen);

        if (n > 0) {
            if (pkt.type == TYPE_DATA) {
                printf("\nPeer: %s", pkt.data);

                packet_t ack = {0};
                ack.type = TYPE_ACK;
                ack.seq = pkt.seq;

                sendto(sock, (char*)&ack, sizeof(ack), 0,
                       (struct sockaddr*)&peer, sizeof(peer));
            }
            else if (pkt.type == TYPE_ACK &&
                     waiting_ack && pkt.seq == send_seq) {
                waiting_ack = 0;
                send_seq ^= 1;
            }
        }

        /*  如果不在等 ACK，允许发送 */
        if (!waiting_ack) {
            char buf[DATA_LEN];
            printf("You: ");
            fflush(stdout);

            if (fgets(buf, sizeof(buf), stdin) == NULL)
                continue;

            memset(&last_pkt, 0, sizeof(last_pkt));
            last_pkt.type = TYPE_DATA;
            last_pkt.seq = send_seq;
            last_pkt.length = strlen(buf);
            memcpy(last_pkt.data, buf, last_pkt.length);

            sendto(sock, (char*)&last_pkt, sizeof(last_pkt), 0,
                   (struct sockaddr*)&peer, sizeof(peer));

            waiting_ack = 1;
        } else {
            sendto(sock, (char*)&last_pkt, sizeof(last_pkt), 0,
                   (struct sockaddr*)&peer, sizeof(peer));
            Sleep(TIMEOUT_MS);
        }
    }
}