#include <iostream>
#include <cstdio>
#include <cstring>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>

const int PORT = 1234;
const int MAX_MESSAGE_LENGTH = 256;

// Forward declarations
void handleConnection(int sockfd);
void handlePing(int sockfd);
void handlePong(int sockfd);

int main()
{
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);

    if (sockfd < 0)
    {
        std::cerr << "Error: Failed to create socket" << std::endl;
        return 1;
    }

    struct sockaddr_in serv_addr;
    std::memset(&serv_addr, 0, sizeof(serv_addr));

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = INADDR_ANY;
    serv_addr.sin_port = htons(PORT);

    if (bind(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0)
    {
        std::cerr << "Error: Failed to bind socket" << std::endl;
        return 1;
    }

    if (listen(sockfd, 5) < 0)
    {
        std::cerr << "Error: Failed to listen on socket" << std::endl;
        return 1;
    }

    while (true)
    {
        struct sockaddr_in cli_addr;
        socklen_t cli_len = sizeof(cli_addr);

        int connfd = accept(sockfd, (struct sockaddr*)&cli_addr, &cli_len);

        if (connfd < 0)
        {
            std::cerr << "Error: Failed to accept connection" << std::endl;
            continue;
        }

        handleConnection(connfd);
    }

    return 0;
}

void handleConnection(int sockfd)
{
    while (true)
    {
        char message[MAX_MESSAGE_LENGTH];
        int n = read(sockfd, message, MAX_MESSAGE_LENGTH - 1);

        if (n < 0)
        {
            std::cerr << "Error: Failed to read from socket" << std::endl;
            return;
        }

        if (n == 0)
        {
            std::cout << "Connection closed" << std::endl;
            return;
        }

        message[n] = '\0';

        if (std::strcmp(message, "PING") == 0)
        {
            handlePing(sockfd);
        }
        else if (std::strcmp(message, "PONG") == 0)
        {
            handlePong(sockfd);
        }
        else
        {
            std::cerr << "Error: Invalid message received" << std::endl;
        }
    }
}