#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <pthread.h>
#include <time.h>

#define PORT 8081
#define BUFFER_SIZE 4096
#define EXPECTED_CONNECTIONS 5
#define TOTAL_TARGET_MB 100

long long global_bytes_received = 0;
int connections_handled = 0;
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
struct timespec start_time, end_time;
int first_connect = 1;

void *handle_client(void *socket_desc) {
    int sock = *(int*)socket_desc;
    free(socket_desc);
    char buffer[BUFFER_SIZE];
    int valread;
    long long thread_bytes = 0;

    while ((valread = read(sock, buffer, BUFFER_SIZE)) > 0) {
        thread_bytes += valread;
    }

    pthread_mutex_lock(&lock);
    global_bytes_received += thread_bytes;
    connections_handled++;
    pthread_mutex_unlock(&lock);

    close(sock);
    return NULL;
}

int main() {
    int server_fd, new_socket;
    struct sockaddr_in address;
    int opt = 1;
    int addrlen = sizeof(address);

    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt))) {
        perror("setsockopt");
        exit(EXIT_FAILURE);
    }

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

    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

    if (listen(server_fd, 5) < 0) {
        perror("listen");
        exit(EXIT_FAILURE);
    }

    printf("TCP Multi-Connection Server listening on port %d...\n", PORT);
    printf("Waiting for %d connections to transfer total %d MB...\n", EXPECTED_CONNECTIONS, TOTAL_TARGET_MB);

    pthread_t threads[EXPECTED_CONNECTIONS];
    int t_count = 0;

    while (t_count < EXPECTED_CONNECTIONS) {
        if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen)) < 0) {
            perror("accept");
            exit(EXIT_FAILURE);
        }

        if (first_connect) {
            clock_gettime(CLOCK_MONOTONIC, &start_time);
            first_connect = 0;
            printf("First connection received. Timer started.\n");
        }

        int *new_sock = malloc(1);
        *new_sock = new_socket;
        
        if (pthread_create(&threads[t_count], NULL, handle_client, (void*)new_sock) < 0) {
            perror("could not create thread");
            return 1;
        }
        t_count++;
    }

    // Wait for all threads to finish
    for (int i = 0; i < EXPECTED_CONNECTIONS; i++) {
        pthread_join(threads[i], NULL);
    }

    clock_gettime(CLOCK_MONOTONIC, &end_time);

    double time_taken = (end_time.tv_sec - start_time.tv_sec) + (end_time.tv_nsec - start_time.tv_nsec) / 1e9;
    double mb = global_bytes_received / (1024.0 * 1024.0);
    double throughput = mb / time_taken;

    printf("\nTest Finished:\n");
    printf("Total Connections: %d\n", connections_handled);
    printf("Total Data Received: %.2f MB\n", mb);
    printf("Time Taken: %.2f seconds\n", time_taken);
    printf("Total Throughput: %.2f MB/s\n", throughput);

    close(server_fd);
    return 0;
}