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

#define PORT 8081
#define BUFFER_SIZE 4096

int main() {
    int server_fd, new_socket;
    struct sockaddr_in address;
    int opt = 1;
    int addrlen = sizeof(address);
    char buffer[BUFFER_SIZE] = {0};

    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, 3) < 0) {
        perror("listen");
        exit(EXIT_FAILURE);
    }

    printf("TCP Performance Server listening on port %d...\n", PORT);

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

    printf("Client connected. Receiving data...\n");

    long long total_bytes = 0;
    int valread;
    struct timespec start, end;
    clock_gettime(CLOCK_MONOTONIC, &start);

    while ((valread = read(new_socket, buffer, BUFFER_SIZE)) > 0) {
        total_bytes += valread;
    }

    clock_gettime(CLOCK_MONOTONIC, &end);

    double time_taken = (end.tv_sec - start.tv_sec) + (end.tv_nsec - start.tv_nsec) / 1e9;
    double mb = total_bytes / (1024.0 * 1024.0);
    double throughput = mb / time_taken;

    printf("Received %.2f MB in %.2f seconds.\n", mb, time_taken);
    printf("Throughput: %.2f MB/s\n", throughput);

    close(new_socket);
    close(server_fd);

    return 0;
}