#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/socket.h>
#include <errno.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>

int main(int argc, char **argv)
{
    const char *addr = "127.0.0.1";
    uint16_t port = 6969;
    int server_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (server_fd < 0) {
        fprintf(stderr, "ERROR: could not create socket: %d\n", errno);
        return(1);
    }

    int option = 1;

    setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR, &option, sizeof(option));
    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port);
    server_addr.sin_addr.s_addr = inet_addr(addr);

    ssize_t err = bind(server_fd, (struct sockaddr*) &server_addr, sizeof(server_addr));
    if (err != 0) {
        fprintf(stderr, "ERROR: could not bind sock: %d\n", errno);
        return(1);
    }

    err = listen(server_fd, 69);
    if (err != 0) {
        fprintf(stderr, "ERROR: could not listen to socket: %d\n", errno);
        return(1);
    }

    printf("listening to http://%s:%d\n", addr, port);

    const char *body = "Hello world!";
    size_t body_len = strlen(body);

    char response[1024];
    int response_len = snprintf(response, sizeof(response),
            "HTTP/1.1 200 OK\r\n"
            "Content-Type: text/plain\r\n"
            "Connection: close\r\n"
            "Content-Length: %zu\r\n"
            "\r\n"
            "%s",
            body_len, body);

    if (response_len < 0 || (size_t) response_len >= sizeof(response)) {
        fprintf(stderr, "ERROR: response buffer too small\n");
        return(1);
    }

    for (;;) {
        struct sockaddr_in client_addr;
        socklen_t client_addrlen = sizeof(client_addr);
        int client_fd = accept(server_fd, (struct sockaddr*) &client_addr, &client_addrlen);
        if (client_fd <0) {
            fprintf(stderr, "ERROR: could not accept connection: %d\n", errno);
            continue;
        }

        char buffer[1024];
        recv(client_fd, buffer, sizeof(buffer), 0);

        if(write(client_fd, response, response_len) < 0) {
            fprintf(stderr, "ERROR: could not write response: %d\n", errno);
        }

        close(client_fd);
    }

    close(server_fd);
    return(0);
}