#include <arpa/inet.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <unistd.h>

volatile sig_atomic_t is_terminated = 0;

enum {
    MAX_PATH_SIZE = 4096,
    PATH_LEFT_INDENT = (int)strlen("GET "),
    PATH_RIGHT_INDENT = (int)strlen(" HTTP/1.1\r\n")
};

void close_connection(int current_fd, FILE** current_stream)
{
    if (*current_stream != NULL) {
        fflush(*current_stream);
        shutdown(current_fd, SHUT_RDWR);
        fclose(*current_stream);
        *current_stream = NULL;
    }
}

void terminate(
    char* line_buffer,
    int socket_fd,
    int current_fd,
    FILE** current_stream)
{
    close_connection(current_fd, current_stream);
    free(line_buffer);
    close(socket_fd);
    exit(0);
}

bool check_termination(
    char* line_buffer,
    int socket_fd,
    int current_fd,
    FILE** current_stream)
{
    if (is_terminated) {
        terminate(line_buffer, socket_fd, current_fd, current_stream);
    }
    return true;
}

void handle_signal(int signo, siginfo_t* siginfo, void* context)
{
    is_terminated = 1;
}

void set_up_sigaction()
{
    struct sigaction signal_action = {.sa_sigaction = handle_signal,
                                      .sa_flags = SA_SIGINFO};
    sigaction(SIGTERM, &signal_action, NULL);
    sigaction(SIGINT, &signal_action, NULL);
}

int set_up_socket(char* port_num)
{
    struct sockaddr_in addr = {AF_INET, 0, 0};
    inet_aton("127.0.0.1", &addr.sin_addr);
    addr.sin_port = htons(strtol(port_num, NULL, 10));

    int socket_fd = socket(AF_INET, SOCK_STREAM, 0);
    bind(socket_fd, (struct sockaddr*)&addr, sizeof(struct sockaddr_in));

    listen(socket_fd, SOMAXCONN);

    return socket_fd;
}

int main(int argc, char** argv)
{
    const int directory_path_len = strlen(argv[2]);
    int socket_fd = set_up_socket(argv[1]);
    set_up_sigaction();

    char* line_buffer = NULL;
    size_t line_len = 0;
    char path[MAX_PATH_SIZE] = {};
    int current_fd = -1;
    FILE* current_stream = NULL;
    while (check_termination(line_buffer, socket_fd, current_fd, &current_stream)) {
        current_fd = accept(socket_fd, NULL, NULL);
        if (current_fd != -1) {
            current_stream = fdopen(current_fd, "r+");

            getline(&line_buffer, &line_len, current_stream);
            check_termination(line_buffer, socket_fd, current_fd, &current_stream);
            memset(path, 0, MAX_PATH_SIZE);
            strncpy(path, argv[2], directory_path_len);
            strncpy(
                path + directory_path_len,
                line_buffer + PATH_LEFT_INDENT,
                strlen(line_buffer) - (PATH_RIGHT_INDENT + PATH_LEFT_INDENT));
            do {
                check_termination(
                    line_buffer, socket_fd, current_fd, &current_stream);
                getline(&line_buffer, &line_len, current_stream);
            } while (!(line_buffer[0] == '\r') || !(line_buffer[1] == '\n'));

            check_termination(
                line_buffer, socket_fd, current_fd, &current_stream);

            switch (access(path, F_OK) + access(path, R_OK)) {
            case -2:
                fprintf(current_stream, "%s", "HTTP/1.1 404 Not Found\r\n\r\n");
                fflush(current_stream);
                break;
            case -1:
                fprintf(current_stream, "%s", "HTTP/1.1 403 Forbidden\r\n\r\n");
                fflush(current_stream);
                break;
            case 0:
                fprintf(current_stream, "%s", "HTTP/1.1 200 OK\r\n");
                fflush(current_stream);
                struct stat file_info = {};
                lstat(path, &file_info);
                fprintf(
                    current_stream,
                    "Content-Length: %d\r\n\r\n",
                    file_info.st_size);
                fflush(current_stream);

                int file_fd = open(path, O_RDONLY);
                char* file_content = mmap(
                    NULL, file_info.st_size, PROT_READ, MAP_SHARED, file_fd, 0);

                write(current_fd, file_content, file_info.st_size);

                munmap(file_content, file_info.st_size);
                close(file_fd);
            }
            close_connection(current_fd, &current_stream);
        }
    }

    return 0;
}