#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <signal.h>
#include <assert.h>
#include <time.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <inttypes.h>
#include <arpa/inet.h>

void usage(char *fileName)
{
    fprintf(stderr, "%s [-p PORT] [-i INDEX] DOC_ROOT\n", fileName);
    exit(EXIT_FAILURE);
}


int serverSocket = 0;
int clientSocket = 0;

void handleSignal(int sig)
{
    if (serverSocket > 0) {
        shutdown(serverSocket, SHUT_RDWR);
        close(serverSocket);
    }
    if (clientSocket > 0) {
        shutdown(clientSocket, SHUT_RDWR);
        close(clientSocket);
    }
    exit(EXIT_SUCCESS);
}

/**
 * Method that checks if the first string starts with another string
 * @brief compare string beginnng with others tring
 * @param a,b - two strings
 */
int startsWith(const char *a, const char *b)
{
   if(strncmp(a, b, strlen(b)) == 0) return 1;
   return 0;
}

int main(int argc, char *argv[]) {

    if (argc < 2) usage(argv[0]);

    char * port = "8080";
    char * file = "index.html";

    int c = 0;
    while ((c = getopt(argc, argv, ":p:i:")) != -1)
    {
        switch (c)
        {
            case 'p':
                port = strdup(optarg);
                break;
            case 'i':
                file = strdup(optarg);
                break;
            case '?':
                usage(argv[0]);
            default:
                assert(0);
                exit(EXIT_FAILURE);
        }
    }

    char * root;

    // check root parameter
    if (optind >= argc) {
        usage(argv[0]);
    }
    else {
        root = argv[optind];
    }

    //-------------------------------------------------------- Create Server Socket --------------------------------------------------

    char* ptr = NULL;
    unsigned short int portValue = (unsigned short int)strtol(port, &ptr, 10);
    if (!ptr)
    {
        fprintf(stderr, "Invalid port %s\n", port);
        exit(EXIT_FAILURE);
    }
    // create
    serverSocket = socket(AF_INET, SOCK_STREAM, 0);
    if (serverSocket == 0) {
        fprintf(stderr, "Bad socket: %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    }

    // set server port
    struct sockaddr_in addr;
    memset(&addr, 0, sizeof addr);
    addr.sin_family = AF_INET;
    addr.sin_port = htons(portValue);
    addr.sin_addr.s_addr = htonl(INADDR_ANY);

    //bind
    if (bind(serverSocket, (struct sockaddr *)&addr, sizeof(struct sockaddr))== -1) {
        fprintf(stderr, "Error when binding %s\n", strerror(errno));
        close(serverSocket);
        exit(EXIT_FAILURE);
    }

    // listen
    if (listen(serverSocket, SOMAXCONN) == -1) {
        fprintf(stderr, "Error when listening %s\n", strerror(errno));
        close(serverSocket);
        exit(EXIT_FAILURE);
    }

    // enable signals
    signal(SIGINT, handleSignal);
    signal(SIGTERM, handleSignal);
    //--------------------------------------------------------------------------------------------------------------------------------

    //-------------------------------------------------------- Accept incoming client connections ------------------------------------
    while (1)
    {
        clientSocket = accept(serverSocket, NULL, NULL);

        if (clientSocket < 0) {
            fprintf(stderr, "Error when accepting client.");
            break;
        }

        char request[1023];
        ssize_t received = recv(clientSocket, request, 1023, 0);

        if (received <= 0) {
            shutdown(clientSocket, SHUT_RDWR);
            close(clientSocket);
            continue;
        }
        //-------------------------------------------------------------------------------------------------- Handle request
        // parse first line
        char *ptr = strstr(request, " HTTP/1.1\r\n");
        // if invalid HTTP header, reply 400 error
        if (!ptr) {
            char errorResponse[1023];
            size_t lenghtError = sprintf(errorResponse, "HTTP/1.1 %d %s\r\nConnection: close\r\n\r\n", 400, "Bad Request");
            send(clientSocket, errorResponse, lenghtError, 0);
        }
        // if unsupported HTTP command except GET, reply 501 error
        else if (strstr(request, "GET ") != request) {
            char errorResponse[1023];
            size_t lenghtError = sprintf(errorResponse, "HTTP/1.1 %d %s\r\nConnection: close\r\n\r\n", 501, "Not implemented");
            send(clientSocket, errorResponse, lenghtError, 0);
        }
        // parse target path from the first line
        else
        {
            *ptr = '\0';                            // erase end
            char *pathname = strdup(root);
            strcat(pathname, "/");
            if (strcmp(request + 4, "/") == 0) strcat(pathname, file);  // if "/" is given, set default file
            else strcat(pathname, request + 5);             // otherwise, set given path
            // try to open file
            FILE *fp = fopen(pathname, "r");
            // if failed, reply 404 error
            if (!fp) {
                char errorResponse[1023];
                size_t lenghtError = sprintf(errorResponse, "HTTP/1.1 %d %s\r\nConnection: close\r\n\r\n", 404, "Not found");
                send(clientSocket, errorResponse, lenghtError, 0);
            }
            else
            {
                // get current timestamp
            char timestamp[1023];
            time_t tmp = time(NULL);
            struct tm t = *localtime(&tmp);
            strftime(timestamp, sizeof(timestamp), "%a, %d %b %Y %T %z", &t);
                // get content length
                int content_length = 0;
                fseek(fp, 0L, SEEK_END);
                content_length = ftell(fp);
                fseek(fp, 0L, SEEK_SET);
                // send HTTP 200 reply
                char respond[1023];
                size_t size = sprintf(respond, "HTTP/1.1 200 OK\r\nDate: %s\r\nContent-Length: %d\r\nConnection: close\r\n\r\n", timestamp, content_length);
                send(clientSocket, respond, size, 0);
                if (content_length > 0) {
                    char data[1023];
                    ssize_t bytes = 0;
                    do{
                        // try to read all data from the file and send to the client
                        bytes = fread(data, 1, 1023, fp);
                        if (bytes > 0) send(clientSocket, data, bytes, 0);
                    } while(bytes > 0);
                }
                //close file handle
                fclose(fp);
            }
        }
        //-------------------------------------------------------------------------------------------------- Handle request over------------------------------------

        shutdown(clientSocket, SHUT_RDWR);
        close(clientSocket);
    }
    //--------------------------------------------------------------------------------------------------------------------------------
    return EXIT_SUCCESS;
}