#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <malloc.h>
#include <time.h>

char* replace(const char* s, const char* find, const char* replace)
{
    const char* p;
    char* ret;

    p = strstr(s, find);

    if (p == NULL)
        return NULL;

    ret = malloc(strlen(s) + strlen(replace) + 1 - strlen(find));

    if (ret == NULL)
        return NULL;

    if (p != s)
        strncpy(ret, s, p-s);

    strcpy(ret + (p-s), replace);
    strcat(ret, p + strlen(find));

    return ret;
}


main()
{
 int server_socket, neuer_socket;
 int laenge, anzahl;
 struct sockaddr_in serverinfo, clientinfo;
 char empfangene_zeichen[1000];
 char web_seite[1000];
 int i, mail_empfang,x, gothelo, fails;
 unsigned short int portnummer = 25;
 char ip_adresse[] = "INADDR_ANY";
 char *msg_get;

struct tm *zeit;
   time_t sekunde;
   char time_str[80];
   time(&sekunde);
   zeit = localtime(&sekunde);

    fails = 0;

 FILE *datei;
 mail_empfang = 0;
 gothelo = 0;
 printf("\n Server: socket()...");

 server_socket = socket(AF_INET, SOCK_STREAM, 0);

 serverinfo.sin_family = AF_INET;
 serverinfo.sin_addr.s_addr = htonl(INADDR_ANY);
 serverinfo.sin_port = htons(portnummer);
 laenge = sizeof(serverinfo);

 printf("\n Server: bind()...");

 bind(server_socket, (struct sockaddr *)&serverinfo, laenge);

 printf("\n Server: listen()...");
 printf("\n Server mit IP %s",ip_adresse);
 printf(" an Port %d wartet...",portnummer);

 listen(server_socket, 3);

wait_again:;

while(1)
{
   strftime(time_str, 80, "%a, %d %b %Y %H:%M:%S",zeit);

    printf("\n Server: accept()...");
    neuer_socket = accept(server_socket, (struct sockaddr *)&clientinfo, &laenge);
        printf("Verbindung mit %s\n\n\n",inet_ntoa(clientinfo.sin_addr));
        sprintf(web_seite, "220 mindcode.ath.cx MindCode ESMTP MAIL service ready at %s +0001\n", time_str);

    write(neuer_socket,web_seite,strlen(web_seite));
        printf("\n SEND > 220 mindcode.ath.cx MindCode ESMTP MAIL service ready at %s +0001\n", time_str);

        if(neuer_socket > 0)
            break;
//TODO: select();
}

 while(1)
   {


new_line:;



    anzahl = read(neuer_socket,empfangene_zeichen,sizeof(empfangene_zeichen));
        empfangene_zeichen[anzahl-1]=0;

        printf("%s\n", empfangene_zeichen);

        if(mail_empfang == 1)
                {

                            if(strncmp(empfangene_zeichen, "QUIT",4) == 0 || strncmp(empfangene_zeichen, "quit",4) == 0)
                                    {
                                    goto skip;
                                    }



            msg_get = replace(empfangene_zeichen, "\n", "<br><br>");

            for(i = 0; i < 12; i++)
            {
                msg_get = replace(msg_get, "\n", "<br>");
                }

// Wahrscheinlich: Wenn kein \n mehr vorhanden, stürzt er ab...

                datei = fopen ("fakemail.html", "a");
                fprintf (datei, msg_get);
                fprintf (datei, "<br>");
                fclose(datei);
              skip:;
            }


        if(strstr( empfangene_zeichen, "HELO" ))
         {
            sprintf(web_seite,"250 OK\n");
            write(neuer_socket,web_seite,strlen(web_seite));
                printf("\n SEND > 250 OK\n");
                gothelo = 1;
                goto new_line;
        }

        if( strstr( empfangene_zeichen, "EHLO" ))
         {
            sprintf(web_seite,"502 5.5.2 Error: command not recognized\n");
            write(neuer_socket,web_seite,strlen(web_seite));
                printf("\n SEND > 502 5.5.2 Error: command not recognized\n");
                goto new_line;
        }


        if( strstr( empfangene_zeichen, "MAIL" ) || strstr( empfangene_zeichen, "mail" ))
         {
            sprintf(web_seite,"250 OK\n");
            write(neuer_socket,web_seite,strlen(web_seite));
                printf("\n SEND > 250 OK\n");
                gothelo == 0;
            goto new_line;
        }

        if( strstr( empfangene_zeichen, "RCPT" ) || strstr( empfangene_zeichen, "rcpt" ))
         {
            sprintf(web_seite,"250 OK\n");
            write(neuer_socket,web_seite,strlen(web_seite));
                printf("\n SEND > 250 OK\n");
            goto new_line;
        }

            if( strstr( empfangene_zeichen, "DATA" ) || strstr( empfangene_zeichen, "data" ))
         {
            sprintf(web_seite,"354 Start mail input; end with <CRLF>.<CRLF>.\n");
            write(neuer_socket,web_seite,strlen(web_seite));
                printf("\n SEND > 354 Start mail input; end with <CRLF>.<CRLF>.\n");

                datei = fopen ("fakemail.html", "a");

                fprintf (datei, "<b><font color=\"green\">---------------- NEW MAIL ----------------<br><br></font></b>");

                fclose(datei);

                mail_empfang = 1;
            goto new_line;
        }


            if( strstr( empfangene_zeichen, "QUIT" ) || strstr( empfangene_zeichen, "quit" ))
         {
                if(gothelo == 1)
                    {
                    sprintf(web_seite,"500 You had nothing to say? Idiot!\n");
                write(neuer_socket,web_seite,strlen(web_seite));
                gothelo == 0;
                    }

                sprintf(web_seite,"221 Have a nice day :-)\n");
            write(neuer_socket,web_seite,strlen(web_seite));
            printf("\n SEND > 221 Have a nice day :-)\n");
            printf(" Server: close()... Beendet %s\n\n\n",inet_ntoa(clientinfo.sin_addr));
        close(neuer_socket);
                neuer_socket = 0;
            datei = fopen ("fakemail.html", "a");
            fprintf (datei, "<br><b><font color=\"green\">---------------- END MAIL ----------------<br><br></font></b>");
                fclose(datei);

                mail_empfang = 0;


                goto wait_again;
        }


        fails +=1;

                if(fails == 7)
                    {
            sprintf(web_seite,"421 4.7.0 You are stupid, get lost!\n");
            write(neuer_socket,web_seite,strlen(web_seite));
                printf("\n SEND > 421 4.7.0 You are stupid, get lost!\n");
            printf(" Server: close()... Beendet %s\n\n\n",inet_ntoa(clientinfo.sin_addr));
        close(neuer_socket);
                neuer_socket = 0;
                fails = 0;
        goto wait_again;
                    }

            sprintf(web_seite,"500 5.5.2 Error: What the fuck?\n");
            write(neuer_socket,web_seite,strlen(web_seite));
                printf("\n SEND > 500 5.5.2 Error: What the fuck?\n");

  }
}