/***************************************************************************************************/
/*               File Name: PrimesUpTo268435456               Written by: Koral Eren               */
/***************************************************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define DIGITS 6 //Don't change
#define BUFSIZE 80 //Don't change

/***************************************User Changeable*********************************************/
#define FILE_PRINT_LIMIT/*=>*/ 1000 /*<=*/// Change this to set after when you want
                                          // to print primes to file.
                                          // 10 < Value < 14630843 - Default is 1000.

int ParseForInt (long*);

int main()
{
     int count, ct;
     unsigned long long int i, j;
     int* primes;
     long limit, a = 2;

     printf ("\n\nThis program can find and display primes up to a desired integer\nless than 268435456\n");

     while (a == 2)
     {

        printf ("\nEnter an integer bigger than two\n(the primes will be calculated up to this number): ");

        while (ParseForInt (&limit) || limit < 3)
        {
            for( i = 0; i < 80; i ++)
                putchar ('*');

                printf ("\nWARNING: Not a valid integer input, check input\n");

            for( i = 0; i < 80; i ++)
                putchar ('*');

            printf ("\nEnter an integer bigger than two\n(the primes will be calculated up to this number): ");
        }

        count = 0;

        primes = malloc (sizeof (int) * limit);

        while (primes == NULL || limit > 268435456)
        {
            for ( i = 0; i < 80; i ++)
                putchar ('*');

            printf ("\nWARNING: Not enough memory or check allowed input range\n");

            for ( i = 0; i < 80; i ++)
                putchar ('*');

            printf ("\nEnter an integer bigger than two\n(the primes will be calculated up to this number): ");

            ParseForInt (&limit);

            free (primes);

            primes = malloc (sizeof (int) * limit);
        }

            for (i = 2; i < limit;i ++)
                primes [i] = 1;

            for (i = 2; i < limit; i ++)
                if (primes [i])
                    for (j = i; (i * j) < limit; j ++)
                        primes [(i*j)] = 0;

            for (i = 2; i < limit; i ++)
                if (primes [i])
                    count ++;


        printf ("\nThere are %d primes up to %d", count, limit);
        printf ("\nDo you want to display them?\n[PRESS 1 FOR YES]\n[PRESS 2 TO RESTART]");
        printf ("\n[PRESS ANY OTHER INTEGER TO EXIT]\nPress [1], [2] or any other integer: ");

        while (ParseForInt (&a))
        {
            for( i = 0; i < 80; i ++)
                putchar ('*');

            printf ("\nWARNING: Not a valid integer input, check input\n");

            for( i = 0; i < 80; i ++)
                putchar ('*');

            printf ("\n[PRESS 1 FOR YES]\n[PRESS 2 TO RESTART]\n[PRESS ANY OTHER INTEGER TO EXIT]");
            printf ("\nPress [1], [2] or any other integer: ");
        }

        printf ("Number pressed: %d\n", a);

        if (a == 1)
        {
            if (count <= FILE_PRINT_LIMIT)
            {
                printf("\nValues of %d primes:\n", count);

                ct = 0;

                for (i = 2; i < limit; i ++)
                {
                    if (primes [i])
                    {
                        printf ("%d. prime: %d\n", (ct + 1), i);
                        ct ++;
                    }
                }

                free (primes);
            }

            else
            {
                printf ("\nList of primes up to %d is large.\nWould you like to print them into a file instead?\n", limit);
                printf ("A new file named -primes.txt- will be created in this programs directory\nif you choose to print them in a file.");
                printf ("\n[PRESS 0 TO ACCEPT]\n[PRESS 1 TO DISCARD AND CONTINUE]\n[PRESS 2 TO RESTART]");
                printf ("\n[PRESS ANY OTHER INTEGER TO EXIT]\nPress [0], [1], [2] or any other integer: ");

                while (ParseForInt (&a))
                {
                    for( i = 0; i < 80; i ++)
                        putchar ('*');

                    printf ("\nWARNING: Not a valid integer input, check input\n");

                    for( i = 0; i < 80; i ++)
                        putchar ('*');

                    printf ("\n[PRESS 0 TO ACCEPT]\n[PRESS 1 TO DISCARD AND CONTINUE]\n[PRESS 2 TO RESTART]");
                    printf ("\n[PRESS ANY OTHER INTEGER TO EXIT]\nPress [0], [1], [2] or any other integer: ");
                }

                printf ("Number pressed: %d\n", a);

                if (a == 0)
                {

                    FILE* fp;

                    if ((fp = fopen ("primes.txt", "w")) == NULL)
                        exit (-1);

                    fprintf (fp, "Primes up to %d:\n", limit);

                    int line_counter = 0;
                    ct = 0;

                    for (i = 2; i < limit; i ++)
                    {
                        if (primes [i])
                        {
                            fprintf (fp, "[%d. prime: %d] ", (ct+1), i);
                            ct ++;
                            line_counter ++;

                            if (((int) line_counter % 10) == 0 && (line_counter != 0))
                                fprintf (fp, "\n");// Skips a line in file after every 10 prints.
                        }


                    }

                    fclose (fp);

                    printf ("Check file!\n");
                }

                else if (a == 1)
                {
                    printf("\nValues of %d primes:\n", count);

                    ct = 0;

                    for (i = 2; i < limit; i ++)
                    {
                        if (primes [i])
                        {
                            printf ("%d. prime: %d\n", (ct+1), i);
                            ct ++;
                        }
                    }
                }
            }

            printf ("[PRESS 2 TO RESTART]");
            printf("\n[PRESS ANY OTHER INTEGER TO EXIT]\nPress [1], [2] or any other integer: ");

           while (ParseForInt (&a))
           {
                for( i = 0; i < 80; i ++)
                    putchar ('*');

                printf ("\nWARNING: Not a valid integer input, check input\n");

                for( i = 0; i < 80; i ++)
                    putchar ('*');

                printf ("\n[PRESS 2 TO RESTART]\n[PRESS ANY OTHER INTEGER TO EXIT]\nPress [1], [2] or any other integer: ");
            }

            printf ("Number pressed: %d\n", a);

        }

        free (primes);

     }

     return (0);
}

int ParseForInt (long* limit)
{
    unsigned int i;
    char input [BUFSIZE];

    if (!fgets (input, sizeof (input), stdin))
        exit(-1);

    else
    {
        for ( i = 0; input [i] != '\0'; i++)
            if (input [i] == ' ' || input [i] == '\t')
                return 1;

        if (!strchr (input, '\n'))
            while (fgets (input, sizeof (input), stdin) && !strchr (input, '\n'));

        else
        {
            char* chk;
            int tmp = (int) strtol (input, &chk, 10);

            if (isspace (*chk) || *chk == 0)
            {
                *limit = tmp;
                return 0;
            }

            else
                return 1;
        }
    }
}