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

// #include </home/ref0il/Desktop/RSA/myBigNum.h>

#define MAX 1000000

int findTheNearestSimple(int n)
{
    int *a = (int*)malloc(n * sizeof(int)),
        i,
        j,
        k;
    memset(a, 0, sizeof(int) * n);
    for(i = 1; 3 * i + 1 < n; i++)
        for(j = 1; (k = i + j + 2 * i * j) < n && j <= i; j++)
            a[k] = 1;
    for(i = n - 1; i >= 1; i--)
        if (a[i] == 0)
            return (2 * i + 1);
    free(a);
}

int gcd(int a, int b)
{
    while (b)
    {
        int c = a % b;
        a = b;
        b = c;
    }
    return abs(a);
}

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

    setlocale(LC_ALL, "Rus");

    if (argc == 1)
    {
        int p, q;
        while (p == q)
        {
            printf("Ввелите число p: ");
            scanf("%i", &p);
            printf("\nВведите число q: ");
            scanf("%i", &q);
            printf("\n");
            if (p == q)
                printf("\nВы ввели 2 одинаковых числа. Введите новое значение для однoго из них.\n\n");
        }

        printf("\nPlease, wait. Key generation in process...\n");
        int p_simple = findTheNearestSimple(p),
        q_simple = findTheNearestSimple(q),
        d,
        d_simple = 0;

        unsigned int n = p_simple*q_simple;

        while (d_simple != 1)
        {
            d = rand()%100;
            d_simple = gcd(d, ((p_simple-1)*(q_simple-1)));
        }

        unsigned int e = 0, e_simple = 0;
        while (e_simple != 1)
        {
            e += 1;
            e_simple = (e*d)%((p_simple-1)*(q_simple-1));
        }
        printf("{%12u,%12u} - Open key\n", e, n);
        printf("{%12i,%12u} - Secret key\n\n", d, n);

        char *Text = malloc(MAX);
        printf("Your message is taken from <input.txt>:\n");
        FILE *fin = fopen("input.txt", "r");
        for (int i = 0; i < 2; i++)
            fgets(Text, MAX, fin);
        printf("%s\n", Text);

        unsigned long long *CryptoText = (unsigned long long*)malloc(MAX * sizeof(unsigned long long));

        printf("\n%-5s%6s%20s%14s%16s\n-------------------------------------------------------------\n",
            "Text", "ASCII", "CryptoText/Block#", "ASCIIdecrypt", "Text decrypt");

        for (long long j = 0, b = 301; j < strlen(Text); j++, b++)
        {
            long long c = 1;
            unsigned long long i = 0;
            long long ASCIIcode = (long long)Text[j] + b;
            while (i < e)
            {
                c *= ASCIIcode;
                c %= n;
                i++;
            }
            CryptoText[j] = c;
        }

        FILE *fout = fopen("output.txt", "w");
        fprintf(fout, "%u %u %u\n", e, d, n);

        for (long long j = 0; j < strlen(Text); j++)
        {
            fprintf(fout, "%lli ", CryptoText[j]);
            printf("%-4c|%6lli|%18llu|%14s|%14s|\n", Text[j], (long long)Text[j], CryptoText[j], "Secret", "Secret");
        }

        printf("\n\nВы закодировали предложение: %s. \nКод вашего зашифрованного предложения хранится в:\noutput.txt", Text);
    }

    if (argc > 1)
    {
        FILE *fin = fopen("output.txt", "r");
        FILE *fout = fopen("output1.txt", "w");
        unsigned int e,
                     d,
                     n;

        fscanf(fin, "%u %u %u", &e, &d, &n);

        unsigned int *Hash = (unsigned int*)malloc(sizeof(unsigned int) * MAX);
        int count = 0;
        while (fscanf(fin, "%i", &Hash[count]) != EOF)
            count++;

        unsigned int *Tdecrypt = (unsigned int*)malloc(sizeof(unsigned int) * MAX);
        for (unsigned int j = 0, b = 301; j < MAX; j++, b++)
        {
            unsigned int m = 1;
            unsigned int i = 0;
            while (i < d)
            {
                m *= Hash[j];
                m %= n;
                i++;
            }
            m -= b;
            Tdecrypt[j] = m;
        }

        free(Hash);
        for (int i = 0; i < count; i++)
            fprintf(fout, "%c", (char)Tdecrypt[i]);

        printf("\nРасшифрованное сообщение было помещено в output1.txt\n\n");

        fclose(fin);
        fclose(fout);
    }

    return 0;
}