#include <stdio.h>
#include <stdlib.h>
#include "rsa.h"
#include "prng.h"

void generateKeys(unsigned long *e, unsigned long *d, unsigned long *n){
    unsigned long p = prng(25);
    unsigned long q = prng(47);
    unsigned long phi = 0;

    // Generate big numbers of p and q
    //generateBigNumber(&p);
    //generateBigNumber(&q);

    // Check if p and q are prime numbers
    if (isPrimeNumber(p) != 0)
        prime_number_finder(&p);

    if (isPrimeNumber(q) != 0)
        prime_number_finder(&q);

    // Calculate n
    *n = p * q;
    
    // We're going to calcule the Euler's totient 
    // Our number are prime number, so, phi = (p - 1) * (q - 1)
    phi = (p - 1)*(q - 1);

    /* We will calculate e for the public key */
    generatePublicKey(phi, e);

    /* We will calcuate d for the private key */
    generatePrivateKey(d, phi, e);

    /* For encrypting
       m = ( message ** e) % n
       exemple!: A -> 0x65
        (65 ** 4033) % 6938083 = 1140958
       For decrypting
        ( m ** d) % n
       Exemple:
        (1140958 ** 830257) % 6938083 = 65
    */
}
static void generateBigNumber(unsigned long *v){
    /*if (*v < 100)
        *v = *v << 6;
    else if (*v >= 100 || *v < 1000)
        *v = *v << 4;
    else
        *v = *v << 2;*/
}
/*
 * This function will identify all the divider of the variable a
 * with the Euclidean algorithm
 */
static int gcd(unsigned long a, unsigned long b){
    // Ou utiliser l'algorithme d'Euclide ?
    int done = 0;
    while (!done){
        if (b == 0)
            done = 1;
        else{
            int tmp = b;
            b = a % b;
            a = tmp;
        }
    }
    return a;
}
/*
 * This function will check if te variable e is a prime number
 * is not, we increment the value to 1 and continue until is a prime number
 */
static void prime_number_finder(unsigned long *e){
    while(isPrimeNumber(*e) != 0)
        *e += 1;
}
static int isPrimeNumber(unsigned long x){ 
    for (int i = 2; i < x; i++){
        if (x % i == 0)
            return 1;
    }
    return 0;
}
static unsigned long generatePublicKey(unsigned long phi, unsigned long *e){
    // Generate e
    *e = prng(61);
    //generateBigNumber(e);

    // Get the coprime with phi
    while ((gcd(phi, *e)) != 1)
        *e += 1;
    
    return *e;
}
static unsigned long generatePrivateKey(unsigned long *d, unsigned long phi, unsigned long *e){
    // Calculate the modular inverse
    int i = 0;
    for (i = 0; i <= phi; i++){
        if ((i * (*e)) % phi == 1){
            *d = i;
            break;
        }
    }
    //*d = *e;
    return *d;
}