#include "rsa.h"
#include "rand.h"
#include <stdbool.h>
#include <stdint.h>

int gcd(int a, int b) {
    while (b != 0) {
        int temp = b;
        b = a % b;
        a = temp;
    }

    return a;
}

int totient(int n) {
    int result = n;

    // Check for prime factors
    for (int p = 2; p * p <= n; p++) {
        if (n % p == 0) {
            // If p is a prime factor of n, remove all occurrences of p
            while (n % p == 0) {
                n /= p;
            }
            result -= result / p;
        }
    }

    // If n is still greater than 1, then it's a prime factor itself
    if (n > 1) {
        result -= result / n;
    }

    return result;
}

uint64_t modexp(uint64_t a, uint64_t b, uint64_t m) {
    uint64_t result = 1;
    a = a % m; // In case a is greater than m

    while (b > 0) {
        // If b is odd, multiply a with result
        if (b % 2 == 1)
            result = (result * a) % m;

        // b must be even now
        b = b >> 1;      // b = b // 2
        a = (a * a) % m; // Change a to a^2
    }

    return result;
}

uint64_t gen_prime(uint64_t min, uint64_t max) {
    uint64_t cand = 0;
    while (!is_prime(cand)) cand = prand_range(min, max);

    return cand;
}

bool is_prime(int n) {
    if (n < 2)
        return false;

    for (int i = 2; i < n / 2 + 1; i++) {
        if (n % i == 0)
            return false;
    }

    return true;
}

int mod_inverse(int e, int phi) {
    for (int d = 0; d < phi; d++) {
        if ((d * e) % phi == 1)
            return d;
    }

    return 0;
}