/*
 * This is a possible solution to the cipher_functions3.cpp program you were asked to write for 
 * this week. It updates the cipher_functions2.cpp progrm by adding the ability to pass a pointer
 * to an array as an argument in each of the encoding functions, and testing this by declaring the 
 * array storing encoded messages as a local variable in main instead of as a global variable.
 *
 */

//Remember tht there are a bunch of libraries that need to be included if we are generating random
//numbers.
#include <iostream>
#include <stdlib.h>
#include <time.h>
#include <math.h>
using namespace std;

//A list of all the functions.
void add_cipher(int *arr, int key, int mod, int n);
void mult_cipher(int *arr, int key, int mod, int n);
void affine_cipher(int *arr, int key1, int key2, int mod, int n);
void add_cipher_rand(int *arr, int mod, int n, int range);
void mult_cipher_rand(int *arr, int mod, int n, int range);
void affine_cipher_rand(int *arr, int mod, int n, int range);
void set_array(int *arr, int n);
int rand_0toN1(int n);

int main() {

	//As was menetioned above, since we now know how to pass a pointer as a function argument, we 
	//can declare all the relevant array variables locally, which is what is done below. An arr_size
	//variable is declared to make it easier to modify the program (as with the #define directive 
	//last week.
	int arr_size = 10;
	int A[arr_size];
	
	//Declare a variable for the range of random numbers, and set the seed for random number 
	//generation.
	int range;
	srand(time(NULL));
	
	//Set all the array values to be the numbers 0 through arr_size-1.
	set_array(A, arr_size);
	
	//Prompt to get the range of random number values.
	cout << "Enter the range of the random cipher keys and press ENTER (note that the actual ";
	cout <<"keys will be from 0 to the number entered minus 1): ";
	cin >> range;
	
	//I only test the random cipher functions, but feel free to test a different set of functions
	//to make sure that everything is working properly.
	
	cout << "The random encoding generated by an additive cipher is: \n";
	//Implement the add_cipher_rand function, and then print out the results. Perhaps you can try
	//and guess from the output what the key was.
	add_cipher_rand(A, arr_size, arr_size, range);
	
	for(int i = 0; i < arr_size; i++) {
		cout << A[i] << ", "; 
	}
	
	//Reset the values in A using the set_array function.
	set_array(A, arr_size);
	
	cout << "The random encoding generated by an multiplicative cipher is: \n";	
	//Implement the mult_cipher_rand funtion, print everything out, and then reset the array.
	mult_cipher_rand(A, arr_size, arr_size, range);
	
	for(int i = 0; i < arr_size; i++) {
		cout << A[i] << ", ";
	}	
	
	set_array(A, arr_size);

	cout << "The random encoding generated by an affine cipher is: \n";
	//Implement the affine_cipher_rand function, and print out the results. Don't worry about 
	//resetting A since we are at the end of the program	
	affine_cipher_rand(A, arr_size, arr_size, range);
	
	for(int i = 0; i < arr_size; i++) {
		cout << A[i] << ", ";
	}
	return 0;
}

//Addative cipher function. It is just like the add_cipher function from cipher_functions2.cpp,
//except that it also takes a pointer to the arry to be modified as a paramter. This allows us to
//remove the global array variable from the program, and instead modify a local array variable.
void add_cipher(int *arr, int key, int mod, int n){
	for(int i = 0; i < n; i++) {
		*arr = (*arr +  key) % mod;
		arr++;
	}
}
	
//Multiplicative cipher function. As with the new add_cipher function, the only difference between
//this mult_cipher function and the one from cipher_functions2.cpp is that it takes a pointer to an
//array local to the main function as an argument.
void mult_cipher(int *arr, int key, int mod, int n){
	for(int i = 0; i < n; i++) {
		*arr = (*arr *  key) % mod;
		arr++;
	}
}

//Affine cipher function. As with the new versions of the add_ciper and mult_cipher function, the 
//only difference between its cipher_functions2.cpp counterpart is that it takes as a paramter a 
//pointer to an array, and modifies this array instead of  globally declared array.
void affine_cipher(int *arr, int multkey, int addkey, int mod, int n){
	for(int i = 0; i < n; i++) {
		*arr = ((*arr *  multkey) + addkey) % mod;
		arr++;
	}
}

//Random version of this weeks add_cipher.cpp function.
void add_cipher_rand(int *arr, int mod, int n, int range) {
	int r = rand_0toN1(range);
	add_cipher(arr, r, mod, n);
}

//Random version of this weeks mult_cipher.cpp function.
void mult_cipher_rand(int *arr, int mod, int n, int range) {
	int r = rand_0toN1(range);
	mult_cipher(arr, r, mod, n);
}

//Random version of thsi weeks affine_cipher.cpp function.
void affine_cipher_rand(int *arr, int mod, int n, int range) {
	int r1 = rand_0toN1(range);
	int r2 = rand_0toN1(range);
	affine_cipher(arr, r1, r2, mod, n);
}

//New version of set_array.cpp function that takes a pointer to an array as well as a parameter, 
//and modifies this array.
void set_array(int *arr, int n){
	for(int i = 0; i < n; i++) {
		*arr = i;
		arr++;
	}
}

//The rand_0toN1 function that should be familiar by now. It takes an integer as a parameter, and 
//returns a number between 0 and that number minus 1. Same as from last week.
int rand_0toN1(int n) {
	return rand() % n;
}