#include <math.h>
#include <assert.h>
#include <stdexcept>
#include "generator.h"

using namespace std;

struct G_state{
	long k;
	long c;
};

G_state *initialize_generator(){
	auto G = new G_state;
	G->k = 0;
	G->c = 0;
	return G;
};

string do_crypto(int k, int c){
	/* this function calls the block cipher
	   do whatever atm */
	k = 0;
	c = 0;
	return "";
}

G_state generate_blocks(G_state G, int k_blocks){
	assert (G.c!=0);
	string r = "";
	for (int i = 0; i < k_blocks; ++i) {
		r += do_crypto(G.k, G.c);
		G.c += 1;
	}
	return G;
}

string generate_random_data(G_state G, uint n){
	string r = "";
	if (n < 0){
		/* this should not be possible */
		printf("[*] error: n cannot be < 0");
		throw invalid_argument("n cannot be < 0");
	} else if (n > pow(2,20)){
		printf("[*] error: n cannot be > 2^20");
		throw invalid_argument("n cannot be > 2^20");
	}
	/* do magic to compute r
	 * r ← first-n-bytes(GenerateBlocks(G, ceil(n/16) )) */
	string rr = to_string(generate_blocks(G,ceil(n/16)).c);
	r = rr.substr(0,n);
	return r;
};