#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <math.h>
#include <time.h>
#include "prng.h"
#include <Arduino.h>

#define MAX_ENTRIES_ENTROPY 100

void init_entropy(){
  struct entropy_pool s_pool;
  randomSeed(analogRead(0));
  while (s_entropy.pool_size < BUFSIZE){
    s_entropy.buf[s_entropy.pool_size++] = random(300);
  }
}

// Define a range ???
unsigned long prng(int seed){
    //int32_t p = 4242;
    unsigned long p = seed;

    //p = 4242;
    //p ^= p << 3; // XOR
    //    1000010010010 -> 4242
    // 1000010010010000 -> 33936
    // 1001010000000010 -> 37890
    //printf("%d\n", p);

    // For small value, increase the value ? 
    p ^= (p << 1) | (p << 2);
    
    // Generate number between 1000 and 5000 ???
    // Or to add X bits to have the key number, for instance 32 bits

    return p;
}

int prng2 () {
    double *pool_entropy = entropy_pool();
    int pos = 0;

    entropy_cpu_clock(pool_entropy, 0,  MAX_ENTRIES_ENTROPY);
    pos++;

    for(int i = 0; i < MAX_ENTRIES_ENTROPY; i++){
        //printf("%f\n", pool_entropy[i]);
    }

    // Get from pool
    // Generate an integer from 0 to 100 (with clock CPU) for instance
    // And to pick up to the pool

    // Generate entropy with the network ?

    free(pool_entropy);
    return(0);
}
double *entropy_pool(){
   double *pool_entropy = (double *)malloc(sizeof(double) * MAX_ENTRIES_ENTROPY);

   if (pool_entropy == NULL){
        //printf("Failed to allocate variables\n");
        exit(-1);
   }
    return pool_entropy;
}
void entropy_cpu_clock(double *entropy, int pos, int max){
   clock_t start_t, end_t;
   double total_t;
   double res = 0;

   start_t = clock();
   //printf("Starting of the program, start_t = %ld\n", start_t);
    
   //printf("Going to scan a big loop, start_t = %ld\n", start_t);
   for(int i = 0; i < 10000000; i++) {
   }
   end_t = clock();
   //printf("End of the big loop, end_t = %ld\n", end_t);
   
   total_t = (double)(end_t - start_t) / CLOCKS_PER_SEC;
   //printf("Total time taken by CPU: %f\n", total_t  );
   //printf("Exiting of the program...\n");

   entropy[pos] = total_t;

   // Test - generate an iteger from 0 to 100

   // Multiply the 10 first entries
    for (int i = 0; i < 10; i++){
        res += entropy[0]; 
    }  

   //printf("Pos: %f\n", ceil(res * 100));
}