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

/*
 * Fill the entropy structure with random data
 */
void init_entropy(){
  if (DEBUG)
    Serial.println("Generation entropy");
  
  // Generate entropy
  int sensorValue = 0;
  while(s_entropy.pool_size < BUFSIZE){
      generateEntropy(s_entropy.position++);
      s_entropy.pool_size++;
      
      // Add a delay for avoiding the same value
      delay(50); 
  }
  if (DEBUG)
    Serial.println("End generation");
}
/*
 * Generate a random value from the analog input
 * Store the value in the entropy structure at the position specified in argument
 */
static void generateEntropy(int position){
  int sensorValue = 0;

  while( sensorValue == 0){
    sensorValue = analogRead(SENSOR_PIN);
    
    if (sensorValue != 0){
      if (DEBUG)
        Serial.println("Value: " + String(sensorValue));

      if(sensorValue <= 10)
        sensorValue = sensorValue << 5;
      else if(sensorValue > 10 && sensorValue <= 100)
        sensorValue = sensorValue << 4;
      
      s_entropy.buf[position] = sensorValue;
      Serial.println("Position: " + String(position));
    }
  }
}

/*
 * For avoiding to reused the seed, we must generate a new one
 */
static unsigned long generateSeed(){
  unsigned long seed;
  int sensorValue = 0;
  if (DEBUG)
    Serial.println("Generate seed");

  while (sensorValue == 0){
    sensorValue = analogRead(SENSOR_PIN);
    seed = sensorValue;
    
    if (DEBUG)
      Serial.println("Seed: " + String(seed));
  }

  return seed;
}
/*
 * Generate a random data from the entropy pool
 */
unsigned long prng(){
    unsigned long p = 0;
    unsigned long pos = generateSeed();
    
    pos += ( (pos << 4));
    pos ^= ( (pos >> 11));
    pos |= (pos << (pos % 15));
    pos = pos % 201;
    
    if (pos > BUFSIZE)
        pos = pos / 2;

    p = s_entropy.buf[pos];

    // Replace the old value
    generateEntropy(pos);
         
    return p;
}