#ifndef __INC_LIB8TION_RANDOM_H
#define __INC_LIB8TION_RANDOM_H

/// @file random8.h
/// Fast, efficient random number generators specifically
/// designed for high-performance LED programming. 

/// @ingroup lib8tion
/// @{

/// @defgroup Random Fast Random Number Generators
/// Fast 8-bit and 16-bit unsigned random number generators. 
/// Significantly faster than Arduino random(), but
/// also somewhat less random.  You can add entropy.
///
/// Pseudo-random number generation follows the form:
///   @code
///   X(n+1) = (2053 * X(n)) + 13849)
///   @endcode
/// @{


/// Multiplier value for pseudo-random number generation
#define FASTLED_RAND16_2053  ((uint16_t)(2053))
/// Increment value for pseudo-random number generation
#define FASTLED_RAND16_13849 ((uint16_t)(13849))

#if defined(LIB8_ATTINY)
/// Multiplies a value by the pseudo-random multiplier
#define APPLY_FASTLED_RAND16_2053(x) (x << 11) + (x << 2) + x
#else
/// Multiplies a value by the pseudo-random multiplier
#define APPLY_FASTLED_RAND16_2053(x) (x * FASTLED_RAND16_2053)
#endif

/// Seed for the random number generator functions
extern uint16_t rand16seed; // = RAND16_SEED;

/// Generate an 8-bit random number
/// @returns random 8-bit number, in the range 0-255
LIB8STATIC uint8_t random8()
{
    rand16seed = APPLY_FASTLED_RAND16_2053(rand16seed) + FASTLED_RAND16_13849;
    // return the sum of the high and low bytes, for better
    //  mixing and non-sequential correlation
    return (uint8_t)(((uint8_t)(rand16seed & 0xFF)) +
                     ((uint8_t)(rand16seed >> 8)));
}

/// Generate a 16-bit random number
/// @returns random 16-bit number, in the range 0-65535
LIB8STATIC uint16_t random16()
{
    rand16seed = APPLY_FASTLED_RAND16_2053(rand16seed) + FASTLED_RAND16_13849;
    return rand16seed;
}

/// Generate an 8-bit random number between 0 and lim
/// @param lim the upper bound for the result, exclusive
LIB8STATIC uint8_t random8(uint8_t lim)
{
    uint8_t r = random8();
    r = (r*lim) >> 8;
    return r;
}

/// Generate an 8-bit random number in the given range
/// @param min the lower bound for the random number, inclusive
/// @param lim the upper bound for the random number, exclusive
LIB8STATIC uint8_t random8(uint8_t min, uint8_t lim)
{
    uint8_t delta = lim - min;
    uint8_t r = random8(delta) + min;
    return r;
}

/// Generate an 16-bit random number between 0 and lim
/// @param lim the upper bound for the result, exclusive
LIB8STATIC uint16_t random16( uint16_t lim)
{
    uint16_t r = random16();
    uint32_t p = (uint32_t)lim * (uint32_t)r;
    r = p >> 16;
    return r;
}

/// Generate an 16-bit random number in the given range
/// @param min the lower bound for the random number, inclusive
/// @param lim the upper bound for the random number, exclusive
LIB8STATIC uint16_t random16( uint16_t min, uint16_t lim)
{
    uint16_t delta = lim - min;
    uint16_t r = random16( delta) + min;
    return r;
}

/// Set the 16-bit seed used for the random number generator
LIB8STATIC void random16_set_seed( uint16_t seed)
{
    rand16seed = seed;
}

/// Get the current seed value for the random number generator
LIB8STATIC uint16_t random16_get_seed()
{
    return rand16seed;
}

/// Add entropy into the random number generator
LIB8STATIC void random16_add_entropy( uint16_t entropy)
{
    rand16seed += entropy;
}

/// @} Random
/// @} lib8tion

#endif
