#include "../rng.h"
#include "mt19937.h"

// more specifically this will be mt19937 - 32 bit


namespace splat {

    std::array<uint32_t,624> mt19937_init(uint32_t seed){

        std::array<uint32_t,624> state;

        state[0] = seed;

        for(int i=1; i<624; i++){
            state[i]= 1812433253*(state[i-1] ^ (state[i-1] >> 30)) + i;
        }

        return state;
    }

    std::array<uint32_t, 624> mt19937_twist(const std::array<uint32_t, 624>& state){

        std::array<uint32_t,624> newstate;

        for(int i=0; i<624; i++){
            uint32_t x;

            // concating the MSB and LSB from next
            if(i+1<624){
                x = (state[i] & 0x80000000) | (state[(i+1)] & 0x7FFFFFFF);
            }else{
                x = (state[i] & 0x80000000) | (newstate[(i+1)%624] & 0x7FFFFFFF);
            }
            
            // does the *A part
            if(x&1){
                x = (x>>1) ^ 0x9908B0DFUL;
            }else{
                x=x>>1;
            }

            uint32_t y;
            if(i+397<624){
                y = state[i+397] ^ x;
            }else{
                y = newstate[(i+397) % 624] ^ x;
            }
            newstate[i] = y;
        }

        return newstate;
    }

    std::array<uint32_t, 624> mt19937_temper(const std::array<uint32_t, 624>& state){
        std::array<uint32_t, 624> tempered;

        for(int i=0; i<624; i++){

            uint32_t y = state[i];
            y = y ^ (y >> 11);
            y = y ^ ((y << 7) & 0x9D2C5680UL);
            y = y ^ ((y << 15) & 0xEFC60000UL);
            tempered[i] = y ^ (y >> 18);
        }

        return tempered;
    }


    mt19937_generator::mt19937_generator(uint32_t genSeed) : PRNG(genSeed) {
                state = mt19937_init(seed);
                nextblock();
    }

    void mt19937_generator::nextblock() {
        state = mt19937_twist(state);
        random_values = mt19937_temper(state);
        position = 0;
    }

    uint32_t mt19937_generator::generate() {
                uint32_t generated = random_values[position];
                position++;
                if(position>=624){
                    nextblock();
                }
                return generated;
    }

    std::string mt19937_generator::getName() {
        return "mt19937-32";
    }

}