#include <metal_stdlib>
#include "loki_header.metal"

unsigned Loki::TausStep(const unsigned z, const int s1, const int s2, const int s3, const unsigned M)
{
    unsigned b=(((z << s1) ^ z) >> s2);
    return (((z & M) << s3) ^ b);
}

thread Loki::Loki(const unsigned seed1, const unsigned seed2, const unsigned seed3) {
    unsigned seed = seed1 * 1099087573UL;
    unsigned seedb = seed2 * 1099087573UL;
    unsigned seedc = seed3 * 1099087573UL;

    // Round 1: Randomise seed
    unsigned z1 = TausStep(seed,13,19,12,429496729UL);
    unsigned z2 = TausStep(seed,2,25,4,4294967288UL);
    unsigned z3 = TausStep(seed,3,11,17,429496280UL);
    unsigned z4 = (1664525*seed + 1013904223UL);

    // Round 2: Randomise seed again using second seed
    unsigned r1 = (z1^z2^z3^z4^seedb);

    z1 = TausStep(r1,13,19,12,429496729UL);
    z2 = TausStep(r1,2,25,4,4294967288UL);
    z3 = TausStep(r1,3,11,17,429496280UL);
    z4 = (1664525*r1 + 1013904223UL);

    // Round 3: Randomise seed again using third seed
    r1 = (z1^z2^z3^z4^seedc);

    z1 = TausStep(r1,13,19,12,429496729UL);
    z2 = TausStep(r1,2,25,4,4294967288UL);
    z3 = TausStep(r1,3,11,17,429496280UL);
    z4 = (1664525*r1 + 1013904223UL);

    this->seed = (z1^z2^z3^z4) * 2.3283064365387e-10;
}

thread float Loki::rand() {
    unsigned hashed_seed = this->seed * 1099087573UL;

    unsigned z1 = TausStep(hashed_seed,13,19,12,429496729UL);
    unsigned z2 = TausStep(hashed_seed,2,25,4,4294967288UL);
    unsigned z3 = TausStep(hashed_seed,3,11,17,429496280UL);
    unsigned z4 = (1664525*hashed_seed + 1013904223UL);

    thread float old_seed = this->seed;

    this->seed = (z1^z2^z3^z4) * 2.3283064365387e-10;

    return old_seed;
}