#define MODULE "rand"

#include "rand/Init.h"
#include "config.h"
#include "cpu/CPU.h"
#include "io/IO.h"
#include "log/Log.h"
#include "rand/Mersenne.h"

static uint64_t state = 0xf5026f5ae96319e9;

static bool has_rdrand = false;
static bool has_rdseed = false;

extern "C" int asm_test_rdseed();

static uint64_t rdtsc()
{
    uint64_t result1;
    uint64_t result2;
    asm volatile("rdtsc" : "=a"(result1), "=d"(result2));
    return result2 << 32 | result1;
}

static uint64_t rdseed()
{
    uint64_t result;
    asm volatile("rdseed %0" : "=r"(result));
    return result;
}

static uint64_t rdrand()
{
    uint64_t result;
    asm volatile("rdrand %0" : "=r"(result));
    return result;
}

void Mersenne::init()
{
    kdbgln("Preparing random number generator");

    has_rdrand = CPU::has_feature(CPU::Features::RDRAND);
    has_rdseed = asm_test_rdseed();

    state ^= (0x45fe1024UL + __moon_version_major()) * (__moon_version_minor() ^ 200UL);

    state ^= 0xe0e4f5332ea75b;

    reseed();

    state ^= Mersenne::get() * 0xffe3;

    state ^= rdtsc();

    Mersenne::seed(state);
}

void Mersenne::reseed()
{
    state ^= rdtsc();

    if (has_rdrand) { state ^= rdrand(); }

    if (has_rdseed) { state ^= rdseed(); }

    state ^= rdtsc();

    state ^= IO::inb(0x40);

    state ^= rdtsc();

    Mersenne::seed(state);
}