#include <bit>

#include "blake2brandom.hpp"

namespace modernRX::blake2b {
    Random::Random(const_span<std::byte> seed, const uint32_t nonce) noexcept {
        constexpr uint32_t Max_Seed_Size{ 60 };
        const auto size{ std::min<size_t>(Max_Seed_Size, seed.size()) };

        std::memcpy(state.data(), seed.data(), size);
        std::memcpy(state.data() + size, &nonce, sizeof(uint32_t));

        // Always rehash at initialization.
        rehashIfNeeded(state.size() + 1); 
    }

    uint8_t Random::getUint8() noexcept {
        rehashIfNeeded(1);
        return static_cast<uint8_t>(state[position++]);
    }

    uint32_t Random::getUint32() noexcept {
        rehashIfNeeded(4);
        const_array<std::byte, 4> u32_bytes{ state[position], state[position + 1], state[position + 2], state[position + 3] };
        position += 4;
        return std::bit_cast<uint32_t>(u32_bytes);
    }

    void Random::rehashIfNeeded(const size_t bytes_needed) noexcept {
        if (position + bytes_needed > state.size()) {
            hash(state, state);
            position = 0;
        }
    }
}