using Dates
using Random

module Utils

# Marsaglia Random Number Generator struct equivalent
mutable struct MarsagliaRng
    q::Vector{UInt32}
    carry::UInt32
    mwc256_initialized::Bool
    mwc256_seed::Int32
    i::UInt8

    function MarsagliaRng(seed::Vector{UInt8})
        q = zeros(UInt32, 256)
        carry = 362436
        mwc256_initialized = false
        mwc256_seed = reinterpret(Int32, seed)[1]
        i = 255
        new(q, carry, mwc256_initialized, mwc256_seed, i)
    end
end

# Default constructor using system time for seeding
function MarsagliaRng()
    ts_nano = UInt8(nanosecond(now()))
    seed = [ts_nano, ts_nano >>> 8, ts_nano >>> 16, ts_nano >>> 24]
    MarsagliaRng(seed)
end

# Random number generator functions
function next_u32(rng::MarsagliaRng)::UInt32
    a = UInt64(809430660)

    if !rng.mwc256_initialized
        j = UInt32(rng.mwc256_seed)
        c1 = UInt32(69069)
        c2 = UInt32(12345)
        rng.mwc256_initialized = true
        for k in 1:256
            j = (c1 * j + c2) % UInt32
            rng.q[k] = j
        end
    end

    rng.i = (rng.i + 1) % 256
    t = a * UInt64(rng.q[rng.i+1]) + UInt64(rng.carry)
    rng.carry = (t >> 32)
    rng.q[rng.i+1] = t % UInt32

    return rng.q[rng.i+1]
end



function next_u64(rng::MarsagliaRng)::UInt64
    UInt64(next_u32(rng))
end

# Sample function for generating a Float64
function rand(rng::MarsagliaRng)::Float64
    mult = 1.0 / typemax(UInt32)
    mult * next_u32(rng)
end

export MarsagliaRg, next_u32, rand

end