package com.infendro.random.prng

import com.infendro.bytearray.padStart
import com.infendro.bytearray.toUByteArray
import com.infendro.bytearray.toULong
import kotlin.math.min
import kotlin.properties.Delegates

class LCG internal constructor() : PRNG() {
    private val a: ULong = 25214903917UL
    private val c: ULong = 11UL
    private val m: ULong = 1UL shl 48

    private var x: ULong by Delegates.notNull()

    override fun seed(
        seed: UByteArray,
    ) {
        val s = seed.padStart(8, 0x00U).takeLast(8).toUByteArray()
        x = s.toULong() % m
    }

    override fun generate(
        count: Int,
    ): UByteArray {
        return buildList {
            while (size < count) {
                x = (a * x + c) % m

                addAll(x.toUByteArray().takeLast(min(count - size, 6)))
            }
        }.toUByteArray()
    }
}