package main

import (
	"fmt"
	"log/slog"
)

func main() {
	// fib_lfsr()
	galois_lfsr()
}

/* taps: 16 14 13 11; feedback polynomial: x^16 + x^14 + x^13 + x^11 + 1 */
func fib_lfsr() {
	startState := uint16(0xACE1)
	lfsr := startState
	var bit uint16
	period := uint64(0)
	for {
		slog.Info("fib_lfsr", "bit", fmt.Sprintf("%01b", lfsr&1), "lfsr", fmt.Sprintf("%016b", lfsr))
		bit = ((lfsr >> 0) ^ (lfsr >> 2) ^ (lfsr >> 3) ^ (lfsr >> 5)) & 1
		lfsr = (lfsr >> 1) | (bit << 15)
		period++
		if period == 15 {
			break
		}
		if lfsr == startState {
			break
		}
	}
	println(period)
}

/* taps: 16 14 13 11; feedback polynomial: x^16 + x^14 + x^13 + x^11 + 1 */
func galois_lfsr() {
	startState := uint16(0xACE1)
	lfsr := startState
	var bit uint16
	period := uint64(0)
	for {
		slog.Info("galois_lfsr", "bit", fmt.Sprintf("%01b", lfsr&1), "lfsr", fmt.Sprintf("%016b", lfsr))
		bit = lfsr & 1
		lfsr >>= 1
		if bit == 1 {
			lfsr ^= 0xB400
		}
		period++
		// if period == 15 {
		// 	break
		// }
		if lfsr == startState {
			break
		}
	}
	println(period)
}