Advent-of-Code-2023/day20/pulsePropagation.go

package day20

import (
	"fmt"
	"log"
	"os"
	"strings"
)

func Run() int {
	fmt.Println("hello from dya 20")

	filename := "day20/input"
	modules := ReadModules(filename)
	InitStuffs(modules)
	log.Print("got modules:\n", modules)

	low, high := Count10000ButtonPresses(modules)
	log.Printf("got low %d and high %d\n", low, high)

	return low * high
}

func Count10000ButtonPresses(modules map[string]Module) (lowSignalsCount, highSignalsCount int) {
	count := 1000
	type counts struct {
		low, high int
		step int
	}
	countsAfterState := make(map[string]counts)
	// after each button press check if reached already known state - cycle is present.
	// then calculate amount of signals before the loop - how much was on that previous state.
	// then diff - how much added after the loop

	// for now let's just print the info on loop

	for i := 0; i < count; i++ {
		stepLow, stepHigh := PropagateButtonPress(modules)
		lowSignalsCount += stepLow
		highSignalsCount += stepHigh
		log.Printf("after step %d low is %d and high is %d", i, lowSignalsCount, highSignalsCount)
		state := ModulesState(modules)

		prevCounts, found := countsAfterState[state]
		if found {
			loopLen := i - prevCounts.step

			log.Printf(">>> found loop. from step %d to step %d. of len %d",
				prevCounts.step, i, loopLen)

			multiplication := count / loopLen

			lowCountInCycle := lowSignalsCount - prevCounts.low
			highCountInCycle := highSignalsCount - prevCounts.high

			lowSignalsCount = lowCountInCycle * multiplication
			highSignalsCount = highCountInCycle * multiplication

			return
		}

		countsAfterState[state] = counts{stepLow, stepHigh, i}
	}

	return
}

func PropagateButtonPress(modules map[string]Module) (lowSignalsCount, highSignalsCount int) {
	signals := []Signal{{From: "button", To: "broadcast", PulseType: LowPulse}}
	lowSignalsCount += 1

	for len(signals) > 0 {
		curSignal := signals[0]
		signals = signals[1:]

		log.Printf("%s -%s-> %s", curSignal.From, curSignal.PulseType, curSignal.To)

		receivingModule, found := modules[curSignal.To]
		if !found {
			log.Print(fmt.Sprintf("signal %+v can't find it's recepient\n", curSignal))
			continue
		}

		newSignals := receivingModule.Receive(curSignal)

		// all newSignals will have same type
		newSignalsAmount := len(newSignals)
		if newSignalsAmount > 0 {
			signals = append(signals, newSignals...)
			someNewSignal := newSignals[0]
			if someNewSignal.PulseType == HighPulse {
				highSignalsCount += newSignalsAmount
			} else {
				lowSignalsCount += newSignalsAmount
			}
		}
	}

	return
}

// process sends single `low pulse` directly to "broadcast"

func ReadModules(filename string) map[string]Module {
	result := make(map[string]Module)
	bytes, err := os.ReadFile(filename)
	if err != nil {
		panic(fmt.Sprint("error reading file: ", filename))
	}

	text := strings.TrimSpace(string(bytes))

	for _, line := range strings.Split(text, "\n") {
		switch {
		case IsLineBroadcast(line):
			parsed := ParseBroadcast(line)
			result["broadcast"] = &parsed
		case IsLineFlipFlop(line):
			parsed := ParseFlipFlop(line)
			result[parsed.Name] = &parsed
		case IsLineConjunction(line):
			parsed := ParseConjunction(line)
			result[parsed.Name] = &parsed
		}

		log.Println(line)
	}

	buttonModule := Button{}
	result["button"] = &buttonModule
	outputModule := Output{}
	result["output"] = &outputModule

	return result
}

func InitStuffs(allModules map[string]Module) {
	for _, module := range allModules {
		if conjunction, ok := module.(*Conjunction); ok {
			conjunction.RegisterInputs(allModules)
		}
	}

}

func ModulesState(allModules map[string]Module) string {
	// relying on printing of map values to be ordered by key
	// https://stackoverflow.com/a/54524991/2788805
	states := make(map[string]string)
	for name, module := range allModules {
		states[name] = module.StateSnapshot()
	}

	return fmt.Sprint(states)
}