aoc2023/day-16/one.go

package main

import (
	"math"

	log "github.com/sirupsen/logrus"
)

const (
	SPACE    = '.'
	V_MIRROR = '|'
	H_MIRROR = '-'
	F_MIRROR = '/'
	B_MIRROR = '\\'
)

const (
	N = iota
	S
	W
	E
)

// only for debugging
var steps int
var dirs = []string{"N", "S", "W", "E"}

func runner(mover *mover, lines []string) {
	for steps < math.MaxInt && mover.Y >= 0 && mover.Y < len(lines) && mover.X >= 0 && mover.X < len(lines[mover.Y]) {
		if nodeInNodes(mover.node, mover.nodes) {
			log.Debug(mover.node, " in nodes, breaking.")
			break
		}

		mover.nodes = append(mover.nodes, mover.node)

		switch lines[mover.Y][mover.X] {
		case SPACE: // '.'
			log.Debug("we have space and direction is ", dirs[mover.direction()])
			mover.move()

		case F_MIRROR: // '/'
			log.Debug("we have forward mirror and direction is ", dirs[mover.direction()])
			switch mover.direction() {
			case N:
				mover.setDirection(E)
			case S:
				mover.setDirection(W)
			case W:
				mover.setDirection(S)
			case E:
				mover.setDirection(N)
			}
			log.Debug("step: ", steps, " ", string(F_MIRROR), " direction changed to ", dirs[mover.direction()])
			mover.move()

		case B_MIRROR: // '\'
			log.Debug("we have backwards mirror and direction is ", dirs[mover.direction()])
			switch mover.direction() {
			case N:
				mover.setDirection(W)
			case S:
				mover.setDirection(E)
			case W:
				mover.setDirection(N)
			case E:
				mover.setDirection(S)
			}
			log.Debug("step: ", steps, " ", string(B_MIRROR), " direction changed to ", dirs[mover.direction()])
			mover.move()

		case V_MIRROR: // '|'
			log.Debug("we have vertical mirror and direction is ", dirs[mover.direction()])
			if mover.direction() == N || mover.direction() == S {
				mover.move()
				continue
			}
			if mover.direction() == W || mover.direction() == E {
				c := mover.coords
				mover.setDirection(N)
				mover.move()
				runner(mover, lines)
				mover.coords = c
				mover.setDirection(S)
				mover.move()
				runner(mover, lines)
			}

		case H_MIRROR: // '-'
			log.Debug("we have horizontal mirror and direction is ", dirs[mover.direction()])
			if mover.direction() == W || mover.direction() == E {
				mover.move()
				continue
			}
			if mover.direction() == N || mover.direction() == S {
				c := mover.coords
				mover.setDirection(W)
				mover.move()
				runner(mover, lines)
				mover.coords = c
				mover.setDirection(E)
				mover.move()
				runner(mover, lines)
			}

		default:
			log.Fatal("unknown node")
		}
	}
	steps++
}

// one
func one(lines []string) int {
	mover := newMover(newNode(0, 0, E))

	runner(mover, lines)

	if log.GetLevel() == log.DebugLevel {
		n := printDebug(mover, lines)
		log.Debug("total: ", n)
	}

	return uniqueNodes(mover)
}