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

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

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

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

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

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

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

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

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

	runner(move, lines)

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

	return uniqueNodes(move)
}