aoc2024/day-15/internal/one/util.go

package one

import (
	"bufio"
	"io"
	"regexp"
	"strings"

	log "github.com/sirupsen/logrus"
)

var reBoxes = regexp.MustCompile(`O`)

func parseLines(r io.Reader) (*graph, string, error) {
	graph := newGraph()
	var directions []string

	var inDirections bool
	var linecount int
	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		line := scanner.Text()
		if len(line) == 0 {
			inDirections = true
			continue
		}

		matches := reBoxes.FindAllStringIndex(line, -1)
		for _, m := range matches {
			graph.boxes[newPoint(m[0], linecount)] = struct{}{}
		}

		if inDirections {
			directions = append(directions, line)
		} else {
			indx := strings.Index(line, "@")
			if indx != -1 {
				log.Debugf("adding start point at (%d, %d)", indx, linecount)
				graph.robot = newPoint(indx, linecount)
			}

			graph.data = append(graph.data, line)
		}

		linecount++
	}

	if err := scanner.Err(); err != nil {
		return nil, "", err
	}

	return graph, strings.Join(directions, ""), nil
}

func replaceAtIndex(s string, r rune, i int) string {
	out := []rune(s)
	out[i] = r
	return string(out)
}