aoc2024/day-21/internal/pad/dirpad.go

package pad

import (
	"slices"
	"strings"

	log "github.com/sirupsen/logrus"
)

type Dirpad struct {
	current   node
	pad       [][]rune
	locations map[rune]coords
}

func NewDirpad() *Dirpad {
	pad := [][]rune{
		{'.', '^', 'A'},
		{'<', 'v', '>'},
	}
	locations := make(map[rune]coords)
	for y, row := range pad {
		for x, value := range row {
			locations[value] = coords{x, y}
		}
	}

	return &Dirpad{
		current:   newNode(2, 0, 'A'),
		pad:       pad,
		locations: locations,
	}
}

func (dp *Dirpad) valueAt(c coords) rune {
	return dp.pad[c.y][c.x]
}

func (dp *Dirpad) nextTarget(c rune) node {
	coords := dp.locations[c]
	return newNode(coords.x, coords.y, c)
}

func (dp *Dirpad) Generate(code string) string {
	var sb strings.Builder
	for _, c := range code {
		target := dp.nextTarget(c)
		moved := newMove(dp.current.x, target.x, dp.current.y, target.y)

		var hb, vb strings.Builder

		for range absInt(moved.x) {
			if moved.x >= 0 {
				hb.WriteRune('>')
			} else {
				hb.WriteRune('<')
			}
		}

		for range absInt(moved.y) {
			if moved.y <= 0 {
				vb.WriteRune('^')
			} else {
				vb.WriteRune('v')
			}
		}

		if dp.valueAt(coords{dp.current.x + moved.x, dp.current.y}) == '.' {
			sb.WriteString(vb.String())
			sb.WriteString(hb.String())
		} else if dp.valueAt(coords{dp.current.x, dp.current.y + moved.y}) == '.' {
			sb.WriteString(hb.String())
			sb.WriteString(vb.String())
		} else if moved.x < 0 {
			sb.WriteString(hb.String())
			sb.WriteString(vb.String())
		} else if moved.x >= 0 {
			sb.WriteString(vb.String())
			sb.WriteString(hb.String())
		}

		sb.WriteRune('A')
		dp.current = target
	}

	log.Tracef("\n%s\n", dp.trace(sb.String()))

	return sb.String()
}

func (dp *Dirpad) trace(visited string) string {
	log.Debug(visited)
	temp := slices.Clone(dp.pad)

	next := coords{2, 0}
	for _, c := range visited {
		next = neighbours(next, c)
		temp[next.y][next.x] = 'X'
	}

	output := []string{}
	for _, row := range temp {
		output = append(output, string(row))
	}
	return strings.Join(output, "\n")
}