aoc2024/day-04/internal/two/neighbours.go

package two

type neighbour struct {
	x         int
	y         int
	direction int
}

func newNeighbour(direction, x, y int) neighbour {
	switch direction {
	case NW:
		return neighbour{x - 1, y + 1, direction}
	case NE:
		return neighbour{x + 1, y + 1, direction}
	case SE:
		return neighbour{x + 1, y - 1, direction}
	case SW:
		return neighbour{x - 1, y - 1, direction}
	default:
		return neighbour{}
	}
}

func (n neighbour) outOfBounds(lines []string) bool {
	return n.x < 0 || n.y < 0 || n.y >= len(lines) || n.x >= len(lines[0])
}

func (n neighbour) value(lines []string) rune {
	return rune(lines[n.y][n.x])
}

type neighbours struct {
	NW neighbour
	NE neighbour
	SE neighbour
	SW neighbour
}

func newNeighbours(x, y int) neighbours {
	return neighbours{
		newNeighbour(NW, x, y),
		newNeighbour(NE, x, y),
		newNeighbour(SE, x, y),
		newNeighbour(SW, x, y),
	}
}

func (n neighbours) all() [4]neighbour {
	return [4]neighbour{n.NW, n.NE, n.SE, n.SW}
}