package year25

import (
	"fmt"

	"git.bizdoc.ro/gabi-public/Advent-of-Code.git/aocutils"
	"git.bizdoc.ro/private/devkit.git/collections/geometry/v2"
)

const Day4PaperRoll = '@'

func Day4Part1(ctx aoc.Context) (any, error) {
	// 4 rolls in 8 adjacent positions
	const maxAdjacentRolls = 4

	var accessibleRolls int
	g, err := geometry.ReaderToByteGrid(ctx.Body)
	if err != nil {
		return nil, fmt.Errorf("day4 part1: failed to read grid: %w", err)
	}

	for c := range g.Points() {
		if g.At(c) != Day4PaperRoll {
			continue
		}

		var count int
		for p := range g.SubgridPointsIter(c.MoveUpLeft(), c.MoveDownRight()) {
			if g.At(p) == Day4PaperRoll {
				count += 1
			}
		}

		if count <= maxAdjacentRolls {
			accessibleRolls += 1
		}
	}

	return accessibleRolls, nil
}

func Day4Part2(ctx aoc.Context) (any, error) {
	// 4 rolls in 8 adjacent positions
	const maxAdjacentRolls = 4

	var totalRemovedRolls int
	g, err := geometry.ReaderToByteGrid(ctx.Body)
	if err != nil {
		return nil, fmt.Errorf("day4 part2: failed to read grid: %w", err)
	}

	for {
		removedRolls := 0
		for c := range g.Points() {
			if g.At(c) != Day4PaperRoll {
				continue
			}

			var count int
			for p := range g.SubgridPointsIter(c.MoveUpLeft(), c.MoveDownRight()) {
				if g.At(p) == Day4PaperRoll {
					count += 1
				}
			}

			if count <= maxAdjacentRolls {
				removedRolls += 1
				g.Set(c, '.') // remove roll from grid
			}
		}

		if removedRolls == 0 {
			break
		}

		totalRemovedRolls += removedRolls
	}

	return totalRemovedRolls, nil
}