package year25

import (
	"bufio"
	"fmt"
	"strconv"
	"strings"

	"git.bizdoc.ro/gabi-public/Advent-of-Code.git/aocutils"
)

func Day3Part1(ctx aocutils.Context) (any, error) {
	return Day3(ctx, 2)
}
func Day3Part2(ctx aocutils.Context) (any, error) {
	return Day3(ctx, 12)
}
func Day3(ctx aocutils.Context, size int) (int64, error) {
	scanner := ctx.Scanner(bufio.ScanLines)
	var sum int64

	findLargetDigit := func(digits []rune) (rune, int) {
		var largestDigit rune
		index := 0

		for i := len(digits) - 1; i >= 0; i-- {
			if digits[i] >= largestDigit {
				largestDigit = digits[i]
				index = i
			}
		}
		return largestDigit, index
	}

	for scanner.Scan() {
		text := strings.TrimSpace(scanner.Text())
		if text == "" {
			continue
		}
		line := []rune(text)
		parts := make([]byte, size)

		for index := range parts {
			digit, start := findLargetDigit(line[:len(line)+index-len(parts)+1])
			line = line[start+1:]
			if digit < '0' || digit > '9' {
				return 0, fmt.Errorf("ivalid char '%c' in line %s", digit, text)
			} else {
				parts[index] = byte(digit)
			}
		}

		partSum, err := strconv.Atoi(string(parts))
		if err != nil {
			return 0, fmt.Errorf("invalid result %s for line %s", string(parts), text)
		}

		ctx.Println("line: ", text)
		ctx.Println("got:  ", string(parts))
		ctx.Println()
		sum += int64(partSum)
	}

	return sum, scanner.Err()
}

func Day3Compact(input string, size int) (total int64, _ error) {
	findLargetDigit := func(digits string, skip int) (digit byte, idx int, next string) {
		for i := len(digits) - 1 - skip; i >= 0; i-- {
			if digits[i] >= digit {
				digit, idx = digits[i], i
			}
		}
		return digit, idx, digits[idx+1:]
	}
	for _, line := range strings.Split(input, "\n") {
		var parts = make([]byte, size)
		for index := range size {
			parts[index], _, line = findLargetDigit(line, size-1-index)
		}
		if partSum, err := strconv.ParseInt(string(parts), 10, 64); err != nil {
			return 0, fmt.Errorf("invalid result %s", string(parts))
		} else {
			total += partSum
		}
	}
	return total, nil
}