package main

import (
	"flag"
	"fmt"
	"os"
	"regexp"
	"strconv"
	"strings"
)

var (
	inputFile = flag.String("input", "input.txt", "input filename")
	digRegex  = regexp.MustCompile(`(?m)\d+`)
)

func NearSymbols(line string, lineLen int, pos []int) (symbols int) {
	// fmt.Printf("looking at %s, line-length=%d\n", line[pos[0]:pos[1]], lineLen)
	for i := pos[0] + lineLen - 1; i < (pos[1] + lineLen + 1); i++ {
		if i < 0 || i >= len(line) {
			// fmt.Printf("skipped invalid index %d (len=%d)\n", i, len(line))
			continue
		}

		// fmt.Println("looking at " + string(line[i]))

		if line[i] != '.' && line[i] != '\n' && (line[i] < 48 || line[i] > 57) {
			fmt.Printf("found %s\n", string(line[i]))
			symbols++
		}
	}
	return
}

func main() {
	flag.Parse()
	input, err := os.ReadFile(*inputFile)
	if err != nil {
		panic(err)
	}

	var sum int
	strIn := string(input)
	lineLen := strings.Index(strIn, "\n") + 1
	allNumbers := digRegex.FindAllStringIndex(strIn, -1)

	for _, numMatch := range allNumbers {
		symbols := 0
		symbols += NearSymbols(strIn, lineLen*-1, numMatch)
		symbols += NearSymbols(strIn, 0, numMatch)
		symbols += NearSymbols(strIn, lineLen, numMatch)

		if symbols > 0 {
			numberAsInt, err := strconv.Atoi(strIn[numMatch[0]:numMatch[1]])
			if err != nil {
				panic(err)
			}
			sum += numberAsInt
			fmt.Printf("%d matched with %d symbols\n", numberAsInt, symbols)
		}
	}

	fmt.Printf("sum: %d\n", sum)
}