package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"regexp"
	"strconv"
	"strings"
)

func proccessLines(path string, f func(string) (stop bool, err error)) error {
	file, err := os.Open(path)
	if err != nil {
		return err
	}
	defer file.Close()
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		stop, err := f(scanner.Text())
		if stop || err != nil {
			return err
		}
	}
	if err := scanner.Err(); err != nil {
		return err
	}
	return nil
}

var matcher = regexp.MustCompile(`([0-9]+)-([0-9]+) ([a-zA-Z]): ([a-zA-Z]+)`)

func part1() {
	totalValid := 0
	err := proccessLines("input.txt", func(line string) (stop bool, err error) {
		results := matcher.FindStringSubmatch(line)
		if results == nil {
			err = fmt.Errorf("invalid line %s", line)
			return
		}
		minCount, err := strconv.Atoi(results[1])
		if err != nil {
			return
		}
		maxCount, err := strconv.Atoi(results[2])
		if err != nil {
			return
		}
		letter := results[3]
		password := results[4]
		// fmt.Printf("Make sure %s is in %s between %d and %d times\n", letter, password, minCount, maxCount)
		// Validate
		count := strings.Count(password, letter)
		if minCount <= count && count <= maxCount {
			totalValid++
		}
		return
	})
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("Total valid %d\n", totalValid)
}

func part2() {
	totalValid := 0
	err := proccessLines("input.txt", func(line string) (stop bool, err error) {
		results := matcher.FindStringSubmatch(line)
		if results == nil {
			err = fmt.Errorf("invalid line %s", line)
			return
		}
		pos1, err := strconv.Atoi(results[1])
		if err != nil {
			return
		}
		pos2, err := strconv.Atoi(results[2])
		if err != nil {
			return
		}
		// 1 vs 0 indexed
		pos1--
		pos2--
		letter := results[3]
		password := results[4]
		// fmt.Printf("Make sure %s is in %s between %d and %d times\n", letter, password, minCount, maxCount)
		// Validate
		if pos1 >= len(password) || pos2 >= len(password) {
			return
		}
		letter1 := string(password[pos1])
		letter2 := string(password[pos2])
		if (letter == letter1 || letter == letter2) && letter1 != letter2 {
			totalValid++
		}
		return
	})
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("Total valid %d\n", totalValid)
}

func main() {
	part1()
	part2()
}