package day4

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

func Run() int {
	fmt.Println("in day 4")
	cards := ReadAllCards()
	result := 0

	for _, card := range cards {
		fmt.Printf("> checking card %+v with points %d", card, card.GetPoints())
		result += card.GetPoints()
	}

	return result
}

type Card struct {
	Title int
	WinningNums []int
	OwnNums []int
}

func ReadAllCards() []Card {
	filename := "day4/example"
	bytes, err := os.ReadFile(filename)
	if err != nil {
		panic(fmt.Sprintf("can't read file %s", filename))
	}
	text := string(bytes)
	lines := strings.Split(text, "\n")
	result := make([]Card, len(lines))

	for _, line := range lines {
		if line == "" {
			continue
		}
		result = append(result, ReadCard(line))
	}

	return result
}

// read line like 'Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53'
func ReadCard(line string) Card {
	result := Card{}
	extractingTitle := strings.Split(line, ":")
	title := extractingTitle[0]
	numberPart := extractingTitle[1]

	titleNumStr := strings.Split(title, " ")[1]
	titleNum, err := strconv.Atoi(titleNumStr)
	if err != nil {
		panic(fmt.Sprintf("error extracting card title: %s, %s", line, titleNumStr))
	}
	result.Title = titleNum

	extractingNumbers := strings.Split(numberPart, "|")
	for _, winningNumStr := range strings.Split(  extractingNumbers[0], " " ) {
		winningNumStr = strings.TrimSpace(winningNumStr)
		if winningNumStr == "" {
			continue
		}
		winningNum, err := strconv.Atoi(winningNumStr)
		if err != nil {
			panic(fmt.Sprintf("error extracting winning card num: %s from  '%s'", line, winningNumStr))
		}
		result.WinningNums = append(result.WinningNums, winningNum)
	}
	for _, ownNumStr := range strings.Split(  extractingNumbers[1], " " ) {
		ownNumStr = strings.TrimSpace(ownNumStr)
		if ownNumStr == "" {
			continue
		}
		ownNum, err := strconv.Atoi(ownNumStr)
		if err != nil {
			panic(fmt.Sprintf("error extracting own card num: %s, %s", line, ownNumStr))
		}
		result.OwnNums = append(result.OwnNums, ownNum)
	}

	return result
}

func (c *Card)GetPoints() int {
	winningSet := make(map[int]any)
	for _, winNum := range c.WinningNums {
		winningSet[winNum] = struct{}{}
	}

	result := 0
	hasMatch := false
	for _, ownNum := range c.OwnNums {
		_, isWinning := winningSet[ownNum]
		if isWinning {
			if !hasMatch {
				result = 1
				hasMatch = true
			} else {
				result *= 2
			}
		}
	}
	return result
}