package day7

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

func Run() int {
	fmt.Print("hello day 7")
	filename := "day7/input"
	input := ReadFile(filename)
	slices.SortFunc(input, CompareHands)
	log.Printf("read the input %+v\n", input)
	slices.SortFunc([]int{}, func(a int, b int) int { return 0 })
	result := 0
	for i, hand := range input {
		result += (i+1) * hand.Bid
	}
	return result
}

type HandType int

const (
	HighCard = iota
	OnePair
	TwoPair
	ThreeKind
	FullHouse
	FourKind
	FiveKind
)

type Hand struct {
	Cards    string
	Grouped  map[rune]int
	HandType HandType
	Bid      int
}

// cmp(a, b) should return a negative number when a < b, a positive number when
// a > b and zero when a == b.
const values string = "23456789TJQKA"

func CompareHands(a Hand, b Hand) int {
	if a.HandType != b.HandType {
		return int(a.HandType) - int(b.HandType)
	}
	return compareString(a.Cards, b.Cards)
}

func compareString(a string, b string) int {
	for i := 0; i < len(a); i++ {
		if a[i] == b[i] {
			continue
		}
		aVal := strings.IndexRune(values, rune(a[i]))
		bVal := strings.IndexRune(values, rune(b[i]))
		return aVal - bVal
	}
	return 0
}

func GetHandType(groupped map[rune]int) HandType {
	var handType HandType
	sizes := make([]int, 0, len(groupped))
	for _, size := range groupped {
		sizes = append(sizes, size)
	}
	slices.Sort(sizes)
	switch {
	case slices.Equal(sizes, []int{5}):
		handType = FiveKind
	case slices.Equal(sizes, []int{1, 4}):
		handType = FourKind
	case slices.Equal(sizes, []int{2, 3}):
		handType = FullHouse
	case slices.Equal(sizes, []int{1, 1, 3}):
		handType = ThreeKind
	case slices.Equal(sizes, []int{1, 2, 2}):
		handType = TwoPair
	case slices.Equal(sizes, []int{1, 1, 1, 2}):
		handType = OnePair
	}

	log.Printf("calc type for %+v.\nsizes: %+v;\n %d", groupped, sizes, handType)
	return handType
}

func ReadFile(filename string) []Hand {
	bytes, err := os.ReadFile(filename)
	if err != nil {
		panic(fmt.Sprintln("error reading file : ", filename))
	}
	text := string(bytes)
	lines := strings.Split(text, "\n")
	linesLen := len(lines)
	result := make([]Hand, 0, linesLen)

	for _, line := range lines {
		log.Println("reading in line : ", line)
		if line == "" {
			continue
		}
		firstSplit := strings.Fields(line)
		cards := firstSplit[0]
		bidStr := firstSplit[1]
		bid, err := strconv.Atoi(bidStr)
		if err != nil {
			panic(fmt.Sprintln("error getting bid from : ", bidStr))
		}
		groupped := make(map[rune]int, 0)
		for _, card := range cards {
			groupped[card] += 1
		}
		hand := Hand{
			Cards:   cards,
			Grouped: groupped,
			Bid:     bid,
			HandType: GetHandType(groupped),
		}
		result = append(result, hand)
	}

	return result
}