package game

import (
	"errors"
	"fmt"
	"math/rand"
	"slices"
	"strings"
)

type PileOfCards interface {
	Size() int
	IsEmpty() bool
	Contains(*Card) bool
	Cards() []*Card
	FilterCards(func(*Card) bool) []*Card
	AddCards(cards []*Card)
	AddCard(card *Card)
	RemoveCard(card *Card)
	RandomCard() *Card
	MoveCard(card *Card, into PileOfCards)
	MoveInto(into PileOfCards)
	ToList() string
	String() string
}

type PileOfCardsBase struct {
	cards []*Card
}

func NewPileOfCards() *PileOfCardsBase {
	return &PileOfCardsBase{[]*Card{}}
}

// Stringify to a []-bracket enclosed comma-seperated list of card names.
func (poc *PileOfCardsBase) String() string {
	cardNames := make([]string, 0, len(poc.Cards()))
	for _, card := range poc.Cards() {
		cardNames = append(cardNames, card.Path())
	}
	return fmt.Sprintf("[%s]", strings.Join(cardNames, ", "))
}

var ErrInvalidPocString = errors.New("invalid PileOfCards format")

// Initialise a PileOfCard from a string.
// Return InvalidPocString on error.
func (poc *PileOfCardsBase) FromString(in string) error {
	if in[0] != '[' || in[len(in)-1] != ']' {
		return ErrInvalidPocString
	}

	in = in[1 : len(in)-1]

	for cardName := range strings.SplitSeq(in, ", ") {
		if card, err := NewCardSafe(cardName); err != nil {
			return err
		} else {
			poc.AddCard(card)
		}
	}
	return nil
}

func (poc *PileOfCardsBase) Size() int {
	return len(poc.cards)
}

func (poc *PileOfCardsBase) IsEmpty() bool {
	return poc.Size() == 0
}

func (poc *PileOfCardsBase) Contains(card *Card) bool {
	return slices.Contains(poc.cards, card)
}

func (poc *PileOfCardsBase) Cards() []*Card {
	return poc.cards
}

func (poc *PileOfCardsBase) FilterCards(f func(*Card) bool) []*Card {
	cards := []*Card{}
	for _, c := range poc.Cards() {
		if f(c) {
			cards = append(cards, c)
		}
	}
	return cards
}

func (poc *PileOfCardsBase) AddPoc(toAdd PileOfCards) {
	poc.AddCards(toAdd.Cards())
}

func (poc *PileOfCardsBase) AddCards(cards []*Card) {
	for _, card := range cards {
		poc.AddCard(card)
	}
}

func (poc *PileOfCardsBase) AddCard(card *Card) {
	// Tokens can not be part of any pile of cards
	if !card.IsToken() {
		poc.cards = append(poc.cards, card)
	}
}

func (poc *PileOfCardsBase) RemoveCard(card *Card) {
	ncards := poc.Size()
	for i, c := range poc.cards {
		if c != card {
			continue
		}

		poc.cards[i] = poc.cards[ncards-1]
		poc.cards = poc.cards[:ncards-1]
		return
	}
}

func (poc *PileOfCardsBase) RandomCard() *Card {
	availCards := poc.Cards()
	var pick int
	if n := len(availCards); n > 1 {
		pick = rand.Intn(n - 1)
	} else {
		pick = 0
	}
	return availCards[pick]
}

func (poc *PileOfCardsBase) MoveCard(c *Card, into PileOfCards) {
	poc.RemoveCard(c)
	into.AddCard(c)
}

func (poc *PileOfCardsBase) MoveInto(into PileOfCards) {
	into.AddCards(poc.cards)
	poc.cards = []*Card{}
}

func (poc *PileOfCardsBase) ToList() (list string) {
	m := make(map[string]int)
	for _, card := range poc.cards {
		path := card.Path()
		m[path]++
	}

	for path, amount := range m {
		list += fmt.Sprintf("%d %s\n", amount, path)
	}

	return list[:len(list)-1]
}

func NewRandomPackFromPool(pool PileOfCards, packSize int) PileOfCards {
	pack := NewPileOfCards()
	for range packSize {
		card := pool.Cards()[rand.Intn(len(pool.Cards())-1)]
		pool.MoveCard(card, pack)
	}
	return pack
}