package processor

import (
	"apskel-pos-be/internal/constants"
	"apskel-pos-be/internal/entities"
	"apskel-pos-be/internal/mappers"
	"apskel-pos-be/internal/models"
	"apskel-pos-be/internal/repository"
	"context"
	"errors"
	"fmt"
	"math"
	"math/rand"
	"time"

	"github.com/google/uuid"
)

// ErrGamePlayRefused wraps every reason a customer cannot play right now: the game,
// its prizes or their EnakCoin. The message says which.
var ErrGamePlayRefused = errors.New("game cannot be played")

const (
	gameCoinCostKey     = "coin_cost"
	defaultGameCoinCost = 1
)

type gameReader interface {
	GetByID(ctx context.Context, id uuid.UUID) (*entities.Game, error)
}

type gamePrizeStock interface {
	GetAvailablePrizes(ctx context.Context, gameID uuid.UUID) ([]entities.GamePrize, error)
	DecreaseStock(ctx context.Context, id uuid.UUID, amount int) error
}

type GamePlayProcessor struct {
	gamePlayRepo  repository.GamePlayRepository
	gameRepo      gameReader
	gamePrizeRepo gamePrizeStock
	wallet        *WalletProcessor
	spendable     spendableReader
	tx            TxRunner
}

func NewGamePlayProcessor(
	gamePlayRepo repository.GamePlayRepository,
	gameRepo gameReader,
	gamePrizeRepo gamePrizeStock,
	wallet *WalletProcessor,
	spendable spendableReader,
	tx TxRunner,
) *GamePlayProcessor {
	return &GamePlayProcessor{
		gamePlayRepo:  gamePlayRepo,
		gameRepo:      gameRepo,
		gamePrizeRepo: gamePrizeRepo,
		wallet:        wallet,
		spendable:     spendable,
		tx:            tx,
	}
}

// CreateGamePlay creates a new game play record
func (p *GamePlayProcessor) CreateGamePlay(ctx context.Context, req *models.CreateGamePlayRequest) (*models.GamePlayResponse, error) {
	// Convert request to entity
	gamePlay := mappers.ToGamePlayEntity(req)

	// Create game play
	err := p.gamePlayRepo.Create(ctx, gamePlay)
	if err != nil {
		return nil, fmt.Errorf("failed to create game play: %w", err)
	}

	return mappers.ToGamePlayResponse(gamePlay), nil
}

// GetGamePlay retrieves a game play by ID
func (p *GamePlayProcessor) GetGamePlay(ctx context.Context, id uuid.UUID) (*models.GamePlayResponse, error) {
	gamePlay, err := p.gamePlayRepo.GetByID(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("game play not found: %w", err)
	}

	return mappers.ToGamePlayResponse(gamePlay), nil
}

// ListGamePlays retrieves game plays with pagination and filtering
func (p *GamePlayProcessor) ListGamePlays(ctx context.Context, query *models.ListGamePlaysQuery) (*models.PaginatedResponse[models.GamePlayResponse], error) {
	// Set default values
	if query.Page <= 0 {
		query.Page = 1
	}
	if query.Limit <= 0 {
		query.Limit = 10
	}
	if query.Limit > 100 {
		query.Limit = 100
	}

	offset := (query.Page - 1) * query.Limit
	// The column was renamed; the old name still sorts the same way.
	if query.SortBy == "token_used" {
		query.SortBy = "coins_used"
	}

	// Get game plays from repository
	gamePlays, total, err := p.gamePlayRepo.List(
		ctx,
		offset,
		query.Limit,
		query.Search,
		query.GameID,
		query.CustomerID,
		query.PrizeID,
		query.SortBy,
		query.SortOrder,
	)
	if err != nil {
		return nil, fmt.Errorf("failed to list game plays: %w", err)
	}

	// Convert to responses
	responses := mappers.ToGamePlayResponsesFromPointers(gamePlays)

	// Calculate pagination info
	totalPages := int((total + int64(query.Limit) - 1) / int64(query.Limit))

	return &models.PaginatedResponse[models.GamePlayResponse]{
		Data: responses,
		Pagination: models.Pagination{
			Page:       query.Page,
			Limit:      query.Limit,
			Total:      total,
			TotalPages: totalPages,
		},
	}, nil
}

// PlayGame plays a game for a customer, paid with EnakCoin (docs/prd-point-coin.md
// F8, K1). Every kind of game spends the same EnakCoin, at the game's
// metadata.coin_cost. Taking the EnakCoin (GAME_SPEND), recording the play and taking
// the prize from stock happen in one transaction, so a play that cannot be completed,
// for instance because the prize just ran out, takes nothing and records nothing.
func (p *GamePlayProcessor) PlayGame(ctx context.Context, req *models.PlayGameRequest) (*models.PlayGameResponse, error) {
	refuse := func(format string, args ...any) error {
		return fmt.Errorf("%w: %s", ErrGamePlayRefused, fmt.Sprintf(format, args...))
	}
	game, err := p.gameRepo.GetByID(ctx, req.GameID)
	if err != nil {
		return nil, fmt.Errorf("game not found: %w", err)
	}
	if !game.IsActive {
		return nil, refuse("game is not active")
	}
	cost, err := gameCoinCost(game.Metadata)
	if err != nil {
		return nil, refuse("%s", err.Error())
	}

	var gamePlay *entities.GamePlay
	var selectedPrize *models.GamePrizeResponse
	err = p.tx.WithTransaction(ctx, func(ctx context.Context) error {
		availablePrizes, err := p.gamePrizeRepo.GetAvailablePrizes(ctx, req.GameID)
		if err != nil {
			return fmt.Errorf("failed to get available prizes: %w", err)
		}
		if len(availablePrizes) == 0 {
			return refuse("no prizes available")
		}
		prizeResponses := make([]models.GamePrizeResponse, len(availablePrizes))
		for i, prize := range availablePrizes {
			prizeResponses[i] = *mappers.ToGamePrizeResponse(&prize)
		}
		selectedPrize = p.selectPrizeByWeight(prizeResponses)

		// Random seed kept for audit.
		randomSeed := fmt.Sprintf("%d", time.Now().UnixNano())
		gamePlay = &entities.GamePlay{
			ID:         uuid.New(),
			GameID:     req.GameID,
			CustomerID: req.CustomerID,
			CoinsUsed:  int(cost),
			RandomSeed: &randomSeed,
		}
		if selectedPrize != nil {
			gamePlay.PrizeID = &selectedPrize.ID
		}

		// The EnakCoin go first: the debit locks the wallet, so plays by the same
		// customer at the same time queue up instead of spending the same balance.
		_, err = p.wallet.Debit(ctx, WalletDebitInput{WalletEntry: WalletEntry{
			CustomerID:    req.CustomerID,
			Currency:      constants.WalletCurrencyCoin,
			Type:          constants.WalletTxTypeGameSpend,
			Amount:        cost,
			ReferenceType: constants.WalletRefTypeGamePlay,
			ReferenceID:   gamePlay.ID,
			Description:   gameSpendDescription(game.Name, selectedPrize),
			Metadata:      entities.Metadata{"game_id": game.ID.String(), "coin_cost": cost},
		}})
		if errors.Is(err, repository.ErrWalletInsufficientBalance) {
			return refuse("not enough EnakCoin: this game costs %d", cost)
		}
		if err != nil {
			return err
		}
		if err := p.gamePlayRepo.Create(ctx, gamePlay); err != nil {
			return err
		}
		if selectedPrize != nil {
			err := p.gamePrizeRepo.DecreaseStock(ctx, selectedPrize.ID, 1)
			if errors.Is(err, repository.ErrGamePrizeOutOfStock) {
				return refuse("the prize just ran out, please play again")
			}
			if err != nil {
				return err
			}
		}
		return nil
	})
	if err != nil {
		return nil, err
	}

	balances, err := p.spendable.SpendableBalances(ctx, req.CustomerID, time.Now())
	if err != nil {
		return nil, err
	}
	return &models.PlayGameResponse{
		GamePlay:       *mappers.ToGamePlayResponse(gamePlay),
		PrizeWon:       selectedPrize,
		CoinsRemaining: balances[constants.WalletCurrencyCoin],
	}, nil
}

// gameCoinCost is what one play of a game costs, from games.metadata.coin_cost: a
// whole number of EnakCoin, 1 when it is not set (F8).
func gameCoinCost(metadata entities.Metadata) (int64, error) {
	raw, ok := metadata[gameCoinCostKey]
	if !ok || raw == nil {
		return defaultGameCoinCost, nil
	}
	var cost int64
	switch v := raw.(type) {
	case float64:
		if v != math.Trunc(v) {
			return 0, fmt.Errorf("the game's coin_cost %v is not a whole number", v)
		}
		cost = int64(v)
	case int:
		cost = int64(v)
	case int64:
		cost = v
	default:
		return 0, fmt.Errorf("the game's coin_cost %v is not a number", raw)
	}
	if cost < 1 {
		return 0, fmt.Errorf("the game's coin_cost must be at least 1, got %d", cost)
	}
	return cost, nil
}

// gameSpendDescription is what the customer's history shows for a play, frozen when it
// happens (§8.1): "Main Spin Wheel: dapat Voucher 10rb".
func gameSpendDescription(gameName string, prize *models.GamePrizeResponse) string {
	description := "Main " + gameName
	if prize != nil {
		description += ": dapat " + prize.Name
	}
	return truncateRunes(description, walletDescriptionLimit)
}

// selectPrizeByWeight selects a prize based on weight distribution
func (p *GamePlayProcessor) selectPrizeByWeight(prizes []models.GamePrizeResponse) *models.GamePrizeResponse {
	if len(prizes) == 0 {
		return nil
	}

	// Calculate total weight
	totalWeight := 0
	for _, prize := range prizes {
		totalWeight += prize.Weight
	}

	if totalWeight == 0 {
		return nil
	}

	// Generate random number
	rand.Seed(time.Now().UnixNano())
	randomNumber := rand.Intn(totalWeight)

	// Select prize based on cumulative weight
	currentWeight := 0
	for _, prize := range prizes {
		currentWeight += prize.Weight
		if randomNumber < currentWeight {
			return &prize
		}
	}

	// Fallback to last prize
	return &prizes[len(prizes)-1]
}