package services

import (
	"context"
	"errors"
	"fmt"

	"github.com/google/uuid"
	"github.com/stripe/stripe-go/v82"
	"github.com/stripe/stripe-go/v82/account"
	"github.com/stripe/stripe-go/v82/accountlink"
	"github.com/stripe/stripe-go/v82/balance"
	"github.com/stripe/stripe-go/v82/transfer"
	"go.uber.org/zap"
	"gorm.io/gorm"

	"veza-backend-api/internal/models"
)

var (
	ErrStripeConnectDisabled = errors.New("Stripe Connect is not enabled")
	ErrNoStripeAccount       = errors.New("seller has no Stripe Connect account")
)

// BalanceResponse is the balance for a connected account
type BalanceResponse struct {
	Connected bool  `json:"connected"` // true if seller has completed Stripe Connect onboarding
	Available int64 `json:"available"` // in minor units (cents)
	Pending   int64 `json:"pending"`   // in minor units (cents)
}

// StripeConnectService handles Stripe Connect operations for seller payouts
type StripeConnectService struct {
	db        *gorm.DB
	secretKey string
	logger    *zap.Logger
}

// NewStripeConnectService creates a new Stripe Connect service
func NewStripeConnectService(db *gorm.DB, secretKey string, logger *zap.Logger) *StripeConnectService {
	return &StripeConnectService{
		db:        db,
		secretKey: secretKey,
		logger:    logger,
	}
}

// CreateOnboardingLink creates or retrieves a Stripe Express account and returns an onboarding URL
func (s *StripeConnectService) CreateOnboardingLink(ctx context.Context, userID uuid.UUID, returnURL, refreshURL string) (string, error) {
	if s.secretKey == "" {
		return "", ErrStripeConnectDisabled
	}
	stripe.Key = s.secretKey

	// Get user email
	var user models.User
	if err := s.db.WithContext(ctx).Where("id = ?", userID).First(&user).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return "", fmt.Errorf("user not found: %w", err)
		}
		return "", err
	}

	// Check if account already exists
	var existing models.SellerStripeAccount
	if err := s.db.WithContext(ctx).Where("user_id = ?", userID).First(&existing).Error; err == nil {
		// Account exists, create new account link for onboarding/update
		params := &stripe.AccountLinkParams{
			Account:    stripe.String(existing.StripeAccountID),
			ReturnURL:  stripe.String(returnURL),
			RefreshURL: stripe.String(refreshURL),
			Type:       stripe.String(string(stripe.AccountLinkTypeAccountOnboarding)),
		}
		link, err := accountlink.New(params)
		if err != nil {
			return "", fmt.Errorf("create account link: %w", err)
		}
		return link.URL, nil
	}

	// Create new Express account
	accountParams := &stripe.AccountParams{
		Type:  stripe.String(string(stripe.AccountTypeExpress)),
		Email: stripe.String(user.Email),
	}
	acct, err := account.New(accountParams)
	if err != nil {
		return "", fmt.Errorf("create stripe account: %w", err)
	}

	// Save to DB
	sa := models.SellerStripeAccount{
		UserID:              userID,
		StripeAccountID:     acct.ID,
		OnboardingCompleted: false,
	}
	if err := s.db.WithContext(ctx).Create(&sa).Error; err != nil {
		return "", fmt.Errorf("save seller stripe account: %w", err)
	}

	// Create account link
	linkParams := &stripe.AccountLinkParams{
		Account:    stripe.String(acct.ID),
		ReturnURL:  stripe.String(returnURL),
		RefreshURL: stripe.String(refreshURL),
		Type:       stripe.String(string(stripe.AccountLinkTypeAccountOnboarding)),
	}
	link, err := accountlink.New(linkParams)
	if err != nil {
		return "", fmt.Errorf("create account link: %w", err)
	}
	return link.URL, nil
}

// HandleOnboardingCallback updates the account status after Stripe redirect
func (s *StripeConnectService) HandleOnboardingCallback(ctx context.Context, userID uuid.UUID) error {
	var sa models.SellerStripeAccount
	if err := s.db.WithContext(ctx).Where("user_id = ?", userID).First(&sa).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return ErrNoStripeAccount
		}
		return err
	}

	if s.secretKey == "" {
		return ErrStripeConnectDisabled
	}
	stripe.Key = s.secretKey

	// Retrieve account from Stripe to get charges_enabled, payouts_enabled
	params := &stripe.AccountParams{}
	acct, err := account.GetByID(sa.StripeAccountID, params)
	if err != nil {
		return fmt.Errorf("get stripe account: %w", err)
	}

	sa.ChargesEnabled = acct.ChargesEnabled
	sa.PayoutsEnabled = acct.PayoutsEnabled
	sa.OnboardingCompleted = acct.DetailsSubmitted
	if err := s.db.WithContext(ctx).Save(&sa).Error; err != nil {
		return fmt.Errorf("update seller stripe account: %w", err)
	}
	return nil
}

// GetBalance returns the balance for a seller's connected account
func (s *StripeConnectService) GetBalance(ctx context.Context, userID uuid.UUID) (*BalanceResponse, error) {
	var sa models.SellerStripeAccount
	if err := s.db.WithContext(ctx).Where("user_id = ?", userID).First(&sa).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return &BalanceResponse{Connected: false, Available: 0, Pending: 0}, nil
		}
		return nil, err
	}

	if s.secretKey == "" {
		return nil, ErrStripeConnectDisabled
	}
	stripe.Key = s.secretKey

	params := &stripe.BalanceParams{}
	params.SetStripeAccount(sa.StripeAccountID)
	bal, err := balance.Get(params)
	if err != nil {
		return nil, fmt.Errorf("get stripe balance: %w", err)
	}

	var available, pending int64
	for _, a := range bal.Available {
		available += a.Amount
	}
	for _, p := range bal.Pending {
		pending += p.Amount
	}
	return &BalanceResponse{Connected: true, Available: available, Pending: pending}, nil
}

// CreateTransfer transfers funds to a connected account (for payout on sale)
func (s *StripeConnectService) CreateTransfer(ctx context.Context, sellerUserID uuid.UUID, amount int64, currency, orderID string) error {
	var sa models.SellerStripeAccount
	if err := s.db.WithContext(ctx).Where("user_id = ?", sellerUserID).First(&sa).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return ErrNoStripeAccount
		}
		return err
	}
	if !sa.PayoutsEnabled {
		return fmt.Errorf("seller account does not have payouts enabled")
	}

	if s.secretKey == "" {
		return ErrStripeConnectDisabled
	}
	stripe.Key = s.secretKey

	params := &stripe.TransferParams{
		Amount:      stripe.Int64(amount),
		Currency:    stripe.String(currency),
		Destination: stripe.String(sa.StripeAccountID),
	}
	if orderID != "" {
		params.AddMetadata("order_id", orderID)
	}
	_, err := transfer.New(params)
	if err != nil {
		return fmt.Errorf("create stripe transfer: %w", err)
	}
	return nil
}