package usecase

import (
	"context"

	"golang.org/x/crypto/bcrypt"

	"github.com/gofrs/uuid/v5"

	"github.com/saveinmed/backend-go/internal/domain"
)

// Repository defines DB contract for the core entities.
type Repository interface {
	CreateCompany(ctx context.Context, company *domain.Company) error
	ListCompanies(ctx context.Context) ([]domain.Company, error)

	CreateProduct(ctx context.Context, product *domain.Product) error
	ListProducts(ctx context.Context) ([]domain.Product, error)

	CreateOrder(ctx context.Context, order *domain.Order) error
	GetOrder(ctx context.Context, id uuid.UUID) (*domain.Order, error)
	UpdateOrderStatus(ctx context.Context, id uuid.UUID, status domain.OrderStatus) error

	CreateUser(ctx context.Context, user *domain.User) error
	ListUsers(ctx context.Context, filter domain.UserFilter) ([]domain.User, int64, error)
	GetUser(ctx context.Context, id uuid.UUID) (*domain.User, error)
	UpdateUser(ctx context.Context, user *domain.User) error
	DeleteUser(ctx context.Context, id uuid.UUID) error
}

// PaymentGateway abstracts Mercado Pago integration.
type PaymentGateway interface {
	CreatePreference(ctx context.Context, order *domain.Order) (*domain.PaymentPreference, error)
}

type Service struct {
	repo Repository
	pay  PaymentGateway
}

// NewService wires use cases together.
func NewService(repo Repository, pay PaymentGateway) *Service {
	return &Service{repo: repo, pay: pay}
}

func (s *Service) RegisterCompany(ctx context.Context, company *domain.Company) error {
	company.ID = uuid.Must(uuid.NewV7())
	return s.repo.CreateCompany(ctx, company)
}

func (s *Service) ListCompanies(ctx context.Context) ([]domain.Company, error) {
	return s.repo.ListCompanies(ctx)
}

func (s *Service) RegisterProduct(ctx context.Context, product *domain.Product) error {
	product.ID = uuid.Must(uuid.NewV7())
	return s.repo.CreateProduct(ctx, product)
}

func (s *Service) ListProducts(ctx context.Context) ([]domain.Product, error) {
	return s.repo.ListProducts(ctx)
}

func (s *Service) CreateOrder(ctx context.Context, order *domain.Order) error {
	order.ID = uuid.Must(uuid.NewV7())
	order.Status = domain.OrderStatusPending
	return s.repo.CreateOrder(ctx, order)
}

func (s *Service) GetOrder(ctx context.Context, id uuid.UUID) (*domain.Order, error) {
	return s.repo.GetOrder(ctx, id)
}

func (s *Service) UpdateOrderStatus(ctx context.Context, id uuid.UUID, status domain.OrderStatus) error {
	return s.repo.UpdateOrderStatus(ctx, id, status)
}

func (s *Service) CreatePaymentPreference(ctx context.Context, id uuid.UUID) (*domain.PaymentPreference, error) {
	order, err := s.repo.GetOrder(ctx, id)
	if err != nil {
		return nil, err
	}
	return s.pay.CreatePreference(ctx, order)
}

func (s *Service) CreateUser(ctx context.Context, user *domain.User, password string) error {
	hashed, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return err
	}

	user.ID = uuid.Must(uuid.NewV7())
	user.PasswordHash = string(hashed)

	return s.repo.CreateUser(ctx, user)
}

func (s *Service) ListUsers(ctx context.Context, filter domain.UserFilter, page, pageSize int) (*domain.UserPage, error) {
	if page < 1 {
		page = 1
	}
	if pageSize <= 0 {
		pageSize = 20
	}

	filter.Limit = pageSize
	filter.Offset = (page - 1) * pageSize

	users, total, err := s.repo.ListUsers(ctx, filter)
	if err != nil {
		return nil, err
	}

	return &domain.UserPage{Users: users, Total: total, Page: page, PageSize: pageSize}, nil
}

func (s *Service) GetUser(ctx context.Context, id uuid.UUID) (*domain.User, error) {
	return s.repo.GetUser(ctx, id)
}

func (s *Service) UpdateUser(ctx context.Context, user *domain.User, newPassword string) error {
	if newPassword != "" {
		hashed, err := bcrypt.GenerateFromPassword([]byte(newPassword), bcrypt.DefaultCost)
		if err != nil {
			return err
		}
		user.PasswordHash = string(hashed)
	}

	return s.repo.UpdateUser(ctx, user)
}

func (s *Service) DeleteUser(ctx context.Context, id uuid.UUID) error {
	return s.repo.DeleteUser(ctx, id)
}