package pricing

import (
	"context"

	"github.com/google/uuid"
)

type Service struct {
	repo Repository
}

func NewService(repo Repository) *Service {
	return &Service{repo: repo}
}

func (s *Service) ListByProduct(ctx context.Context, productID uuid.UUID) ([]*PriceTier, error) {
	return s.repo.ListByProduct(ctx, productID)
}

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

func (s *Service) Create(ctx context.Context, productID, unitID uuid.UUID, quantity float64, priceCents int64, position int) (*PriceTier, error) {
	t := &PriceTier{
		ID:         uuid.New(),
		ProductID:  productID,
		UnitID:     unitID,
		Quantity:   quantity,
		PriceCents: priceCents,
		Position:   position,
	}
	if err := s.repo.Create(ctx, t); err != nil {
		return nil, err
	}
	return t, nil
}

func (s *Service) Update(ctx context.Context, id uuid.UUID, unitID uuid.UUID, quantity float64, priceCents int64, position int) (*PriceTier, error) {
	t, err := s.repo.FindByID(ctx, id)
	if err != nil {
		return nil, err
	}
	t.UnitID = unitID
	t.Quantity = quantity
	t.PriceCents = priceCents
	t.Position = position
	if err := s.repo.Update(ctx, t); err != nil {
		return nil, err
	}
	return t, nil
}

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

// PriceForQuantity is the centralized pricing calculation used by the
// orders module: given a chosen tier and how many of that tier package the
// customer wants, it returns the authoritative total in cents. The
// frontend never gets to supply a price directly.
func (s *Service) PriceForQuantity(ctx context.Context, tierID uuid.UUID, multiplier int64) (totalCents int64, tier *PriceTier, err error) {
	t, err := s.repo.FindByID(ctx, tierID)
	if err != nil {
		return 0, nil, err
	}
	if multiplier < 1 {
		multiplier = 1
	}
	return t.PriceCents * multiplier, t, nil
}