package processor

import (
	"context"
	"fmt"

	"apskel-pos-be/internal/mappers"
	"apskel-pos-be/internal/models"
	"apskel-pos-be/internal/repository"

	"github.com/google/uuid"
)

type InventoryProcessor interface {
	CreateInventory(ctx context.Context, req *models.CreateInventoryRequest) (*models.InventoryResponse, error)
	UpdateInventory(ctx context.Context, id uuid.UUID, req *models.UpdateInventoryRequest) (*models.InventoryResponse, error)
	DeleteInventory(ctx context.Context, id uuid.UUID) error
	GetInventoryByID(ctx context.Context, id uuid.UUID) (*models.InventoryResponse, error)
	ListInventory(ctx context.Context, filters map[string]interface{}, page, limit int) ([]models.InventoryResponse, int, error)
	AdjustInventory(ctx context.Context, productID, outletID uuid.UUID, req *models.InventoryAdjustmentRequest) (*models.InventoryResponse, error)
	GetLowStockItems(ctx context.Context, outletID uuid.UUID) ([]models.InventoryResponse, error)
	GetZeroStockItems(ctx context.Context, outletID uuid.UUID) ([]models.InventoryResponse, error)
}

type InventoryProcessorImpl struct {
	inventoryRepo repository.InventoryRepository
	productRepo   ProductRepository
	outletRepo    OutletRepository
}

func NewInventoryProcessorImpl(
	inventoryRepo repository.InventoryRepository,
	productRepo ProductRepository,
	outletRepo OutletRepository,
) *InventoryProcessorImpl {
	return &InventoryProcessorImpl{
		inventoryRepo: inventoryRepo,
		productRepo:   productRepo,
		outletRepo:    outletRepo,
	}
}

func (p *InventoryProcessorImpl) CreateInventory(ctx context.Context, req *models.CreateInventoryRequest) (*models.InventoryResponse, error) {
	_, err := p.productRepo.GetByID(ctx, req.ProductID)
	if err != nil {
		return nil, fmt.Errorf("invalid product: %w", err)
	}

	// Validate outlet exists
	_, err = p.outletRepo.GetByID(ctx, req.OutletID)
	if err != nil {
		return nil, fmt.Errorf("invalid outlet: %w", err)
	}

	// Check if inventory already exists for this product-outlet combination
	existingInventory, err := p.inventoryRepo.GetByProductAndOutlet(ctx, req.ProductID, req.OutletID)
	if err == nil && existingInventory != nil {
		return nil, fmt.Errorf("inventory already exists for product %s in outlet %s", req.ProductID, req.OutletID)
	}

	// Map request to entity
	inventoryEntity := mappers.CreateInventoryRequestToEntity(req)

	// Create inventory
	if err := p.inventoryRepo.Create(ctx, inventoryEntity); err != nil {
		return nil, fmt.Errorf("failed to create inventory: %w", err)
	}

	// Get inventory with relations for response
	inventoryWithRelations, err := p.inventoryRepo.GetWithRelations(ctx, inventoryEntity.ID)
	if err != nil {
		return nil, fmt.Errorf("failed to retrieve created inventory: %w", err)
	}

	// Map entity to response model
	response := mappers.InventoryEntityToResponse(inventoryWithRelations)
	return response, nil
}

func (p *InventoryProcessorImpl) UpdateInventory(ctx context.Context, id uuid.UUID, req *models.UpdateInventoryRequest) (*models.InventoryResponse, error) {
	// Get existing inventory
	existingInventory, err := p.inventoryRepo.GetByID(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("inventory not found: %w", err)
	}

	// Apply updates to entity
	mappers.UpdateInventoryEntityFromRequest(existingInventory, req)

	// Update inventory
	if err := p.inventoryRepo.Update(ctx, existingInventory); err != nil {
		return nil, fmt.Errorf("failed to update inventory: %w", err)
	}

	// Get updated inventory with relations for response
	inventoryWithRelations, err := p.inventoryRepo.GetWithRelations(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("failed to retrieve updated inventory: %w", err)
	}

	// Map entity to response model
	response := mappers.InventoryEntityToResponse(inventoryWithRelations)
	return response, nil
}

func (p *InventoryProcessorImpl) DeleteInventory(ctx context.Context, id uuid.UUID) error {
	// Check if inventory exists
	_, err := p.inventoryRepo.GetByID(ctx, id)
	if err != nil {
		return fmt.Errorf("inventory not found: %w", err)
	}

	// Delete inventory
	if err := p.inventoryRepo.Delete(ctx, id); err != nil {
		return fmt.Errorf("failed to delete inventory: %w", err)
	}

	return nil
}

func (p *InventoryProcessorImpl) GetInventoryByID(ctx context.Context, id uuid.UUID) (*models.InventoryResponse, error) {
	inventoryEntity, err := p.inventoryRepo.GetWithRelations(ctx, id)
	if err != nil {
		return nil, fmt.Errorf("inventory not found: %w", err)
	}

	response := mappers.InventoryEntityToResponse(inventoryEntity)
	return response, nil
}

func (p *InventoryProcessorImpl) ListInventory(ctx context.Context, filters map[string]interface{}, page, limit int) ([]models.InventoryResponse, int, error) {
	offset := (page - 1) * limit

	inventoryEntities, total, err := p.inventoryRepo.List(ctx, filters, limit, offset)
	if err != nil {
		return nil, 0, fmt.Errorf("failed to list inventory: %w", err)
	}

	responses := make([]models.InventoryResponse, len(inventoryEntities))
	for i, entity := range inventoryEntities {
		response := mappers.InventoryEntityToResponse(entity)
		if response != nil {
			responses[i] = *response
		}
	}

	return responses, int(total), nil
}

func (p *InventoryProcessorImpl) AdjustInventory(ctx context.Context, productID, outletID uuid.UUID, req *models.InventoryAdjustmentRequest) (*models.InventoryResponse, error) {
	// Validate product exists
	_, err := p.productRepo.GetByID(ctx, productID)
	if err != nil {
		return nil, fmt.Errorf("invalid product: %w", err)
	}

	// Validate outlet exists
	_, err = p.outletRepo.GetByID(ctx, outletID)
	if err != nil {
		return nil, fmt.Errorf("invalid outlet: %w", err)
	}

	// Perform quantity adjustment
	adjustedInventory, err := p.inventoryRepo.AdjustQuantity(ctx, productID, outletID, req.Delta)
	if err != nil {
		return nil, fmt.Errorf("failed to adjust inventory quantity: %w", err)
	}

	// Get inventory with relations for response
	inventoryWithRelations, err := p.inventoryRepo.GetWithRelations(ctx, adjustedInventory.ID)
	if err != nil {
		return nil, fmt.Errorf("failed to retrieve adjusted inventory: %w", err)
	}

	// Map entity to response model
	response := mappers.InventoryEntityToResponse(inventoryWithRelations)
	return response, nil
}

func (p *InventoryProcessorImpl) GetLowStockItems(ctx context.Context, outletID uuid.UUID) ([]models.InventoryResponse, error) {
	// Validate outlet exists
	_, err := p.outletRepo.GetByID(ctx, outletID)
	if err != nil {
		return nil, fmt.Errorf("invalid outlet: %w", err)
	}

	inventoryEntities, err := p.inventoryRepo.GetLowStock(ctx, outletID)
	if err != nil {
		return nil, fmt.Errorf("failed to get low stock items: %w", err)
	}

	responses := make([]models.InventoryResponse, len(inventoryEntities))
	for i, entity := range inventoryEntities {
		response := mappers.InventoryEntityToResponse(entity)
		if response != nil {
			responses[i] = *response
		}
	}

	return responses, nil
}

func (p *InventoryProcessorImpl) GetZeroStockItems(ctx context.Context, outletID uuid.UUID) ([]models.InventoryResponse, error) {
	// Validate outlet exists
	_, err := p.outletRepo.GetByID(ctx, outletID)
	if err != nil {
		return nil, fmt.Errorf("invalid outlet: %w", err)
	}

	inventoryEntities, err := p.inventoryRepo.GetZeroStock(ctx, outletID)
	if err != nil {
		return nil, fmt.Errorf("failed to get zero stock items: %w", err)
	}

	responses := make([]models.InventoryResponse, len(inventoryEntities))
	for i, entity := range inventoryEntities {
		response := mappers.InventoryEntityToResponse(entity)
		if response != nil {
			responses[i] = *response
		}
	}

	return responses, nil
}