package main

import (
	"fmt"

	messages "git.tornberg.me/go-cart-actor/pkg/messages"
)

// mutation_add_request.go
//
// Registers the AddRequest mutation. This mutation is a higher-level intent
// (add by SKU + quantity) which may translate into either:
//   - Increasing quantity of an existing line (same SKU), OR
//   - Creating a new item by performing a product lookup (via getItemData inside CartGrain.AddItem)
//
// Behavior:
//   - Validates non-empty SKU and quantity > 0
//   - If an item with the SKU already exists: increments its quantity
//   - Else delegates to CartGrain.AddItem (which itself produces an AddItem mutation)
//   - Totals recalculated automatically (WithTotals)
//
// NOTE:
//   - This handler purposely avoids duplicating the detailed AddItem logic;
//     it reuses CartGrain.AddItem which then flows through the AddItem mutation
//     registry handler.
//   - Double total recalculation can occur (AddItem has WithTotals too), but
//     is acceptable for clarity. Optimize later if needed.
//
// Potential future improvements:
//   - Stock validation before increasing quantity
//   - Reservation logic or concurrency guards around stock updates
//   - Coupon / pricing rules applied conditionally during add-by-sku
func init() {
	RegisterMutation[messages.AddRequest](
		"AddRequest",
		func(g *CartGrain, m *messages.AddRequest) error {
			if m == nil {
				return fmt.Errorf("AddRequest: nil payload")
			}
			if m.Sku == "" {
				return fmt.Errorf("AddRequest: sku is empty")
			}
			if m.Quantity < 1 {
				return fmt.Errorf("AddRequest: invalid quantity %d", m.Quantity)
			}

			// Existing line: accumulate quantity only.
			if existing, found := g.FindItemWithSku(m.Sku); found {
				existing.Quantity += int(m.Quantity)
				return nil
			}

			// New line: delegate to higher-level AddItem flow (product lookup).
			// We intentionally ignore the returned *CartGrain; registry will
			// do totals again after this handler returns (harmless).
			_, err := g.AddItem(m.Sku, int(m.Quantity), m.Country, m.StoreId)
			return err
		},
		WithTotals(),
	)
}