package cart

import (
	"fmt"

	messages "git.k6n.net/go-cart-actor/pkg/messages"
)

// mutation_remove_delivery.go
//
// Registers the RemoveDelivery mutation.
//
// Behavior:
//   - Removes the delivery entry whose Id == payload.Id.
//   - If not found, returns an error.
//   - Cart totals are recalculated (WithTotals) after removal.
//   - Items previously associated with that delivery simply become "without delivery";
//     subsequent delivery mutations can reassign them.
//
// Differences vs legacy:
//   - Legacy logic decremented TotalPrice explicitly before recalculating.
//     Here we rely solely on UpdateTotals() to recompute from remaining
//     deliveries and items (simpler / single source of truth).
//
// Future considerations:
//   - If delivery pricing logic changes (e.g., dynamic taxes per delivery),
//     UpdateTotals() may need enhancement to incorporate delivery tax properly.

func RemoveDelivery(g *CartGrain, m *messages.RemoveDelivery) error {
	if m == nil {
		return fmt.Errorf("RemoveDelivery: nil payload")
	}
	if g.PaymentInProgress > 0 {
		return ErrPaymentInProgress
	}
	targetID := uint32(m.Id)
	index := -1
	for i, d := range g.Deliveries {
		if d.Id == targetID {
			index = i
			break
		}
	}
	if index == -1 {
		return fmt.Errorf("RemoveDelivery: delivery id %d not found", m.Id)
	}

	// Remove delivery (order not preserved beyond necessity)
	g.Deliveries = append(g.Deliveries[:index], g.Deliveries[index+1:]...)
	g.UpdateTotals()
	return nil
}