package main

import (
	"fmt"

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

// 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 init() {
	RegisterMutation[messages.RemoveDelivery](
		"RemoveDelivery",
		func(g *CartGrain, m *messages.RemoveDelivery) error {
			if m == nil {
				return fmt.Errorf("RemoveDelivery: nil payload")
			}
			targetID := int(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:]...)
			return nil
		},
		WithTotals(),
	)
}