package cart

import (
	"context"
	"fmt"
	"log"
	"time"

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

// mutation_remove_item.go
//
// Registers the RemoveItem mutation.
//
// Behavior:
//   - Removes the cart line whose local cart line Id == payload.Id
//   - Cascades: also removes any line whose ParentId points at a removed line
//     (transitively), so removing a parent removes its child sub-articles
//   - If no such line exists returns an error
//   - Releases reservations for every removed line and recalculates totals
//
// Notes:
//   - This removes only the line items; any deliveries referencing a removed
//     item are NOT automatically adjusted (mirrors prior logic). If future
//     semantics require pruning delivery.item_ids you can extend this handler.
//   - If multiple lines somehow shared the same Id (should not happen), all
//     matches are removed—data integrity relies on unique line Ids.

func (c *CartMutationContext) RemoveItem(g *CartGrain, m *messages.RemoveItem) error {
	if m == nil {
		return fmt.Errorf("RemoveItem: nil payload")
	}

	targetID := uint32(m.Id)

	found := false
	for _, it := range g.Items {
		if it.Id == targetID {
			found = true
			break
		}
	}
	if !found {
		return fmt.Errorf("RemoveItem: item id %d not found", m.Id)
	}

	// Collect the target and, transitively, any children pointing at a removed
	// line. Loops until no further descendants are found (handles nesting).
	remove := map[uint32]bool{targetID: true}
	for {
		grew := false
		for _, it := range g.Items {
			if it.ParentId != nil && remove[*it.ParentId] && !remove[it.Id] {
				remove[it.Id] = true
				grew = true
			}
		}
		if !grew {
			break
		}
	}

	kept := g.Items[:0]
	for _, it := range g.Items {
		if remove[it.Id] {
			if it.ReservationEndTime != nil && it.ReservationEndTime.After(time.Now()) {
				if err := c.ReleaseItem(context.Background(), g.Id, it.Sku, it.StoreId); err != nil {
					log.Printf("unable to release reservation for item %d: %v", it.Id, err)
				}
			}
			continue
		}
		kept = append(kept, it)
	}
	g.Items = kept
	g.UpdateTotals()
	return nil
}