59 lines
1.5 KiB
Go
59 lines
1.5 KiB
Go
package main
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import (
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"fmt"
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messages "git.tornberg.me/go-cart-actor/pkg/messages"
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)
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// mutation_change_quantity.go
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//
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// Registers the ChangeQuantity mutation.
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//
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// Behavior:
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// - Locates an item by its cart-local line item Id (not source item_id).
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// - If requested quantity <= 0 the line is removed.
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// - Otherwise the line's Quantity field is updated.
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// - Totals are recalculated (WithTotals).
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//
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// Error handling:
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// - Returns an error if the item Id is not found.
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// - Returns an error if payload is nil (defensive).
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//
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// Concurrency:
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// - Uses the grain's RW-safe mutation pattern: we mutate in place under
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// the grain's implicit expectation that higher layers control access.
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// (If strict locking is required around every mutation, wrap logic in
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// an explicit g.mu.Lock()/Unlock(), but current model mirrors prior code.)
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func init() {
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RegisterMutation[messages.ChangeQuantity](
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"ChangeQuantity",
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func(g *CartGrain, m *messages.ChangeQuantity) error {
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if m == nil {
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return fmt.Errorf("ChangeQuantity: nil payload")
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}
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foundIndex := -1
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for i, it := range g.Items {
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if it.Id == int(m.Id) {
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foundIndex = i
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break
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}
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}
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if foundIndex == -1 {
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return fmt.Errorf("ChangeQuantity: item id %d not found", m.Id)
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}
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if m.Quantity <= 0 {
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// Remove the item
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g.Items = append(g.Items[:foundIndex], g.Items[foundIndex+1:]...)
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return nil
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}
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g.Items[foundIndex].Quantity = int(m.Quantity)
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return nil
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},
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WithTotals(),
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)
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}
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