Implement curse of binding

server/item/enchantment/curse_of_binding.go

@@ -0,0 +1,51 @@
+package enchantment
+
+import (
+	"github.com/df-mc/dragonfly/server/item"
+	"github.com/df-mc/dragonfly/server/world"
+)
+
+// CurseOfBinding is an enchantment that prevents the removal of an equipped item enchanted with the curse of binding from its armour slot.
+type CurseOfBinding struct{}
+
+// Name ...
+func (CurseOfBinding) Name() string {
+	return "Curse of Binding"
+}
+
+// MaxLevel ...
+func (CurseOfBinding) MaxLevel() int {
+	return 1
+}
+
+// Cost ...
+func (CurseOfBinding) Cost(level int) (int, int) {
+	return 25, 50
+}
+
+// Rarity ...
+func (CurseOfBinding) Rarity() item.EnchantmentRarity {
+	return item.EnchantmentRarityVeryRare
+}
+
+// CompatibleWithEnchantment ...
+func (CurseOfBinding) CompatibleWithEnchantment(item.EnchantmentType) bool {
+	return true
+}
+
+// CompatibleWithItem ...
+func (CurseOfBinding) CompatibleWithItem(i world.Item) bool {
+	_, isArmour := i.(item.Armour)
+
+	return isArmour
+}
+
+// Treasure ...
+func (CurseOfBinding) Treasure() bool {
+	return true
+}
+
+// Curse ...
+func (CurseOfBinding) Curse() bool {
+	return true
+}

server/item/enchantment/register.go

@@ -30,7 +30,7 @@ func init() {
 	// TODO: (24) Lure.
 	// TODO: (25) Frost Walker.
 	item.RegisterEnchantment(26, Mending{})
-	// TODO: (27) Curse of Binding.
+	item.RegisterEnchantment(27, CurseOfBinding{})
 	item.RegisterEnchantment(28, CurseOfVanishing{})
 	// TODO: (29) Impaling.
 	// TODO: (30) Riptide.

server/player/player.go

@@ -2930,6 +2930,11 @@ func (p *Player) useContext() *item.UseContext {
 			srcIt, _ := srcInv.Item(src)
 			dstIt, _ := dstInv.Item(dst)
 
+			// If dstIt is enchanted with curse of binding, do not swap.
+			if _, isCursed := dstIt.Enchantment(enchantment.CurseOfBinding{}); isCursed && !p.GameMode().CreativeInventory() {
+				return
+			}
+
 			ctx := event.C()
 			_ = call(ctx, src, srcIt, srcInv.Handler().HandleTake)
 			_ = call(ctx, src, dstIt, srcInv.Handler().HandlePlace)

server/session/handler_item_stack_request.go

@@ -6,6 +6,7 @@ import (
 	"github.com/df-mc/dragonfly/server/entity"
 	"github.com/df-mc/dragonfly/server/event"
 	"github.com/df-mc/dragonfly/server/item"
+	"github.com/df-mc/dragonfly/server/item/enchantment"
 	"github.com/df-mc/dragonfly/server/item/inventory"
 	"github.com/go-gl/mathgl/mgl64"
 	"github.com/sandertv/gophertunnel/minecraft/protocol"
@@ -157,6 +158,12 @@ func (h *ItemStackRequestHandler) handleTransfer(from, to protocol.StackRequestS
 	if (dest.Count()+int(count) > dest.MaxCount()) && !dest.Empty() {
 		return fmt.Errorf("client tried adding %v to item count %v, but max is %v", count, dest.Count(), dest.MaxCount())
 	}
+
+	// Do not allow an equipped item cursed with binding to be transferred.
+	if curseOfBinding(from.ContainerID, i, s) || curseOfBinding(to.ContainerID, dest, s) {
+		return fmt.Errorf("client attempted to transfer an equipped armour item enchanted with the curse of binding")
+	}
+
 	if dest.Empty() {
 		dest = i.Grow(-math.MaxInt32)
 	}
@@ -197,6 +204,11 @@ func (h *ItemStackRequestHandler) handleSwap(a *protocol.SwapStackRequestAction,
 		return err
 	}
 
+	// Do not allow an equipped item cursed with binding to be swapped out by cursor or touch screen.
+	if curseOfBinding(a.Destination.ContainerID, dest, s) || curseOfBinding(a.Source.ContainerID, i, s) {
+		return fmt.Errorf("client attempted to swap an equipped armour item enchanted with the curse of binding")
+	}
+
 	h.setItemInSlot(a.Source, dest, s)
 	h.setItemInSlot(a.Destination, i, s)
 	h.collectRewards(s, invA, int(a.Source.Slot))
@@ -254,6 +266,11 @@ func (h *ItemStackRequestHandler) handleDrop(a *protocol.DropStackRequestAction,
 		return err
 	}
 
+	// Do not allow an equipped item cursed with binding to be dropped.
+	if curseOfBinding(a.Source.ContainerID, i, s) {
+		return fmt.Errorf("client attempted to drop an equipped armour item enchanted with the curse of binding")
+	}
+
 	n := s.c.Drop(i.Grow(int(a.Count) - i.Count()))
 	h.setItemInSlot(a.Source, i.Grow(-n), s)
 	return nil
@@ -512,3 +529,15 @@ func call(ctx *event.Context, slot int, it item.Stack, f func(ctx *event.Context
 	}
 	return nil
 }
+
+// curseOfBinding returns true if an ItemStackRequestHandler should be cancelled as a result of the given combination of
+// containerID, item and session. containerID should be the ID of the container where i is currently.
+func curseOfBinding(containerID byte, i item.Stack, s *Session) bool {
+	if containerID != protocol.ContainerArmor || s.c.GameMode().CreativeInventory() {
+		return false
+	}
+
+	_, isCursed := i.Enchantment(enchantment.CurseOfBinding{})
+
+	return isCursed
+}