Implement totems

server/entity/action.go

@@ -44,6 +44,9 @@ type PickedUpAction struct {
 // FireworkExplosionAction is a world.EntityAction that makes a Firework rocket display an explosion particle.
 type FireworkExplosionAction struct{ action }
 
+// TotemUseAction is a world.EntityAction that displays the totem use particles and animation.
+type TotemUseAction struct{ action }
+
 // action implements the Action interface. Structures in this package may embed it to gets its functionality
 // out of the box.
 type action struct{}

server/item/register.go

@@ -116,6 +116,7 @@ func init() {
 	world.RegisterItem(Spyglass{})
 	world.RegisterItem(Stick{})
 	world.RegisterItem(Sugar{})
+	world.RegisterItem(Totem{})
 	world.RegisterItem(TropicalFish{})
 	world.RegisterItem(TurtleShell{})
 	world.RegisterItem(WarpedFungusOnAStick{})

server/item/totem.go

@@ -0,0 +1,14 @@
+package item
+
+// Totem is an uncommon combat item that can save holders from death.
+type Totem struct{}
+
+// MaxCount always returns 1.
+func (Totem) MaxCount() int {
+	return 1
+}
+
+// EncodeItem ...
+func (Totem) EncodeItem() (name string, meta int16) {
+	return "minecraft:totem_of_undying", 0
+}

server/player/player.go

@@ -584,9 +584,24 @@ func (p *Player) Hurt(dmg float64, src world.DamageSource) (float64, bool) {
 			damageLeft -= a
 		} else {
 			p.SetAbsorption(a - damageLeft)
+
 			damageLeft = 0
 		}
 	}
+
+	if p.Health()-damageLeft <= mgl64.Epsilon {
+		hand, offHand := p.HeldItems()
+		if _, ok := offHand.Item().(item.Totem); ok {
+			p.applyTotemEffects()
+			p.SetHeldItems(hand, offHand.Grow(-1))
+			return 0, false
+		} else if _, ok := hand.Item().(item.Totem); ok {
+			p.applyTotemEffects()
+			p.SetHeldItems(hand.Grow(-1), offHand)
+			return 0, false
+		}
+	}
+
 	p.addHealth(-damageLeft)
 
 	if src.ReducedByArmour() {
@@ -623,6 +638,25 @@ func (p *Player) Hurt(dmg float64, src world.DamageSource) (float64, bool) {
 	return totalDamage, true
 }
 
+// applyTotemEffects is an unexported function that is used to handle totem effects.
+func (p *Player) applyTotemEffects() {
+	p.addHealth(2 - p.Health())
+
+	for _, e := range p.Effects() {
+		p.RemoveEffect(e.Type())
+	}
+
+	p.AddEffect(effect.New(effect.Regeneration{}, 2, time.Second*40))
+	p.AddEffect(effect.New(effect.FireResistance{}, 1, time.Second*40))
+	p.AddEffect(effect.New(effect.Absorption{}, 2, time.Second*5))
+
+	p.World().PlaySound(p.Position(), sound.Totem{})
+
+	for _, viewer := range p.viewers() {
+		viewer.ViewEntityAction(p, entity.TotemUseAction{})
+	}
+}
+
 // FinalDamageFrom resolves the final damage received by the player if it is attacked by the source passed
 // with the damage passed. FinalDamageFrom takes into account things such as the armour worn and the
 // enchantments on the individual pieces.

server/session/world.go

@@ -771,6 +771,11 @@ func (s *Session) playSound(pos mgl64.Vec3, t world.Sound, disableRelative bool)
 		pk.SoundType = packet.SoundEventComposterReady
 	case sound.LecternBookPlace:
 		pk.SoundType = packet.SoundEventLecternBookPlace
+	case sound.Totem:
+		s.writePacket(&packet.LevelEvent{
+			EventType: packet.LevelEventSoundTotemUsed,
+			Position:  vec64To32(pos),
+		})
 	}
 	s.writePacket(pk)
 }
@@ -914,6 +919,11 @@ func (s *Session) ViewEntityAction(e world.Entity, a world.EntityAction) {
 				EventData: (rid << 16) | int32(meta),
 			})
 		}
+	case entity.TotemUseAction:
+		s.writePacket(&packet.ActorEvent{
+			EntityRuntimeID: s.entityRuntimeID(e),
+			EventType:       packet.ActorEventTalismanActivate,
+		})
 	}
 }
 

server/world/sound/item.go

@@ -70,3 +70,6 @@ type GoatHorn struct {
 // FireCharge is a sound played when a player lights a block on fire with a fire charge, or when a dispenser or a
 // blaze shoots a fireball.
 type FireCharge struct{ sound }
+
+// Totem is a sound played when a player uses a totem.
+type Totem struct{ sound }