item/enchantment: Implemented thorns enchantment (#553)

Co-authored-by: DaPigGuy <mcpepig123@gmail.com>

server/entity/damage/source.go

@@ -1,6 +1,8 @@
 package damage
 
-import "github.com/df-mc/dragonfly/server/world"
+import (
+	"github.com/df-mc/dragonfly/server/world"
+)
 
 type (
 	// Source represents the source of the damage dealt to an entity. This source may be passed to the Hurt()
@@ -68,6 +70,12 @@ type (
 		Projectile, Owner world.Entity
 	}
 
+	// SourceThorns is used for damage caused by thorns.
+	SourceThorns struct {
+		// Owner holds the entity wearing the thorns armour.
+		Owner world.Entity
+	}
+
 	// SourceBlock is used for damage caused by a block, such as an anvil.
 	SourceBlock struct {
 		// Block is the block that caused the damage.
@@ -103,5 +111,7 @@ func (SourceLava) ReducedByResistance() bool                { return true }
 func (SourceLava) ReducedByArmour() bool                    { return true }
 func (SourceProjectile) ReducedByResistance() bool          { return true }
 func (SourceProjectile) ReducedByArmour() bool              { return true }
+func (SourceThorns) ReducedByResistance() bool              { return true }
+func (SourceThorns) ReducedByArmour() bool                  { return false }
 func (SourceBlock) ReducedByResistance() bool               { return true }
 func (SourceBlock) ReducedByArmour() bool                   { return true }

server/item/enchantment/register.go

@@ -8,7 +8,7 @@ func init() {
 	item.RegisterEnchantment(2, FeatherFalling{})
 	// TODO: (3) Blast Protection.
 	item.RegisterEnchantment(4, ProjectileProtection{})
-	// TODO: (5) Thorns.
+	item.RegisterEnchantment(5, Thorns{})
 	item.RegisterEnchantment(6, Respiration{})
 	item.RegisterEnchantment(7, DepthStrider{})
 	item.RegisterEnchantment(8, AquaAffinity{})

server/item/enchantment/thorns.go

@@ -0,0 +1,35 @@
+package enchantment
+
+import (
+	"github.com/df-mc/dragonfly/server/item"
+	"github.com/df-mc/dragonfly/server/world"
+)
+
+// Thorns is an enchantment that inflicts damage on attackers.
+type Thorns struct{}
+
+// Name ...
+func (Thorns) Name() string {
+	return "Thorns"
+}
+
+// MaxLevel ...
+func (Thorns) MaxLevel() int {
+	return 3
+}
+
+// Rarity ...
+func (Thorns) Rarity() item.EnchantmentRarity {
+	return item.EnchantmentRarityVeryRare
+}
+
+// CompatibleWithEnchantment ...
+func (Thorns) CompatibleWithEnchantment(item.EnchantmentType) bool {
+	return true
+}
+
+// CompatibleWithItem ...
+func (Thorns) CompatibleWithItem(i world.Item) bool {
+	_, ok := i.(item.Armour)
+	return ok
+}

server/player/player.go

@@ -28,6 +28,7 @@ import (
 	"github.com/df-mc/dragonfly/server/world/sound"
 	"github.com/go-gl/mathgl/mgl64"
 	"github.com/google/uuid"
+	"golang.org/x/exp/maps"
 	"golang.org/x/text/language"
 	"math"
 	"math/rand"
@@ -557,11 +558,40 @@ func (p *Player) Hurt(dmg float64, source damage.Source) (float64, bool) {
 		p.Exhaust(0.1)
 
 		damageToArmour := int(math.Max(math.Floor(dmg/4), 1))
+		var damageToAttacker int
+		thornsArmour := map[int]item.Stack{}
 		for slot, it := range p.armour.Slots() {
 			if _, ok := it.Item().(item.Durable); ok {
+				if e, ok := it.Enchantment(enchantment.Thorns{}); ok && rand.Float64() < float64(e.Level())*0.15 {
+					damageToArmour++
+					thornsArmour[slot] = it
+					if e.Level() > 10 {
+						damageToAttacker += e.Level() - 10
+					} else {
+						damageToAttacker += 1 + rand.Intn(4)
+					}
+				}
 				_ = p.armour.Inventory().SetItem(slot, p.damageItem(it, damageToArmour))
 			}
 		}
+
+		if length := len(thornsArmour); length > 0 {
+			slot := maps.Keys(thornsArmour)[rand.Intn(length)]
+			item := thornsArmour[slot]
+
+			_ = p.armour.Inventory().SetItem(slot, p.damageItem(item, 2))
+			if damageToAttacker > 0 {
+				var attacker world.Entity
+				if s, ok := source.(damage.SourceEntityAttack); ok {
+					attacker = s.Attacker
+				} else if s, ok := source.(damage.SourceProjectile); ok {
+					attacker = s.Owner
+				}
+				if l, ok := attacker.(entity.Living); ok {
+					l.Hurt(float64(damageToAttacker), damage.SourceThorns{Owner: attacker})
+				}
+			}
+		}
 	}
 
 	w, pos := p.World(), p.Position()