server/entity: Match Bedrock arrow damage

server/entity/arrow.go

@@ -1,6 +1,8 @@
 package entity
 
 import (
+	"math/rand/v2"
+
 	"github.com/df-mc/dragonfly/server/block/cube"
 	"github.com/df-mc/dragonfly/server/internal/nbtconv"
 	"github.com/df-mc/dragonfly/server/item"
@@ -41,10 +43,26 @@ var arrowConf = ProjectileBehaviourConfig{
 	Gravity:               0.05,
 	Drag:                  0.01,
 	Damage:                2.0,
+	damageCalculator:      calculateArrowDamage,
 	Sound:                 sound.ArrowHit{},
 	SurviveBlockCollision: true,
 }
 
+// calculateArrowDamage calculates arrow damage using Bedrock Edition's formula. Arrows
+// add 97% of their velocity to their base damage. Critical arrows deal 9-10
+// damage before Power is applied.
+func calculateArrowDamage(baseDamage, velocity float64, critical bool, powerLevel int) float64 {
+	damage := baseDamage + velocity*0.97
+	if critical {
+		damage += rand.Float64()*damage/2 + rand.Float64()*2
+		damage = min(10, max(9, damage))
+	}
+	if powerLevel > 0 {
+		damage *= 1 + float64(powerLevel+1)*0.25
+	}
+	return damage
+}
+
 // boolByte returns 1 if the bool passed is true, or 0 if it is false.
 func boolByte(b bool) uint8 {
 	if b {
@@ -70,6 +88,8 @@ func (arrowType) BBox(world.Entity) cube.BBox {
 func (arrowType) DecodeNBT(m map[string]any, data *world.EntityData) {
 	conf := arrowConf
 	conf.Damage = float64(nbtconv.Float32(m, "Damage"))
+	conf.powerLevel = int(nbtconv.Uint8(m, "enchantPower"))
+	conf.Critical = nbtconv.Bool(m, "crit")
 	conf.Potion = potion.From(nbtconv.Int32(m, "auxValue") - 1)
 	conf.DisablePickup = !nbtconv.Bool(m, "player")
 	if !nbtconv.Bool(m, "isCreative") {
@@ -85,12 +105,13 @@ func (arrowType) EncodeNBT(data *world.EntityData) map[string]any {
 	b := data.Data.(*ProjectileBehaviour)
 	m := map[string]any{
 		"Damage":       float32(b.conf.Damage),
+		"crit":         boolByte(b.conf.Critical),
 		"enchantPunch": byte(b.conf.KnockBackForceAddend / enchantment.Punch.KnockBackMultiplier()),
 		"auxValue":     int32(b.conf.Potion.Uint8() + 1),
 		"player":       boolByte(!b.conf.DisablePickup),
 		"isCreative":   boolByte(b.conf.PickupItem.Empty()),
 	}
-	// TODO: Save critical flag if Minecraft ever saves it?
+	m["enchantPower"] = byte(b.conf.powerLevel)
 	if b.collided {
 		m["StuckToBlockPos"] = nbtconv.PosToInt32Slice(b.collisionPos)
 	}

server/entity/projectile.go

@@ -32,6 +32,10 @@ type ProjectileBehaviourConfig struct {
 	// back. The base damage is multiplied with the velocity of the projectile
 	// to calculate the final damage of the projectile.
 	Damage float64
+	// damageCalculator calculates the final damage of the projectile. If nil,
+	// Damage is multiplied by the projectile's velocity.
+	damageCalculator func(baseDamage, velocity float64, critical bool, powerLevel int) float64
+	powerLevel       int
 	// Potion is the potion effect that is applied to an entity when the
 	// projectile hits it.
 	Potion potion.Potion
@@ -293,9 +297,14 @@ func (lt *ProjectileBehaviour) hitBlockSurviving(e *Ent, r trace.BlockResult, m
 func (lt *ProjectileBehaviour) hitEntity(victim world.Entity, e *Ent, vel mgl64.Vec3) {
 	owner, _ := lt.conf.Owner.Entity(e.tx)
 	src := ProjectileDamageSource{Projectile: e, Owner: owner}
-	dmg := math.Ceil(lt.conf.Damage * vel.Len())
-	if lt.conf.Critical {
-		dmg += rand.Float64() * dmg / 2
+	var dmg float64
+	if lt.conf.damageCalculator == nil {
+		dmg = math.Ceil(lt.conf.Damage * vel.Len())
+		if lt.conf.Critical {
+			dmg += rand.Float64() * dmg / 2
+		}
+	} else {
+		dmg = lt.conf.damageCalculator(lt.conf.Damage, vel.Len(), lt.conf.Critical, lt.conf.powerLevel)
 	}
 	// TODO: Piercing arrows should bypass shield blocking when shields are implemented.
 	if _, vulnerable, ok := HurtEntity(victim, dmg, src); ok && vulnerable {

server/entity/register.go

@@ -53,6 +53,7 @@ var conf = world.EntityRegistryConfig{
 		tip := arrow.Tip.(potion.Potion)
 		conf := arrowConf
 		conf.Damage, conf.Potion, conf.Owner = arrow.Damage, tip, arrow.Owner.H()
+		conf.powerLevel = arrow.PowerLevel
 		conf.KnockBackForceAddend = float64(arrow.PunchLevel) * enchantment.Punch.KnockBackMultiplier()
 		conf.DisablePickup = arrow.DisablePickup
 		if arrow.ObtainArrowOnPickup {

server/item/bow.go

@@ -61,16 +61,16 @@ func (Bow) Release(releaser Releaser, tx *world.Tx, ctx *UseContext, duration ti
 	}
 
 	held, _ := releaser.HeldItems()
-	damage, punchLevel, burnDuration, consume := 2.0, 0, time.Duration(0), !creative
+	powerLevel, punchLevel, burnDuration, consume := 0, 0, time.Duration(0), !creative
 	for _, enchant := range held.Enchantments() {
 		if f, ok := enchant.Type().(interface{ BurnDuration() time.Duration }); ok {
 			burnDuration = f.BurnDuration()
 		}
 		if _, ok := enchant.Type().(interface{ KnockBackMultiplier() float64 }); ok {
 			punchLevel = enchant.Level()
 		}
-		if p, ok := enchant.Type().(interface{ PowerDamage(int) float64 }); ok {
-			damage += p.PowerDamage(enchant.Level())
+		if _, ok := enchant.Type().(interface{ PowerDamage(int) float64 }); ok {
+			powerLevel = enchant.Level()
 		}
 		if i, ok := enchant.Type().(interface{ ConsumesArrows() bool }); ok && !i.ConsumesArrows() {
 			consume = false
@@ -84,7 +84,8 @@ func (Bow) Release(releaser Releaser, tx *world.Tx, ctx *UseContext, duration ti
 		Rotation: releaser.Rotation().Neg(),
 	}
 	projectile := tx.AddEntity(create(opts, world.ArrowSpawnConfig{
-		Damage:              damage,
+		Damage:              1,
+		PowerLevel:          powerLevel,
 		Owner:               releaser,
 		Critical:            force >= 1,
 		ObtainArrowOnPickup: !creative && consume,

server/item/crossbow.go

@@ -133,7 +133,7 @@ func (c Crossbow) ReleaseCharge(releaser Releaser, tx *world.Tx, ctx *UseContext
 	}
 
 	arrowConf := world.ArrowSpawnConfig{
-		Damage:              9,
+		Damage:              1,
 		Owner:               releaser,
 		Critical:            true,
 		ObtainArrowOnPickup: !creative,
@@ -179,7 +179,7 @@ func (c Crossbow) shoot(releaser Releaser, tx *world.Tx, offsetAngle float64, ar
 		arrowConf.Tip = c.Item.Item().(Arrow).Tip
 		arrow := createArrow(world.EntitySpawnOpts{
 			Position: torsoPosition(releaser),
-			Velocity: dirVec.Mul(5.15),
+			Velocity: dirVec.Mul(3.15),
 			Rotation: rot.Neg(),
 		}, arrowConf)
 		tx.AddEntity(arrow)

server/world/entity.go

@@ -509,6 +509,8 @@ type EntityRegistryConfig struct {
 type ArrowSpawnConfig struct {
 	// Damage specifies the base damage dealt by the arrow.
 	Damage float64
+	// PowerLevel specifies the level of the Power enchantment applied to the arrow.
+	PowerLevel int
 	// Owner is the entity that fired the arrow.
 	Owner Entity
 	// Critical specifies if the arrow should deal critical damage.