Item Entities and Dropping Items

api/src/main/kotlin/org/kryptonmc/api/event/player/ItemDropEvent.kt

@@ -0,0 +1,30 @@
+/*
+ * This file is part of the Krypton API, licensed under the MIT license.
+ *
+ * Copyright (C) 2021 KryptonMC and the contributors to the Krypton project.
+ *
+ * This project is licensed under the terms of the MIT license.
+ * For more details, please reference the LICENSE file in the api top-level directory.
+ */
+package org.kryptonmc.api.event.player
+
+import org.kryptonmc.api.entity.player.Player
+import org.kryptonmc.api.event.ComponentResult
+import org.kryptonmc.api.event.ResultedEvent
+import org.kryptonmc.api.item.ItemStack
+
+/**
+ * Called when a player attempts to drop an item.
+ *
+ * @param player the player dropping the item
+ * @param item the item to be dropped
+ */
+
+public data class ItemDropEvent(
+    @get:JvmName("player") public val player: Player,
+    @get:JvmName("item") public val item: ItemStack
+) : ResultedEvent<ComponentResult> {
+
+    override var result: ComponentResult = ComponentResult.allowed()
+}
+

server/src/main/kotlin/org/kryptonmc/krypton/entity/EntityFactory.kt

@@ -67,6 +67,7 @@ import org.kryptonmc.krypton.entity.projectile.KryptonSpectralArrow
 import org.kryptonmc.krypton.entity.projectile.KryptonThrownPotion
 import org.kryptonmc.krypton.entity.projectile.KryptonTrident
 import org.kryptonmc.krypton.entity.projectile.KryptonWitherSkull
+import org.kryptonmc.krypton.entity.item.KryptonItemEntity
 import org.kryptonmc.krypton.registry.InternalRegistries
 import org.kryptonmc.krypton.util.logger
 import org.kryptonmc.krypton.world.KryptonWorld
@@ -122,7 +123,8 @@ object EntityFactory {
         EntityTypes.WITHER_SKULL to ::KryptonWitherSkull,
         EntityTypes.WOLF to ::KryptonWolf,
         EntityTypes.ZOMBIE to ::KryptonZombie,
-        EntityTypes.FISHING_HOOK to ::KryptonFishingHook
+        EntityTypes.FISHING_HOOK to ::KryptonFishingHook,
+        EntityTypes.ITEM to ::KryptonItemEntity
     )
 
     @Suppress("UNCHECKED_CAST")

server/src/main/kotlin/org/kryptonmc/krypton/entity/KryptonEntity.kt

@@ -120,6 +120,10 @@ abstract class KryptonEntity(
     final override var location: Vector3d = Vector3d.ZERO
     final override var rotation: Vector2f = Vector2f.ZERO
     final override var velocity: Vector3d = Vector3d.ZERO
+        set(value) {
+            field = value
+            viewers.forEach { it.session.send(PacketOutEntityVelocity(this)) }
+        }
     final override var boundingBox = BoundingBox.zero()
     final override var dimensions = EntityDimensions.fixed(type.dimensions.width, type.dimensions.height)
     final override var isOnGround = true

server/src/main/kotlin/org/kryptonmc/krypton/entity/item/KryptonItemEntity.kt

@@ -0,0 +1,86 @@
+package org.kryptonmc.krypton.entity.item
+
+import net.kyori.adventure.text.Component
+import org.kryptonmc.api.entity.EntityTypes
+import org.kryptonmc.api.inventory.InventoryHolder
+import org.kryptonmc.api.util.BoundingBox
+import org.kryptonmc.krypton.entity.KryptonEntity
+import org.kryptonmc.krypton.entity.KryptonLivingEntity
+import org.kryptonmc.krypton.entity.metadata.MetadataKeys
+import org.kryptonmc.krypton.item.KryptonItemStack
+import org.kryptonmc.krypton.packet.out.play.PacketOutCollectItem
+import org.kryptonmc.krypton.util.forEachEntityInBounds
+import org.kryptonmc.krypton.world.KryptonWorld
+import org.kryptonmc.nbt.CompoundTag
+import org.kryptonmc.nbt.util.UUID
+import org.spongepowered.math.vector.Vector3d
+
+class KryptonItemEntity(world: KryptonWorld) : KryptonEntity(world, EntityTypes.ITEM) {
+
+    init {
+        data.add(MetadataKeys.ITEM.ITEM)
+    }
+
+    var age: Short = 0
+    var health: Short = 5
+    var pickupDelay: Short = 10
+    var owner: UUID? = null
+    var thrower: UUID? = null
+
+    var item: KryptonItemStack
+        get() = data[MetadataKeys.ITEM.ITEM]
+        set(value) = data.set(MetadataKeys.ITEM.ITEM, value)
+    override fun load(tag: CompoundTag) {
+        super.load(tag)
+        age = tag.getShort("Age")
+        health = tag.getShort("Health")
+        pickupDelay = tag.getShort("PickupDelay")
+        if (tag.hasUUID("Owner")) owner = tag.getUUID("Owner")
+        if (tag.hasUUID("Thrower")) thrower = tag.getUUID("Thrower")
+        val itemNBT = tag.getCompound("Item")
+        item = KryptonItemStack(itemNBT)
+        if (item.isEmpty()) remove()
+    }
+
+    private fun entityPickupItem(entity: KryptonLivingEntity) {
+        // TODO: Reduce stack to fit a full inventory and leave remainder
+        if (entity is InventoryHolder) {
+            entity.inventory.add(item)
+        }
+        // TODO: Perhaps consider only sending this to players in range?
+        world.playerManager.sendToAll(PacketOutCollectItem(id, entity.id, item.amount))
+        item.amount = 0 // destroy next tick
+    }
+
+    override fun tick() {
+        if (item.isEmpty()) {
+            remove()
+            return
+        }
+        super.tick()
+        if (pickupDelay > 0 && pickupDelay != DELAY_NO_PICKUP) pickupDelay--
+        if (pickupDelay.toInt() == 0) {
+            server.sendMessage(Component.text("delay 0"))
+            // Item pickup zone
+            val minimum = Vector3d.from(location.x() - 1.0, location.y() - 0.5, location.z() - 1.0)
+            val maximum = Vector3d.from(location.x() + 1.0, location.y() + 0.5, location.z() + 1.0)
+            world.entityManager.forEachEntityInBounds(BoundingBox.of(minimum, maximum)) {
+                if (it.isAlive && it is KryptonLivingEntity) {
+                    // TODO: Test for mob pick up and handle item merge
+                    server.sendMessage(Component.text("Ent found"))
+                    server.sendMessage(it.name)
+                    entityPickupItem(it)
+                    return@forEachEntityInBounds
+                }
+            }
+        }
+        if (age != AGE_NO_DESPAWN) age++
+        if (age >= AGE_DESPAWN) remove()
+    }
+
+    companion object {
+        const val DELAY_NO_PICKUP: Short = 32767 // The delay value that prevents item pickup
+        const val AGE_NO_DESPAWN: Short = -32768 // The age value that prevents age from incrementing
+        const val AGE_DESPAWN: Short = 6000 // The age value that despawns the item entity
+    }
+}

server/src/main/kotlin/org/kryptonmc/krypton/entity/metadata/MetadataKeys.kt

@@ -60,6 +60,7 @@ object MetadataKeys {
     @JvmField val AXOLOTL = AxolotlKeys
     @JvmField val BEE = BeeKeys
     @JvmField val CAT = CatKeys
+    @JvmField val ITEM = ItemKeys
     @JvmField val FOX = FoxKeys
     @JvmField val GOAT = GoatKeys
     @JvmField val MOOSHROOM = MooshroomKeys
@@ -227,6 +228,11 @@ object MetadataKeys {
         @JvmField val COLLAR_COLOR = create(22, MetadataSerializers.VAR_INT, Registries.DYE_COLORS.idOf(DyeColors.RED))
     }
 
+    object ItemKeys {
+
+        @JvmField val ITEM = create(8, MetadataSerializers.SLOT, KryptonItemStack.Factory.empty())
+    }
+
     object FoxKeys {
 
         @JvmField val TYPE = create(17, MetadataSerializers.VAR_INT, FoxType.RED.ordinal)

server/src/main/kotlin/org/kryptonmc/krypton/entity/player/KryptonPlayer.kt

@@ -45,7 +45,9 @@ import org.kryptonmc.api.entity.attribute.AttributeTypes
 import org.kryptonmc.api.entity.player.ChatVisibility
 import org.kryptonmc.api.entity.player.Player
 import org.kryptonmc.api.event.player.ChangeGameModeEvent
+import org.kryptonmc.api.event.player.ItemDropEvent
 import org.kryptonmc.api.event.player.PerformActionEvent
+import org.kryptonmc.api.item.ItemStack
 import org.kryptonmc.api.item.ItemTypes
 import org.kryptonmc.api.permission.PermissionFunction
 import org.kryptonmc.api.permission.PermissionProvider
@@ -69,6 +71,7 @@ import org.kryptonmc.krypton.entity.EquipmentSlot
 import org.kryptonmc.krypton.entity.KryptonEntity
 import org.kryptonmc.krypton.entity.KryptonEquipable
 import org.kryptonmc.krypton.entity.KryptonLivingEntity
+import org.kryptonmc.krypton.entity.item.KryptonItemEntity
 import org.kryptonmc.krypton.entity.metadata.MetadataKeys
 import org.kryptonmc.krypton.inventory.KryptonPlayerInventory
 import org.kryptonmc.krypton.item.KryptonItemStack
@@ -104,6 +107,7 @@ import org.kryptonmc.krypton.packet.out.play.PacketOutUnloadChunk
 import org.kryptonmc.krypton.packet.out.play.PacketOutUpdateHealth
 import org.kryptonmc.krypton.packet.out.play.PacketOutUpdateViewPosition
 import org.kryptonmc.krypton.service.KryptonVanishService
+import org.kryptonmc.krypton.util.*
 import org.kryptonmc.krypton.statistic.KryptonStatisticsTracker
 import org.kryptonmc.krypton.util.BossBarManager
 import org.kryptonmc.krypton.util.Directions
@@ -122,6 +126,7 @@ import java.net.InetSocketAddress
 import java.time.Instant
 import java.util.Locale
 import java.util.UUID
+import java.util.concurrent.ThreadLocalRandom
 import kotlin.math.abs
 import kotlin.math.max
 import kotlin.math.min
@@ -944,6 +949,52 @@ class KryptonPlayer(
         }
     }
 
+    fun dropHeldItem() {
+        val heldItem = inventory.heldItem(Hand.MAIN)
+        if (heldItem.isEmpty()) return
+
+        // Update held item amount
+        heldItem.amount--
+        inventory.setHeldItem(Hand.MAIN, heldItem)
+
+        // drop the item
+        dropItem(heldItem)
+    }
+
+    fun dropItem(itemStack: ItemStack) {
+        server.eventManager.fire(ItemDropEvent(this, itemStack)).thenAcceptAsync({
+            if (!it.result.isAllowed) return@thenAcceptAsync
+            val singleStack = itemStack.copy() as KryptonItemStack
+            singleStack.amount = 1
+            val itemEntity = KryptonItemEntity(world)
+            itemEntity.thrower = uuid
+            itemEntity.item = singleStack
+            itemEntity.location = location.add(0.0, 1.62 - 0.3, 0.0) // eye height - some magic value??
+            val itemVelocity = getDirectionVector().mul(0.3)
+            // Glowstone's method. Seems sane however it uses guess work. I don't blame them. Just look at the vanilla source...
+            // https://github.com/GlowstoneMC/Glowstone/blob/dev/src/main/java/net/glowstone/entity/GlowHumanEntity.java
+            val random = ThreadLocalRandom.current()
+            val offset = 0.02
+            itemVelocity.add(
+                random.nextDouble(offset) - offset / 2,
+                random.nextDouble(0.12),
+                random.nextDouble(offset) - offset / 2
+            )
+            world.entityManager.spawn(itemEntity)
+            itemEntity.velocity = itemVelocity
+        }, session.channel.eventLoop())
+        return
+    }
+
+    private fun getDirectionVector(): Vector3d {
+        // Similar to wiki.vg/bukkit impl
+        val y = kotlin.math.sin(Math.toRadians(rotation.y().toDouble()))
+        val xz = kotlin.math.cos(Math.toRadians(rotation.y().toDouble()))
+        val x = -xz * kotlin.math.sin(Math.toRadians(rotation.x().toDouble()))
+        val z = xz * kotlin.math.cos(Math.toRadians(rotation.x().toDouble()))
+        return Vector3d.from(x, y, z)
+    }
+
     companion object {
 
         private const val FLYING_ACHIEVEMENT_MINIMUM_SPEED = 25

server/src/main/kotlin/org/kryptonmc/krypton/entity/player/PlayerBlockHandler.kt

@@ -19,6 +19,8 @@
 package org.kryptonmc.krypton.entity.player
 
 import org.kryptonmc.api.block.Block
+import org.kryptonmc.api.item.ItemStack
+import org.kryptonmc.krypton.entity.item.KryptonItemEntity
 import org.kryptonmc.api.entity.Hand
 import org.kryptonmc.api.event.player.PlaceBlockEvent
 import org.kryptonmc.api.util.Direction
@@ -36,6 +38,7 @@ import org.kryptonmc.krypton.world.block.BlockHitResult
 import org.kryptonmc.krypton.world.block.handler
 import org.kryptonmc.krypton.world.block.isGameMasterBlock
 import org.spongepowered.math.vector.Vector3d
+import java.util.concurrent.ThreadLocalRandom
 import org.spongepowered.math.vector.Vector3i
 
 class PlayerBlockHandler(private val player: KryptonPlayer) {
@@ -229,13 +232,29 @@ class PlayerBlockHandler(private val player: KryptonPlayer) {
         if (hasChanged) block.handler().destroy(world, x, y, z, block)
 
         if (isCreative) return true // We're done, since the bit after this is for mining, which doesn't happen in creative
+        dropLoot(block, x, y, z)
         val item = player.inventory.mainHand
         val hasCorrectTool = player.hasCorrectTool(block)
         item.type.handler().mineBlock(player, item, world, block, x, y, z)
         if (hasChanged && hasCorrectTool) block.handler().onDestroy(player, block, x, y, z, item)
         return true
     }
 
+    private fun dropLoot(block: Block, x: Int, y: Int, z: Int) {
+        // TODO: Use loot tables
+        val itemEntity = KryptonItemEntity(world)
+        val blockItem = block.asItem() ?: return
+        itemEntity.item = ItemStack.of(blockItem) as KryptonItemStack
+        val entityHeight = itemEntity.dimensions.height
+        val random = ThreadLocalRandom.current()
+        itemEntity.location = Vector3d.from(
+            x.toDouble()+(0.5)+random.nextDouble(-0.25, 0.25),
+            y.toDouble()+(0.5)+random.nextDouble(-0.25, 0.25)-(entityHeight/2f),
+            z.toDouble()+(0.5)+random.nextDouble(-0.25, 0.25))
+        world.entityManager.spawn(itemEntity)
+        itemEntity.velocity = Vector3d.from(random.nextDouble() * 0.2 - 0.1, 0.2, random.nextDouble() * 0.2 - 0.1)
+    }
+
     companion object {
 
         private const val MAXIMUM_DISTANCE_FROM_BLOCK = 36.0

server/src/main/kotlin/org/kryptonmc/krypton/network/handlers/PlayHandler.kt

@@ -18,6 +18,8 @@
  */
 package org.kryptonmc.krypton.network.handlers
 
+
+import java.util.concurrent.ThreadLocalRandom
 import com.mojang.brigadier.StringReader
 import net.kyori.adventure.audience.MessageType
 import net.kyori.adventure.key.InvalidKeyException
@@ -41,6 +43,8 @@ import org.kryptonmc.api.resource.ResourcePack
 import org.kryptonmc.api.world.GameMode
 import org.kryptonmc.krypton.KryptonServer
 import org.kryptonmc.krypton.commands.KryptonPermission
+import org.kryptonmc.krypton.entity.item.KryptonItemEntity
+import org.kryptonmc.krypton.entity.monster.KryptonCreeper
 import org.kryptonmc.krypton.entity.player.KryptonPlayer
 import org.kryptonmc.krypton.inventory.KryptonPlayerInventory
 import org.kryptonmc.krypton.item.handler
@@ -276,6 +280,9 @@ class PlayHandler(
             PacketInPlayerDigging.Status.STARTED, PacketInPlayerDigging.Status.FINISHED, PacketInPlayerDigging.Status.CANCELLED -> {
                 player.blockHandler.handleBlockBreak(packet)
             }
+            PacketInPlayerDigging.Status.DROP_ITEM -> {
+                player.dropHeldItem()
+            }
             PacketInPlayerDigging.Status.UPDATE_STATE -> {
                 val handler = player.inventory[player.inventory.heldSlot].type.handler()
                 if (handler !is ItemTimedHandler) return

server/src/main/kotlin/org/kryptonmc/krypton/packet/PacketRegistry.kt

@@ -82,6 +82,7 @@ import org.kryptonmc.krypton.packet.out.play.PacketOutEntitySoundEffect
 import org.kryptonmc.krypton.packet.out.play.PacketOutEntityStatus
 import org.kryptonmc.krypton.packet.out.play.PacketOutEntityTeleport
 import org.kryptonmc.krypton.packet.out.play.PacketOutEntityVelocity
+import org.kryptonmc.krypton.packet.out.play.PacketOutCollectItem
 import org.kryptonmc.krypton.packet.out.play.PacketOutHeadLook
 import org.kryptonmc.krypton.packet.out.play.PacketOutInitializeWorldBorder
 import org.kryptonmc.krypton.packet.out.play.PacketOutJoinGame
@@ -245,6 +246,7 @@ object PacketRegistry {
         register<PacketOutStopSound>(0x5E)
         register<PacketOutPlayerListHeaderFooter>(0x5F)
         register<PacketOutNBTQueryResponse>(0x60)
+        register<PacketOutCollectItem>(0x61)
         register<PacketOutEntityTeleport>(0x62)
         register<PacketOutAttributes>(0x64)
         register<PacketOutDeclareRecipes>(0x66)

server/src/main/kotlin/org/kryptonmc/krypton/packet/out/play/PacketOutCollectItem.kt

@@ -0,0 +1,37 @@
+/*
+ * This file is part of the Krypton project, licensed under the GNU General Public License v3.0
+ *
+ * Copyright (C) 2021 KryptonMC and the contributors of the Krypton project
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.kryptonmc.krypton.packet.out.play
+
+import io.netty.buffer.ByteBuf
+import org.kryptonmc.krypton.packet.Packet
+import org.kryptonmc.krypton.util.writeVarInt
+
+@JvmRecord
+data class PacketOutCollectItem(
+    val collectedEntityId: Int,
+    val collectorEntityId: Int,
+    val count: Int
+) : Packet {
+
+    override fun write(buf: ByteBuf) {
+        buf.writeVarInt(collectedEntityId)
+        buf.writeVarInt(collectorEntityId)
+        buf.writeVarInt(count)
+    }
+}