feat: Shift+F 메뉴 GUI 구현

- EssentialsMenuGui 추가 (스폰, 좌표, 제작대, TPA 바로가기)
- Mixin으로 손 바꾸기 패킷 가로채기 (빈 손에서도 작동)
- Shift+F: 손 바꾸기 차단 + 메뉴 GUI 열기
- /메뉴, /menu 명령어 추가
- 도움말에 메뉴 카테고리 추가

Essentials/src/main/java/com/beemer/essentials/mixin/ServerGamePacketListenerImplMixin.java

@@ -0,0 +1,37 @@
+package com.beemer.essentials.mixin;
+
+import com.beemer.essentials.event.MenuKeyHandler;
+import net.minecraft.network.protocol.game.ServerboundPlayerActionPacket;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.server.network.ServerGamePacketListenerImpl;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+/**
+ * 손 바꾸기 패킷 가로채기
+ * Shift + F 조합으로 메뉴 GUI 열기
+ */
+@Mixin(ServerGamePacketListenerImpl.class)
+public class ServerGamePacketListenerImplMixin {
+
+    @Shadow
+    public ServerPlayer player;
+
+    @Inject(method = "handlePlayerAction", at = @At("HEAD"), cancellable = true)
+    private void onHandlePlayerAction(ServerboundPlayerActionPacket packet, CallbackInfo ci) {
+        // 손 바꾸기 액션인지 확인
+        if (packet.getAction() == ServerboundPlayerActionPacket.Action.SWAP_ITEM_WITH_OFFHAND) {
+            // Shift를 누르고 있으면 메뉴 열기
+            if (player.isShiftKeyDown()) {
+                // 패킷 처리 취소 (실제 손 바꾸기 방지)
+                ci.cancel();
+
+                // 메뉴 GUI 열기
+                MenuKeyHandler.INSTANCE.openMenuFromPacket(player);
+            }
+        }
+    }
+}

Essentials/src/main/kotlin/com/beemer/essentials/Essentials.kt

@@ -34,5 +34,6 @@ class Essentials(modEventBus: IEventBus) {
         NeoForge.EVENT_BUS.register(HeadCommand)
         NeoForge.EVENT_BUS.register(HelpCommand)
         NeoForge.EVENT_BUS.register(WorkbenchCommand)
+        NeoForge.EVENT_BUS.register(MenuCommand)
     }
 }

Essentials/src/main/kotlin/com/beemer/essentials/command/HelpCommand.kt

@@ -75,6 +75,12 @@ object HelpCommand {
         // 제작대
         sendCategory(player, "제작대", ChatFormatting.WHITE)
         sendCommand(player, "/제작대", "제작대 열기")
+        player.sendSystemMessage(Component.empty())
+
+        // 메뉴
+        sendCategory(player, "메뉴", ChatFormatting.LIGHT_PURPLE)
+        sendCommand(player, "/메뉴", "메뉴 GUI 열기")
+        sendCommand(player, "Shift + F", "메뉴 GUI 열기 (단축키)")
 
         val footer =
                 Component.literal("═══════════════════════════════").withStyle {

Essentials/src/main/kotlin/com/beemer/essentials/command/MenuCommand.kt

@@ -0,0 +1,23 @@
+package com.beemer.essentials.command
+
+import com.beemer.essentials.gui.openEssentialsMenu
+import net.minecraft.commands.Commands
+import net.minecraft.server.level.ServerPlayer
+import net.neoforged.bus.api.SubscribeEvent
+import net.neoforged.neoforge.event.RegisterCommandsEvent
+
+object MenuCommand {
+    @SubscribeEvent
+    fun onRegisterCommands(event: RegisterCommandsEvent) {
+        // /메뉴, /menu - 메뉴 GUI 열기
+        listOf("메뉴", "menu").forEach { command ->
+            event.dispatcher.register(
+                    Commands.literal(command).executes { context ->
+                        val player = context.source.entity as? ServerPlayer ?: return@executes 0
+                        openEssentialsMenu(player)
+                        1
+                    }
+            )
+        }
+    }
+}

Essentials/src/main/kotlin/com/beemer/essentials/event/MenuKeyHandler.kt

@@ -0,0 +1,44 @@
+package com.beemer.essentials.event
+
+import com.beemer.essentials.gui.openEssentialsMenu
+import java.util.UUID
+import java.util.concurrent.ConcurrentHashMap
+import net.minecraft.server.level.ServerPlayer
+
+/**
+ * Shift + F (손 바꾸기) 패킷 감지하여 메뉴 GUI 열기
+ *
+ * 동작 방식:
+ * 1. 플레이어가 Shift를 누르고 있는 상태에서
+ * 2. F키(손 바꾸기)를 누르면
+ * 3. 손 바꾸기 패킷을 취소하고 메뉴 GUI를 엽니다
+ *
+ * Mixin으로 패킷을 가로채기 때문에 빈 손에서도 작동합니다.
+ */
+object MenuKeyHandler {
+    // 메뉴 열기 쿨다운 (밀리초 단위, 더블 감지 방지)
+    private val cooldowns = ConcurrentHashMap<UUID, Long>()
+    private const val COOLDOWN_MS = 500L
+
+    /** Mixin에서 호출 - 패킷 감지 시 메뉴 열기 */
+    fun openMenuFromPacket(player: ServerPlayer) {
+        if (isOnCooldown(player.uuid)) return
+
+        setCooldown(player.uuid)
+        openEssentialsMenu(player)
+    }
+
+    private fun isOnCooldown(uuid: UUID): Boolean {
+        val lastTime = cooldowns[uuid] ?: return false
+        return System.currentTimeMillis() - lastTime < COOLDOWN_MS
+    }
+
+    private fun setCooldown(uuid: UUID) {
+        cooldowns[uuid] = System.currentTimeMillis()
+    }
+
+    /** 플레이어 로그아웃 시 상태 정리 */
+    fun cleanup(uuid: UUID) {
+        cooldowns.remove(uuid)
+    }
+}

Essentials/src/main/kotlin/com/beemer/essentials/gui/EssentialsMenuGui.kt

@@ -0,0 +1,268 @@
+package com.beemer.essentials.gui
+
+import net.minecraft.ChatFormatting
+import net.minecraft.core.component.DataComponents
+import net.minecraft.nbt.CompoundTag
+import net.minecraft.network.chat.Component
+import net.minecraft.server.level.ServerPlayer
+import net.minecraft.world.Container
+import net.minecraft.world.SimpleContainer
+import net.minecraft.world.SimpleMenuProvider
+import net.minecraft.world.entity.player.Inventory
+import net.minecraft.world.entity.player.Player
+import net.minecraft.world.inventory.AbstractContainerMenu
+import net.minecraft.world.inventory.ClickType
+import net.minecraft.world.inventory.ContainerLevelAccess
+import net.minecraft.world.inventory.CraftingMenu
+import net.minecraft.world.inventory.MenuType
+import net.minecraft.world.inventory.Slot
+import net.minecraft.world.item.ItemStack
+import net.minecraft.world.item.Items
+import net.minecraft.world.item.component.CustomData
+import net.minecraft.world.item.component.ItemLore
+
+/** Essentials 메뉴 GUI - Shift+F로 열기 스폰, 좌표, 제작대 등 주요 기능 바로가기 */
+class EssentialsMenuGui(
+        syncId: Int,
+        playerInv: Inventory,
+        val container: Container,
+        val viewer: ServerPlayer
+) : AbstractContainerMenu(MenuType.GENERIC_9x3, syncId) {
+
+    companion object {
+        const val CONTAINER_SIZE = 27
+
+        // 메뉴 아이템 슬롯 위치
+        const val SLOT_SPAWN = 10 // 스폰
+        const val SLOT_COORDINATES = 12 // 좌표
+        const val SLOT_WORKBENCH = 14 // 제작대
+        const val SLOT_TPA = 16 // TPA
+    }
+
+    init {
+        // 컨테이너 슬롯 추가
+        for (i in 0 until CONTAINER_SIZE) {
+            val x = 8 + (i % 9) * 18
+            val y = 18 + (i / 9) * 18
+            addSlot(
+                    object : Slot(container, i, x, y) {
+                        override fun mayPickup(player: Player): Boolean = false
+                        override fun mayPlace(stack: ItemStack): Boolean = false
+                    }
+            )
+        }
+
+        // 플레이어 인벤토리 슬롯
+        for (row in 0 until 3) {
+            for (col in 0 until 9) {
+                val index = col + row * 9 + 9
+                val x = 8 + col * 18
+                val y = 86 + row * 18
+                addSlot(Slot(playerInv, index, x, y))
+            }
+        }
+        for (col in 0 until 9) {
+            val x = 8 + col * 18
+            val y = 144
+            addSlot(Slot(playerInv, col, x, y))
+        }
+    }
+
+    override fun clicked(slotId: Int, button: Int, clickType: ClickType, player: Player) {
+        if (slotId !in 0 until CONTAINER_SIZE || player !is ServerPlayer) {
+            super.clicked(slotId, button, clickType, player)
+            return
+        }
+
+        val stack = slots[slotId].item
+        val tag = stack.get(DataComponents.CUSTOM_DATA)?.copyTag() ?: return
+        val action = tag.getString("action")
+
+        when (action) {
+            "spawn" -> {
+                player.closeContainer()
+                // 스폰 명령어 실행
+                player.server.commands.performPrefixedCommand(
+                        player.createCommandSourceStack(),
+                        "스폰"
+                )
+            }
+            "coordinates" -> {
+                player.closeContainer()
+                // 좌표 GUI 열기
+                player.server.commands.performPrefixedCommand(
+                        player.createCommandSourceStack(),
+                        "좌표"
+                )
+            }
+            "workbench" -> {
+                player.closeContainer()
+                // 제작대 열기
+                openWorkbench(player)
+            }
+            "tpa" -> {
+                player.closeContainer()
+                // TPA GUI 열기
+                player.server.commands.performPrefixedCommand(
+                        player.createCommandSourceStack(),
+                        "tpa"
+                )
+            }
+        }
+    }
+
+    private fun openWorkbench(player: ServerPlayer) {
+        val access =
+                object : ContainerLevelAccess {
+                    override fun <T : Any> evaluate(
+                            function:
+                                    java.util.function.BiFunction<
+                                            net.minecraft.world.level.Level,
+                                            net.minecraft.core.BlockPos,
+                                            T>
+                    ): java.util.Optional<T> {
+                        return java.util.Optional.ofNullable(
+                                function.apply(player.level(), player.blockPosition())
+                        )
+                    }
+                }
+
+        player.openMenu(
+                SimpleMenuProvider(
+                        { containerId, inventory, _ ->
+                            object : CraftingMenu(containerId, inventory, access) {
+                                override fun stillValid(player: Player): Boolean = true
+                            }
+                        },
+                        Component.translatable("container.crafting")
+                )
+        )
+    }
+
+    override fun stillValid(player: Player): Boolean = true
+    override fun quickMoveStack(player: Player, index: Int): ItemStack = ItemStack.EMPTY
+}
+
+/** 메뉴 컨테이너 생성 */
+fun createEssentialsMenuContainer(): SimpleContainer {
+    val container = SimpleContainer(27)
+
+    // 배경을 회색 유리판으로 채우기
+    val fillerItem = ItemStack(Items.GRAY_STAINED_GLASS_PANE)
+    fillerItem.set(
+            DataComponents.CUSTOM_NAME,
+            Component.literal(" ").withStyle { it.withColor(ChatFormatting.DARK_GRAY) }
+    )
+    for (i in 0 until 27) {
+        container.setItem(i, fillerItem.copy())
+    }
+
+    // 스폰 버튼
+    val spawnItem = ItemStack(Items.GRASS_BLOCK)
+    spawnItem.set(
+            DataComponents.CUSTOM_NAME,
+            Component.literal("스폰으로 이동").withStyle {
+                it.withColor(ChatFormatting.GREEN).withBold(true)
+            }
+    )
+    spawnItem.set(
+            DataComponents.LORE,
+            ItemLore(
+                    listOf(
+                            Component.literal("클릭하여 스폰으로 이동합니다.").withStyle {
+                                it.withColor(ChatFormatting.GRAY)
+                            }
+                    )
+            )
+    )
+    spawnItem.set(
+            DataComponents.CUSTOM_DATA,
+            CustomData.of(CompoundTag().apply { putString("action", "spawn") })
+    )
+    container.setItem(EssentialsMenuGui.SLOT_SPAWN, spawnItem)
+
+    // 좌표 버튼
+    val coordItem = ItemStack(Items.COMPASS)
+    coordItem.set(
+            DataComponents.CUSTOM_NAME,
+            Component.literal("저장된 좌표").withStyle {
+                it.withColor(ChatFormatting.YELLOW).withBold(true)
+            }
+    )
+    coordItem.set(
+            DataComponents.LORE,
+            ItemLore(
+                    listOf(
+                            Component.literal("클릭하여 좌표 목록을 엽니다.").withStyle {
+                                it.withColor(ChatFormatting.GRAY)
+                            }
+                    )
+            )
+    )
+    coordItem.set(
+            DataComponents.CUSTOM_DATA,
+            CustomData.of(CompoundTag().apply { putString("action", "coordinates") })
+    )
+    container.setItem(EssentialsMenuGui.SLOT_COORDINATES, coordItem)
+
+    // 제작대 버튼
+    val workbenchItem = ItemStack(Items.CRAFTING_TABLE)
+    workbenchItem.set(
+            DataComponents.CUSTOM_NAME,
+            Component.literal("제작대 열기").withStyle {
+                it.withColor(ChatFormatting.GOLD).withBold(true)
+            }
+    )
+    workbenchItem.set(
+            DataComponents.LORE,
+            ItemLore(
+                    listOf(
+                            Component.literal("클릭하여 제작대를 엽니다.").withStyle {
+                                it.withColor(ChatFormatting.GRAY)
+                            }
+                    )
+            )
+    )
+    workbenchItem.set(
+            DataComponents.CUSTOM_DATA,
+            CustomData.of(CompoundTag().apply { putString("action", "workbench") })
+    )
+    container.setItem(EssentialsMenuGui.SLOT_WORKBENCH, workbenchItem)
+
+    // TPA 버튼
+    val tpaItem = ItemStack(Items.ENDER_PEARL)
+    tpaItem.set(
+            DataComponents.CUSTOM_NAME,
+            Component.literal("플레이어 텔레포트").withStyle {
+                it.withColor(ChatFormatting.AQUA).withBold(true)
+            }
+    )
+    tpaItem.set(
+            DataComponents.LORE,
+            ItemLore(
+                    listOf(
+                            Component.literal("클릭하여 다른 플레이어에게 이동합니다.").withStyle {
+                                it.withColor(ChatFormatting.GRAY)
+                            }
+                    )
+            )
+    )
+    tpaItem.set(
+            DataComponents.CUSTOM_DATA,
+            CustomData.of(CompoundTag().apply { putString("action", "tpa") })
+    )
+    container.setItem(EssentialsMenuGui.SLOT_TPA, tpaItem)
+
+    return container
+}
+
+/** 메뉴 GUI 열기 */
+fun openEssentialsMenu(player: ServerPlayer) {
+    val container = createEssentialsMenuContainer()
+    player.openMenu(
+            SimpleMenuProvider(
+                    { windowId, inv, _ -> EssentialsMenuGui(windowId, inv, container, player) },
+                    Component.literal("Essentials 메뉴").withStyle { it.withBold(true) }
+            )
+    )
+}

Essentials/src/main/resources/META-INF/accesstransformer.cfg

@@ -0,0 +1,3 @@
+# Essentials Access Transformer
+# ServerGamePacketListenerImpl의 player 필드에 접근하기 위한 설정은 필요 없음
+# NeoForge에서 ServerPlayer 접근 가능

Essentials/src/main/resources/essentials.mixins.json

@@ -10,6 +10,7 @@
     "PlayerInfoPacketMixin",
     "PlayerListMixin",
     "PlayerMixin",
+    "ServerGamePacketListenerImplMixin",
     "ServerPlayerMixin"
   ],
   "client": [],