Added menu pagination

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/EcoGUIFactory.kt

@@ -1,10 +1,12 @@
 package com.willfp.eco.internal.gui
 
 import com.willfp.eco.core.gui.GUIFactory
+import com.willfp.eco.core.gui.menu.Menu
 import com.willfp.eco.core.gui.menu.MenuBuilder
 import com.willfp.eco.core.gui.slot.SlotBuilder
 import com.willfp.eco.core.gui.slot.functional.SlotProvider
 import com.willfp.eco.internal.gui.menu.EcoMenuBuilder
+import com.willfp.eco.internal.gui.page.DelegateMenu
 import com.willfp.eco.internal.gui.slot.EcoSlotBuilder
 
 object EcoGUIFactory : GUIFactory {
@@ -15,4 +17,8 @@ object EcoGUIFactory : GUIFactory {
     override fun createMenuBuilder(rows: Int): MenuBuilder {
         return EcoMenuBuilder(rows)
     }
-}
+
+    override fun blendMenuState(base: Menu, additional: Menu): Menu {
+        return DelegateMenu(base, additional)
+    }
+}

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/menu/EcoMenu.kt

@@ -21,9 +21,9 @@ class EcoMenu(
     private val rows: Int,
     private val componentsAtPoints: Map<Anchor, List<OffsetComponent>>,
     private val title: String,
-    private val onClose: CloseHandler,
-    private val onRender: (Player, Menu) -> Unit,
-    private val onOpen: OpenHandler
+    private val onClose: List<CloseHandler>,
+    private val onRender: List<(Player, Menu) -> Unit>,
+    private val onOpen: List<OpenHandler>
 ) : Menu {
     private fun getPossiblyReactiveSlot(row: Int, column: Int, player: Player?, menu: Menu?): Slot {
         if (row < 1 || row > this.rows || column < 1 || column > 9) {
@@ -65,14 +65,14 @@ class EcoMenu(
 
         player.openInventory(inventory)
 
-        onOpen.handle(player, this)
+        onOpen.forEach { it.handle(player, this) }
 
         inventory.asRenderedInventory()?.generateCaptive()
         return inventory
     }
 
     fun handleClose(event: InventoryCloseEvent) {
-        onClose.handle(event, this)
+        onClose.forEach { it.handle(event, this) }
         event.inventory.asRenderedInventory()?.generateCaptive()
         MenuHandler.unregisterInventory(event.inventory)
     }
@@ -137,7 +137,8 @@ class EcoMenu(
         player.openInventory.topInventory.asRenderedInventory()?.render()
     }
 
-    fun runOnRender(player: Player) = onRender(player, this)
+    fun runOnRender(player: Player) =
+        onRender.forEach { it(player, this) }
 }
 
 data class OffsetComponent(

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/menu/EcoMenuBuilder.kt

@@ -13,9 +13,9 @@ import java.util.function.Consumer
 class EcoMenuBuilder(private val rows: Int) : MenuBuilder {
     private var title = "Menu"
     private val components = mutableMapOf<Anchor, MutableList<GUIComponent>>()
-    private var onClose = CloseHandler { _, _ -> }
-    private var onOpen = OpenHandler { _, _ -> }
-    private var onRender: (Player, Menu) -> Unit = { _, _ -> }
+    private var onClose = mutableListOf<CloseHandler>()
+    private var onOpen = mutableListOf<OpenHandler>()
+    private var onRender = mutableListOf<(Player, Menu) -> Unit>()
 
     override fun getRows() = rows
 
@@ -42,17 +42,17 @@ class EcoMenuBuilder(private val rows: Int) : MenuBuilder {
     }
 
     override fun onClose(action: CloseHandler): MenuBuilder {
-        onClose = action
+        onClose += action
         return this
     }
 
     override fun onOpen(action: OpenHandler): MenuBuilder {
-        onOpen = action
+        onOpen += action
         return this
     }
 
     override fun onRender(action: BiConsumer<Player, Menu>): MenuBuilder {
-        onRender = { a, b -> action.accept(a, b) }
+        onRender += { a, b -> action.accept(a, b) }
         return this
     }
 

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/page/DelegateMenu.kt

@@ -0,0 +1,25 @@
+package com.willfp.eco.internal.gui.page
+
+import com.willfp.eco.core.gui.menu.Menu
+import org.bukkit.entity.Player
+
+class DelegateMenu(
+    private val base: Menu,
+    private val additional: Menu
+) : Menu by base {
+    override fun getState(player: Player): Map<String, Any> {
+        return base.getState(player) + additional.getState(player)
+    }
+
+    override fun addState(player: Player, key: String, value: Any?) {
+        base.addState(player, key, value)
+    }
+
+    override fun clearState(player: Player) {
+        base.clearState(player)
+    }
+
+    override fun removeState(player: Player, key: String) {
+        base.removeState(player, key)
+    }
+}

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/slot/EcoSlot.kt

@@ -33,15 +33,6 @@ open class EcoSlot(
         return updater.update(player, menu, prev) ?: ItemStack(Material.AIR)
     }
 
-    fun getItemStack(
-        player: Player,
-        menu: Menu
-    ): ItemStack {
-        val prev = provider.provide(player, menu)
-        val updated = updater.update(player, menu, prev)
-        return updated ?: ItemStack(Material.AIR)
-    }
-
     override fun isCaptive(): Boolean {
         return false
     }