Add InventoryEffectItem class

pylon-core/src/main/kotlin/io/github/pylonmc/pylon/core/item/base/PylonInventoryEffectItem.kt

@@ -0,0 +1,52 @@
+package io.github.pylonmc.pylon.core.item.base
+
+import io.github.pylonmc.pylon.core.PylonCore
+import io.github.pylonmc.pylon.core.config.PylonConfig
+import io.github.pylonmc.pylon.core.item.PylonItem
+import org.bukkit.Bukkit
+import org.bukkit.NamespacedKey
+import org.bukkit.entity.Player
+import org.bukkit.persistence.PersistentDataType
+import org.bukkit.scheduler.BukkitTask
+import org.jetbrains.annotations.MustBeInvokedByOverriders
+import java.util.*
+
+interface PylonInventoryEffectItem : PylonInventoryTicker {
+    @MustBeInvokedByOverriders
+    override fun onTick(player: Player) {
+        tasks.putIfAbsent(itemKey, HashMap())
+        tasks[itemKey]!![player.uniqueId]?.cancel()
+        if (!player.persistentDataContainer.has(itemKey)) {
+            player.persistentDataContainer.set(itemKey, PersistentDataType.BOOLEAN, true)
+            onAddedToInventory(player)
+        }
+        tasks[itemKey]!![player.uniqueId] = Bukkit.getScheduler().runTaskLater(PylonCore.javaPlugin, Runnable {
+            player.persistentDataContainer.remove(itemKey)
+            onRemovedFromInventory(player)
+        }, tickInterval * PylonConfig.inventoryTickerBaseRate + 1)
+    }
+
+    /**
+     * Remove the effect from the player. Best-effort removal therefore is no guarantee that the player is still connected or that the
+     * [PylonItem.stack] is up to date with the actual ItemStack when it runs.
+     */
+    @MustBeInvokedByOverriders
+    fun onRemovedFromInventory(player: Player) {
+        player.persistentDataContainer.remove(itemKey)
+    }
+
+    /**
+     * Apply the effect of this item onto the player
+     */
+    @MustBeInvokedByOverriders
+    fun onAddedToInventory(player: Player) {
+        player.persistentDataContainer.set(itemKey, PersistentDataType.BOOLEAN, true)
+    }
+
+    val itemKey: NamespacedKey
+        get() = NamespacedKey((this as PylonItem).key.namespace, key.key + "_effect")
+
+    companion object {
+        private val tasks = HashMap<NamespacedKey, HashMap<UUID, BukkitTask>>()
+    }
+}