Add kept items expression and effect

src/main/java/ch/njol/skript/effects/EffKeepItems.java

@@ -0,0 +1,114 @@
+/**
+ *   This file is part of Skript.
+ *
+ *  Skript 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.
+ *
+ *  Skript 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 Skript.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright Peter Güttinger, SkriptLang team and contributors
+ */
+package ch.njol.skript.effects;
+
+import java.util.Iterator;
+import java.util.List;
+
+import org.bukkit.event.Event;
+import org.bukkit.event.entity.PlayerDeathEvent;
+import org.bukkit.inventory.ItemStack;
+import org.eclipse.jdt.annotation.Nullable;
+
+import ch.njol.skript.Skript;
+import ch.njol.skript.aliases.ItemType;
+import ch.njol.skript.doc.Description;
+import ch.njol.skript.doc.Events;
+import ch.njol.skript.doc.Examples;
+import ch.njol.skript.doc.Name;
+import ch.njol.skript.doc.RequiredPlugins;
+import ch.njol.skript.doc.Since;
+import ch.njol.skript.expressions.ExprDrops;
+import ch.njol.skript.lang.Effect;
+import ch.njol.skript.lang.Expression;
+import ch.njol.skript.lang.SkriptParser.ParseResult;
+import ch.njol.util.Kleenean;
+
+@Name("Keep Items")
+@Description({
+	"Keeps the given items from dropping in a 'death of player' event.",
+	"Note: this effect will only keep items that have been in the drops.",
+	"Use the <a href='expressions.html#ExprKeptItems'>kept items</a> expression for items outside of the drops."
+})
+@Examples({
+	"on death of player:",
+		"\tkeep the drops"
+})
+@Events("death")
+@RequiredPlugins("Paper (keep specific items)")
+@Since("INSERT VERSION")
+public class EffKeepItems extends Effect {
+
+	static {
+		Skript.registerEffect(EffKeepItems.class, "keep %itemtypes% [from ([the] drops|dropping)]");
+	}
+
+	private static final boolean SPIGOT = !Skript.methodExists(PlayerDeathEvent.class, "getItemsToKeep");
+	private boolean keepAll;
+
+	private Expression<ItemType> items;
+
+	@Override
+	public boolean init(Expression<?>[] exprs, int matchedPattern, Kleenean isDelayed, ParseResult parseResult) {
+		if (!getParser().isCurrentEvent(PlayerDeathEvent.class)) {
+			Skript.error("'keep items' can only be used in a 'death of player' event.");
+			return false;
+		}
+		keepAll = exprs[0] instanceof ExprDrops;
+
+		if (SPIGOT && !keepAll) {
+			Skript.error("Can't keep specific items in a Spigot server.");
+			return false;
+		}
+
+		items = (Expression<ItemType>) exprs[0];
+		return true;
+	}
+
+	@Override
+	protected void execute(Event event) {
+		if (!(event instanceof PlayerDeathEvent))
+			return;
+
+		PlayerDeathEvent e = (PlayerDeathEvent) event;
+		List<ItemStack> drops = e.getDrops();
+
+		if (keepAll) {
+			e.setKeepInventory(true);
+			drops.clear();
+			return;
+		}
+
+		List<ItemStack> keptItems = e.getItemsToKeep();
+		// We make sure the items we're keeping are part of the drops this way
+		List<ItemStack> itemsToKeep = items.stream(event)
+			.filter(item -> item.isContainedIn(drops))
+			.map(ItemType::getRandom)
+			.toList();
+
+		keptItems.addAll(itemsToKeep);
+		drops.removeAll(itemsToKeep);
+	}
+
+	@Override
+	public String toString(@Nullable Event event, boolean debug) {
+		return "keep " + items.toString(event, debug) + " from the drops";
+	}
+
+}

src/main/java/ch/njol/skript/expressions/ExprKeptItems.java

@@ -0,0 +1,147 @@
+/**
+ *   This file is part of Skript.
+ *
+ *  Skript 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.
+ *
+ *  Skript 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 Skript.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Copyright Peter Güttinger, SkriptLang team and contributors
+ */
+package ch.njol.skript.expressions;
+
+import java.util.List;
+
+import org.bukkit.event.Event;
+import org.bukkit.event.entity.PlayerDeathEvent;
+import org.bukkit.inventory.ItemStack;
+import org.eclipse.jdt.annotation.Nullable;
+
+import ch.njol.skript.Skript;
+import ch.njol.skript.aliases.ItemType;
+import ch.njol.skript.classes.Changer.ChangeMode;
+import ch.njol.skript.doc.Description;
+import ch.njol.skript.doc.Events;
+import ch.njol.skript.doc.Examples;
+import ch.njol.skript.doc.Name;
+import ch.njol.skript.doc.RequiredPlugins;
+import ch.njol.skript.doc.Since;
+import ch.njol.skript.lang.Expression;
+import ch.njol.skript.lang.ExpressionType;
+import ch.njol.skript.lang.SkriptParser.ParseResult;
+import ch.njol.skript.lang.util.SimpleExpression;
+import ch.njol.util.Kleenean;
+import ch.njol.util.coll.CollectionUtils;
+
+@Name("Kept Items")
+@Description({
+	"The kept items in a 'death of player' event.",
+	"Note: this expression won't remove the items from the drops when changed.",
+	"Use the <a href='effects.html#EffKeepItems'>keep items</a> effect for that."
+})
+@Examples({
+	"on death of player:",
+		"\tset kept items to the drops where [input isn't victim's tool]"
+})
+@Events("death")
+@RequiredPlugins("Paper")
+@Since("INSERT VERSION")
+public class ExprKeptItems extends SimpleExpression<ItemType> {
+
+	static {
+		if (Skript.methodExists(PlayerDeathEvent.class, "getItemsToKeep"))
+			Skript.registerExpression(ExprKeptItems.class, ItemType.class, ExpressionType.SIMPLE, "[the] kept items");
+
+	}
+
+	@Override
+	public boolean init(Expression<?>[] exprs, int matchedPattern, Kleenean isDelayed, ParseResult parseResult) {
+		if (!getParser().isCurrentEvent(PlayerDeathEvent.class)) {
+			Skript.error("'kept items' can only be used in a 'death of player' event.");
+			return false;
+		}
+		return true;
+	}
+
+	@Override
+	@Nullable 
+	protected ItemType[] get(Event event) {
+		if (!(event instanceof PlayerDeathEvent))
+			return null;
+
+		return ((PlayerDeathEvent) event).getItemsToKeep()
+			.stream()
+			.map(ItemType::new)
+			.toArray(ItemType[]::new);
+	}
+
+	@Override
+	@Nullable 
+	public Class<?>[] acceptChange(ChangeMode mode) {
+		switch (mode) {
+			case ADD:
+			case REMOVE:
+			case REMOVE_ALL:
+			case DELETE:
+			case RESET:
+				return CollectionUtils.array(ItemType.class);
+			default:
+				return null;
+		}
+	}
+
+	@Override
+	public void change(Event event, @Nullable Object[] delta, ChangeMode mode) {
+		if (!(event instanceof PlayerDeathEvent))
+			return;
+
+		List<ItemStack> keptItems = ((PlayerDeathEvent) event).getItemsToKeep();
+		boolean canChange = delta != null;
+		// Clear items before adding the new values
+		if ((mode == ChangeMode.SET && canChange) || mode == ChangeMode.DELETE || mode == ChangeMode.RESET)
+			keptItems.clear();
+
+		if (!canChange)
+			return;
+
+		for (Object o : delta) {
+			ItemType item = (ItemType) o;
+			switch (mode) {
+				case ADD:
+				case SET:
+					item.addTo(keptItems);
+					break;
+				case REMOVE:
+					item.removeFrom(keptItems);
+					break;
+				case REMOVE_ALL:
+					item.removeAll(keptItems);
+					break;
+			}
+		}
+	}
+
+	@Override
+	public boolean isSingle() {
+		return false;
+	}
+
+	@Override
+	public Class<? extends ItemType> getReturnType() {
+		return ItemType.class;
+	}
+
+	@Override
+	public String toString(@Nullable Event event, boolean debug) {
+		return "the kept items";
+	}
+
+}