InventoryClickEvent Hotbar Button (PR #2648, issue #2643)

* InventoryClickEvent#getHotbarButton()

* Revert Changes

* Create ExprHotbarButton.java

* Clean Imports

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

@@ -0,0 +1,80 @@
+/**
+ *   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 2011-2017 Peter Güttinger and contributors
+ */
+package ch.njol.skript.expressions;
+
+import org.bukkit.event.Event;
+import org.bukkit.event.inventory.InventoryClickEvent;
+import org.eclipse.jdt.annotation.Nullable;
+
+import ch.njol.skript.ScriptLoader;
+import ch.njol.skript.Skript;
+import ch.njol.skript.doc.Description;
+import ch.njol.skript.doc.Examples;
+import ch.njol.skript.doc.Name;
+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;
+
+@Name("Hotbar Button")
+@Description("The hotbar button clicked in an <a href='events.html#inventory_click>inventory click</a> event.")
+@Examples({"on inventory click:",
+		"	send \"You clicked the hotbar button %hotbar button%!\""})
+@Since("INSERT VERSION")
+public class ExprHotbarButton extends SimpleExpression<Number> {
+
+	static {
+		Skript.registerExpression(ExprHotbarButton.class, Number.class, ExpressionType.SIMPLE, "[the] hotbar button");
+	}
+
+	@Override
+	public boolean init(Expression<?>[] exprs, int matchedPattern, Kleenean isDelayed, ParseResult parser) {
+		if (!ScriptLoader.isCurrentEvent(InventoryClickEvent.class)) {
+			Skript.error("The 'hotbar button' expression may only be used in an inventory click event.");
+			return false;
+		}
+		return true;
+	}
+
+	@Nullable
+	@Override
+	protected Number[] get(Event e) {
+		if (e instanceof InventoryClickEvent)
+			return new Number[] {Integer.valueOf(((InventoryClickEvent) e).getHotbarButton())};
+		return null;
+	}
+
+	@Override
+	public boolean isSingle() {
+		return true;
+	}
+
+	@Override
+	public Class<? extends Number> getReturnType() {
+		return Number.class;
+	}
+
+	@Override
+	public String toString(@Nullable Event e, boolean debug) {
+		return "the hotbar button";
+	}
+}