Add requirement API (no group check methods yet)

api/src/main/java/de/erethon/dungeonsxl/api/DungeonsAPI.java

@@ -65,6 +65,13 @@ public interface DungeonsAPI extends Plugin {
     @Deprecated
     Registry<String, Class<? extends Trigger>> getTriggerRegistry();
 
+    /**
+     * Returns a {@link Registry} of the requirement types.
+     *
+     * @return a {@link Registry} of the requirement types
+     */
+    Registry<String, Class<? extends Requirement>> getRequirementRegistry();
+
     /**
      * Returns a {@link Registry} of the reward types.
      *

api/src/main/java/de/erethon/dungeonsxl/api/Requirement.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2014-2020 Daniel Saukel
+ *
+ * This library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * This program 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 GNULesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+package de.erethon.dungeonsxl.api;
+
+import org.bukkit.configuration.ConfigurationSection;
+import org.bukkit.entity.Player;
+
+/**
+ * Something a player needs to fulfill in order to be allowed to start the game (= trigger a ready sign).
+ *
+ * @author Daniel Saukel
+ */
+public interface Requirement {
+
+    /**
+     * Sets up the requirement from the given requirements {@link de.erethon.dungeonsxl.api.game.GameRule} section.
+     *
+     * @param config the requirements config section
+     */
+    void setup(ConfigurationSection config);
+
+    /**
+     * Returns if the given player fulfills the requirements. If true, this lets him start the game (= trigger a ready sign).
+     *
+     * @param player the player
+     * @return if the given player fulfills the requirements
+     */
+    boolean check(Player player);
+
+    /**
+     * This is fired after the {@link #check(Player)} has been accepted. It demands the requirement from the given player. This may be empty for a "key" or may
+     * take something away for a "fee" requirement.
+     *
+     * @param player the player
+     */
+    void demand(Player player);
+
+}