[Bleeding] Added Help API. Addresses BUKKIT-863

By: rmichela <deltahat@gmail.com>

paper-api/src/main/java/org/bukkit/help/HelpMap.java

@@ -0,0 +1,44 @@
+package org.bukkit.help;
+
+/**
+ * The HelpMap tracks all help topics registered in a Bukkit server. When the server starts up or is reloaded,
+ * help is processed and topics are added in the following order:
+ *
+ * 1. General topics are loaded from the help.yml
+ * 2. Plugins load and optionally call {@code addTopic()}
+ * 3. Registered plugin commands are processed by {@link HelpTopicFactory} objects to create topics
+ * 4. Topic contents are amended as directed in help.yml
+ */
+public interface HelpMap {
+    /**
+     * Returns a help topic for a given topic name.
+     *
+     * @param topicName The help topic name to look up.
+     * @return A {@link HelpTopic} object matching the topic name or null if none can be found.
+     */
+    public HelpTopic getHelpTopic(String topicName);
+
+    /**
+     * Adds a topic to the server's help index.
+     *
+     * @param topic The new help topic to add.
+     */
+    public void addTopic(HelpTopic topic);
+
+    /**
+     * Clears out the contents of the help index. Normally called during server reload.
+     */
+    public void clear();
+
+    /**
+     * Associates a {@link HelpTopicFactory} object with given command base class. Plugins typically
+     * call this method during {@code onLoad()}. Once registered, the custom HelpTopicFactory will
+     * be used to create a custom {@link HelpTopic} for all commands deriving from the {@code commandClass}
+     * base class.
+     *
+     * @param commandClass The class for which the custom HelpTopicFactory applies. Must derive from {@link org.bukkit.command.Command}.
+     * @param factory The {@link HelpTopicFactory} implementation to associate with the {@code commandClass}.
+     * @throws IllegalArgumentException Thrown if {@code commandClass} does not derive from Command.
+     */
+    public void registerHelpTopicFactory(Class commandClass, HelpTopicFactory factory);
+}