package org.bukkit.help;

import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;

/**
 * HelpTopic implementations are displayed to the user when the user uses the
 * /help command.
 * <p>
 * Custom implementations of this class can work at two levels. A simple
 * implementation only needs to set the value of {@code name}, {@code
 * shortText}, and {@code fullText} in the constructor. This base class will
 * take care of the rest.
 * <p>
 * Complex implementations can be created by overriding the behavior of all
 * the methods in this class.
 */
public abstract class HelpTopic
{
	protected String name;
	protected String shortText;
	protected String fullText;
	protected String amendedPermission;

	/**
	 * Determines if a {@link Player} is allowed to see this help topic.
	 * <p>
	 * HelpTopic implementations should take server administrator wishes into
	 * account as set by the {@link HelpTopic#amendCanSee(String)} function.
	 *
	 * @param player The Player in question.
	 * @return True of the Player can see this help topic, false otherwise.
	 */
	public abstract boolean canSee(CommandSender player);

	/**
	 * Allows the server administrator to override the permission required to
	 * see a help topic.
	 * <p>
	 * HelpTopic implementations should take this into account when
	 * determining topic visibility on the {@link
	 * HelpTopic#canSee(org.bukkit.command.CommandSender)} function.
	 *
	 * @param amendedPermission The permission node the server administrator
	 *                          wishes to apply to this topic.
	 */
	public void amendCanSee(String amendedPermission)
	{
		this.amendedPermission = amendedPermission;
	}

	/**
	 * Returns the name of this help topic.
	 *
	 * @return The topic name.
	 */
	public String getName()
	{
		return name;
	}

	/**
	 * Returns a brief description that will be displayed in the topic index.
	 *
	 * @return A brief topic description.
	 */
	public String getShortText()
	{
		return shortText;
	}

	/**
	 * Returns the full description of this help topic that is displayed when
	 * the user requests this topic's details.
	 * <p>
	 * The result will be paginated to properly fit the user's client.
	 *
	 * @param forWho The player or console requesting the full text. Useful
	 *               for further security trimming the command's full text based on
	 *               sub-permissions in custom implementations.
	 * @return A full topic description.
	 */
	public String getFullText(CommandSender forWho)
	{
		return fullText;
	}

	/**
	 * Allows the server admin (or another plugin) to add or replace the
	 * contents of a help topic.
	 * <p>
	 * A null in either parameter will leave that part of the topic unchanged.
	 * In either amending parameter, the string {@literal <text>} is replaced
	 * with the existing contents in the help topic. Use this to append or
	 * prepend additional content into an automatically generated help topic.
	 *
	 * @param amendedShortText The new topic short text to use, or null to
	 *                         leave alone.
	 * @param amendedFullText  The new topic full text to use, or null to leave
	 *                         alone.
	 */
	public void amendTopic(String amendedShortText, String amendedFullText)
	{
		shortText = applyAmendment(shortText, amendedShortText);
		fullText = applyAmendment(fullText, amendedFullText);
	}

	/**
	 * Developers implementing their own custom HelpTopic implementations can
	 * use this utility method to ensure their implementations comply with the
	 * expected behavior of the {@link HelpTopic#amendTopic(String, String)}
	 * method.
	 *
	 * @param baseText  The existing text of the help topic.
	 * @param amendment The amending text from the amendTopic() method.
	 * @return The application of the amending text to the existing text,
	 * according to the expected rules of amendTopic().
	 */
	protected String applyAmendment(String baseText, String amendment)
	{
		if(amendment == null)
		{
			return baseText;
		}
		else
		{
			return amendment.replace("<text>", baseText);
		}
	}
}