// License: GPL. For details, see LICENSE file.
package org.openstreetmap.josm.gui.help;

import java.awt.Component;
import java.util.Locale;

import javax.swing.AbstractButton;
import javax.swing.Action;
import javax.swing.JComponent;
import javax.swing.JMenu;
import javax.swing.KeyStroke;

import org.openstreetmap.josm.actions.HelpAction;
import org.openstreetmap.josm.gui.MainApplication;
import org.openstreetmap.josm.spi.preferences.Config;
import org.openstreetmap.josm.tools.LanguageInfo;
import org.openstreetmap.josm.tools.LanguageInfo.LocaleType;
import org.openstreetmap.josm.tools.Utils;

/**
 * Provides utility methods for help system.
 * @since 2252
 */
public final class HelpUtil {

    private HelpUtil() {
        // Hide default constructor for utils classes
    }

    /**
     * Replies the base wiki URL.
     *
     * @return the base wiki URL
     */
    public static String getWikiBaseUrl() {
        return Config.getPref().get("help.baseurl", Config.getUrls().getJOSMWebsite());
    }

    /**
     * Replies the base wiki URL for help pages
     *
     * @return the base wiki URL for help pages
     */
    public static String getWikiBaseHelpUrl() {
        return getWikiBaseUrl() + "/wiki";
    }

    /**
     * Replies the URL on the wiki for an absolute help topic. The URL is encoded in UTF-8.
     *
     * @param absoluteHelpTopic the absolute help topic
     * @return the url
     * @see #buildAbsoluteHelpTopic
     */
    public static String getHelpTopicUrl(String absoluteHelpTopic) {
        if (absoluteHelpTopic == null)
            return null;
        String ret = getWikiBaseHelpUrl();
        ret = ret.replaceAll("\\/+$", "");
        absoluteHelpTopic = absoluteHelpTopic.replace(" ", "%20");
        absoluteHelpTopic = absoluteHelpTopic.replaceAll("^\\/+", "/");
        return ret + absoluteHelpTopic;
    }

    /**
     * Replies the URL to the edit page for the absolute help topic.
     *
     * @param absoluteHelpTopic the absolute help topic
     * @return the URL to the edit page
     */
    public static String getHelpTopicEditUrl(String absoluteHelpTopic) {
        String topicUrl = getHelpTopicUrl(absoluteHelpTopic);
        if (topicUrl != null)
            topicUrl = topicUrl.replaceAll("#[^#]*$", ""); // remove optional fragment
        return topicUrl + "?action=edit";
    }

    /**
     * Extracts the relative help topic from an URL. Replies null, if
     * no relative help topic is found.
     *
     * @param url the url
     * @return the relative help topic in the URL, i.e. "/Action/New"
     */
    public static String extractRelativeHelpTopic(String url) {
        String topic = extractAbsoluteHelpTopic(url);
        if (topic == null)
            return null;
        String topicPrefix = getHelpTopicPrefix(LocaleType.ENGLISH);
        if (topicPrefix != null)
            topicPrefix = topicPrefix.replaceAll("^\\/+", "");
        String pattern = "/[A-Z][a-z]{1,2}(_[A-Z]{2})?:" + topicPrefix;
        if (url.matches(pattern)) {
            return topic.substring(pattern.length());
        }
        return null;
    }

    /**
     * Extracts the absolute help topic from an URL. Replies null, if
     * no absolute help topic is found.
     *
     * @param url the url
     * @return the absolute help topic in the URL, i.e. "/De:Help/Action/New"
     */
    public static String extractAbsoluteHelpTopic(String url) {
        if (url == null || !url.startsWith(getWikiBaseHelpUrl())) return null;
        String topic = url.substring(getWikiBaseHelpUrl().length());
        String prefix = getHelpTopicPrefix(LocaleType.ENGLISH);
        if (prefix == null || topic.startsWith(prefix))
            return topic;

        String pattern = "/[A-Z][a-z]{1,2}(_[A-Z]{2})?:" + prefix.replaceAll("^\\/+", "");
        if (topic.matches(pattern))
            return topic;

        return null;
    }

    /**
     * Replies the help topic prefix for the given locale. Examples:
     * <ul>
     *   <li>/Help if the  locale is a locale with language "en"</li>
     *   <li>/De:Help if the  locale is a locale with language "de"</li>
     * </ul>
     *
     * @param type the type of the locale to use
     * @return the help topic prefix
     * @since 5915
     */
    private static String getHelpTopicPrefix(LocaleType type) {
        String ret = LanguageInfo.getWikiLanguagePrefix(type);
        if (ret == null)
            return ret;
        ret = '/' + ret + Config.getPref().get("help.pathhelp", "/Help").replaceAll("^\\/+", ""); // remove leading /
        return ret.replaceAll("\\/+", "\\/"); // collapse sequences of //
    }

    /**
     * Replies the absolute, localized help topic for the given topic.
     *
     * Example: for a topic "/Dialog/RelationEditor" and the locale "de", this method
     * replies "/De:Help/Dialog/RelationEditor"
     *
     * @param topic the relative help topic. Home help topic assumed, if null.
     * @param type the locale. {@link Locale#ENGLISH} assumed, if null.
     * @return the absolute, localized help topic
     * @since 5915
     */
    public static String buildAbsoluteHelpTopic(String topic, LocaleType type) {
        String prefix = getHelpTopicPrefix(type);
        if (prefix == null || Utils.isStripEmpty(topic) || "/".equals(topic.trim()))
            return prefix;
        prefix += '/' + topic;
        return prefix.replaceAll("\\/+", "\\/"); // collapse sequences of //
    }

    /**
     * Replies the context specific help topic configured for <code>context</code>.
     * @param context The UI object used as context
     *
     * @return the help topic. null, if no context specific help topic is found
     */
    public static String getContextSpecificHelpTopic(Object context) {
        if (context == null)
            return null;
        if (context instanceof Helpful)
            return ((Helpful) context).helpTopic();
        if (context instanceof JMenu) {
            JMenu b = (JMenu) context;
            if (b.getClientProperty("help") != null)
                return (String) b.getClientProperty("help");
            return null;
        }
        if (context instanceof AbstractButton) {
            AbstractButton b = (AbstractButton) context;
            if (b.getClientProperty("help") != null)
                return (String) b.getClientProperty("help");
            return getContextSpecificHelpTopic(b.getAction());
        }
        if (context instanceof Action)
            return (String) ((Action) context).getValue("help");
        if (context instanceof JComponent && ((JComponent) context).getClientProperty("help") != null)
            return (String) ((JComponent) context).getClientProperty("help");
        if (context instanceof Component)
            return getContextSpecificHelpTopic(((Component) context).getParent());
        return null;
    }

    /**
     * Replies the global help action, if available. Otherwise, creates an instance of {@link HelpAction}.
     *
     * @return instance of help action
     */
    private static Action getHelpAction() {
        if (MainApplication.getMenu() != null) {
            return MainApplication.getMenu().help;
        }
        return HelpAction.createWithoutShortcut();
    }

    /**
     * Makes a component aware of context sensitive help.
     *
     * A relative help topic doesn't start with /Help and doesn't include a locale code.
     * Example: /Dialog/RelationEditor is a relative help topic, /De:Help/Dialog/RelationEditor is not.
     *
     * @param component the component
     * @param relativeHelpTopic the help topic. Set to the default help topic if null.
     */
    public static void setHelpContext(JComponent component, String relativeHelpTopic) {
        component.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke("F1"), "help");
        component.getActionMap().put("help", getHelpAction());
        component.putClientProperty("help", relativeHelpTopic == null ? "/" : relativeHelpTopic);
    }

    /**
     * This is a simple marker method for help topic literals. If you declare a help
     * topic literal in the source you should enclose it in ht(...).
     *
     *  <strong>Example</strong>
     *  <pre>
     *     String helpTopic = ht("/Dialog/RelationEditor");
     *  or
     *     putValue("help", ht("/Dialog/RelationEditor"));
     *  </pre>
     *
     * @param helpTopic Help topic to mark
     * @return {@code helpTopic}
     */
    public static String ht(String helpTopic) {
        // this is just a marker method
        return helpTopic;
    }
}