jspwiki-main/src/main/java/org/apache/wiki/rss/RSSGenerator.java

/* 
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    to you under the Apache License, Version 2.0 (the
    "License"); you may not use this file except in compliance
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       http://www.apache.org/licenses/LICENSE-2.0

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    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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    specific language governing permissions and limitations
    under the License.  
 */
package org.apache.wiki.rss;

import org.apache.wiki.api.core.Context;
import org.apache.wiki.api.core.Engine;
import org.apache.wiki.api.core.Page;
import org.apache.wiki.util.TextUtil;

import java.util.List;
import java.util.Properties;

/**
 *  The master class for generating different kinds of Feeds (including RSS1.0, 2.0 and Atom).
 *  <p>
 *  This class can produce quite a few different styles of feeds.  The following modes are available:
 *  
 *  <ul>
 *  <li><b>wiki</b> - All the changes to the given page are enumerated and announced as diffs.</li>
 *  <li><b>full</b> - Each page is only considered once.  This produces a very RecentChanges-style feed,
 *                   where each page is only listed once, even if it has changed multiple times.</li>
 *  <li><b>blog</b> - Each page change is assumed to be a blog entry, so no diffs are produced, but
 *                    the page content is always completely in the entry in rendered HTML.</li>
 *
 *  @since  1.7.5.
 */
public interface RSSGenerator {

    /** Parameter value to represent RSS 1.0 feeds.  Value is <tt>{@value}</tt>. */
    String RSS10 = "rss10";

    /** Parameter value to represent RSS 2.0 feeds.  Value is <tt>{@value}</tt>. */
    String RSS20 = "rss20";
    
    /** Parameter value to represent Atom feeds.  Value is <tt>{@value}</tt>.  */
    String ATOM  = "atom";

    /** Parameter value to represent a 'blog' style feed. Value is <tt>{@value}</tt>. */
    String MODE_BLOG = "blog";
    
    /** Parameter value to represent a 'wiki' style feed. Value is <tt>{@value}</tt>. */
    String MODE_WIKI = "wiki";

    /** Parameter value to represent a 'full' style feed. Value is <tt>{@value}</tt>. */
    String MODE_FULL = "full";

    /**
     *  Defines the property name for the RSS channel description.  Default value for the channel description is an empty string.
     *
     *  @since 1.7.6.
     */
    String PROP_CHANNEL_DESCRIPTION = "jspwiki.rss.channelDescription";

    /**
     *  Defines the property name for the RSS channel language.  Default value for the language is "en-us".
     *
     *  @since 1.7.6.
     */
    String PROP_CHANNEL_LANGUAGE = "jspwiki.rss.channelLanguage";

    /** Defines the property name for the RSS channel title.  Value is <tt>{@value}</tt>. */
    String PROP_CHANNEL_TITLE = "jspwiki.rss.channelTitle";

    /**
     *  Defines the property name for the RSS generator main switch.
     *
     *  @since 1.7.6.
     */
    String PROP_GENERATE_RSS = "jspwiki.rss.generate";

    /**
     *  Defines the property name for the RSS file that the wiki should generate.
     *
     *  @since 1.7.6.
     */
    String PROP_RSSFILE = "jspwiki.rss.fileName";

    /**
     *  Defines the property name for the RSS generation interval in seconds.
     *
     *  @since 1.7.6.
     */
    String PROP_INTERVAL = "jspwiki.rss.interval";

    /** Defines the property name for the RSS author.  Value is <tt>{@value}</tt>. */
    String PROP_RSS_AUTHOR = "jspwiki.rss.author";

    /** Defines the property name for the RSS author email.  Value is <tt>{@value}</tt>. */
    String PROP_RSS_AUTHOREMAIL = "jspwiki.rss.author.email";

    /**
     * Start the RSS generator & generator thread
     *
     * @param engine the engine
     * @param properties the properties
     */
    void initialize( Engine engine, Properties properties );

    /**
     *  Generates the RSS resource.  You probably want to output this result into a file or something, or serve as output from a servlet.
     *
     *  @return A RSS 1.0 feed in the "full" mode.
     */
    String generate();

    /**
     * Generates a feed based on a context and list of changes.
     *
     * @param wikiContext The WikiContext
     * @param changed A list of Entry objects
     * @param mode The mode (wiki/blog)
     * @param type The type (RSS10, RSS20, ATOM).  Default is RSS 1.0
     * @return Fully formed XML.
     * @throws IllegalArgumentException If an illegal mode is given.
     */
    String generateFeed( final Context wikiContext, final List< Page > changed, final String mode, final String type ) throws IllegalArgumentException;

    /**
     * Returns <code>true</code> if RSS generation is enabled.
     *
     * @return whether RSS generation is currently enabled
     */
    boolean isEnabled();

    /**
     * Turns RSS generation on or off. This setting is used to set the "enabled" flag only for use by callers, and does not
     * actually affect whether the {@link #generate()} or {@link #generateFeed(Context, List, String, String)} methods output anything.
     *
     * @param enabled whether RSS generation is considered enabled.
     */
    void setEnabled( final boolean enabled );

    /**
     * returns the rss file.
     *
     * @return the rss file.
     */
    String getRssFile();

    /**
     *  Generates an RSS feed for the entire wiki.  Each item should be an instance of the RSSItem class.
     *
     *  @param wikiContext A WikiContext
     *  @param feed A Feed to generate the feed to.
     *  @return feed.getString().
     */
    String generateFullWikiRSS( Context wikiContext, Feed feed );

    /**
     * Create RSS/Atom as if this page was a wikipage (in contrast to Blog mode).
     *
     * @param wikiContext The WikiContext
     * @param changed A List of changed WikiPages.
     * @param feed A Feed object to fill.
     * @return the RSS representation of the wiki context
     */
    String generateWikiPageRSS( Context wikiContext, List< Page > changed, Feed feed );

    /**
     *  Creates RSS from modifications as if this page was a blog (using the WeblogPlugin).
     *
     *  @param wikiContext The WikiContext, as usual.
     *  @param changed A list of the changed pages.
     *  @param feed A valid Feed object.  The feed will be used to create the RSS/Atom, depending on which kind of an object you want to put in it.
     *  @return A String of valid RSS or Atom.
     */
    String generateBlogRSS( Context wikiContext, List< Page > changed, Feed feed );

    /**
     *  Does the required formatting and entity replacement for XML.
     *  
     *  @param s String to format.
     *  @return A formatted string.
     */
    // FIXME: Replicates Feed.format().
    static String format( String s ) {
        s = TextUtil.replaceString( s, "&", "&amp;" );
        s = TextUtil.replaceString( s, "<", "&lt;" );
        s = TextUtil.replaceString( s, "]]>", "]]&gt;" );

        return s.trim();
    }

    /**
     * Returns the content type of this RSS feed.
     *
     * @since 2.3.15
     * @param mode the RSS mode: {@link #RSS10}, {@link #RSS20} or {@link #ATOM}.
     * @return the content type
     */
    static String getContentType( final String mode ) {
        if( mode.equals( RSS10 ) || mode.equals( RSS20 ) ) {
            return "application/rss+xml";
        } else if( mode.equals( ATOM ) ) {
            return "application/atom+xml";
        }

        return "application/octet-stream"; // Unknown type
    }

}