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006    to you under the Apache License, Version 2.0 (the
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009
010       http://www.apache.org/licenses/LICENSE-2.0
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015    KIND, either express or implied.  See the License for the
016    specific language governing permissions and limitations
017    under the License.  
018 */
019package org.apache.wiki.api.filters;
020
021import org.apache.wiki.api.core.Context;
022import org.apache.wiki.api.core.Engine;
023import org.apache.wiki.api.exceptions.FilterException;
024
025import java.lang.reflect.Method;
026import java.util.Properties;
027
028import static org.apache.wiki.api.filters.FilterSupportOperations.executePageFilterPhase;
029import static org.apache.wiki.api.filters.FilterSupportOperations.methodOfNonPublicAPI;
030
031
032/**
033 *  <p>Provides a definition for a page filter. A page filter is a class that can be used to transform the WikiPage content being saved or
034 *  being loaded at any given time.</p>
035 *  <p>Note that the Context#getPage() method always returns the context in which text is rendered, i.e. the original request. Thus the
036 *  content may actually be different content than what what the Context#getPage() implies! This happens often if you are for example
037 *  including multiple pages on the same page.</p>
038 *  <p>PageFilters must be thread-safe! There is only one instance of each PageFilter per each Engine invocation. If you need to store data
039 *  persistently, use VariableManager, or WikiContext.</p>
040 *  <p><strong>Design notes</strong></p>
041 *  <p>As of 2.5.30, initialize() gains access to the Engine.</p>
042 *  <p>As of 2.11.0.M7, almost all methods from BasicPageFilter end up here as default methods.</p>
043 *  <p>In order to preserve backwards compatibility with filters not using the public API, these default methods checks if a given filter
044 *  is using the old, non public API and, if that's the case attempt to execute the old, non public api corresponding method. If the filter
045 *  uses the public API, then the default callback is used. None of the default callbacks do anything, so it is a good idea for you to
046 *  implement only methods that you need.</p>
047 */
048public interface PageFilter {
049
050    /**
051     *  Is called whenever the a new PageFilter is instantiated and reset.
052     *  
053     *  @param engine The Engine which owns this PageFilter
054     *  @param properties The properties ripped from filters.xml.
055     *  @throws FilterException If the filter could not be initialized. If this is thrown, the filter is not added to the internal queues.
056     */
057    void initialize( Engine engine, Properties properties ) throws FilterException;
058
059    /**
060     *  This method is called whenever a page has been loaded from the provider, but not yet been sent through the markup-translation
061     *  process.  Note that you cannot do HTML translation here, because it will be escaped.
062     *
063     *  @param context The current context.
064     *  @param content WikiMarkup.
065     *  @return The modified wikimarkup content. Default implementation returns the markup as received.
066     *  @throws FilterException If something goes wrong.  Throwing this causes the entire page processing to be abandoned.
067     */
068    default String preTranslate( final Context context, final String content ) throws FilterException {
069        final Method m = methodOfNonPublicAPI( this, "preTranslate", "org.apache.wiki.WikiContext", "java.lang.String" );
070        return executePageFilterPhase( () -> content, m, this, context, content );
071        // return content;
072    }
073
074    /**
075     *  This method is called after a page has been fed through the translation process, so anything you are seeing here is translated
076     *  content.  If you want to do any of your own WikiMarkup2HTML translation, do it here.
077     *  
078     *  @param context The WikiContext.
079     *  @param htmlContent The translated HTML.
080     *  @return The modified HTML. Default implementation returns the translated html as received.
081     *  @throws FilterException If something goes wrong.  Throwing this causes the entire page processing to be abandoned.
082     */
083    default String postTranslate( final Context context, final String htmlContent ) throws FilterException {
084        final Method m = methodOfNonPublicAPI( this, "postTranslate", "org.apache.wiki.WikiContext", "java.lang.String" );
085        return executePageFilterPhase( () -> htmlContent, m, this, context, htmlContent );
086        // return htmlContent;
087    }
088
089    /**
090     *  This method is called before the page has been saved to the PageProvider.
091     *  
092     *  @param context The WikiContext
093     *  @param content The wikimarkup that the user just wanted to save.
094     *  @return The modified wikimarkup. Default implementation returns the markup as received.
095     *  @throws FilterException If something goes wrong.  Throwing this causes the entire page processing to be abandoned.
096     */
097    default String preSave( final Context context, final String content ) throws FilterException {
098        final Method m = methodOfNonPublicAPI( this, "preSave", "org.apache.wiki.WikiContext", "java.lang.String" );
099        return executePageFilterPhase( () -> content, m, this, context, content );
100        // return content;
101    }
102
103    /**
104     *  This method is called after the page has been successfully saved. If the saving fails for any reason, then this method will not
105     *  be called.
106     *  <p>
107     *  Since the result is discarded from this method, this is only useful for things like counters, etc.
108     *  
109     *  @param context The WikiContext
110     *  @param content The content which was just stored.
111     *  @throws FilterException If something goes wrong.  As the page is already saved, This is just logged.
112     */
113    default void postSave( final Context context, final String content ) throws FilterException {
114        final Method m = methodOfNonPublicAPI( this, "postSave", "org.apache.wiki.WikiContext", "java.lang.String" );
115        executePageFilterPhase( () -> null, m, this, content );
116        // empty method
117    }
118
119    /**
120     *  Called for every filter, e.g. on wiki engine shutdown. Use this if you have to 
121     *  clean up or close global resources you allocated in the initialize() method.
122     * 
123     *  @param engine The Engine which owns this filter.
124     *  @since 2.5.36
125     */
126    default void destroy( final Engine engine ) {
127        final Method m = methodOfNonPublicAPI( this, "destroy", "org.apache.wiki.WikiEngine" );
128        executePageFilterPhase( () -> null, m, this, engine );
129        // empty method
130    }
131
132}