IndentEngine.java

/*
 *                 Sun Public License Notice
 * 
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 * 
 * The Original Code is NetBeans. The Initial Developer of the Original
 * Code is Sun Microsystems, Inc. Portions Copyright 1997-2003 Sun
 * Microsystems, Inc. All Rights Reserved.
 */

package org.openide.text;

import java.io.Writer;
import java.util.Collections;
import java.util.Enumeration;
import javax.swing.text.*;
import org.openide.ServiceType;
import org.openide.util.HelpCtx;
import org.openide.util.Lookup;

/** Indentation engine for formating text in documents.
* Provides mapping between MIME types and engines, so anybody
* can find appropriate type of engine for type of document.
*
* @author Jaroslav Tulach
*/
public abstract class IndentEngine extends ServiceType {

    static final long serialVersionUID = -8548906260608507035L;
    
    private static final String HELP_ID = "editing.indentation"; // !!! NOI18N

    /** hashtable mapping MIME type to engine (String, IndentEngine) */
    private static java.util.HashMap map = new java.util.HashMap (7);

    public HelpCtx getHelpCtx() {
        return new HelpCtx(HELP_ID);
    }
    
    /** Indents the current line. Should not effect any other
    * lines.
    * @param doc the document to work on
    * @param offset the offset of a character on the line
    * @return new offset of the original character
    */
    public abstract int indentLine (Document doc, int offset);

    /** Inserts new line at given position and indents the new line with
    * spaces.
    *
    * @param doc the document to work on
    * @param offset the offset of a character on the line
    * @return new offset to place cursor to
    */
    public abstract int indentNewLine (Document doc, int offset);

    /** Creates writer that formats text that is inserted into it.
    * The writer should not modify the document but use the 
    * provided writer to write to. Usually the underlaying writer
    * will modify the document itself and optionally it can remember
    * the current position in document. That is why the newly created
    * writer should do no buffering.
    * <P>
    * The provided document and offset are only informational,
    * should not be modified but only used to find correct indentation
    * strategy.
    *
    * @param doc document 
    * @param offset position to begin inserts at
    * @param writer writer to write to
    * @return new writer that will format written text and pass it
    *   into the writer
    */
    public abstract Writer createWriter (Document doc, int offset, Writer writer);

    /** Allow subclasses to decide whether they are suitable
     * for the given mime-type or not.
     * @param mime mime-type string
     * @return true if this engine is suitable for the given mime-type.
     */
    protected boolean acceptMimeType(String mime) {
        return false;
    }

    /**
     * @deprecated IndentEngine now is a ServiceType
     */
    
    public synchronized static void register (String mime, IndentEngine eng) {
        map.put (mime, eng);
    }
        
    /** Returns enumeration of all registered indentation engines.
     * @return enumeration of IndentEngine
     */
    public static Enumeration indentEngines() {
        return Collections.enumeration(Lookup.getDefault().lookup(new Lookup.Template(IndentEngine.class)).allInstances());
    }

    /** Finds engine associated with given mime type.
    * If no engine is associated returns default one.
    */
    public synchronized static IndentEngine find (String mime) {
        Enumeration en = indentEngines();
        while (en.hasMoreElements()) {
            IndentEngine eng = (IndentEngine)en.nextElement();
            if (eng.acceptMimeType(mime)) {
                return eng;
            }
        }

        IndentEngine eng = (IndentEngine) map.get (mime);
        if (eng != null) {
            return eng;
        }

        return getDefault();
    }

    /** Finds engine associated with given document.
    * If no engine is associated returns default one.
    */
    public static IndentEngine find (Document doc) {
        Object o = doc.getProperty("indentEngine"); // NOI18N
        if (o instanceof IndentEngine) {
            return (IndentEngine)o;
        } else {
            o = doc.getProperty("mimeType"); // NOI18N
            String s = (o instanceof String) ? (String)o : "text/plain"; // NOI18N
            return find(s);
        }
    }

    private static IndentEngine INSTANCE = null;
    /** Returns a simple indentation engine that does no formatting. */
    public static synchronized IndentEngine getDefault () {
        if (INSTANCE == null) {
            INSTANCE = new Default();
        }
        return INSTANCE;
    }

    /** Default indentation engine.
    */
    private static final class Default extends IndentEngine {

        private static final long serialVersionUID = 4493180326470838469L;
        
        Default() {}
        
        public int indentLine (Document doc, int offset) {
            return offset;
        }

        public int indentNewLine (Document doc, int offset) {
            try {
                doc.insertString (offset, "\n", null); // NOI18N
            } catch (BadLocationException ex) {
                // ignore
            }
            return offset + 1;
        }

        public Writer createWriter (Document doc, int offset, Writer writer) {
            return writer;
        }

        protected boolean acceptMimeType (String mime) {
            return true;
        }

        public HelpCtx getHelpCtx () {
            return new HelpCtx(Default.class);
        }

    }
}