command.hippieCompletion.description = Context insensitive completion

command.hippieCompletion.name = Hippie Completion

      <command

            name="%command.hippieCompletion.name"

            description="%command.hippieCompletion.description"

            categoryId="org.eclipse.ui.category.edit"

            id="org.eclipse.ui.edit.text.hippieCompletion">

      </command>

      <!-- TODO Keybinding -->

      <keyBinding

            commandId="org.eclipse.ui.edit.text.hippieCompletion"

            contextId="org.eclipse.ui.textEditorScope"

            keySequence="Alt+/"

            keyConfigurationId="org.eclipse.ui.defaultAcceleratorConfiguration">

       </keyBinding>

		action = new HippieCompleteAction(EditorMessages.getResourceBundle(), "Editor.HippieCompletion.", this); //$NON-NLS-1$

		// TODO action.setHelpContextId(IAbstractTextEditorHelpContextIds.HIPPIE_COMPLETION_ACTION);

		action.setActionDefinitionId(ITextEditorActionDefinitionIds.HIPPIE_COMPLETION);

		setAction(ITextEditorActionConstants.HIPPIE_COMPLETION, action);

        markAsContentDependentAction(ITextEditorActionConstants.HIPPIE_COMPLETION, true);

	/** 

	 * Name of the action for emacs style hippie completion. 

	 * Value: <code>"HIPPIE_COMPLETION"</code>

	 * @since 3.1

	 */

	static final String HIPPIE_COMPLETION= "HIPPIE_COMPLETION"; //$NON-NLS-1$

	/**

	 * Action definition ID of the edit -> text complete action

	 * Value: <code>"org.eclipse.ui.edit.text.hippieCompletion"</code>).

	 * @since 3.1

	 */

	public static final String HIPPIE_COMPLETION= "org.eclipse.ui.edit.text.hippieCompletion"; //$NON-NLS-1$

/*******************************************************************************

 * Copyright (c) 2000, 2005 IBM Corporation and others.

 * All rights reserved. This program and the accompanying materials 

 * are made available under the terms of the Common Public License v1.0

 * which accompanies this distribution, and is available at

 * http://www.eclipse.org/legal/cpl-v10.html

 * 

 * Contributors:

 *     Genady Beryozkin, me@genady.org - initial API and implementation

 *     IBM Corporation - fixes and cleaning

 *******************************************************************************/

package org.eclipse.ui.texteditor;

import java.util.ArrayList;

import java.util.HashSet;

import java.util.Iterator;

import java.util.LinkedList;

import java.util.ResourceBundle;

import org.eclipse.jface.text.BadLocationException;

import org.eclipse.jface.text.DocumentEvent;

import org.eclipse.jface.text.FindReplaceDocumentAdapter;

import org.eclipse.jface.text.IDocument;

import org.eclipse.jface.text.IDocumentListener;

import org.eclipse.jface.text.IRegion;

import org.eclipse.jface.text.ITextSelection;

import org.eclipse.jface.viewers.ISelectionChangedListener;

import org.eclipse.jface.viewers.ISelectionProvider;

import org.eclipse.jface.viewers.SelectionChangedEvent;

import org.eclipse.ui.IEditorInput;

import org.eclipse.ui.IEditorPart;

import org.eclipse.ui.IEditorReference;

/**

 * This class implements the emacs style completion action.

 * Completion action is a stateful action, as the user may invoke

 * it several times in a row in order to scroll the possible completions.

 * 

 * 

 * TODO: Work on backward suggestions

 * TODO: Sort by editor type

 * TODO: Provide history option

 * 

 * @author Genady Beryozkin, me@genady.org

 */

public class HippieCompleteAction extends TextEditorAction {

    /**

     * The document that will be manipulated

     */

	private IDocument fDocument;

    /**

     * The selection provider associated with the text editor. 

     */

    private ISelectionProvider fSelectionProvider;

	/** 

	 * The completion state that is used to continue the iteration over suggestions

	 */

	private CompletionState fLastCompletion= null;

    /**

     * Modification lock that will prevent invalidation of the completion state when the

     * completion action modifies the document

     */

	private boolean fModifyingLock= false;

	SelectionChangeListener fSelectionListener;

	DocumentChangeListener fContentListener;

	/* (non-Javadoc)

	 * @see org.eclipse.ui.texteditor.TextEditorAction#setEditor(org.eclipse.ui.texteditor.ITextEditor)

	 */

	public void setEditor(ITextEditor editor) {

		super.setEditor(editor);

		fSelectionListener= new SelectionChangeListener();

		fContentListener= new DocumentChangeListener();

	}

    /**

     * This class accompanies the {@link HippieCompleteAction#checkValidPosition()} method

     * to invalidate completion state when the selection changes.

     */

	class SelectionChangeListener implements ISelectionChangedListener {

		public void selectionChanged(SelectionChangedEvent event) {

			if (!fModifyingLock) {

				fLastCompletion= null;

			}

		}

	}

    /**

     * Invalidate the completion state when the document contents changes not

     * as the result of the completion action itself. This is needed since

     * the {@link HippieCompleteAction#update()} method is only called when the

     * {@link HippieCompleteAction#fModifyingLock} is already false.

     */

	class DocumentChangeListener implements IDocumentListener {

		public void documentAboutToBeChanged(DocumentEvent event) {

		}

		public void documentChanged(DocumentEvent event) {

			if (!fModifyingLock) {

				fLastCompletion= null;

			}

		}

	}	

	/**

	 * Perform the next completion.

	 */

	private void completeNext() {

		// we don't wish to receive events on our own changes

		fModifyingLock= true;

		try {

			fDocument.replace(fLastCompletion.startOffset, fLastCompletion.length, 

					fLastCompletion.suggestions[fLastCompletion.nextSuggestion]);

		} catch (BadLocationException e) {

			// we should never get here

			throw new IllegalStateException(e.toString());

		}

		// advance the suggestion state

		fLastCompletion.advance();

		// move the cursor to the insertion point

		((AbstractTextEditor) getTextEditor()).getSourceViewer().setSelectedRange(fLastCompletion.startOffset+fLastCompletion.length, 0);

		// allow changes

		fModifyingLock= false;

	}

	/**

	 * This class represents the state of the last completion process.

	 * Each time the user moves to a new position and calls this action

	 * an instance of this inner classs is created  and saved in

	 * {@link #fLastCompletion}.

	 */

	private static class CompletionState {

		/** The list of suggestions that was computed when the completion

		 * action was first invoked 

		 */

		final String[] suggestions;

		/** The caret position at which we insert the suggestions */

		final int startOffset;

		/** The length of the last suggestion string */

		int length;

		/** The index of next suggestion (index into the suggestion array) */

		int nextSuggestion;

		CompletionState(String[] suggestions, int startOffset) {

			this.suggestions= suggestions;

			this.startOffset= startOffset;

			length= 0;

			nextSuggestion= 0;

		}

		public void advance() {

			length= suggestions[nextSuggestion].length();

			nextSuggestion= (nextSuggestion + 1) % suggestions.length;	

		}

	}

	/**

	 * @param bundle the resource bundle

	 * @param prefix a prefix to be prepended to the various resource keys

	 *   (described in <code>ResourceAction</code> constructor), or 

	 *   <code>null</code> if none

	 * @param editor the text editor

	 */

	protected HippieCompleteAction(ResourceBundle bundle, String prefix, ITextEditor editor) {

		super(bundle, prefix, editor);

	}

	/* (non-Javadoc)

	 * @see org.eclipse.jface.action.Action#run()

	 */

	public void run() {

        checkValidPosition();

		if (fLastCompletion != null) 

		{

			completeNext();

			return;

		} 

		String prefix= getCurrentPrefix();

		if (prefix == null) {

			getTextEditor().getSite().getShell().getDisplay().beep();

			return;

		}

		String[] suggestions= getSuggestions(prefix);

		// if it is single empty suggestion

		if (suggestions.length == 1) {

			getTextEditor().getSite().getShell().getDisplay().beep();

			return;

		}

		fLastCompletion= new CompletionState(suggestions, 

				((ITextSelection) getTextEditor().getSelectionProvider().getSelection()).getOffset());

		completeNext();

	}

    /**

     * Invalidate the completion state if the cursor is not located at

     * the expected position.

     */

    private void checkValidPosition() {

        if (fLastCompletion != null) {

            if (fLastCompletion.startOffset + fLastCompletion.length != 

                ((ITextSelection)fSelectionProvider.getSelection()).getOffset()) {

                fLastCompletion= null;

            }

        }

    }

	/**

	 * Create the array of suggestions. It scan all open text editors

	 * and prefers suggestion from the currently open editor.

	 * It also addes the empty suggestion at the end.

	 * @param prefix the prefix to search for

	 * @return the list of all possible suggestions in the currently open editors

	 */

	public String[] getSuggestions(String prefix) {

		// Change the order of open editors, to make the active editor

		// to appear first.

		IEditorReference editorsArray[]= getTextEditor().getSite().getWorkbenchWindow().getActivePage().getEditorReferences();

		ArrayList editorsVector= new ArrayList();

		for (int i= 0; i < editorsArray.length; i++) {

			IEditorPart realEditor= editorsArray[i].getEditor(false);

			if (realEditor != null) {

				editorsVector.add(realEditor);

			}

		}

		editorsVector.remove(getTextEditor());

		editorsVector.add(0, getTextEditor());

		// collect the suggestions from all open text editors

		LinkedList suggestions= new LinkedList();

		for (int i= 0; i < editorsVector.size(); i++) {

			if (editorsVector.get(i) instanceof ITextEditor) {

				ITextEditor textEditor= (ITextEditor) editorsVector.get(i);

				IEditorInput input= textEditor.getEditorInput();

				IDocument doc= textEditor.getDocumentProvider().getDocument(input);

				try {

					suggestions.addAll(getForwardSuggestions(doc, prefix));

				} catch (BadLocationException e) {

                    // do nothing 

                    // TODO log the exception

				}

			}

		}

		makeUnique(suggestions);

		// add the empty suggestion

		suggestions.add(""); //$NON-NLS-1$

		return (String[])suggestions.toArray(new String[0]);

	}

	/**

	 * Remove duplicate suggestions (excluding the prefix), leaving the closest to list head. 

	 * @param suggestions a modifiable list of suggestions.

	 */

	private void makeUnique(LinkedList suggestions) {

		HashSet seenAlready= new HashSet();

		for (Iterator i= suggestions.iterator(); i.hasNext();) {

			String suggestion= (String) i.next();

			if (seenAlready.contains(suggestion)) {

				i.remove();

			} else {

				seenAlready.add(suggestion);

			}

		}

	}

	/**

	 * Copied from {@link FindReplaceDocumentAdapter}.

	 * 

	 * Converts a non-regex string to a pattern

	 * that can be used with the regex search engine.

	 * 

	 * @param string the non-regex pattern

	 * @return the string converted to a regex pattern

	 */

	private static String asRegPattern(String string) {

		StringBuffer out= new StringBuffer(string.length());

		boolean quoting= false;

		for (int i= 0, length= string.length(); i < length; i++) {

			char ch= string.charAt(i);

			if (ch == '\\') {

				if (quoting) {

					out.append("\\E"); //$NON-NLS-1$

					quoting= false;

				}

				out.append("\\\\"); //$NON-NLS-1$

				continue;								

			}

			if (!quoting) {

				out.append("\\Q"); //$NON-NLS-1$

				quoting= true;

			}

			out.append(ch);

		}

		if (quoting)

			out.append("\\E"); //$NON-NLS-1$

		return out.toString();

	}

	/**

	 * Return the list of completion suggestions the correspond to the provided

	 * prefix

	 * 

	 * @param document

	 * @param prefix

	 * @return an {@link ArrayList} of possible completions, excluding the common prefix

	 * @throws BadLocationException

	 */

	private static ArrayList getForwardSuggestions(IDocument document, String prefix) throws BadLocationException {

		ArrayList res= new ArrayList();

		FindReplaceDocumentAdapter searcher= new 

			FindReplaceDocumentAdapter(document);

		// search only at word boundaries 

		String searchPattern= "\\b" + asRegPattern(prefix); //$NON-NLS-1$

		IRegion reg= searcher.find(0, searchPattern, true, true, false, true);

		while (reg != null) {

			// try to complete to a word

			IRegion word= searcher.find(reg.getOffset(), "\\w+", true, true, false, true); //$NON-NLS-1$

			if (word.getLength() > reg.getLength() ) { // empty suggestion will be added later

				String found= document.get(word.getOffset(), word.getLength());

				res.add(found.substring(prefix.length()));

			}

			int nextPos= word.getOffset() + word.getLength();

			if (nextPos >= document.getLength() ) {

				break;

			}

			reg= searcher.find(nextPos, searchPattern, true, true, false, true);

		}

		return res;

	}

	/**

	 * Return the part of a word before the caret.

	 * If the caret is not at a middle/end of a word, 

	 * returns null.

	 * @return the prefix at the current cursor position that will be used in the search for possible completions

	 */

	private String getCurrentPrefix() {

		ITextSelection selection= (ITextSelection) getTextEditor().getSelectionProvider().getSelection();

		if (selection.getLength() > 0) {

			return null;

		}

		int pos= selection.getOffset();

        String docText= fDocument.get();

        int prevNonAlpha= pos;

        while (prevNonAlpha > 0 && 

        	    Character.isJavaIdentifierPart(docText.charAt(prevNonAlpha-1))) 

        {

        	prevNonAlpha--;

        }

        if (prevNonAlpha != pos) {

            return docText.substring(prevNonAlpha, pos);

        }

        return null;

	}

    /* (non-Javadoc)

     * @see org.eclipse.ui.texteditor.TextEditorAction#update()

     */

    public void update() {

        super.update();

        if (fDocument != null) {

            fDocument.removeDocumentListener(fContentListener);

        }

        if (fSelectionProvider != null) {

            fSelectionProvider.removeSelectionChangedListener(fSelectionListener);

        }

        ITextEditor editor= getTextEditor();

        IEditorInput input= editor.getEditorInput();

        fSelectionProvider= editor.getSelectionProvider(); 

        fSelectionProvider.addSelectionChangedListener(fSelectionListener);

        IDocument oldDocument = fDocument;

        fDocument= editor.getDocumentProvider().getDocument(input);

        fDocument.addDocumentListener(fContentListener);

        if (fDocument != oldDocument) {

            fLastCompletion = null; // invalidate completion state on editor reuse 

        }

    }

}