package org.drools.eclipse.editors.completion;



import java.util.Collections;

import java.util.Iterator;

import java.util.List;



import org.eclipse.jface.text.BadLocationException;

import org.eclipse.jface.text.IDocument;

import org.eclipse.jface.text.ITextViewer;

import org.eclipse.jface.text.contentassist.ICompletionProposal;

import org.eclipse.jface.text.contentassist.IContentAssistProcessor;

import org.eclipse.jface.text.contentassist.IContextInformation;

import org.eclipse.jface.text.contentassist.IContextInformationValidator;

import org.eclipse.ui.IEditorPart;



/**

 *

 * @author <a href="mailto:kris_verlaenen@hotmail.com">Kris Verlaenen</a>

 */

public abstract class AbstractCompletionProcessor implements IContentAssistProcessor {



    private IEditorPart editor;



    public AbstractCompletionProcessor(IEditorPart editor) {

    	this.editor = editor;

    }



    protected IEditorPart getEditor() {

    	return editor;

    }



	public ICompletionProposal[] computeCompletionProposals(ITextViewer viewer, int documentOffset) {

    	List proposals = getCompletionProposals(viewer, documentOffset);

    	if (proposals == null) {

    		return new ICompletionProposal[0];

    	}

        Collections.sort(proposals, new RuleCompletionProposal.RuleCompletionProposalComparator());

        return (ICompletionProposal[]) proposals.toArray(new ICompletionProposal[proposals.size()]);

	}



	/**

	 * Returns a list of RuleCompletionProposals.

	 *

	 * @param viewer

	 * @param documentOffset

	 * @return

	 */

	protected abstract List getCompletionProposals(ITextViewer viewer, int documentOffset);



    /**

     *  Filter out the proposals whose content does not start with the given prefix.

     */

    protected static void filterProposalsOnPrefix(String prefix, List props) {

    	if ( prefix != null && prefix.trim().length() > 0 ) {

    		Iterator iterator = props.iterator();

            String prefixLc = prefix.toLowerCase();

    		while ( iterator.hasNext() ) {

                ICompletionProposal item = (ICompletionProposal) iterator.next();

                String content = item.getDisplayString().toLowerCase();

                if ( !content.toLowerCase().startsWith( prefixLc ) ) {

                    iterator.remove();

                }

    		}

    	}

    }



    /**

     * Read some text from behind the cursor position.

     * This provides context to both filter what is shown based

     * on what the user has typed in, and also to provide more information for the

     * list of suggestions based on context.

     */

    protected String readBackwards(int documentOffset, IDocument doc) throws BadLocationException {

        int startPart = doc.getPartition(documentOffset).getOffset();

        String prefix = doc.get(startPart, documentOffset - startPart);

        return prefix;

    }



	/*

	 * @see IContentAssistProcessor

	 */

	public char[] getCompletionProposalAutoActivationCharacters() {

		return null;

	}



	/*

	 * @see IContentAssistProcessor

	 */

	public char[] getContextInformationAutoActivationCharacters() {

		return null;

	}



	/*

	 * @see IContentAssistProcessor

	 */

	public IContextInformationValidator getContextInformationValidator() {

		return null;

	}



	/*

	 * @see IContentAssistProcessor

	 */

	public IContextInformation[] computeContextInformation(ITextViewer viewer, int documentOffset) {

		return null;

	}



	/*

	 * @see IContentAssistProcessor

	 */

	public String getErrorMessage() {

		return null;

	}

}