/***********************************************************************************************************************************
 * Copyright (c) 2000, 2004 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: IBM Corporation - initial API and implementation
 **********************************************************************************************************************************/
package net.sourceforge.phpeclipse.wiki.editor;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

import net.sourceforge.phpeclipse.wiki.editor.model.WikipediaSection;
import net.sourceforge.phpeclipse.wiki.editor.model.WikipediaText;

import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.jface.resource.ImageRegistry;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.ITextSelection;
import org.eclipse.jface.text.ITextViewer;
import org.eclipse.jface.text.Region;
import org.eclipse.jface.text.TextUtilities;
import org.eclipse.jface.text.contentassist.CompletionProposal;
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.jface.text.templates.DocumentTemplateContext;
import org.eclipse.jface.text.templates.Template;
import org.eclipse.jface.text.templates.TemplateContext;
import org.eclipse.jface.text.templates.TemplateContextType;
import org.eclipse.jface.text.templates.TemplateException;
import org.eclipse.jface.text.templates.TemplateProposal;
import org.eclipse.swt.graphics.Image;

public class WikiCompletionProcessor implements IContentAssistProcessor {

  private static final String TEMPLATE_ICON = "icons/template.gif";

//  private static final String PREPARATION_TEMPLATE_CTX = "net.sourceforge.phpeclipse.wiki.editor.preparation";

  private static final String INGREDIENTS_TEMPLATE_CTX = "net.sourceforge.phpeclipse.wiki.editor.templates";

  private static final class ProposalComparator implements Comparator {
    public int compare(Object o1, Object o2) {
      return ((TemplateProposal) o2).getRelevance() - ((TemplateProposal) o1).getRelevance();
    }
  }

  private static final Comparator fgProposalComparator = new ProposalComparator();

  private final WikiEditor fEditor;

  public WikiCompletionProcessor(WikiEditor editor) {
    fEditor = editor;
  }

  public ICompletionProposal[] computeCompletionProposals(ITextViewer viewer, int offset) {
    WikipediaSection section = fEditor.getSection();
    if (section == null)
      return null;

    ITextSelection selection = (ITextSelection) viewer.getSelectionProvider().getSelection();
    // adjust offset to start of normalized selection:
    if (selection.getOffset() != offset)
      offset = selection.getOffset();

    String prefix = getPrefix(viewer, offset);
    Region region = new Region(offset - prefix.length(), prefix.length() + selection.getLength());

    ICompletionProposal[] templateProposals = computeTemplateProposals(viewer, region, section, prefix);
//    ICompletionProposal[] ingredientProposals = computeIngredientsProposals(viewer, region, recipe, prefix);
//    ICompletionProposal[] titleProposals = computeTitleProposals(viewer, region, recipe, prefix);
    List result = new ArrayList();
//    result.addAll(Arrays.asList(ingredientProposals));
    result.addAll(Arrays.asList(templateProposals));
//    result.addAll(Arrays.asList(titleProposals));

    return (ICompletionProposal[]) result.toArray(new ICompletionProposal[result.size()]);
  }

  private ICompletionProposal[] computeTitleProposals(ITextViewer viewer, IRegion region, WikipediaText recipe, String prefix) {
    List props = new ArrayList(2);
    //		if (recipe.getIngredientsSection() == null)
    //			props.add(createTitleProposal("Zutaten:", region, viewer));
    //		if (recipe.getPreparationSection() == null)
    //			props.add(createTitleProposal("Zubereitung:", region, viewer));
    return (ICompletionProposal[]) props.toArray(new ICompletionProposal[props.size()]);
  }

  private CompletionProposal createTitleProposal(String name, IRegion region, ITextViewer viewer) {
    String lineDelimiter = TextUtilities.getDefaultLineDelimiter(viewer.getDocument());
    return new CompletionProposal(name + lineDelimiter, region.getOffset(), region.getLength(), region.getOffset() + name.length()
        + lineDelimiter.length(), null, name, null, null);
  }

  private ICompletionProposal[] computeIngredientsProposals(ITextViewer viewer, IRegion region, WikipediaText recipe, String prefix) {
    return new ICompletionProposal[0];
    //		Step[] steps= recipe.getSteps();
    //		if (steps == null || steps.length == 0)
    //			return new ICompletionProposal[0];
    //		
    //		int offset= region.getOffset();
    //		Step first= steps[0];
    //		if (offset < first.getOffset())
    //			return new ICompletionProposal[0];
    //		
    //		Ingredient[] ingredients= recipe.getIngredients();
    //		if (ingredients == null)
    //			return new ICompletionProposal[0];
    //		
    //		prefix= prefix.toLowerCase();
    //		
    //		ArrayList proposals= new ArrayList();
    //		for (int i= 0; i < ingredients.length; i++) {
    //			String ingredient= ingredients[i].getName();
    //			if (ingredient.toLowerCase().startsWith(prefix))
    //				proposals.add(new CompletionProposal(ingredient, offset, region.getLength(), ingredient.length()));
    //		}
    //		return (ICompletionProposal[]) proposals.toArray(new ICompletionProposal[proposals.size()]);
  }

  private TemplateContextType getContextType(WikipediaSection section, int offset) {
//    if (recipe.getPreparationSection() != null && recipe.getPreparationSection().getOffset() < offset)
//      return WikiEditorPlugin.getDefault().getContextTypeRegistry().getContextType(PREPARATION_TEMPLATE_CTX);
//    else
      return WikiEditorPlugin.getDefault().getContextTypeRegistry().getContextType(INGREDIENTS_TEMPLATE_CTX);
  }

  /**
   * Creates a concrete template context for the given region in the document. This involves finding out which context fType is valid
   * at the given location, and then creating a context of this fType. The default implementation returns a
   * <code>DocumentTemplateContext</code> for the context fType at the given location.
   * 
   * @param viewer
   *          the viewer for which the context is created
   * @param region
   *          the region into <code>document</code> for which the context is created
   * @return a template context that can handle template insertion at the given location, or <code>null</code>
   */
  private TemplateContext createContext(ITextViewer viewer, IRegion region, WikipediaSection recipe) {
    TemplateContextType contextType = getContextType(recipe, region.getOffset());
    if (contextType != null) {
      IDocument document = viewer.getDocument();
      return new DocumentTemplateContext(contextType, document, region.getOffset(), region.getLength());
    }
    return null;
  }

  private ICompletionProposal[] computeTemplateProposals(ITextViewer viewer, IRegion region, WikipediaSection recipe, String prefix) {
    TemplateContext context = createContext(viewer, region, recipe);
    if (context == null)
      return new ICompletionProposal[0];

    ITextSelection selection = (ITextSelection) viewer.getSelectionProvider().getSelection();
    context.setVariable("selection", selection.getText()); // name of the selection variables {line, word}_selection

    String id = context.getContextType().getId();
    Template[] templates = WikiEditorPlugin.getDefault().getTemplateStore().getTemplates(id);

    List matches = new ArrayList();
    for (int i = 0; i < templates.length; i++) {
      Template template = templates[i];
      try {
        context.getContextType().validate(template.getPattern());
      } catch (TemplateException e) {
        continue;
      }
      int relevance = getRelevance(template, prefix);
      if (relevance > 0) {
        matches.add(new TemplateProposal(template, context, region, getImage(template), relevance));
      }
    }

    Collections.sort(matches, fgProposalComparator);

    return (ICompletionProposal[]) matches.toArray(new ICompletionProposal[matches.size()]);
  }

  /**
   * Returns the relevance of a template given a prefix. The default implementation returns a number greater than zero if the
   * template name starts with the prefix, and zero otherwise.
   * 
   * @param template
   *          the template to compute the relevance for
   * @param prefix
   *          the prefix after which content assist was requested
   * @return the relevance of <code>template</code>
   * @see #getPrefix(ITextViewer, int)
   */
  private int getRelevance(Template template, String prefix) {
    if (template.getName().startsWith(prefix))
      return 90;
    return 0;
  }

  private String getPrefix(ITextViewer viewer, int offset) {
    int i = offset;
    IDocument document = viewer.getDocument();
    if (i > document.getLength())
      return "";

    try {
      while (i > 0) {
        char ch = document.getChar(i - 1);
        if (!Character.isLetterOrDigit(ch))
          break;
        i--;
      }

      return document.get(i, offset - i);
    } catch (BadLocationException e) {
      return "";
    }
  }

  /**
   * Always return the default image.
   */
  private Image getImage(Template template) {
    ImageRegistry registry = WikiEditorPlugin.getDefault().getImageRegistry();
    Image image = registry.get(TEMPLATE_ICON);
    if (image == null) {
      ImageDescriptor desc = WikiEditorPlugin.imageDescriptorFromPlugin("net.sourceforge.phpeclipse.wiki.editor", TEMPLATE_ICON);
      registry.put(TEMPLATE_ICON, desc);
      image = registry.get(TEMPLATE_ICON);
    }
    return image;
  }

  public IContextInformation[] computeContextInformation(ITextViewer viewer, int offset) {
    return null;
  }

  public char[] getCompletionProposalAutoActivationCharacters() {
    return null;
  }

  public char[] getContextInformationAutoActivationCharacters() {
    return null;
  }

  public String getErrorMessage() {
    return null;
  }

  public IContextInformationValidator getContextInformationValidator() {
    return null;
  }
}