package nl.tudelft.goal.ut2004.visualizer.gui.widgets;
   
   import java.awt.Component;
   import java.awt.event.ActionListener;
   import java.awt.event.KeyAdapter;
   import java.awt.event.KeyEvent;
   import java.util.List;
   
   import javax.swing.ComboBoxEditor;
  import javax.swing.JComboBox;
  import javax.swing.JTextField;
  import javax.swing.SwingUtilities;
  
  class SuggestionFieldEditor implements ComboBoxEditor {
  
  	private final JTextField textField;
  	private final SuggestionModel model;
  	private int nextSuggestionIndex = 0;
  	private final JComboBox combobox;
  
  	public SuggestionFieldEditor(JComboBox combobox, SuggestionModel model) {
  		this.textField = new JTextField();
  		this.model = model;
  		this.combobox = combobox;
  		this.textField.addKeyListener(new Listener());
  	}
  
  	private class Listener extends KeyAdapter {
  
  		@Override
  		public void keyPressed(final KeyEvent e) {
  			// Invoke later to update after the key event has actually been done.
  			SwingUtilities.invokeLater(new Runnable() {
  				@Override
  				public void run() {
  					updateSuggestion(isAutoCompletionRequest(e));
  				}
  			});
  		}
  	}
  
  	private boolean isAutoCompletionRequest(KeyEvent e) {
  		return e.isControlDown() && e.getKeyChar() == ' ';
  	}
  
  	private void updateSuggestion(boolean complete) {
  
  		// Hide popup, it will change.
  		combobox.hidePopup();
  
  		String query = getUnselectedText();
  
  		// Get suggestion from provider, should take care to
  		// update model to only show new suggestions.
  		List<String> suggestions = model.sugestFor(query);
  
  		// Only complete on request if we have results
  		if (suggestions.size() > 0
  		// And only if the user isn't deleting text
  		// Or wants a completion.
  				&& (isQueryEdited(query) || complete)) {
  			nextSuggestionIndex %= suggestions.size();
  			String suggestion = suggestions.get(nextSuggestionIndex++);
  
  			updateCompletion(complete, query, suggestion);
  
  		} else {
  			// Reset counter if we did not provide a suggestion.
  			nextSuggestionIndex = 0;
  		}
  
  		// Show popup box with trimmed list of suggestions
  		// as promised by the provider.
  		combobox.showPopup();
  	}
  
  	private String previousQuery = null;
  
  	/**
  	 * Checks if the user tries to change the suggestion.
  	 * 
  	 * A suggestion is changed iff query.startsWith(previousQuery) && query.lenght() > previousQuery.lenght().
  	 */
  	private boolean isQueryEdited(String query) {
  		boolean edited = previousQuery != null
  				&& query.length() > previousQuery.length()
  				&& query.startsWith(previousQuery);
  
  		previousQuery = query;
  		return edited;
  	}
  
  	/**
  	 * Updates the text field with the suggestion. Ensures that if the suggestion is a completion it gets appended and highlighted. Unless the user requested
  	 * the suggestion to be shown.
  	 * 
  	 * @param showSuggestion
  	 *            iff the user requested to see the selection.
  	 * @param query
 	 *            the query made by the user.
 	 * @param suggestion
 	 *            the suggestion that matches the query.
 	 */
 	private void updateCompletion(boolean showSuggestion, String query,
 			String suggestion) {
 
 		// We complete either because we were asked to
 		if (showSuggestion
 		// Or because we have a sensible completion
 				|| (suggestion.startsWith(query) && query.length() > 0)) {
 
 			textField.setText(suggestion);
 
 			// If we completed because we have a completion mark it
 			// as such.
 			if (suggestion.startsWith(query)) {
 				textField.select(query.length(), suggestion.length());
 			}
 			// Otherwise make it a suggestion.
 			else {
 				textField.select(suggestion.indexOf(query) + query.length(),
 						suggestion.length());
 			}
 		}
 	}
 
 	/**
 	 * Returns the section of the text that the user provided as input.
 	 * 
 	 * This method assumes the user has accepted the completion when it is no longer highlighted until the last character.
 	 * 
 	 * @return the original text the user put in.
 	 */
 	private String getUnselectedText() {
 
 		String selected = textField.getSelectedText();
 		String fullText = textField.getText();
 
 		// Does the selection match that of a completion?
 		if (selected != null && fullText.endsWith(selected)) {
 			return fullText.substring(0, fullText.indexOf(selected));
 		}
 
 		// User accepted suggestion.
 		return fullText;
 	}
 
 	@Override
 	public Component getEditorComponent() {
 		return textField;
 	}
 
 	@Override
 	public Object getItem() {
 		return model.getItem(textField.getText());
 	}
 
 	@Override
 	public void removeActionListener(ActionListener l) {
 		textField.removeActionListener(l);
 	}
 
 	@Override
 	public void addActionListener(ActionListener l) {
 		textField.addActionListener(l);
 
 	}
 
 	@Override
 	public void selectAll() {
 		textField.selectAll();
 	}
 
 	@Override
 	public void setItem(Object item) {
 		if (item != null) {
 			textField.setText(item.toString());
 		} else {
 			textField.setText("");
 		}
 	}
 
 }