/*
 * Copyright (c) 2012, the Dart project authors.
 * 
 * Licensed under the Eclipse Public License v1.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 * 
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.dart.tools.ui.text.dart;

import org.eclipse.core.runtime.Assert;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.DocumentEvent;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.ITextViewer;
import org.eclipse.jface.text.Position;
import org.eclipse.jface.text.contentassist.ICompletionProposal;
import org.eclipse.jface.text.contentassist.ICompletionProposalExtension;
import org.eclipse.jface.text.contentassist.ICompletionProposalExtension2;
import org.eclipse.jface.text.contentassist.IContextInformation;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;

/**
 * An enhanced implementation of the <code>ICompletionProposal</code> interface implementing all the
 * extension interfaces. It uses a position to track its replacement offset and length. The position
 * must be set up externally.
 */
public class PositionBasedCompletionProposal implements ICompletionProposal,
    ICompletionProposalExtension, ICompletionProposalExtension2 {

  /** The string to be displayed in the completion proposal popup */
  private String fDisplayString;
  /** The replacement string */
  private String fReplacementString;
  /** The replacement position. */
  private Position fReplacementPosition;
  /** The cursor position after this proposal has been applied */
  private int fCursorPosition;
  /** The image to be displayed in the completion proposal popup */
  private Image fImage;
  /** The context information of this proposal */
  private IContextInformation fContextInformation;
  /** The additional info of this proposal */
  private String fAdditionalProposalInfo;
  /** The trigger characters */
  private char[] fTriggerCharacters;

  /**
   * Creates a new completion proposal based on the provided information. The replacement string is
   * considered being the display string too. All remaining fields are set to <code>null</code>.
   * 
   * @param replacementString the actual string to be inserted into the document
   * @param replacementPosition the position of the text to be replaced
   * @param cursorPosition the position of the cursor following the insert relative to
   *          replacementOffset
   */
  public PositionBasedCompletionProposal(String replacementString, Position replacementPosition,
      int cursorPosition) {
    this(replacementString, replacementPosition, cursorPosition, null, null, null, null, null);
  }

  /**
   * Creates a new completion proposal. All fields are initialized based on the provided
   * information.
   * 
   * @param replacementString the actual string to be inserted into the document
   * @param replacementPosition the position of the text to be replaced
   * @param cursorPosition the position of the cursor following the insert relative to
   *          replacementOffset
   * @param image the image to display for this proposal
   * @param displayString the string to be displayed for the proposal
   * @param contextInformation the context information associated with this proposal
   * @param additionalProposalInfo the additional information associated with this proposal
   * @param triggers the trigger characters
   */
  public PositionBasedCompletionProposal(String replacementString, Position replacementPosition,
      int cursorPosition, Image image, String displayString,
      IContextInformation contextInformation, String additionalProposalInfo, char[] triggers) {
    Assert.isNotNull(replacementString);
    Assert.isTrue(replacementPosition != null);

    fReplacementString = replacementString;
    fReplacementPosition = replacementPosition;
    fCursorPosition = cursorPosition;
    fImage = image;
    fDisplayString = displayString;
    fContextInformation = contextInformation;
    fAdditionalProposalInfo = additionalProposalInfo;
    fTriggerCharacters = triggers;
  }

  @Override
  public void apply(IDocument document) {
    try {
      document.replace(
          fReplacementPosition.getOffset(),
          fReplacementPosition.getLength(),
          fReplacementString);
    } catch (BadLocationException x) {
      // ignore
    }
  }

  @Override
  public void apply(IDocument document, char trigger, int offset) {
    // not called any more
  }

  @Override
  public void apply(ITextViewer viewer, char trigger, int stateMask, int offset) {
    apply(viewer.getDocument());
  }

  @Override
  public String getAdditionalProposalInfo() {
    return fAdditionalProposalInfo;
  }

  @Override
  public IContextInformation getContextInformation() {
    return fContextInformation;
  }

  @Override
  public int getContextInformationPosition() {
    return fReplacementPosition.getOffset();
  }

  @Override
  public String getDisplayString() {
    if (fDisplayString != null) {
      return fDisplayString;
    }
    return fReplacementString;
  }

  @Override
  public Image getImage() {
    return fImage;
  }

  @Override
  public Point getSelection(IDocument document) {
    return new Point(fReplacementPosition.getOffset() + fCursorPosition, 0);
  }

  @Override
  public char[] getTriggerCharacters() {
    return fTriggerCharacters;
  }

  @Override
  public boolean isValidFor(IDocument document, int offset) {
    // not called any more
    return false;
  }

  @Override
  public void selected(ITextViewer viewer, boolean smartToggle) {
  }

  @Override
  public void unselected(ITextViewer viewer) {
  }

  @Override
  public boolean validate(IDocument document, int offset, DocumentEvent event) {
    try {
      String content = document.get(
          fReplacementPosition.getOffset(),
          offset - fReplacementPosition.getOffset());
      if (fReplacementString.startsWith(content)) {
        return true;
      }
    } catch (BadLocationException e) {
      // ignore concurrently modified document
    }
    return false;
  }
}