/*******************************************************************************
 * Copyright (c) 2000, 2016 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.text.contentassist;

import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Point;

import org.eclipse.jface.text.IDocument;


/**
 * The interface of completion proposals generated by content assist processors. A completion
 * proposal contains information used to present the proposed completion to the user, to insert the
 * completion should the user select it, and to present context information for the chosen
 * completion once it has been inserted.
 * <p>
 * In order to provide backward compatibility for clients of <code>ICompletionProposal</code>,
 * extension interfaces are used to provide a means of evolution. The following extension interfaces
 * exist:
 * </p>
 * <ul>
 * <li>{@link org.eclipse.jface.text.contentassist.ICompletionProposalExtension} since version 2.0
 * introducing the following functions:
 * <ul>
 * <li>handling of trigger characters other than ENTER</li>
 * <li>completion proposal validation for a given offset</li>
 * <li>context information can be freely positioned</li>
 * </ul>
 * </li>
 * <li>{@link org.eclipse.jface.text.contentassist.ICompletionProposalExtension2} since version 2.1
 * introducing the following functions:
 * <ul>
 * <li>handling of trigger characters with modifiers</li>
 * <li>visual indication for selection of a proposal</li>
 * </ul>
 * </li>
 * <li>{@link org.eclipse.jface.text.contentassist.ICompletionProposalExtension3} since version 3.0
 * introducing the following functions:
 * <ul>
 * <li>provision of a custom information control creator</li>
 * <li>provide a custom completion text and offset for prefix completion</li>
 * </ul>
 * </li>
 * <li>{@link org.eclipse.jface.text.contentassist.ICompletionProposalExtension4} since version 3.1
 * introducing the following functions:
 * <ul>
 * <li>specify whether a proposal is automatically insertable</li>
 * </ul>
 * </li>
 * <li>{@link org.eclipse.jface.text.contentassist.ICompletionProposalExtension5} since version 3.2
 * introducing the following function:
 * <ul>
 * <li>Allow background computation of the additional info</li>
 * </ul>
 * </li>
 * <li>{@link org.eclipse.jface.text.contentassist.ICompletionProposalExtension6} since version 3.4
 * introducing the following function:
 * <ul>
 * <li>Allow styled ranges in the display string.</li>
 * </ul>
 * </li>
 * <li>{@link org.eclipse.jface.text.contentassist.ICompletionProposalExtension7} since version 3.11
 * introducing the following function:
 * <ul>
 * <li>Emphasize ranges in the styled display string of the proposal that match the token at the
 * current caret offset.</li>
 * </ul>
 * </li>
 * </ul>
 *
 * <p>
 * This interface can be implemented by clients. By default, clients use
 * {@link org.eclipse.jface.text.contentassist.CompletionProposal} as the standard implementer of
 * this interface.
 * </p>
 *
 * @see IContentAssistProcessor
 */
public interface ICompletionProposal {

	/**
	 * Inserts the proposed completion into the given document.
	 *
	 * @param document the document into which to insert the proposed completion
	 */
	void apply(IDocument document);

	/**
	 * Returns the new selection after the proposal has been applied to
	 * the given document in absolute document coordinates. If it returns
	 * <code>null</code>, no new selection is set.
	 *
	 * A document change can trigger other document changes, which have
	 * to be taken into account when calculating the new selection. Typically,
	 * this would be done by installing a document listener or by using a
	 * document position during {@link #apply(IDocument)}.
	 *
	 * @param document the document into which the proposed completion has been inserted
	 * @return the new selection in absolute document coordinates
	 */
	Point getSelection(IDocument document);

	/**
	 * Returns optional additional information about the proposal. The additional information will
	 * be presented to assist the user in deciding if the selected proposal is the desired choice.
	 * <p>
	 * If {@link ICompletionProposalExtension5} is implemented, this method should not be called any
	 * longer. This method may be deprecated in a future release.
	 * </p>
	 *
	 * @return the additional information or <code>null</code>
	 */
	String getAdditionalProposalInfo();

	/**
	 * Returns the string to be displayed in the list of completion proposals.
	 *
	 * @return the string to be displayed
	 *
	 * @see ICompletionProposalExtension6#getStyledDisplayString()
	 * @see ICompletionProposalExtension7#getStyledDisplayString(IDocument, int, BoldStylerProvider)
	 */
	String getDisplayString();

	/**
	 * Returns the image to be displayed in the list of completion proposals.
	 * The image would typically be shown to the left of the display string.
	 *
	 * @return the image to be shown or <code>null</code> if no image is desired
	 */
	Image getImage();

	/**
	 * Returns optional context information associated with this proposal.
	 * The context information will automatically be shown if the proposal
	 * has been applied.
	 *
	 * @return the context information for this proposal or <code>null</code>
	 */
	IContextInformation getContextInformation();
}
