/*******************************************************************************
 * Copyright (c) 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.phpdt.core;

import net.sourceforge.phpdt.core.compiler.IProblem;

/**
 * Abstract base class for a completion requestor which is passed completion
 * proposals as they are generated in response to a code assist request.
 * <p>
 * This class is intended to be subclassed by clients.
 * </p>
 * <p>
 * The code assist engine normally invokes methods on completion requestors in
 * the following sequence:
 * 
 * <pre>
 *  requestor.beginReporting();
 *  requestor.accept(proposal_1);
 *  requestor.accept(proposal_2);
 *  ...
 *  requestor.endReporting();
 * </pre>
 * 
 * If, however, the engine is unable to offer completion proposals for whatever
 * reason, <code>completionFailure</code> is called with a problem object
 * describing why completions were unavailable. In this case, the sequence of
 * calls is:
 * 
 * <pre>
 * requestor.beginReporting();
 * requestor.completionFailure(problem);
 * requestor.endReporting();
 * </pre>
 * 
 * In either case, the bracketing <code>beginReporting</code>
 * <code>endReporting</code>
 * calls are always made.
 * </p>
 * <p>
 * The class was introduced in 3.0 as a more evolvable replacement for the
 * <code>ICompletionRequestor</code> interface.
 * </p>
 * 
 * @see ICodeAssist
 * @since 3.0
 */
public abstract class CompletionRequestor {

	/**
	 * The set of CompletionProposal kinds that this requestor ignores;
	 * <code>0</code> means the set is empty. 1 << completionProposalKind
	 */
	private int ignoreSet = 0;

	/**
	 * Creates a new completion requestor. The requestor is interested in all
	 * kinds of completion proposals; none will be ignored.
	 */
	public CompletionRequestor() {
		// do nothing
	}

	/**
	 * Returns whether the given kind of completion proposal is ignored.
	 * 
	 * @param completionProposalKind
	 *            one of the kind constants declared on
	 *            <code>CompletionProposal</code>
	 * @return <code>true</code> if the given kind of completion proposal is
	 *         ignored by this requestor, and <code>false</code> if it is of
	 *         interest
	 * @see #setIgnored(int, boolean)
	 * @see CompletionProposal#getKind()
	 */
	public final boolean isIgnored(int completionProposalKind) {
		if (completionProposalKind < CompletionProposal.ANONYMOUS_CLASS_DECLARATION
				|| completionProposalKind > CompletionProposal.VARIABLE_DECLARATION) {
			throw new IllegalArgumentException();
		}
		return 0 != (this.ignoreSet & (1 << completionProposalKind));
	}

	/**
	 * Sets whether the given kind of completion proposal is ignored.
	 * 
	 * @param completionProposalKind
	 *            one of the kind constants declared on
	 *            <code>CompletionProposal</code>
	 * @param ignore
	 *            <code>true</code> if the given kind of completion proposal
	 *            is ignored by this requestor, and <code>false</code> if it
	 *            is of interest
	 * @see #isIgnored(int)
	 * @see CompletionProposal#getKind()
	 */
	public final void setIgnored(int completionProposalKind, boolean ignore) {
		if (completionProposalKind < CompletionProposal.ANONYMOUS_CLASS_DECLARATION
				|| completionProposalKind > CompletionProposal.VARIABLE_DECLARATION) {
			throw new IllegalArgumentException();
		}
		if (ignore) {
			this.ignoreSet |= (1 << completionProposalKind);
		} else {
			this.ignoreSet &= ~(1 << completionProposalKind);
		}
	}

	/**
	 * Pro forma notification sent before reporting a batch of completion
	 * proposals.
	 * <p>
	 * The default implementation of this method does nothing. Clients may
	 * override.
	 * </p>
	 */
	public void beginReporting() {
		// do nothing
	}

	/**
	 * Pro forma notification sent after reporting a batch of completion
	 * proposals.
	 * <p>
	 * The default implementation of this method does nothing. Clients may
	 * override.
	 * </p>
	 */
	public void endReporting() {
		// do nothing
	}

	/**
	 * Notification of failure to produce any completions. The problem object
	 * explains what prevented completing.
	 * <p>
	 * The default implementation of this method does nothing. Clients may
	 * override to receive this kind of notice.
	 * </p>
	 * 
	 * @param problem
	 *            the problem object
	 */
	public void completionFailure(IProblem problem) {
		// default behavior is to ignore
	}

	/**
	 * Proposes a completion. Has no effect if the kind of proposal is being
	 * ignored by this requestor. Callers should consider checking
	 * {@link #isIgnored(int)} before avoid creating proposal objects that would
	 * only be ignored.
	 * <p>
	 * Similarly, implementers should check
	 * {@link #isIgnored(int) isIgnored(proposal.getKind())} and ignore
	 * proposals that have been declared as uninteresting. The proposal object
	 * passed in only valid for the duration of this call; implementors must not
	 * hang on to these objects.
	 * 
	 * @param proposal
	 *            the completion proposal
	 * @exception IllegalArgumentException
	 *                if the proposal is null
	 */
	public abstract void accept(CompletionProposal proposal);
}