/*
 * Copyright (c) OSGi Alliance (2011, 2013). All Rights Reserved.
 * 
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * 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 org.osgi.service.resolver;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import org.osgi.resource.Requirement;

Indicates failure to resolve a set of requirements.
 If a resolution failure is caused by a missing mandatory dependency a resolver may include any requirements it has considered in the resolution exception. Clients may access this set of dependencies via the getUnresolvedRequirements() method. 

Resolver implementations may extend this class to provide extra state
information about the reason for the resolution failure.
Author:
$Id: 2bcc0ac8ebfaf169dd301493303d23ce613ac8b9 $/**
 * Indicates failure to resolve a set of requirements.
 * 
 * <p>
 * If a resolution failure is caused by a missing mandatory dependency a
 * resolver may include any requirements it has considered in the resolution
 * exception. Clients may access this set of dependencies via the
 * {@link #getUnresolvedRequirements()} method.
 * 
 * <p>
 * Resolver implementations may extend this class to provide extra state
 * information about the reason for the resolution failure.
 * 
 * @author $Id: 2bcc0ac8ebfaf169dd301493303d23ce613ac8b9 $
 */
public class ResolutionException extends Exception {

	private static final long				serialVersionUID	= 1L;

	private final transient Collection<Requirement>	unresolvedRequirements;

	
Create a ResolutionException with the specified message, cause and unresolved requirements. 
Params:
message – The message.
cause – The cause of this exception.
unresolvedRequirements – The unresolved mandatory requirements from mandatory resources or null if no unresolved requirements information is provided./**
	 * Create a {@code ResolutionException} with the specified message, cause
	 * and unresolved requirements.
	 * 
	 * @param message The message.
	 * @param cause The cause of this exception.
	 * @param unresolvedRequirements The unresolved mandatory requirements from
	 *        mandatory resources or {@code null} if no unresolved requirements
	 *        information is provided.
	 */
	public ResolutionException(String message, Throwable cause, Collection<Requirement> unresolvedRequirements) {
		super(message, cause);
		if ((unresolvedRequirements == null) || unresolvedRequirements.isEmpty()) {
			this.unresolvedRequirements = null;
		} else {
			this.unresolvedRequirements = Collections.unmodifiableCollection(new ArrayList<Requirement>(unresolvedRequirements));
		}
	}

	
Create a ResolutionException with the specified message. 
Params:
message – The message./**
	 * Create a {@code ResolutionException} with the specified message.
	 * 
	 * @param message The message.
	 */
	public ResolutionException(String message) {
		super(message);
		unresolvedRequirements = null;
	}

	
Create a ResolutionException with the specified cause. 
Params:
cause – The cause of this exception./**
	 * Create a {@code ResolutionException} with the specified cause.
	 * 
	 * @param cause The cause of this exception.
	 */
	public ResolutionException(Throwable cause) {
		super(cause);
		unresolvedRequirements = null;
	}

	@SuppressWarnings("unchecked")
	private static Collection<Requirement> emptyCollection() {
		return Collections.EMPTY_LIST;
	}

	
Return the unresolved requirements, if any, for this exception.

The unresolved requirements are provided for informational purposes and
the specific set of unresolved requirements that are provided after a
resolve failure is not defined.
Returns:
A collection of the unresolved requirements for this exception.
        The returned collection may be empty if no unresolved
        requirements information is available./**
	 * Return the unresolved requirements, if any, for this exception.
	 * 
	 * <p>
	 * The unresolved requirements are provided for informational purposes and
	 * the specific set of unresolved requirements that are provided after a
	 * resolve failure is not defined.
	 * 
	 * @return A collection of the unresolved requirements for this exception.
	 *         The returned collection may be empty if no unresolved
	 *         requirements information is available.
	 */
	public Collection<Requirement> getUnresolvedRequirements() {
		return (unresolvedRequirements != null) ? unresolvedRequirements : emptyCollection();
	}
}