/*
 * Copyright 2008 the original author or authors.
 * 
 * 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.wamblee.system.graph.component;

import org.wamblee.system.core.ProvidedInterface;
import org.wamblee.system.core.SystemAssemblyException;
import org.wamblee.system.graph.DefaultEdge;
import org.wamblee.system.graph.Edge;
import org.wamblee.system.graph.Node;
import org.wamblee.system.graph.Visitor;

/**
 * Visitor that creates links between required and provided interfaces as
 * described by the edges in the graph.
 * 
 * Specically it links together (1) required and provided interfaces of internal component 
 * of a container and (2) the providers of externally required interfaces and internal required
 * interfaces. 
 * 
 * @author Erik Brakkee
 * 
 */
public class LinkVisitor implements Visitor {

    @Override
    public void visitEdge(Edge aEdge) {
        Node from = aEdge.getFrom();
        Node to = aEdge.getTo();
        if (from instanceof RequiredInterfaceNode) {
            RequiredInterfaceNode required = (RequiredInterfaceNode) from;
            if (to instanceof ProvidedInterfaceNode) {

                ProvidedInterfaceNode provided = (ProvidedInterfaceNode) to;
                required.getRequired().setProvider(provided.getProvided());

            } else if (to instanceof ExternalRequiredInterfaceNode) {
                ExternalRequiredInterfaceNode external = (ExternalRequiredInterfaceNode) to;
                ProvidedInterface provider = external.getRequired()
                        .getProvider();
                if (provider == null && !required.getRequired().isOptional()) {
                    throw new SystemAssemblyException("Mandatory interface '"
                            + from + "' is not provided.");
                }
                if ( provider != null ) { 
                    required.getRequired().setProvider(provider);
                }
            }
        } else if (from instanceof ProvidedInterfaceNode) {
            // Provided interfaces can only be published after the system has
            // started.
        }
    }

    @Override
    public void visitNode(Node aNode) {
        // Empty.
    }

}