package org.codehaus.plexus.component.composition;
   
   /*
    * Copyright 2001-2006 Codehaus Foundation.
    *
    * 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.
   */
  
  import java.util.List;
  
  import org.codehaus.plexus.PlexusConstants;
  import org.codehaus.plexus.component.repository.ComponentDescriptor;
  import org.codehaus.plexus.component.repository.ComponentRequirement;
  import org.codehaus.plexus.component.repository.ComponentRequirementList;
  import org.codehaus.plexus.util.StringUtils;
  import org.codehaus.plexus.util.dag.CycleDetectedException;
  import org.codehaus.plexus.util.dag.DAG;
  
  /**
   * @author Jason van Zyl
   * @author <a href="mailto:michal.maczka@dimatics.com">Michal Maczka</a>
   */
  public class DefaultCompositionResolver implements CompositionResolver {
      private DAG dag = new DAG();
  
      public void addComponentDescriptor(ComponentDescriptor<?> componentDescriptor)
              throws CycleDetectedInComponentGraphException {
          String key = getDAGKey(componentDescriptor.getRole(), componentDescriptor.getRoleHint());
  
          List<ComponentRequirement> requirements = componentDescriptor.getRequirements();
  
          for (ComponentRequirement requirement : requirements) {
              try {
                  if (requirement instanceof ComponentRequirementList) {
                      for (String hint : ((ComponentRequirementList) requirement).getRoleHints()) {
                          dag.addEdge(key, getDAGKey(requirement.getRole(), hint));
                      }
                  } else {
                      dag.addEdge(key, getDAGKey(requirement.getRole(), requirement.getRoleHint()));
                  }
              } catch (CycleDetectedException e) {
                  throw new CycleDetectedInComponentGraphException("Cyclic requirement detected", e);
              }
          }
      }
  
      /**
       * @see org.codehaus.plexus.component.composition.CompositionResolver#getRequirements(String,String)
       */
      public List getRequirements(String role, String roleHint) {
          return dag.getChildLabels(getDAGKey(role, roleHint));
      }
  
      /**
       * @see org.codehaus.plexus.component.composition.CompositionResolver#findRequirements(String,String)
       */
      public List findRequirements(String role, String roleHint) {
          return dag.getParentLabels(getDAGKey(role, roleHint));
      }
  
      private String getDAGKey(String role, String roleHint) {
          return role
                  + SEPARATOR_CHAR
                  + (StringUtils.isNotEmpty(roleHint) ? roleHint : PlexusConstants.PLEXUS_DEFAULT_HINT);
      }
  }