package org.springframework.roo.addon.jpa.addon;

import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.ReferenceCardinality;
import org.apache.felix.scr.annotations.ReferencePolicy;
import org.apache.felix.scr.annotations.ReferenceStrategy;
import org.springframework.roo.addon.jpa.addon.identifier.Identifier;
import org.springframework.roo.addon.jpa.addon.identifier.IdentifierService;
import org.springframework.roo.classpath.itd.AbstractItdMetadataProvider;
import org.springframework.roo.classpath.persistence.PersistenceMemberLocator;
import org.springframework.roo.model.JavaType;

/**
 * Abstract class to make {@link IdentifierService} collection available to
 * subclasses.
 * 
 * @author Alan Stewart
 * @author Ben Alex
 * @since 1.1
 */
@Component(componentAbstract = true)
@Reference(name = "identifierService", strategy = ReferenceStrategy.EVENT,
    policy = ReferencePolicy.DYNAMIC, referenceInterface = IdentifierService.class,
    cardinality = ReferenceCardinality.OPTIONAL_MULTIPLE)
public abstract class AbstractIdentifierServiceAwareMetadataProvider extends
    AbstractItdMetadataProvider {

  private final Set<IdentifierService> identifierServices = new HashSet<IdentifierService>();

  protected void bindIdentifierService(final IdentifierService identifierService) {
    synchronized (identifierServices) {
      identifierServices.add(identifierService);
    }
  }

  /**
   * Locates any {@link Identifier} that is applicable to this
   * {@link JavaType}.
   * <p>
   * See {@link IdentifierService#getIdentifiers(JavaType)} for the full
   * contract of what this method returns. Note this method simply returns the
   * first non-null result of invoking
   * {@link IdentifierService#getIdentifiers(JavaType)}. It returns null if no
   * provider is authoritative.
   * 
   * @param javaType the entity or PK identifier class for which column
   *            information is desired (required)
   * @return the applicable identifiers, or null if no registered
   *         {@link IdentifierService} was authoritative for this type TODO
   *         made obsolete by {@link PersistenceMemberLocator}?
   */
  protected List<Identifier> getIdentifiersForType(final JavaType javaType) {
    List<Identifier> identifierServiceResult = null;
    synchronized (identifierServices) {
      for (final IdentifierService service : identifierServices) {
        identifierServiceResult = service.getIdentifiers(javaType);
        if (identifierServiceResult != null) {
          // Someone has authoritatively indicated the fields for this
          // PK, so we don't need to continue looping
          break;
        }
      }
    }
    return identifierServiceResult;
  }

  protected void unbindIdentifierService(final IdentifierService identifierService) {
    synchronized (identifierServices) {
      identifierServices.remove(identifierService);
    }
  }
}