scim-spec/scim-spec-schema/src/main/java/edu/psu/swe/scim/spec/extension/ScimExtensionRegistry.java

package edu.psu.swe.scim.spec.extension;

import java.util.HashMap;
import java.util.Map;

import edu.psu.swe.scim.spec.annotation.ScimExtensionType;
import edu.psu.swe.scim.spec.exception.InvalidExtensionException;
import edu.psu.swe.scim.spec.resources.ScimExtension;
import edu.psu.swe.scim.spec.resources.ScimResource;
import lombok.extern.slf4j.Slf4j;

@Slf4j
public final class ScimExtensionRegistry {
    
  private static final ScimExtensionRegistry INSTANCE = new ScimExtensionRegistry();
  
  private Map<Class<? extends ScimResource>, Map<String, Class<? extends ScimExtension>>> registry;
  
  private ScimExtensionRegistry() {
    registry = new HashMap<Class<? extends ScimResource>, Map<String, Class<? extends ScimExtension>>>();
  }
  
  public Class<? extends ScimExtension> getExtensionClass(Class<? extends ScimResource> resourceClass, String urn) {
    Class<? extends ScimExtension> extensionClass = null;
    if(registry.containsKey(resourceClass)) {
      Map<String, Class<? extends ScimExtension>> resourceMap = registry.get(resourceClass);
      if(resourceMap.containsKey(urn)) {
        extensionClass = resourceMap.get(urn);
      }
    }
    return extensionClass;
  }
  
  public static ScimExtensionRegistry getInstance() {
    return INSTANCE;
  }
  
  public void registerExtension(Class<? extends ScimResource> resourceClass, Class<? extends ScimExtension> extensionClass) {
    ScimExtensionType[] se = extensionClass.getAnnotationsByType(ScimExtensionType.class);

    if (se.length == 0 || se.length > 1) {
      throw new InvalidExtensionException("Registered extensions must have an ScimExtensionType annotation");
    }
    
    String urn = se[0].id();
    
    log.debug("Registering extension for URN: " + urn);
    log.debug("    (associated resource class: " + resourceClass.getSimpleName() + ")");
    log.debug("    (associated extension class: " + extensionClass.getSimpleName() + ")");
    
    Map<String, Class<? extends ScimExtension>> resourceMap = registry.get(resourceClass);
    if(resourceMap == null) {
      resourceMap = new HashMap<>();
      registry.put(resourceClass, resourceMap);
    }
    
    if(!resourceMap.containsKey(urn)) {
      resourceMap.put(urn, extensionClass);
    }
  }

}