package org.naftulin.configmgr.parsers;

 import java.net.URL;

 import java.util.Collections;

 import java.util.List;

 import org.naftulin.configmgr.ConfigurationManagementEntry;

 import org.naftulin.configmgr.ConfigurationManagementEntryImpl;

 import org.naftulin.configmgr.ConfigurationManagerException;

 import org.naftulin.configmgr.ConfigurationType;

 import org.naftulin.configmgr.content.NameValuePairImpl;

 /**

  * Invokes {@link ExternalRecordAdapter external record adapter} with parameters specified in configuration record.

  * Used to connect external configurations to be managed by configuration managment engine.

  * 

  * @author Henry Naftulin

  * @since 1.0

  */

 public class ExternalConfigurationParserImpl implements ConfigEntryParser {

         private static final long serialVersionUID = 1L;

         private List<NameValuePairImpl> nameValuePairs;

         private String externalRecordAdapterClass;

         private ExternalRecordAdapter adapter;

         /**

          * Sets the full class name for the {@link ExternalRecordAdapter ExternalRecordAdapter} class.

          * @param externalRecordAdapterClass the full class name for the {@link ExternalRecordAdapter ExternalRecordAdapter} class.

          */

         public synchronized void setExternalRecordAdapterClass(final String externalRecordAdapterClass) {

                 this.externalRecordAdapterClass = externalRecordAdapterClass;

         }

         /**

          * Invokes {@link ExternalRecordAdapter external record adapter} with parameters specified in configuration record.

          * If the adaptor is not created yet, create it and call load method, otherwise, calls reload.

          * @param key the key for the external configuration.

          * @param fileUrl ignored.

          * @return the configuraion managment entry corresponding to the external configuration.

          * @exception ConfigurationManagementEntry if external configuration cannot be instatiated or has problems 

          *                 loading or reloading.

          */

         public synchronized ConfigurationManagementEntry getConfigurationManagementEntry(final String key, final URL fileUrl) throws ConfigurationManagerException {

                 ConfigurationManagementEntry entry = null;

                 Object configuratonContent = null;

                 //if adapter is not created yet for this configuration, create it and call load method,

                 //otherwise call reload method.

                 if (adapter == null) {

                         if (key == null) { 

                                 throw new ConfigurationManagerException("key is null, please provide the key in you master configuraton file for all the external cofigurations");

                         }

                         if (externalRecordAdapterClass == null) {

                                 throw new ConfigurationManagerException("adater is null, please provide the custom created adaptor class (implemeting " + ExternalRecordAdapter.class.getName() +" interface) in you master configuraton file for external cofiguraton with key =" + key);

                         }

                         Class<ExternalRecordAdapter> adapterClass;

                         try {                                

                                 adapterClass = (Class<ExternalRecordAdapter>) Class.forName(externalRecordAdapterClass);

                                 adapter = adapterClass.newInstance();                                

                                 configuratonContent = adapter.load(getNameValuePairs());

                         } catch (ClassNotFoundException e) {

                                 throw new ConfigurationManagerException("adater implemented by class " + externalRecordAdapterClass +" was not found in the classpath, please provide the custom created adaptor class (implemeting " + ExternalRecordAdapter.class.getName() +" interface) in you master configuraton file for external cofiguraton with key =" + key, e);        

                         } catch (InstantiationException e) {

                                 throw new ConfigurationManagerException("adater implemented by class " + externalRecordAdapterClass +" could not be instatiated. Please provide the custom created adaptor class (implemeting " + ExternalRecordAdapter.class.getName() +" interface) with default, no argument constructor, in you master configuraton file for external cofiguraton with key =" + key, e);

                         } catch (IllegalAccessException e) {

                                 throw new ConfigurationManagerException("adater implemented by class " + externalRecordAdapterClass +" could not be instatiated for security reasons. Please provide the custom created adaptor class (implemeting " + ExternalRecordAdapter.class.getName() +" interface) with default, in you master configuraton file for external cofiguraton with key =" + key + ". You might also want to check the security policy that affects instatiation of this file.", e);

                         }                        

                 } else {

                         configuratonContent = adapter.reload(getNameValuePairs());                        

                 }

                 entry = new ConfigurationManagementEntryImpl(key, "External Configuration inplemented by class " + externalRecordAdapterClass + " with the following info: " + adapter.getInfo(nameValuePairs), configuratonContent, this, ConfigurationType.EXTERNAL);

                 return entry;

         }

         /**

          * Returns the named value list parsed from the master configuration.

          * @return the named value list parsed from the master configuration.

          */

         public List<NameValuePairImpl> getNameValuePairs() {

                 return Collections.unmodifiableList(nameValuePairs);

         }

         /**

          * Sets the named value list

          * @param nameValuePairs the named value pair list.

          */

         public void setNameValuePairs(final List<NameValuePairImpl> nameValuePairs) {

                 this.nameValuePairs = nameValuePairs;

         }

 }