/*******************************************************************************
 * Copyright 2017 Graz University of Technology
 * EAAF-Core Components has been developed in a cooperation between EGIZ,  
 * A-SIT+, A-SIT, and Graz University of Technology.
 *
 * Licensed under the EUPL, Version 1.2 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * https://joinup.ec.europa.eu/news/understanding-eupl-v12
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 *******************************************************************************/
/*******************************************************************************
 *******************************************************************************/
/*******************************************************************************
 *******************************************************************************/
package at.gv.egiz.eaaf.modules.pvp2.impl.metadata;

import java.io.IOException;
import java.security.cert.CertificateException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Timer;

import javax.xml.namespace.QName;

import org.apache.commons.lang3.StringUtils;
import org.opensaml.saml2.metadata.EntitiesDescriptor;
import org.opensaml.saml2.metadata.EntityDescriptor;
import org.opensaml.saml2.metadata.RoleDescriptor;
import org.opensaml.saml2.metadata.provider.ChainingMetadataProvider;
import org.opensaml.saml2.metadata.provider.HTTPMetadataProvider;
import org.opensaml.saml2.metadata.provider.MetadataFilter;
import org.opensaml.saml2.metadata.provider.MetadataProvider;
import org.opensaml.saml2.metadata.provider.MetadataProviderException;
import org.opensaml.saml2.metadata.provider.ObservableMetadataProvider;
import org.opensaml.xml.XMLObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import at.gv.egiz.eaaf.core.api.IDestroyableObject;
import at.gv.egiz.eaaf.core.api.IGarbageCollectorProcessing;
import at.gv.egiz.eaaf.core.exceptions.EAAFConfigurationException;
import at.gv.egiz.eaaf.modules.pvp2.api.metadata.IPVPMetadataProvider;
import at.gv.egiz.eaaf.modules.pvp2.api.metadata.IRefreshableMetadataProvider;

public abstract class AbstractChainingMetadataProvider extends SimpleMetadataProvider
	implements ObservableMetadataProvider, IGarbageCollectorProcessing, 
	IRefreshableMetadataProvider, IDestroyableObject, IPVPMetadataProvider {

	private static final Logger log = LoggerFactory.getLogger(AbstractChainingMetadataProvider.class);
	
	private MetadataProvider internalProvider = null;
	private static Object mutex = new Object();	
	private Timer timer = null; 
	
		
	public AbstractChainingMetadataProvider() {
		internalProvider = new ChainingMetadataProvider();	
		
	}
	
	public final Timer getTimer() {
		return this.timer;
		
	}
	
	/* (non-Javadoc)
	 * @see at.gv.egovernment.moa.id.config.auth.IGarbageCollectorProcessing#runGarbageCollector()
	 */
	@Override
	public void runGarbageCollector() {
		synchronized (mutex) {			
			/**add new Metadataprovider or remove Metadataprovider which are not in use any more.**/
			try {
				log.trace("Check consistence of PVP2X metadata");	
				addAndRemoveMetadataProvider(); 
					
			} catch (EAAFConfigurationException e) {
				log.error("Access to MOA-ID configuration FAILED.", e);
					
			}
		}
		
	}
			
	public void fullyDestroy() {
		internalDestroy();
			
	}
	
	@Override
	public synchronized boolean refreshMetadataProvider(String entityID) {
		try {			
			//check if metadata provider is already loaded
			try {
				if (internalProvider.getEntityDescriptor(entityID) != null)
					return true;
				
			} catch (MetadataProviderException e) {}
			
			
			//reload metadata provider 
			String metadataURL = getMetadataURL(entityID);
			if (StringUtils.isNotEmpty(metadataURL)) {
				Map<String, HTTPMetadataProvider> actuallyLoadedProviders = getAllActuallyLoadedProviders();

				// check if MetadataProvider is actually loaded
				if (actuallyLoadedProviders.containsKey(metadataURL)) {
					actuallyLoadedProviders.get(metadataURL).refresh();						
					log.info("SAML2 metadata for service provider: " 
							+ entityID + " is refreshed.");
					return true;
						
				} else {
					//load new Metadata Provider
					if (timer == null)
						timer = new Timer(true);

					ChainingMetadataProvider chainProvider = (ChainingMetadataProvider) internalProvider;											
					chainProvider.addMetadataProvider(createNewMetadataProvider(entityID));
					
					emitChangeEvent();						
					log.info("SAML2 metadata for service provider: " 
							+ entityID + " is added.");
					return true;
						
				}
															
			} else
				log.debug("Can not refresh SAML2 metadata: NO SAML2 metadata URL for SP with Id: " + entityID);
																	
		} catch (MetadataProviderException e) {
			log.warn("Refresh SAML2 metadata for service provider: " 
					+ entityID + " FAILED.", e);
			
		} catch (IOException e) {
			log.warn("Refresh SAML2 metadata for service provider: " 
					+ entityID + " FAILED.", e);
			
		} catch (EAAFConfigurationException e) {			
			log.warn("Refresh SAML2 metadata for service provider: " 
					+ entityID + " FAILED.", e);
			
		} catch (CertificateException e) {
			log.warn("Refresh SAML2 metadata for service provider: " 
					+ entityID + " FAILED.", e);
			
		}
		
		return false;
		
	}
			
	public void internalDestroy() {
		if (internalProvider != null && internalProvider instanceof ChainingMetadataProvider) {
			log.info("Destrorying PVP-Authentication MetaDataProvider.");
			ChainingMetadataProvider chainProvider = (ChainingMetadataProvider) internalProvider;				
			
			List<MetadataProvider> providers = chainProvider.getProviders();
			for (MetadataProvider provider : providers) {
				if (provider instanceof HTTPMetadataProvider) {
					HTTPMetadataProvider httpprovider = (HTTPMetadataProvider) provider;
					log.debug("Destroy HTTPMetadataProvider +" + httpprovider.getMetadataURI());
					httpprovider.destroy();
					
				} else {
					log.warn("MetadataProvider can not be destroyed.");
				}
			}
				
			internalProvider = new ChainingMetadataProvider();
			
			if (timer != null)
				timer.cancel();
			
		} else {
			log.warn("ReInitalize MOAMetaDataProvider is not possible! MOA-ID Instance has to be restarted manualy");
		}
	}
	
	
	/* (non-Javadoc)
	 * @see at.gv.egovernment.moa.id.protocols.pvp2x.metadata.IEAAFMetadataProvider#requireValidMetadata()
	 */
	@Override
	public boolean requireValidMetadata() {
		return internalProvider.requireValidMetadata();
	}

	/* (non-Javadoc)
	 * @see at.gv.egovernment.moa.id.protocols.pvp2x.metadata.IEAAFMetadataProvider#setRequireValidMetadata(boolean)
	 */
	@Override
	public void setRequireValidMetadata(boolean requireValidMetadata) {
		internalProvider.setRequireValidMetadata(requireValidMetadata);
	}

	/* (non-Javadoc)
	 * @see at.gv.egovernment.moa.id.protocols.pvp2x.metadata.IEAAFMetadataProvider#getMetadataFilter()
	 */
	@Override
	public MetadataFilter getMetadataFilter() {
		return internalProvider.getMetadataFilter();
	}

	/* (non-Javadoc)
	 * @see at.gv.egovernment.moa.id.protocols.pvp2x.metadata.IEAAFMetadataProvider#setMetadataFilter(org.opensaml.saml2.metadata.provider.MetadataFilter)
	 */
	@Override
	public void setMetadataFilter(MetadataFilter newFilter)
			throws MetadataProviderException {
		internalProvider.setMetadataFilter(newFilter);
	}

	/* (non-Javadoc)
	 * @see at.gv.egovernment.moa.id.protocols.pvp2x.metadata.IEAAFMetadataProvider#getMetadata()
	 */
	@Override
	public XMLObject getMetadata() throws MetadataProviderException {
		return internalProvider.getMetadata();
	}

	/* (non-Javadoc)
	 * @see at.gv.egovernment.moa.id.protocols.pvp2x.metadata.IEAAFMetadataProvider#getEntitiesDescriptor(java.lang.String)
	 */
	@Override
	public EntitiesDescriptor getEntitiesDescriptor(String entitiesID)
			throws MetadataProviderException {
		EntitiesDescriptor entitiesDesc = null;
		try {
			entitiesDesc = internalProvider.getEntitiesDescriptor(entitiesID);
		
			if (entitiesDesc == null) {
				log.debug("Can not find PVP metadata for entityID: " + entitiesID 
						+ " Start refreshing process ...");
				if (refreshMetadataProvider(entitiesID))
					return internalProvider.getEntitiesDescriptor(entitiesID);
									
			}			
			
		} catch (MetadataProviderException e) {
			log.debug("Can not find PVP metadata for entityID: " + entitiesID 
					+ " Start refreshing process ...");
			if (refreshMetadataProvider(entitiesID))
				return internalProvider.getEntitiesDescriptor(entitiesID);
			
		}	
		
		return entitiesDesc;
	}

	/* (non-Javadoc)
	 * @see at.gv.egovernment.moa.id.protocols.pvp2x.metadata.IEAAFMetadataProvider#getEntityDescriptor(java.lang.String)
	 */
	@Override
	public EntityDescriptor getEntityDescriptor(String entityID)
			throws MetadataProviderException {
		EntityDescriptor entityDesc = null;
		try {
			entityDesc = internalProvider.getEntityDescriptor(entityID);
			if (entityDesc == null) {
				log.debug("Can not find PVP metadata for entityID: " + entityID 
						+ " Start refreshing process ...");
				if (refreshMetadataProvider(entityID))
					return internalProvider.getEntityDescriptor(entityID);
									
			}
			
		} catch (MetadataProviderException e) {
			log.debug("Can not find PVP metadata for entityID: " + entityID 
					+ " Start refreshing process ...");
			if (refreshMetadataProvider(entityID))
				return internalProvider.getEntityDescriptor(entityID);
			
		}
		
//		if (entityDesc != null)
//			lastAccess.put(entityID, new Date());
		
		return entityDesc;
	}

	/* (non-Javadoc)
	 * @see at.gv.egovernment.moa.id.protocols.pvp2x.metadata.IEAAFMetadataProvider#getRole(java.lang.String, javax.xml.namespace.QName)
	 */
	@Override
	public List<RoleDescriptor> getRole(String entityID, QName roleName)
			throws MetadataProviderException {		
		List<RoleDescriptor> result = internalProvider.getRole(entityID, roleName);
		
//		if (result != null)
//			lastAccess.put(entityID, new Date());
		
		return result; 
	}

	/* (non-Javadoc)
	 * @see at.gv.egovernment.moa.id.protocols.pvp2x.metadata.IEAAFMetadataProvider#getRole(java.lang.String, javax.xml.namespace.QName, java.lang.String)
	 */
	@Override
	public RoleDescriptor getRole(String entityID, QName roleName,
			String supportedProtocol) throws MetadataProviderException {
		RoleDescriptor result = internalProvider.getRole(entityID, roleName, supportedProtocol);
		
//		if (result != null)
//			lastAccess.put(entityID, new Date());
		
		return result; 
	}

	/* (non-Javadoc)
	 * @see org.opensaml.saml2.metadata.provider.ObservableMetadataProvider#getObservers()
	 */
	@Override
	public List<Observer> getObservers() {
		return ((ChainingMetadataProvider) internalProvider).getObservers();
	}

	
	/**
	 * Get the URL to metadata for a specific entityID
	 * 
	 * @param entityId
	 * @return
	 * @throws EAAFConfigurationException 
	 */
	protected abstract String getMetadataURL(String entityId) throws EAAFConfigurationException;
	
	/**
	 * Creates a new implementation specific SAML2 metadata provider
	 * 
	 * @param entityId
	 * @return
	 * @throws EAAFConfigurationException
	 * @throws IOException 
	 * @throws CertificateException 
	 * @throws ConfigurationException 
	 */
	protected abstract MetadataProvider createNewMetadataProvider(String entityId) throws EAAFConfigurationException, IOException, CertificateException;
	
	/**
	 * Get a List of metadata URLs for all SAML2 SPs from configuration 
	 * 
	 * @throws EAAFConfigurationException
	 */
	protected abstract List<String> getAllMetadataURLsFromConfiguration() throws EAAFConfigurationException;
	
	
	protected void emitChangeEvent() {
		if ((getObservers() == null) || (getObservers().size() == 0)) {
			return;
		}

		List<Observer> tempObserverList = new ArrayList<Observer>(getObservers());
		for (ObservableMetadataProvider.Observer observer : tempObserverList)
			if (observer != null)
				observer.onEvent(this);
	}
	
	private Map<String, HTTPMetadataProvider> getAllActuallyLoadedProviders() {
		Map<String, HTTPMetadataProvider> loadedproviders = new HashMap<String, HTTPMetadataProvider>();
		ChainingMetadataProvider chainProvider = (ChainingMetadataProvider) internalProvider;
		
		//make a Map of all actually loaded HTTPMetadataProvider
		List<MetadataProvider> providers = chainProvider.getProviders();
		for (MetadataProvider provider : providers) {
			if (provider instanceof HTTPMetadataProvider) {
				HTTPMetadataProvider httpprovider = (HTTPMetadataProvider) provider;
				loadedproviders.put(httpprovider.getMetadataURI(), httpprovider);

			}
		}
		
		return loadedproviders;		
	}
	
	private void addAndRemoveMetadataProvider() throws EAAFConfigurationException {
		if (internalProvider != null && internalProvider instanceof ChainingMetadataProvider) {
			log.info("Reload MOAMetaDataProvider.");
			
			/*OpenSAML ChainingMetadataProvider can not remove a MetadataProvider (UnsupportedOperationException)
			 *The ChainingMetadataProvider use internal a unmodifiableList to hold all registrated MetadataProviders.*/ 
			Map<String, MetadataProvider> providersinuse = new HashMap<String, MetadataProvider>();
			ChainingMetadataProvider chainProvider = (ChainingMetadataProvider) internalProvider;
			
			//get all actually loaded metadata providers
			Map<String, HTTPMetadataProvider> loadedproviders = getAllActuallyLoadedProviders();
						
			/* TODO: maybe add metadata provider destroy after timeout.
			 *       But could be a problem if one Metadataprovider load an EntitiesDescriptor 
			 *       with more the multiple EntityDescriptors. If one of this EntityDesciptors 
			 *       are expired the full EntitiesDescriptor is removed. 
			 *       
			 *       Timeout requires a better solution in this case! 
			 */
									
			//load all SAML2 SPs form configuration and 
			//compare actually loaded Providers with configured SAML2 SPs			
			List<String> allMetadataURLs = getAllMetadataURLsFromConfiguration();
			
			if (allMetadataURLs != null) {
				Iterator<String> metadataURLInterator = allMetadataURLs.iterator();
				while (metadataURLInterator.hasNext()) {
					String metadataurl = metadataURLInterator.next();			
					try {
						if (StringUtils.isNotEmpty(metadataurl)) {						
							if (loadedproviders.containsKey(metadataurl)) {									
								//	SAML2 SP is actually loaded, to nothing
								providersinuse.put(metadataurl, loadedproviders.get(metadataurl));
								loadedproviders.remove(metadataurl);
													
							}
						}
					} catch (Throwable e) {
						log.error(
						"Failed to add Metadata (unhandled reason: " + e.getMessage(), e);
										
					}	
				}
			}
			
			//remove all actually loaded MetadataProviders with are not in ConfigurationDB any more
			Collection<HTTPMetadataProvider> notusedproviders = loadedproviders.values();
			for (HTTPMetadataProvider provider : notusedproviders) {
				String metadataurl = provider.getMetadataURI();				
				try {					
					provider.destroy();
					
					/*OpenSAML ChainingMetadataProvider can not remove a MetadataProvider (UnsupportedOperationException)
					 *The ChainingMetadataProvider use internal a unmodifiableList to hold all registrated MetadataProviders.*/
					//chainProvider.removeMetadataProvider(provider);					
					log.info("Remove not used MetadataProvider with MetadataURL " + metadataurl);
					
				} catch (Throwable e) {
					log.error("HTTPMetadataProvider with URL " + metadataurl 
							+ " can not be removed from the list of actually loaded Providers.", e);
					
				}
				
			}
			
			try {
				chainProvider.setProviders(new ArrayList<MetadataProvider>(providersinuse.values()));				
				emitChangeEvent();
								
			} catch (MetadataProviderException e) {
				log.warn("ReInitalize AbstractMetaDataProvider is not possible! Service has to be restarted manualy", e);
														
			}
			
		} else
			log.warn("ReInitalize AbstractMetaDataProvider is not possible! Service has to be restarted manualy");
		
	}
}