/**
 * 
 */
package org.gcube.accounting.persistence;

import java.io.File;
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import org.gcube.accounting.datamodel.UsageRecord;
import org.gcube.accounting.datamodel.implementations.ServiceUsageRecord;
import org.gcube.accounting.exception.InvalidValueException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * @author Luca Frosini (ISTI - CNR) http://www.lucafrosini.com/
 */
public abstract class Persistence {

	private static final Logger logger = LoggerFactory.getLogger(Persistence.class);
	
	private static final String ACCOUTING_FALLBACK_FILENAME = "accountingFallback.log";
	
	/**
	 * The singleton instance of persistence
	 */
	protected static Persistence persistence;
	protected static FallbackPersistence fallback;
	
	
	private static File file(File file) throws IllegalArgumentException {
		
		if (file.isDirectory())
			throw new IllegalArgumentException(file.getAbsolutePath() + " cannot be used in write mode because it's folder");

		//create folder structure it does not exist
		if (!file.getParentFile().exists())
			file.getParentFile().mkdirs();
		
		return file;
		
	}
	
	static {
		
		File file;
		/*
		try {
			ContainerContext containerContext = ProviderFactory.provider().containerContext();
			org.gcube.smartgears.persistence.Persistence smartgearPersistence = containerContext.persistence();
			file = smartgearPersistence.writefile(ACCOUTING_FALLBACK_FILENAME);
		} catch(Exception e){
			file =  file(new File(".", ACCOUTING_FALLBACK_FILENAME).getAbsolutePath());
		}
		*/
		
		file =  file(new File(".", ACCOUTING_FALLBACK_FILENAME));
		fallback = new FallbackPersistence(file);
		try {
			/*
			ServiceLoader<Persistence> serviceLoader = ServiceLoader.load(Persistence.class);
			for (Persistence foundPersistence : serviceLoader) {
				if(foundPersistence.getClass().isInstance(FallbackPersistence.class)){
					continue;
				}
				try {
					logger.debug(String.format("Testing %s", persistence.getClass().getSimpleName()));
					foundPersistence.prepareConnection();
					persistence = foundPersistence;
					break;
				} catch (Exception e) {
					logger.debug(String.format("%s not initialized correctly. It will not be used", persistence.getClass().getSimpleName()));
				}
			}
			if(persistence==null){
				persistence = fallback;
			}
			*/
			persistence = new CouchDBPersistence();
		} catch(Exception e){
			logger.error("Unable to instance {}. Using fallback as default", 
					CouchDBPersistence.class.getSimpleName());
			persistence = fallback;
		}
	}
	
	public static UsageRecord createTestRawUsageRecord(){
		UsageRecord usageRecord = new ServiceUsageRecord();
		try {
			usageRecord.setCreatorId("accounting");
			usageRecord.setConsumerId("accounting");
			
			usageRecord.setResourceScope("/gcube/devsec");
	
			Calendar creatingTime = new GregorianCalendar();
			//Calendar startTime = new GregorianCalendar();
			//Calendar endTime = new GregorianCalendar();
	
			usageRecord.setCreationTime(creatingTime);
			//usageRecord.setStartTime(startTime);
			//usageRecord.setEndTime(endTime);
			
			usageRecord.setResourceSpecificProperty("ConnectionTest", "Test");
			
		} catch (InvalidValueException e1) {
			
		}
		
		return usageRecord;
	}
	
	
	/**
	 * Pool for thread execution
	 */
	private ExecutorService pool;
	
	/**
	 * @return the singleton instance of persistence
	 * @throws Exception  if fails
	 */
	public static Persistence getInstance() {
		return persistence;
	}
	
	protected Persistence() {
		pool = Executors.newCachedThreadPool();
	}
	
	/**
	 * Prepare the connection to persistence.
	 * This method must be used by implementation class to open 
	 * the connection with the persistence storage, DB, file etc.
	 * @throws Exception if fails
	 */
	protected abstract void prepareConnection() throws Exception;
	
	/**
	 * Prepare the connection and try to write a test record on default 
	 * persistence and fallback persistence.
	 * This method should not be re-implemented from subclass.
	 * @throws Exception if fails
	 */
	public void connect() throws Exception {
		prepareConnection();
		this.account(createTestRawUsageRecord());
	}
	
	/**
	 * This method contains the code to save the {@link #UsageRecord}
	 * 
	 */
	protected abstract void reallyAccount(UsageRecord usageRecord) throws Exception;
	
	private void accountWithFallback(UsageRecord usageRecord) throws Exception {
		String persistenceName = getInstance().getClass().getSimpleName();
		try {
			//logger.debug("Going to account {} using {}", usageRecord, persistenceName);
			persistence.reallyAccount(usageRecord);
			logger.debug("{} accounted succesfully from {}.", usageRecord, persistenceName);
		} catch (Exception e) {
			String fallabackPersistenceName = fallback.getClass().getSimpleName();
			try {
				logger.error("{} was not accounted succesfully from {}. Trying to use {}.", 
						usageRecord, persistenceName, fallabackPersistenceName);
				fallback.reallyAccount(usageRecord);
				logger.debug("{} accounted succesfully from {}", 
						usageRecord, fallabackPersistenceName);
			}catch(Exception ex){
				logger.error("{} was not accounted at all", usageRecord);
				throw e;
			}
		}
	}
	
	/**
	 * Persist the {@link #UsageRecord}.
	 * This method account the record in a separated thread. So that the
	 * program can continue the execution.
	 * If the persistence fails the class write that the record in a local file
	 * so that the {@link #UsageRecord} can be recorder later.
	 * @param usageRecord the {@link #UsageRecord} to persist
	 */
	public void account(final UsageRecord usageRecord){
		Runnable runnable = new Runnable(){
			@Override
			public void run(){
				try {
					persistence.accountWithFallback(usageRecord);
				} catch (Exception e) {
					logger.error("Error accouting UsageRecod", e.getCause());
				}
			}
		};
		pool.execute(runnable);
	}
	
	public abstract void close() throws Exception;
	
}