package org.openslx.imagemaster.serverconnection;

import java.io.IOException;
import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.apache.log4j.Logger;
import org.openslx.imagemaster.Globals;
import org.openslx.imagemaster.crcchecker.CRCFile;
import org.openslx.imagemaster.db.DbImage;
import org.openslx.imagemaster.db.DbUser;
import org.openslx.imagemaster.thrift.iface.DownloadInfos;
import org.openslx.imagemaster.thrift.iface.ImageData;
import org.openslx.imagemaster.thrift.iface.ImageDataError;
import org.openslx.imagemaster.thrift.iface.ImageDataException;
import org.openslx.imagemaster.thrift.iface.UploadError;
import org.openslx.imagemaster.thrift.iface.UploadException;
import org.openslx.imagemaster.thrift.iface.UploadInfos;
import org.openslx.imagemaster.util.RandomString;

/**
 * Processing the up- and download of images.
 * Handles who is authorized and knows which blocks are missing / need to be sent
 */
public class ImageProcessor
{

	private static final Logger log = Logger.getLogger( ImageProcessor.class );

	/**
	 * The amount of blocks that is return in UploadInfos (after request of satellite)
	 */
	private static final int AMOUNT = 20;
	/**
	 * The uploading images.
	 * Key: imageUUID,
	 * Value: uploadingImageInfos
	 */
	private static Map<String, UploadingImage> uploadingImages = new ConcurrentHashMap<>();

	/**
	 * The UUIDs of the images that need to be checked by the crc checker.
	 */
	private static List<String> imagesToCheck = new LinkedList<>();

	/**
	 * The downloading clients.
	 * Key: serverSessionId
	 * Value: downloadingClientInfos
	 */
	private static HashMap<String, DownloadingClient> downloadingClients = new HashMap<>();

	/**
	 * Checks if this image is already uploading and returns a new list with missing blocks if so.
	 * Puts the new image into processing list else.
	 * 
	 * @param serverSessionId The uploading server
	 * @param imageData The data of the image
	 * @return
	 * @throws UploadException If some error occurred during the process
	 */
	public static UploadInfos getUploadInfos( String serverSessionId, ImageData imageData, List<Integer> crcSums )
			throws UploadException, ImageDataException
	{
		// check image data
		if ( DbImage.exists( imageData.uuid ) ) {
			throw new ImageDataException( ImageDataError.INVALID_DATA, "UUID already existing." );
		} else if ( imageData.imageName == null || imageData.imageName.isEmpty() ) {
			throw new ImageDataException( ImageDataError.INVALID_DATA, "Image name not set." );
		} else if ( imageData.imageName == null || imageData.imageOwner.isEmpty() ) {
			throw new ImageDataException( ImageDataError.INVALID_DATA, "Image owner not set." );
		} else if ( imageData.contentOperatingSystem == null || imageData.contentOperatingSystem.isEmpty() ) {
			throw new ImageDataException( ImageDataError.INVALID_DATA, "Content operating system not set." );
		} else if ( imageData.fileSize <= 0 ) {
			throw new ImageDataException( ImageDataError.INVALID_DATA, "File size is too small." );
		} else if ( !DbUser.exists( imageData.imageOwner ) ) {
			throw new ImageDataException( ImageDataError.INVALID_DATA, "User is not known." );
		}

		String uuid = imageData.uuid;
		String token;
		String filepath;
		int nBlocks;
		int[] allBlocks;
		UploadingImage image;

		synchronized ( uploadingImages ) {
			// check if image is already uploading
			if ( ( image = uploadingImages.get( uuid ) ) != null ) {
				log.debug( "Image is already uploading.. returning some missing blocks" );
				List<Integer> missing = getNMissingBlocks( image, AMOUNT );
				if ( missing.isEmpty() ) {
					uploadDone( uuid );
					return new UploadInfos( null, 0, missing );
				}
				return new UploadInfos( image.getToken(), Globals.getSslSocketPort(), missing );
			}

			// insert new image
			if ( !CRCFile.sumsAreValid( crcSums ) )
				throw new UploadException( UploadError.INVALID_CRC, "CRC sums were invalid." );
			filepath = Globals.getImageDir() + "/" + uuid + ".vmdk";
			token = RandomString.generate( 100, false );
			nBlocks = (int)Math.ceil( imageData.fileSize / Globals.blockSize );
			allBlocks = new int[ nBlocks ];	// initalize array with all zeros which mean that this block is missing
			image = new UploadingImage( token, allBlocks, new Timestamp( System.currentTimeMillis() ), uuid, filepath );
			uploadingImages.put( uuid, image );
		}

		CRCFile crcFile;
		try {
			// try to write crc file ...
			crcFile = CRCFile.writeCrcFile( crcSums, Globals.getImageDir() + "/" + uuid + ".crc" );
		} catch ( IOException e ) {
			// ... and keep it in ram if it fails
			crcFile = new CRCFile( crcSums );
		}
		image.setCrcFile( crcFile );

		ConnectionHandler.addConnection( token, filepath, Connection.UPLOADING ).image = image;
		DbImage.insert( imageData, System.currentTimeMillis(), token, nBlocks, serverSessionId, filepath );
		imagesToCheck.add( uuid );

		log.debug( "Returning UploadInfos. Client should goint to start the upload. " );
		return new UploadInfos( token, Globals.getSslSocketPort(), getNMissingBlocks( image, AMOUNT ) );
	}

	public static DownloadInfos getDownloadInfos( String serverSessionId, String uuid, List<Integer> requestedBlocks )
	{
		// check if server is already downloading
		if ( downloadingClients.containsKey( serverSessionId ) ) {
			DownloadingClient client = downloadingClients.get( serverSessionId );

			// remove download if done
			if ( requestedBlocks.isEmpty() )
			{
				downloadDone( serverSessionId, uuid );
				return new DownloadInfos();
			}

			if ( client.isDownloading( uuid ) )
			{
				// client was downloading this image
				// update the requested blocks
				client.requestBlocks( uuid, requestedBlocks );
				return new DownloadInfos( client.getToken( uuid ), Globals.getSslSocketPort() );
			}

			// server was downloading another image and now gets a new connection for this new download
			String token = RandomString.generate( 100, false );
			String filepath = DbImage.getImageByUUID( uuid ).imagePath;
			ConnectionHandler.addConnection( token, filepath, Connection.DOWNLOADING );

			client.addDownload( uuid, requestedBlocks, token );
			downloadingClients.put( serverSessionId, client );
			return new DownloadInfos( token, Globals.getSslSocketPort() );
		}

		// insert new client and start listener
		synchronized ( downloadingClients ) {
			String token = RandomString.generate( 100, false );
			String filepath = DbImage.getImageByUUID( uuid ).imagePath;

			DownloadingClient client = new DownloadingClient();
			client.addDownload( uuid, requestedBlocks, token );
			downloadingClients.put( serverSessionId, client );

			ConnectionHandler.addConnection( token, filepath, Connection.DOWNLOADING ).client = client;
			return new DownloadInfos( token, Globals.getSslSocketPort() );
		}
	}

	private static void downloadDone( String serverSessionId, String uuid )
	{
		synchronized ( downloadingClients ) {
			DownloadingClient client = downloadingClients.get( serverSessionId );
			client.removeDownload( uuid );
			ConnectionHandler.removeConnection( client.getToken( uuid ) );
			if ( !client.hasDownloads() ) {
				downloadingClients.remove( serverSessionId );
			}
		}
	}

	/**
	 * Returns a specified number of missing blocks.
	 * 
	 * @param imageUUID The image of which you want to get the missing blocks from
	 * @param amount The amount of blocks that you want to get
	 * @return The missing blocks
	 */
	private static List<Integer> getNMissingBlocks( UploadingImage image, int amount )
	{
		int size = image.getAmountOfMissingBlocks();
		if ( amount > size )
			amount = size;

		List<Integer> result = new ArrayList<>( amount );

		int got = 0;
		for ( int i = 0; i < image.getNumberOfBlocks(); i++ ) {
			if ( image.needsRequest( i ) ) {
				result.add( i );
				got++;
			}
			if ( got == amount )
				break;
		}

		return result;
	}

	/**
	 * Is triggered when an upload of an image is done.
	 * Removes image from process list, updates db entry and moves file on hard drive.
	 * 
	 * @param uuid
	 */
	private static void uploadDone( String uuid )
	{
		synchronized ( imagesToCheck ) {
			imagesToCheck.remove( uuid );
		}

		UploadingImage image;
		synchronized ( uploadingImages ) {
			image = uploadingImages.remove( uuid );
		}
		image.getDbImage().updateMissingBlocks( null );
		// file was already downloaded in the right location by the updownloader class.
		// remove the connection so that it can be used by a new client
		ConnectionHandler.removeConnection( image.getToken() );
	}

	public static List<UploadingImage> getImagesToCheck()
	{
		List<UploadingImage> result = new LinkedList<>();
		Iterator<String> iter = imagesToCheck.iterator();
		while ( iter.hasNext() ) {
			result.add( uploadingImages.get( iter.next() ) );
		}
		return result;
	}

	public static List<Integer> getRequestedBlocks( String token )
	{
		// for the downloader
		return null;
	}

	/**
	 * Checks pending uploads in database and adds them to process list again.
	 */
	static
	{
		List<DbImage> list = DbImage.getUploadingImages();
		for ( DbImage image : list ) {
			String token = image.token;
			ConnectionHandler.addConnection( token, image.imagePath, Connection.UPLOADING );
			UploadingImage infos = new UploadingImage( token, image.blockStatus, image.timestamp,
					image.uuid, image.imagePath );
			CRCFile crcFile = new CRCFile( Globals.getImageDir() + "/" + image.uuid + ".crc" );
			try {
				if ( !crcFile.isValid() )
					continue;
			} catch ( IOException e ) {
				continue;
			}
			infos.setCrcFile( crcFile );
			uploadingImages.put( image.uuid, infos );
		}
		log.info( "Added " + list.size() + " pending upload(s) to process list again." );
	}

	public static void init()
	{
	}
}