package fileserv;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.util.List;
import java.util.concurrent.ThreadPoolExecutor;

import org.apache.log4j.Logger;
import org.openslx.filetransfer.DataReceivedCallback;
import org.openslx.filetransfer.Downloader;
import org.openslx.filetransfer.FileRange;
import org.openslx.filetransfer.WantRangeCallback;
import org.openslx.imagemaster.thrift.iface.UserInfo;

public class ActiveUpload {
	private static final Logger LOGGER = Logger.getLogger(ActiveUpload.class);

	/**
	 * This is an active upload, so on our end, we have a Downloader.
	 */
	private Downloader download = null;

	private final File destinationFile;

	private final RandomAccessFile outFile;

	private final ChunkList chunks;

	private final long fileSize;

	/**
	 * User owning this uploaded file.
	 */
	private final UserInfo owner;

	// TODO: Use HashList for verification

	public ActiveUpload(UserInfo owner, File destinationFile, long fileSize, List<ByteBuffer> sha1Sums)
			throws FileNotFoundException {
		this.destinationFile = destinationFile;
		this.outFile = new RandomAccessFile(destinationFile, "rw");
		this.chunks = new ChunkList(fileSize, sha1Sums);
		this.owner = owner;
		this.fileSize = fileSize;
	}

	/**
	 * Add another connection for this file transfer. Currently only one
	 * connection is allowed, but this might change in the future.
	 * 
	 * @param connection
	 * @return true if the connection is accepted, false if it should be
	 *         discarded
	 */
	public synchronized boolean addConnection(Downloader connection, ThreadPoolExecutor pool) {
		if (download != null || chunks.isComplete())
			return false;
		download = connection;
		pool.execute(new Runnable() {
			@Override
			public void run() {
				CbHandler cbh = new CbHandler();
				if (!download.download(cbh, cbh) && cbh.currentChunk != null) {
					// If the download failed and we have a current chunk, put it back into
					// the queue, so it will be handled again later...
					chunks.markFailed(cbh.currentChunk);
				}
			}
		});
		return true;
	}

	/**
	 * Write some data to the local file. Thread safe so we could
	 * have multiple concurrent connections later.
	 * 
	 * @param fileOffset
	 * @param dataLength
	 * @param data
	 * @return
	 */
	private boolean writeFileData(long fileOffset, int dataLength, byte[] data) {
		synchronized (outFile) {
			try {
				outFile.seek(fileOffset);
				outFile.write(data, 0, dataLength);
			} catch (IOException e) {
				LOGGER.error("Cannot write to '" + destinationFile
						+ "'. Disk full, network storage error, bad permissions, ...?", e);
				return false;
			}
		}
		return true;
	}

	/**
	 * Get user owning this upload. Can be null in special cases.
	 * 
	 * @return instance of UserInfo for the according user.
	 */
	public UserInfo getOwner() {
		return this.owner;
	}

	public boolean isComplete() {
		return chunks.isComplete() && destinationFile.length() == this.fileSize;
	}

	public File getDestinationFile() {
		return this.destinationFile;
	}

	public long getSize() {
		return this.fileSize;
	}

	/**
	 * Callback class for an instance of the Downloader, which supplies
	 * the Downloader with wanted file ranges, and handles incoming data.
	 */
	private class CbHandler implements WantRangeCallback, DataReceivedCallback {
		/**
		 * The current chunk being transfered.
		 */
		public FileChunk currentChunk = null;

		@Override
		public boolean dataReceived(long fileOffset, int dataLength, byte[] data) {
			// TODO: Maybe cache in RAM and write full CHUNK_SIZE blocks at a time?
			// Would probably help with slower storage, especially if it's using
			// rotating disks and we're running multiple uploads.
			// Also we wouldn't have to re-read a block form disk for sha1 checking.
			return writeFileData(fileOffset, dataLength, data);
		}

		@Override
		public FileRange get() {
			if (currentChunk != null) {
				// TODO: A chunk was requested before, check hash and requeue if not matching
				// This needs to be async (own thread) so will be a little complicated
			}
			// Get next missing chunk
			currentChunk = chunks.getMissing();
			if (currentChunk == null)
				return null; // No more chunks, returning null tells the Downloader we're done.
			return currentChunk.range;
		}
	}

	// TODO: Clean up old stale uploads

}