package protocolP2P;
import protocolP2P.Payload;
import protocolP2P.RequestResponseCode;
import exception.TransmissionError;
import exception.ProtocolError;
import exception.InternalError;
import exception.SizeError;
import java.io.UnsupportedEncodingException;

/** Representation of payload for load request.
 * @author	Louis Royer
 * @author	Flavien Haas
 * @author	JS Auge
 * @version	1.0
 */
public class LoadRequest extends Payload {
	private String filename;

	/** Constructor (typically used by the server) with a filename parameter.
	 * @param filename	name of the file to download. Must not be empty.
	 * @throws	InternalError
	 */
	public LoadRequest(String filename) throws InternalError {
		super(RequestResponseCode.LOAD_REQUEST);
		/* assert to help debugging */
		assert filename.length() != 0 : "Payload size of LoadRequest must not be empty";
		if (filename.length() == 0) {
			throw new InternalError();
		}
		this.filename = filename;
	}

	/** Constructor (typically used by client) with a byte[] parameter containing the datagram received.
	 * @param datagram	the full datagram received
	 * @throws	SizeError
	 * @throws	InternalError
	 * @throws	ProtocolError
	 * @throws	TransmissionError
	 */
	protected LoadRequest(byte[] datagram) throws TransmissionError, SizeError, ProtocolError, InternalError {
		super(datagram);
		/* assert to help debugging */
		assert requestResponseCode == RequestResponseCode.LOAD_REQUEST : "LoadRequest subclass is incompatible with this datagram, request/response code must be checked before using this constructor";
		/* InternalErrorException */
		if (requestResponseCode!= RequestResponseCode.LOAD_REQUEST) {
			throw new InternalError();
		}
		int size = getPayloadSize(datagram);
		try {
			filename = new String(datagram, 8, size, "UTF-8");
		} catch (UnsupportedEncodingException e) {
			throw new InternalError();
		}
	}

	/** Returns a byte[] containing datagram with padding.
	 * This datagram is still incomplete and should not be send directly.
	 * ProtocolP2PDatagram will use this method to generate the complete datagram.
	 * @return datagram with padding
	 * @throws	InternalError
	 */
	protected byte[] toDatagram() throws InternalError {
		// compute size
		int size = 8 + filename.length();
		byte[] datagram = new byte[size]; // java initialize all to zero
		// set request/response code
		datagram[RequestResponseCode.RRCODE_POSITION] = requestResponseCode.codeValue;
		// bits 16-31 are reserved for future use
		setPayloadSize(size - 8, datagram);
		// Write filename
		int bCount = 8;
		try {
			byte[] sb = filename.getBytes("UTF-8");
			for(byte b : sb) {
				datagram[bCount] = b;
				bCount += 1;
			}
		} catch (UnsupportedEncodingException e) {
			throw new InternalError();
		}
		return datagram;
	}

	/** filename getter.
	 * @return	filename
	 */
	public String getFilename() {
		return filename;
	}
}