/**
 * 
 */
package org.jivesoftware.smackx.filetransfer;

import java.io.InputStream;
import java.io.OutputStream;

import org.jivesoftware.smack.XMPPException;
import org.jivesoftware.smack.packet.IQ;
import org.jivesoftware.smackx.Form;
import org.jivesoftware.smackx.FormField;
import org.jivesoftware.smackx.packet.DataForm;
import org.jivesoftware.smackx.packet.StreamInitiation;

/**
 * After the file transfer negotiation process is completed according to
 * JEP-0096, the negotation process is passed off to a particular stream
 * negotiator. The stream negotiator will then negotiate the chosen stream and
 * return the stream to transfer the file.
 * 
 * 
 * @author Alexander Wenckus
 * 
 */
public abstract class StreamNegotiator {

	/**
	 * Creates the initiation acceptance packet to forward to the stream
	 * initiator.
	 * 
	 * @param streamInitiationOffer
	 *            The offer from the stream initatior to connect for a stream.
	 * @param namespace
	 *            The namespace that relates to the accepted means of transfer.
	 * @return The response to be forwarded to the initator.
	 */
	public StreamInitiation createInitiationAccept(
			StreamInitiation streamInitiationOffer, String namespace) {
		StreamInitiation response = new StreamInitiation();
		response.setTo(streamInitiationOffer.getFrom());
		response.setFrom(streamInitiationOffer.getTo());
		response.setType(IQ.Type.RESULT);
		response.setPacketID(streamInitiationOffer.getPacketID());

		DataForm form = new DataForm(Form.TYPE_SUBMIT);
		FormField field = new FormField(
				FileTransferNegotiator.STREAM_DATA_FIELD_NAME);
		field.addValue(namespace);
		form.addField(field);

		response.setFeatureNegotiationForm(form);
		return response;
	}

    /**
	 * This method handles the file stream download negotiation process. The
	 * appropriate stream negotiator's initiate incoming stream is called after
	 * an appropriate file transfer method is selected. The manager will respond
	 * to the initatior with the selected means of transfer, then it will handle
	 * any negotation specific to the particular transfer method. This method
	 * returns the InputStream, ready to transfer the file.
	 * 
	 * @param initiation
	 *            The initation that triggered this download.
	 * @return After the negotation process is complete, the InputStream to
	 *         write a file to is returned.
	 * @throws XMPPException
	 *             If an error occurs during this process an XMPPException is
	 *             thrown.
	 */
	public abstract InputStream initiateIncomingStream(
			StreamInitiation initiation) throws XMPPException;

	/**
	 * This method handles the file upload stream negotiation process. The
	 * particular stream negotiator is determined during the file transfer
	 * negotiation process. This method returns the OutputStream to transmit the
	 * file to the remote user.
	 * 
	 * @param streamID
	 *            The streamID that uniquely identifies the file transfer.
	 * @param initiator
	 *            The fully-qualified JID of the initiator of the file transfer.
	 * @param target
	 *            The fully-qualified JID of the target or reciever of the file
	 *            transfer.
	 * @return The negotiated stream ready for data.
	 * @throws XMPPException
	 *             If an error occurs during the negotiation process an
	 *             exception will be thrown.
	 */
	public abstract OutputStream initiateOutgoingStream(String streamID,
			String initiator, String target) throws XMPPException;

	/**
	 * Returns the XMPP namespace reserved for this particular type of file
	 * transfer.
	 * 
	 * @return Returns the XMPP namespace reserved for this particular type of
	 *         file transfer.
	 */
	public abstract String getNamespace();

}