package jmri.jmrix.loconet.loconetovertcp;

import java.util.StringTokenizer;
import jmri.jmrix.loconet.LnNetworkPortController;
import jmri.jmrix.loconet.LnPacketizer;
import jmri.jmrix.loconet.LocoNetMessage;
import jmri.jmrix.loconet.LocoNetMessageException;
import jmri.jmrix.loconet.LocoNetSystemConnectionMemo;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Converts Stream-based I/O over the LocoNetOverTcp system network
 * connection to/from LocoNet messages. The "LocoNetInterface"
 * side sends/receives LocoNetMessage objects. The connection to a
 * LnPortnetworkController is via a pair of *Streams, which then carry sequences
 * of characters for transmission.
 * <p>
 * Messages come to this via the main GUI thread, and are forwarded back to
 * listeners in that same thread. Reception and transmission are handled in
 * dedicated threads by RcvHandler and XmtHandler objects. Those are internal
 * classes defined here. The thread priorities are:
 * <ul>
 *   <li> RcvHandler - at highest available priority
 *   <li> XmtHandler - down one, which is assumed to be above the GUI
 *   <li> (everything else)
 * </ul>
 *
 * Some of the message formats used in this class are Copyright Digitrax, Inc.
 * and used with permission as part of the JMRI project. That permission does
 * not extend to uses in other software products. If you wish to use this code,
 * algorithm or these message formats outside of JMRI, please contact Digitrax
 * Inc for separate permission.
 *
 * @author Bob Jacobsen Copyright (C) 2001
 * @author Alex Shepherd Copyright (C) 2003, 2006
 */
public class LnOverTcpPacketizer extends LnPacketizer {

    static final String RECEIVE_PREFIX = "RECEIVE";
    static final String SEND_PREFIX = "SEND";

    public LnOverTcpPacketizer(LocoNetSystemConnectionMemo m) {
        super(m);
        xmtHandler = new XmtHandler();
        rcvHandler = new RcvHandler(this);
    }

    public LnNetworkPortController networkController = null;

    @Override
    public boolean isXmtBusy() {
        if (networkController == null) {
            return false;
        }
        return true;
    }

    /**
     * Make connection to an existing LnPortnetworkController object.
     *
     * @param p Port networkController for connected. Save this for a later
     *          disconnect call
     */
    public void connectPort(LnNetworkPortController p) {
        istream = p.getInputStream();
        ostream = p.getOutputStream();
        if (networkController != null) {
            log.warn("connectPort: connect called while connected");
        }
        networkController = p;
    }

    /** Starts a new receive thread after a reconnect. */
    public void restartRcvThread() {
        rcvThread = jmri.util.ThreadingUtil.newThread(rcvHandler, "LocoNet receive handler"); // NOI18N
        rcvThread.setDaemon(true);
        rcvThread.setPriority(Thread.MAX_PRIORITY);
        rcvThread.start();
    }

    /**
     * Break connection to existing LnPortnetworkController object. Once broken,
     * attempts to send via "message" member will fail.
     *
     * @param p previously connected port
     */
    public void disconnectPort(LnNetworkPortController p) {
        istream = null;
        ostream = null;
        if (networkController != p) {
            log.warn("disconnectPort: disconnect called from non-connected LnPortnetworkController");
        }
        networkController = null;
    }

    /**
     * Captive class to handle incoming characters. This is a permanent loop,
     * looking for input messages in character form on the stream connected to
     * the LnPortnetworkController via <code>connectPort</code>.
     */
    class RcvHandler implements Runnable {

        /**
         * Remember the LnPacketizer object.
         */
        LnOverTcpPacketizer trafficController;

        public RcvHandler(LnOverTcpPacketizer lt) {
            trafficController = lt;
        }

        // readline is deprecated, but there are no problems
        // with multi-byte characters here.
        @SuppressWarnings("deprecation")  // InputStream#readline
        @Override
        public void run() {

            String rxLine;
            while (! Thread.interrupted()) {  // loop permanently, program close will exit
                try {
                    // Start by looking for a complete line.
                    // This will block until input is returned, even if the thread is interrupted.
                    rxLine = istream.readLine();
                    if (Thread.interrupted()) {
                        // This indicates normal termination of the thread
                        // followed by some input being provided by readLine above.
                        // We return immediately to end the thread, rather than
                        // processing the no-long-relevant input.
                        return;
                    }
                    if (rxLine == null) {
                        log.info("run: server closed connection, attempting recovery");
                        if (trafficController.networkController != null) {
                            trafficController.networkController.recover();
                        }
                        return;
                    }

                    log.debug("Received: {}", rxLine);

                    StringTokenizer st = new StringTokenizer(rxLine);
                    if (st.nextToken().equals(RECEIVE_PREFIX)) {
                        LocoNetMessage msg = null;
                        int opCode = Integer.parseInt(st.nextToken(), 16);
                        int byte2 = Integer.parseInt(st.nextToken(), 16);

                        // Decide length
                        switch ((opCode & 0x60) >> 5) {
                            default:  // not really possible, but this closes selection for SpotBugs
                            case 0:
                                /* 2 byte message */

                                msg = new LocoNetMessage(2);
                                break;

                            case 1:
                                /* 4 byte message */

                                msg = new LocoNetMessage(4);
                                break;

                            case 2:
                                /* 6 byte message */

                                msg = new LocoNetMessage(6);
                                break;

                            case 3:
                                /* N byte message */

                                if (byte2 < 2) {
                                    log.error("LocoNet message length invalid: {} opcode: {}",
                                            byte2, Integer.toHexString(opCode));
                                }
                                msg = new LocoNetMessage(byte2);
                                break;
                        }

                        // message exists, now fill it
                        msg.setOpCode(opCode);
                        msg.setElement(1, byte2);
                        int len = msg.getNumDataElements();
                        //log.debug("len: {}", len);

                        for (int i = 2; i < len; i++) {
                            // check for message-blocking error
                            int b = Integer.parseInt(st.nextToken(), 16);
                            // log.debug("char {} is: {}", i, Integer.toHexString(b));
                            if ((b & 0x80) != 0) {
                                log.warn("LocoNet message with opCode: {} ended early. Expected length: {} seen length: {} unexpected byte: {}", Integer.toHexString(opCode), len, i, Integer.toHexString(b));
                                throw new LocoNetMessageException();
                            }
                            msg.setElement(i, b);
                        }

                        // message is complete, dispatch it !!
                        if (log.isDebugEnabled()) {
                            log.debug("queue message for notification");
                        }

                        final LocoNetMessage thisMsg = msg;
                        final LnPacketizer thisTc = trafficController;
                        // return a notification via the queue to ensure end
                        Runnable r = new Runnable() {
                            LocoNetMessage msgForLater = thisMsg;
                            LnPacketizer myTc = thisTc;

                            @Override
                            public void run() {
                                myTc.notify(msgForLater);
                            }
                        };
                        javax.swing.SwingUtilities.invokeLater(r);
                    }
                    // done with this one
                } catch (LocoNetMessageException e) {
                    // just let it ride for now
                    log.warn("run: unexpected LocoNetMessageException: ", e);
                } catch (java.io.EOFException e) {
                    // posted from idle port when enableReceiveTimeout used
                    log.debug("EOFException, is LocoNet serial I/O using timeouts?");
                } catch (java.io.IOException e) {
                    // fired when write-end of HexFile reaches end
                    log.debug("IOException, should only happen with HexFile: ", e);
                    log.info("End of file");
//                    disconnectPort(networkController);
                    return;
                } // normally, we don't catch RuntimeException, but in this
                // permanently running loop it seems wise.
                catch (RuntimeException e) {
                    log.warn("run: unexpected Exception: ", e);
                }
            } // end of permanent loop
        }
    }

    /**
     * Captive class to handle transmission.
     */
    class XmtHandler implements Runnable {

        @Override
        public void run() {

            while (true) {   // loop permanently
                // any input?
                try {
                    // get content; blocks write until present
                    log.debug("check for input");

                    byte msg[] = xmtList.take();

                    // input - now send
                    try {
                        if (ostream != null) {
                            // Commented out as the original LnPortnetworkController always returned true.
                            // if (!networkController.okToSend()) log.warn("LocoNet port not ready to receive"); // TCP, not RS232, so message is a real warning
                            log.debug("start write to stream");
                            StringBuffer packet = new StringBuffer(msg.length * 3 + SEND_PREFIX.length() + 2);
                            packet.append(SEND_PREFIX);
                            String hexString;
                            for (int Index = 0; Index < msg.length; Index++) {
                                packet.append(' ');
                                hexString = Integer.toHexString(msg[Index] & 0xFF).toUpperCase();
                                if (hexString.length() == 1) {
                                    packet.append('0');
                                }
                                packet.append(hexString);
                            }
                            if (log.isDebugEnabled()) { // Avoid building unneeded Strings
                                log.debug("Write to LbServer: {}", packet.toString());
                            }
                            packet.append("\r\n");
                            ostream.write(packet.toString().getBytes());
                            ostream.flush();
                            log.debug("end write to stream");
                        } else {
                            // no stream connected
                            log.warn("sendLocoNetMessage: no connection established");
                        }
                    } catch (java.io.IOException e) {
                        log.warn("sendLocoNetMessage: IOException: {}", e.toString());
                        // write failed; connection likely dropped
                        if (networkController != null) {
                            networkController.recover();
                        }
                    }
                } catch (InterruptedException ie) {
                    return; // ending the thread
                }
            }
        }
    }

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

}