package jmri.jmrix.secsi.simulator;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;
import jmri.jmrix.secsi.SerialMessage;
import jmri.jmrix.secsi.SerialPortController; // no special xSimulatorController
import jmri.jmrix.secsi.SerialReply;
import jmri.jmrix.secsi.SecsiSystemConnectionMemo;
import jmri.util.ImmediatePipedOutputStream;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Provide access to a simulated SECSI system.
 * <p>
 * Currently, the Secsi SimulatorAdapter reacts to the following commands sent from the user
 * interface with an appropriate reply {@link #generateReply(SerialMessage)}:
 * <ul>
 *     <li>Poll (length = 1, reply length = 2)
 * </ul>
 *
 * Based on jmri.jmrix.grapevine.simulator.SimulatorAdapter 2018
 * <p>
 * NOTE: Some material in this file was modified from other portions of the
 * support infrastructure.
 *
 * @author Paul Bender, Copyright (C) 2009-2010
 * @author Mark Underwood, Copyright (C) 2015
 * @author Egbert Broerse, Copyright (C) 2018
 */
public class SimulatorAdapter extends SerialPortController implements Runnable {

    // private control members
    private Thread sourceThread;

    private boolean outputBufferEmpty = true;
    private boolean checkBuffer = true;

    /**
     * Create a new SimulatorAdapter.
     */
    public SimulatorAdapter() {
        super(new SecsiSystemConnectionMemo("V", Bundle.getMessage("SecsiSimulatorName"))); // pass customized user name
        setManufacturer(jmri.jmrix.secsi.SerialConnectionTypeList.TRACTRONICS);
    }

    /**
     * {@inheritDoc}
     * Simulated input/output pipes.
     */
    @Override
    public String openPort(String portName, String appName) {
        try {
            PipedOutputStream tempPipeI = new ImmediatePipedOutputStream();
            log.debug("tempPipeI created");
            pout = new DataOutputStream(tempPipeI);
            inpipe = new DataInputStream(new PipedInputStream(tempPipeI));
            log.debug("inpipe created {}", inpipe != null);
            PipedOutputStream tempPipeO = new ImmediatePipedOutputStream();
            outpipe = new DataOutputStream(tempPipeO);
            pin = new DataInputStream(new PipedInputStream(tempPipeO));
        } catch (java.io.IOException e) {
            log.error("init (pipe): Exception: {}", e.toString());
        }
        opened = true;
        return null; // indicates OK return
    }

    /**
     * Set if the output buffer is empty or full. This should only be set to
     * false by external processes.
     *
     * @param s true if output buffer is empty; false otherwise
     */
    synchronized public void setOutputBufferEmpty(boolean s) {
        outputBufferEmpty = s;
    }

    /**
     * Can the port accept additional characters? The state of CTS determines
     * this, as there seems to be no way to check the number of queued bytes and
     * buffer length. This might go false for short intervals, but it might also
     * stick off if something goes wrong.
     *
     * @return true if port can accept additional characters; false otherwise
     */
    public boolean okToSend() {
        if (checkBuffer) {
            log.debug("Buffer Empty: {}", outputBufferEmpty);
            return (outputBufferEmpty);
        } else {
            log.debug("No Flow Control or Buffer Check");
            return (true);
        }
    }

    /**
     * Set up all of the other objects to operate with a SECSI
     * connected to this port.
     */
    @Override
    public void configure() {
        // connect to the traffic controller
        log.debug("set tc for memo {}", getSystemConnectionMemo().getUserName());
        ((SecsiSystemConnectionMemo) getSystemConnectionMemo()).getTrafficController().connectPort(this);
        // do the common manager config
        ((SecsiSystemConnectionMemo) getSystemConnectionMemo()).configureManagers();

        // start the simulator
        sourceThread = new Thread(this);
        sourceThread.setName("Secsi Simulator");
        sourceThread.setPriority(Thread.MIN_PRIORITY);
        sourceThread.start();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void connect() throws java.io.IOException {
        log.debug("connect called");
        super.connect();
    }

    // Base class methods for the SECSI SerialPortController simulated interface

    /**
     * {@inheritDoc}
     */
    @Override
    public DataInputStream getInputStream() {
        if (!opened || pin == null) {
            log.error("getInputStream called before load(), stream not available");
        }
        log.debug("DataInputStream pin returned");
        return pin;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public DataOutputStream getOutputStream() {
        if (!opened || pout == null) {
            log.error("getOutputStream called before load(), stream not available");
        }
        log.debug("DataOutputStream pout returned");
        return pout;
    }

    /**
     * {@inheritDoc}
     * @return always true, given this SimulatorAdapter is running
     */
    @Override
    public boolean status() {
        return opened;
    }

    /**
     * {@inheritDoc}
     *
     * @return null
     */
    @Override
    public String[] validBaudRates() {
        log.debug("validBaudRates should not have been invoked");
        return new String[]{};
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int[] validBaudNumbers() {
        return new int[]{};
    }

    @Override
    public String getCurrentBaudRate() {
        return "";
    }

    @Override
    public String getCurrentPortName(){
        return "";
    }

    @Override
    public void run() { // start a new thread
        // This thread has one task. It repeatedly reads from the input pipe
        // and writes an appropriate response to the output pipe. This is the heart
        // of the Secsi command station simulation.
        log.info("Secsi Simulator Started");
        while (true) {
            try {
                synchronized (this) {
                    wait(50);
                }
            } catch (InterruptedException e) {
                log.debug("interrupted, ending");
                return;
            }
            SerialMessage m = readMessage();
            SerialReply r;
            if (log.isTraceEnabled()) {
                StringBuilder buf = new StringBuilder();
                if (m != null) {
                    for (int i = 0; i < m.getNumDataElements(); i++) {
                        buf.append(Integer.toHexString(0xFF & m.getElement(i))).append(" ");
                    }
                } else {
                    buf.append("null message buffer");
                }
                log.trace("Secsi Simulator Thread received message: {}", buf ); // generates a lot of traffic
            }
            if (m != null) {
                r = generateReply(m);
                if (r != null) { // ignore errors and null replies
                    writeReply(r);
                    if (log.isDebugEnabled()) {
                        StringBuilder buf = new StringBuilder();
                        for (int i = 0; i < r.getNumDataElements(); i++) {
                            buf.append(Integer.toHexString(0xFF & r.getElement(i))).append(" ");
                        }
                        log.debug("Secsi Simulator Thread sent reply: {}", buf );
                    }
                }
            }
        }
    }

    /**
     * Read one incoming message from the buffer
     * and set outputBufferEmpty to true.
     */
    private SerialMessage readMessage() {
        SerialMessage msg = null;
        // log.debug("Simulator reading message"); // lots of traffic in loop
        try {
            if (inpipe != null && inpipe.available() > 0) {
                msg = loadChars();
            }
        } catch (java.io.IOException e) {
            // should do something meaningful here.
        }
        setOutputBufferEmpty(true);
        return (msg);
    }

    // operational instance variable (not preserved between runs)
    protected boolean[] nodesSet = new boolean[128]; // node init received and replied?

    /**
     * This is the heart of the simulation. It translates an
     * incoming SerialMessage into an outgoing SerialReply.
     * See {@link jmri.jmrix.secsi.SerialNode#markChanges(SerialReply)} and
     * the (draft) secsi <a href="../package-summary.html">Binary Message Format Summary</a>.
     *
     * @param msg the message received in the simulated node
     * @return a single Secsi message to confirm the requested operation, or a series
     * of messages for each (fictitious) node/pin/state. To ignore certain commands, return null.
     */
    private SerialReply generateReply(SerialMessage msg) {
        int nodeaddr = msg.getAddr();
        log.debug("Generate Reply to message for node {} (string = {})", nodeaddr, msg.toString());
        SerialReply reply = new SerialReply();  // reply length is determined by highest byte added
//        if (nodesSet[nodeaddr] != true) { // only Polls expect a reply from the node
         switch (msg.getNumDataElements()) {
             case 1: // poll message, but reading msg received often fails (see case 9)
                 log.debug("Poll message detected by simulator");
                 reply.setElement(0, nodeaddr); // node address from msg element(0)
                 reply.setElement(1, 0x30); // poll reply contains just 2 elements, second is 0x48 (see SerialMessage#isPoll())
                 nodesSet[nodeaddr] = true; // mark node as inited
                 log.debug("Poll reply generated {}", reply.toString());
                 return reply;
             case 5: // standard secsi sensor state request message
                 if (((SecsiSystemConnectionMemo) getSystemConnectionMemo()).getTrafficController().getNode(nodeaddr).getSensorsActive()) { // input (sensors) status reply
                     int payload = 0b0101; // dummy stand in for sensor status report; should we fetch known state from jmri node?
                     for (int j = 0; j < 3; j++) {
                         payload |= j << 4;
                         reply.setElement(j + 1, payload);
                     }
                     log.debug("Status Reply generated {}", reply.toString());
                 }
                 return reply;
             case 9:
                 // use this message to confirm node poll?
                 //reply.setElement(0, nodeaddr); // node address from msg element(0)
                 //reply.setElement(1, 48); // poll reply contains just 2 elements, second is 0x48 (see SerialMessage#isPoll())
                 log.debug("Outpacket received"); // Poll Reply generated: {}", reply.toString());
                 return null; // reply;
             default:
                 log.debug("Message (other) ignored");
                 return null;
         }
        // Poll will give an error:
        // jmrix.AbstractMRTrafficController ERROR - Transmit thread terminated prematurely by:
        // java.lang.ArrayIndexOutOfBoundsException: 1 [secsi.SerialTrafficController Transmit thread]
    }

    /**
     * Write reply to output.
     * <p>
     * Adapted from jmri.jmrix.nce.simulator.SimulatorAdapter.
     *
     * @param r reply on message
     */
    private void writeReply(SerialReply r) {
        if (r == null) {
            return; // there is no reply to be sent
        }
        for (int i = 0; i < r.getNumDataElements(); i++) {
            try {
                outpipe.writeByte((byte) r.getElement(i));
            } catch (java.io.IOException ex) {
            }
        }
        try {
            outpipe.flush();
        } catch (java.io.IOException ex) {
        }
    }

    private int[] lastChars = new int[9]; // temporary store of bytes received, excluding node address
    private int nextNodeAddress;
    private boolean lastCharLoaded = false;

    /**
     * Get characters from the input source. No opcode, so must read per byte.
     * Length will be either 1, 5 or 9 bytes.
     * <p>
     * Only used in the Receive thread.
     *
     * @return filled message, only when the message is complete.
     * @throws IOException when presented by the input source.
     */
    private SerialMessage loadChars() throws java.io.IOException {
        int i = 1;
        int char0;
        byte nextByte;

        // get 1st byte, see if ending too soon
        if (lastCharLoaded && (nextNodeAddress < 0x2F)) { // use char previously read fom pipe as element 0 (node address)
            char0 = nextNodeAddress;
            lastCharLoaded = false;
        } else {
            try {
                byte byte0 = readByteProtected(inpipe);
                char0 = (byte0 & 0xFF);
                log.debug("loadChars read {}", char0);
            } catch (java.io.IOException e) {
                lastCharLoaded = false; // we lost track
                log.debug("loadChars aborted while reading char 0");
                return null;
            }
        }
        if (char0 > 0x2F) {
            // skip as not a node address
            log.debug("bit not valid as node address");
        }

        // try if what is received is a series of outpackets
        for (i = 1; i < 9; i++) { // reading next max 8 bytes
            log.debug("reading rest of message in simulator, element {}", i);
            try {
                nextByte = readByteProtected(inpipe);
            } catch (java.io.IOException e) {
                log.debug("loadChars aborted after {} chars", i);
                lastCharLoaded = false; // we lost track
                //i = i - 1; // current message complete at previous char
                log.debug("overshot reading Secsi message at element {}. Ready", i);
                break;
            }
            log.debug("loadChars read {} (item {})", Integer.toHexString(nextByte & 0xFF), i);
            // check if it is one of the 8 byte 0x .. 7x Outpackets series
            if ((nextByte & 0xFF) >> 4 == i - 1) { // pattern for next element in range of increasing 0x .. 7x Outpackets
                lastChars[i] = (nextByte & 0xFF);
                log.debug("matched item {} in series: {}", i, (nextByte & 0xFF) >> 4);
            } else if ((nextByte & 0xFF) < 0x2F) { // if it's not, store last item read as first element of next message
                // nextChar could be node address again, in that case the preceding was perhaps a single node poll message
                // but on node 00 could follow the first of the outputpacket series 00 10 etc.
                nextNodeAddress = (nextByte & 0xFF); // store value in array
                lastCharLoaded = true;
                i = Math.max(1, i - 1); // current message complete at previous char
                log.debug("overshot reading Secsi message at element {}. Next node = {}", i, nextNodeAddress);
                break;
            } else { // we lost this series, but previous item could have been the next new node address
                if ((lastChars[i - 1] >= 0) && (lastChars[i - 1] < 0x2F)) { // valid as node address
                    nextNodeAddress = lastChars[i - 1];
                    lastCharLoaded = true; // store last byte read as possible next node address
                    i = Math.max(1, i - 1); // current message complete before previous char
                    log.debug("overshot Secsi message at element {}. Next node = {}", i, nextNodeAddress);
                    break;
                } else { // unhandled message type
                    lastCharLoaded = false; // discard last byte read as not making sense
                    i = Math.max(1, i - 1); // current message complete at previous char
                    log.debug("unhandled Secsi message from element {}", i);
                    break;
                }
            }
        }

        // copy bytes to Message
        SerialMessage msg = new SerialMessage(i);
        msg.setElement(0, char0); // address
        for (int k = 1; k < i; k++) { // copy remaining bytes if i > 1
            msg.setElement(k, lastChars[k]);
        }
        log.debug("Secsi message received by simulator, length = {}", i);
        if (msg.getNumDataElements() == 1) {
            nodesSet[char0] = false; // reset first node poll
        }
        return msg;
    }

    /**
     * Read a single byte, protecting against various timeouts, etc.
     * <p>
     * When a port is set to have a receive timeout (via the
     * enableReceiveTimeout() method), some will return zero bytes or an
     * EOFException at the end of the timeout. In that case, the read should be
     * repeated to get the next real character.
     * <p>
     * Copied from DCCppSimulatorAdapter, byte[] from XNetSimAdapter
     */
    private byte readByteProtected(DataInputStream istream) throws java.io.IOException {
        byte[] rcvBuffer = new byte[1];
        while (true) { // loop will repeat until character found
            int nchars;
            nchars = istream.read(rcvBuffer, 0, 1);
            if (nchars > 0) {
                return rcvBuffer[0];
            }
        }
    }

    // streams to share with user class
    private DataOutputStream pout = null; // this is provided to classes who want to write to us
    private DataInputStream pin = null; // this is provided to classes who want data from us
    // internal ends of the pipes
    private DataOutputStream outpipe = null; // feed pin
    private DataInputStream inpipe = null; // feed pout

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

}