package jmri.jmrix.oaktree.simulator;

import java.io.*;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

// no special xSimulatorController
import jmri.jmrix.oaktree.*;
import jmri.util.ImmediatePipedOutputStream;

/**
 * Provide access to a simulated OakTree system.
 * <p>
 * Currently, the OakTree 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.oaktree.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
 */
@SuppressWarnings("javadoc")
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 OakTreeSystemConnectionMemo("O", Bundle.getMessage("OakTreeSimulatorName"))); // pass customized user name
        setManufacturer(jmri.jmrix.oaktree.SerialConnectionTypeList.OAK);
    }

    /**
     * {@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 an OakTree
     * connected to this port.
     */
    @Override
    public void configure() {
        // connect to the traffic controller
        log.debug("set tc for memo {}", getSystemConnectionMemo().getUserName());
        ((OakTreeSystemConnectionMemo) getSystemConnectionMemo()).getTrafficController().connectPort(this);
        // do the common manager config
        ((OakTreeSystemConnectionMemo) getSystemConnectionMemo()).configureManagers();

        // start the simulator
        sourceThread = new Thread(this);
        sourceThread.setName("OakTree 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 OakTree 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 OakTree command station simulation.
        log.info("OakTree 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("OakTree 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("OakTree 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);
    }

    /**
     * This is the heart of the simulation. It translates an
     * incoming SerialMessage into an outgoing SerialReply.
     * See {@link jmri.jmrix.oaktree.SerialNode#markChanges(SerialReply)} and
     * the (draft) OakTree <a href="../package-summary.html">Binary Message Format Summary</a>.
     *
     * @param msg the message received in the simulated node
     * @return a single AokTree 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
         switch (msg.getElement(1)) {
             case 48: // OakTree poll message
                 reply.setElement(0, nodeaddr);
                 reply.setElement(1, 0x50);
                 if (((OakTreeSystemConnectionMemo) getSystemConnectionMemo()).getTrafficController().getNode(nodeaddr) == null) {
                     log.debug("OakTree Sim generateReply getNode({}) = null", nodeaddr);
                 } else {
                     if (((OakTreeSystemConnectionMemo) getSystemConnectionMemo()).getTrafficController().getNode(nodeaddr).getSensorsActive()) { // input (sensors) status reply
                         log.debug("OakTree Sim generateReply for node {}", nodeaddr);
                         int payload = 0b0001; // dummy stand in for sensor status report; should we fetch known state from jmri node?
                         for (int j = 1; j < 3; j++) {
                             payload |= j << 4;
                             reply.setElement(j + 1, payload); // there could be > 5 elements TODO see SerialNode#markChanges
                         }
                     } else {
                         return null; // prevent NPE
                     }
                 }
                 log.debug("Status Reply generated {}", reply.toString());
                 return reply;
             default:
                 log.debug("Message ignored");
                 return null;
         }
    }

    /**
     * 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) {
        }
    }

    /**
     * Get characters from the input source.
     * Length is always 5 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;
        SerialMessage msg = new SerialMessage(5);

        // get 1st byte
        try {
            byte byte0 = readByteProtected(inpipe);
            char0 = (byte0 & 0xFF);
            log.debug("loadChars read {}", char0);
            msg.setElement(0, char0); // address
        } catch (java.io.IOException e) {
            log.debug("loadChars aborted while reading char 0");
            return null;
        }
        if (char0 > 0xFF) {
            // skip as not a node address
            log.debug("bit not valid as node address");
        }

        // read in remaining packets
        for (i = 1; i < 4; i++) { // read next 4 bytes
            log.debug("reading rest of message in simulator, element {}", i);
            try {
                nextByte = readByteProtected(inpipe);
                msg.setElement(i, nextByte);
            } catch (java.io.IOException e) {
                log.debug("loadChars aborted after {} chars", i);
                break;
            }
            log.debug("loadChars read {} (item {})", Integer.toHexString(nextByte & 0xFF), i);
        }

        log.debug("OakTree message received by simulator");
        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);

}