package jmri.jmrix.xpa;

import java.util.Arrays;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Encodes a message to an XpressNet command station via an XPA and a modem.
 *
 * @author Paul Bender Copyright (C) 2004
 */
public class XpaMessage implements jmri.jmrix.Message {

    public final static int MAX_SIZE = 64;

    private int _nDataChars = 0;
    private byte[] _dataChars = null;

    // create a new one
    public XpaMessage(int i) {
        if (i < 1) {
            log.error("invalid length in call to ctor");
        }
        _nDataChars = i;
        _dataChars = new byte[i];
    }

    // create a new one, given a string containing the message.
    public XpaMessage(String s) {
        if (s.length() < 1) {
            log.error("zero length string in call to ctor");
        }
        _nDataChars = s.length();
        _dataChars = s.getBytes();
    }

    // create a new one with default MAX_SIZE
    public XpaMessage() {
        this(MAX_SIZE);
    }

    // copy one
    public XpaMessage(XpaMessage m) {
        if (m == null) {
            log.error("copy ctor of null message");
            return;
        }
        _nDataChars = m._nDataChars;
        _dataChars = new byte[_nDataChars];
        System.arraycopy(m._dataChars, 0, _dataChars, 0, _nDataChars);
    }

    // compare two XpaMessages.
    @Override
    public boolean equals(Object m) {
        if (m != null && m instanceof XpaMessage
                && ((XpaMessage) m).getNumDataElements() == this.getNumDataElements()) {
            return Arrays.equals(((XpaMessage) m)._dataChars, _dataChars);
        }
        return false;
    }

    @Override
    public int hashCode() {
        int hash = 5;
        hash = 79 * hash + this._nDataChars;
        hash = 79 * hash + Arrays.hashCode(this._dataChars);
        return hash;
    }

    // accessors to the bulk data
    @Override
    public int getNumDataElements() {
        return _nDataChars;
    }

    @Override
    public int getElement(int n) {
        return _dataChars[n];
    }

    @Override
    public void setElement(int n, int v) {
        _dataChars[n] = (byte) (v & 0x7F);
    }

    // display format
    @Override
    public String toString() {
        StringBuilder s = new StringBuilder();
        for (int i = 0; i < _nDataChars; i++) {
            s.append((char) _dataChars[i]);
        }
        return s.toString();
    }

    // static methods to return a formatted message
    static XpaMessage getDefaultInitMsg() {
        return new XpaMessage("ATX0E0;");
    }


    /* Get a message which sends an Estop or Everything off command
     to the layout.  This will toggle the Estop commands.
     XPA settings can change the behavior of this command.  It may
     only work with a single locomotive, or it may kill the entire
     layout.
     */
    static XpaMessage getEStopMsg() {
        return new XpaMessage("ATDT0;");
    }

    // Locomotive Messages

    /*
     Get a message which sends an "Idle" (zero speed) command
     to a specific locomotive on the layout.
     */
    static XpaMessage getIdleMsg(int address) {
        return new XpaMessage("ATDT#" + address + "*5;");
    }

    /**
     * Get a message for an "Increase Speed" command
     * to a specific locomotive on the layout.  To make
     * calculations easy, this uses a single speed step increase.
     *
     * @param address   throttle loco address for message
     * @param steps     amount of speed steps to change to increase
     * @return message for the requested change
     */
    static XpaMessage getIncSpeedMsg(int address, int steps) {
        StringBuilder buf = new StringBuilder("ATDT#" + address + "*");
        String message;
        for (int i = 0; i < steps; i++) {
            buf.append("3");
        }
        message = buf.toString() + ";";
        return new XpaMessage(message);
    }

    /**
     * Get a message for a "Decrease Speed" command
     * to a specific locomotive on the layout.  To make
     * calculations easy, this uses a single speed step decrease.
     *
     * @param address   throttle loco address for message
     * @param steps     amount of speed steps to change to decrease
     * @return message for the requested change
     */
    static XpaMessage getDecSpeedMsg(int address, int steps) {
        StringBuilder buf = new StringBuilder("ATDT#" + address + "*");
        String Message;
        for (int i = 0; i < steps; i++) {
            buf.append("1");
        }
        Message = buf.toString() + ";";
        return new XpaMessage(Message);
    }

    /*
     Get a message for a "Direction Forward" command
     to a specific locomotive on the layout.
     */
    static XpaMessage getDirForwardMsg(int address) {
        return new XpaMessage("ATDT#" + address + "*52;");
    }

    /*
     Get a message for a "Direction Reverse" command
     to a specific locomotive on the layout.
     */
    static XpaMessage getDirReverseMsg(int address) {
        return new XpaMessage("ATDT#" + address + "*58;");
    }

    /*
     Get a message which sends a "Toggle Function" command
     to a specific locomotive on the layout.
     */
    static XpaMessage getFunctionMsg(int address, int function) {
        return new XpaMessage("ATDT#" + address + "**" + function + ";");
    }

    // Switch Commands

    /*
     Get a message for a "Switch Position Normal" command
     to a specific accessory decoder on the layout.
     */
    static XpaMessage getSwitchNormalMsg(int address) {
        return new XpaMessage("ATDT#" + address + "#3;");
    }

    /*
     Get a message for a "Switch Position Reverse" command
     to a specific accessory decoder on the layout.
     */
    static XpaMessage getSwitchReverseMsg(int address) {
        return new XpaMessage("ATDT#" + address + "#1;");
    }

    // Xpa Device Settings
    /* Get a message for setting a Device value */
    public static XpaMessage getDeviceSettingMsg(int setting) {
        return new XpaMessage("ATDT*" + setting + "*");
    }

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

}