/**
 * Copyright (c) 2014 Digi International Inc.,
 * All rights not expressly granted are reserved.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Digi International Inc. 11001 Bren Road East, Minnetonka, MN 55343
 * =======================================================================
 */
package com.digi.xbee.api.packet.common;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Arrays;
import java.util.LinkedHashMap;

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

import com.digi.xbee.api.models.ATStringCommands;
import com.digi.xbee.api.packet.XBeeAPIPacket;
import com.digi.xbee.api.packet.APIFrameType;
import com.digi.xbee.api.utils.HexUtils;

/**
 * This class represents an AT Command XBee packet. Packet is built
 * using the parameters of the constructor or providing a valid API payload.
 * 
 * <p>Used to query or set module parameters on the local device. This API
 * command applies changes after executing the command. (Changes made to
 * module parameters take effect once changes are applied.).</p>
 * 
 * <p>Command response is received as an {@code ATCommandResponsePacket}.</p>
 * 
 * @see ATCommandResponsePacket
 * @see com.digi.xbee.api.packet.XBeeAPIPacket
 */
public class ATCommandPacket extends XBeeAPIPacket {

        // Constants.
        private static final int MIN_API_PAYLOAD_LENGTH = 4; // 1 (Frame type) + 1 (frame ID) + 2 (AT command)
        
        // Variables.
        private final String command;
        
        private byte[] parameter;
        
        private Logger logger;
        
        /**
         * Creates a new {@code ATCommandPacket} object from the given payload.
         * 
         * @param payload The API frame payload. It must start with the frame type 
         *                corresponding to a AT Command packet ({@code 0x08}).
         *                The byte array must be in {@code OperatingMode.API} mode.
         * 
         * @return Parsed AT Command packet.
         * 
         * @throws IllegalArgumentException if {@code payload[0] != APIFrameType.AT_COMMAND.getValue()} or
         *                                  if {@code payload.length < }{@value #MIN_API_PAYLOAD_LENGTH} or
         *                                  if {@code frameID < 0} or
         *                                  if {@code frameID > 255}.
         * @throws NullPointerException if {@code payload == null}.
         */
        public static ATCommandPacket createPacket(byte[] payload) {
                if (payload == null)
                        throw new NullPointerException("AT Command packet payload cannot be null.");
                
                // 1 (Frame type) + 1 (frame ID) + 2 (AT command)
                if (payload.length < MIN_API_PAYLOAD_LENGTH)
                        throw new IllegalArgumentException("Incomplete AT Command packet.");
                
                if ((payload[0] & 0xFF) != APIFrameType.AT_COMMAND.getValue())
                        throw new IllegalArgumentException("Payload is not an AT Command packet.");
                
                // payload[0] is the frame type.
                int index = 1;
                
                // Frame ID byte.
                int frameID = payload[index] & 0xFF;
                index = index + 1;
                
                // 2 bytes of AT command, starting at 2nd byte.
                String command = new String(new byte[]{payload[index], payload[index + 1]});
                index = index + 2;
                
                // Get data.
                byte[] parameterData = null;
                if (index < payload.length)
                        parameterData = Arrays.copyOfRange(payload, index, payload.length);
                
                return new ATCommandPacket(frameID, command, parameterData);
        }
        
        /**
         * Class constructor. Instantiates a new {@code ATCommandPacket} object
         * with the given parameters.
         * 
         * @param frameID XBee API frame ID.
         * @param command AT command.
         * @param parameter AT command parameter as String, {@code null} if it is 
         *                  not required.
         * 
         * @throws IllegalArgumentException if {@code frameID < 0} or
         *                                  if {@code frameID > 255}.
         * @throws NullPointerException if {@code command == null}.
         */
        public ATCommandPacket(int frameID, String command, String parameter) {
                this(frameID, command, parameter == null ? null : parameter.getBytes());
        }
        
        /**
         * Class constructor. Instantiates a new {@code ATCommandPacket} object
         * with the given parameters.
         * 
         * @param frameID XBee API frame ID.
         * @param command AT command.
         * @param parameter AT command parameter {@code null} if it is not required.
         * 
         * @throws IllegalArgumentException if {@code frameID < 0} or
         *                                  if {@code frameID > 255}.
         * @throws NullPointerException if {@code command == null}.
         */
        public ATCommandPacket(int frameID, String command, byte[] parameter) {
                super(APIFrameType.AT_COMMAND);
                
                if (command == null)
                        throw new NullPointerException("AT command cannot be null.");
                if (frameID < 0 || frameID > 255)
                        throw new IllegalArgumentException("Frame ID must be between 0 and 255.");
                
                this.frameID = frameID;
                this.command = command;
                this.parameter = parameter;
                this.logger = LoggerFactory.getLogger(ATCommandPacket.class);
        }
        
        /*
         * (non-Javadoc)
         * @see com.digi.xbee.api.packet.XBeeAPIPacket#getAPIPacketSpecificData()
         */
        @Override
        protected byte[] getAPIPacketSpecificData() {
                ByteArrayOutputStream os = new ByteArrayOutputStream();
                try {
                        os.write(command.getBytes());
                        if (parameter != null)
                                os.write(parameter);
                } catch (IOException e) {
                        logger.error(e.getMessage(), e);
                }
                return os.toByteArray();
        }
        
        /*
         * (non-Javadoc)
         * @see com.digi.xbee.api.packet.XBeeAPIPacket#needsAPIFrameID()
         */
        @Override
        public boolean needsAPIFrameID() {
                return true;
        }
        
        /**
         * Returns the AT command.
         * 
         * @return The AT command.
         */
        public String getCommand() {
                return command;
        }
        
        /**
         * Sets the AT command parameter as String.
         * 
         * @param parameter The AT command parameter as String.
         */
        public void setParameter(String parameter) {
                if (parameter == null)
                        this.parameter = null;
                else
                        this.parameter = parameter.getBytes();
        }
        
        /**
         * Sets the AT command parameter.
         * 
         * @param parameter The AT command parameter.
         */
        public void setParameter(byte[] parameter) {
                this.parameter = parameter;
        }
        
        /**
         * Returns the AT command parameter.
         * 
         * @return The AT command parameter.
         */
        public byte[] getParameter() {
                return parameter;
        }
        
        /**
         * Returns the AT command parameter as String.
         * 
         * @return The AT command parameter as String, {@code null} if no parameter 
         *         is set.
         */
        public String getParameterAsString() {
                if (parameter == null)
                        return null;
                return new String(parameter);
        }
        
        /*
         * (non-Javadoc)
         * @see com.digi.xbee.api.packet.XBeeAPIPacket#isBroadcast()
         */
        @Override
        public boolean isBroadcast() {
                return false;
        }
        
        /*
         * (non-Javadoc)
         * @see com.digi.xbee.api.packet.XBeeAPIPacket#getAPIPacketParameters()
         */
        @Override
        public LinkedHashMap<String, String> getAPIPacketParameters() {
                LinkedHashMap<String, String> parameters = new LinkedHashMap<String, String>();
                parameters.put("AT Command", HexUtils.prettyHexString(HexUtils.byteArrayToHexString(command.getBytes())) + " (" + command + ")");
                if (parameter != null) {
                        if (ATStringCommands.get(command) != null)
                                parameters.put("Parameter", HexUtils.prettyHexString(HexUtils.byteArrayToHexString(parameter)) + " (" + new String(parameter) + ")");
                        else
                                parameters.put("Parameter", HexUtils.prettyHexString(HexUtils.byteArrayToHexString(parameter)));
                }
                return parameters;
        }
}