/**
* When a device reports data to the IoT platform, the IoT platform calls this API to decode the original data of the device into JSON data that complies with the product model definition.
* The API name and input parameters have been defined. You only need to implement the API.
* @param byte[] payload    Original code stream reported by the device
* @param string topic      Topic to which an MQTT device reports data. This parameter is not carried when a non-MQTT device reports data.
* @return string json      JSON character string that complies with the product model definition
 */
function decode(payload, topic) {
    var jsonObj = {};
    return JSON.stringify(jsonObj);
}

/**
* When the IoT platform delivers a command, it calls this API to encode the JSON data defined in the product model into the original code stream of the device.
* The API name and input parameter format have been defined. You only need to implement the API.
* @param string json      JSON character string that complies with the product model definition
* @return byte[] payload   Original code stream after being encoded
 */
function encode(json) {
    var payload = [];
    return payload;
}

// Upstream message type
var MSG_TYPE_PROPERTIES_REPORT = 'properties_report'; //Reporting device properties
The var MSG_TYPE_COMMAND_RSP = 'command_response'; //Returning a command response
The var MSG_TYPE_PROPERTIES_SET_RSP = 'properties_set_response'; //Returning a property setting response
var MSG_TYPE_PROPERTIES_GET_RSP = 'properties_get_response'; //Returning a property query response
var MSG_TYPE_MESSAGE_UP = 'message_up'; //Reporting message devices
//Downstream message type
var MSG_TYPE_COMMANDS = 'commands'; //Delivering a command
var MSG_TYPE_PROPERTIES_SET = 'properties_set'; //Delivering a property setting request
 varMSG_TYPE_PROPERTIES_GET='properties_get';//Delivering a property query request
var MSG_TYPE_MESSAGE_DOWN = 'messages'; //Delivering platform messages
//Mapping between topics and message types for upstream messages sent by devices
var TOPIC_REG_EXP = {
    'properties_report': new RegExp('\\$oc/devices/(\\S+)/sys/properties/report'),
    'properties_set_response': new RegExp('\\$oc/devices/(\\S+)/sys/properties/set/response/request_id=(\\S+)'),
    'properties_get_response': new RegExp('\\$oc/devices/(\\S+)/sys/properties/get/response/request_id=(\\S+)'),
    'command_response': new RegExp('\\$oc/devices/(\\S+)/sys/commands/response/request_id=(\\S+)'),
    'message_up': new RegExp('\\$oc/devices/(\\S+)/sys/messages/up')
};
/*
Example: When a smoke detector reports properties and returns a command response, it uses binary code streams. The JavaScript script will decode the binary code streams into JSON data that complies with the product model definition.
Input parameters:
  payload:[0x00, 0x50, 0x00, 0x5a]
  topic:$oc/devices/cf40f3c4-7152-41c6-a201-a2333122054a/sys/properties/report
Output parameters:
  {"msg_type":"properties_report","services":[{"service_id":"smokerdector","properties":{"level":80,"temperature":90}}]}
Input parameters:
  payload: [0x02, 0x00, 0x00, 0x01]
  topic: $oc/devices/cf40f3c4-7152-41c6-a201-a2333122054a/sys/commands/response/request_id=bf40f0c4-4022-41c6-a201-c5133122054a
Output parameters:
  {"msg_type":"command_response","result_code":0,"command_name":"SET_ALARM","service_id":"smokerdector","paras":{"value":"1"}}
*/
function decode(payload, topic) {
    var jsonObj = {};
    var msgType = '';
   //If the topic parameter exists, parse the message type based on the topic parameter.
    if (null != topic) {
        msgType = topicParse(topic);
    }
    //Perform the AND operation on the payload by using 0xFF to obtain the corresponding complementary code.
    var uint8Array = new Uint8Array(payload.length);
    for (var i = 0; i < payload.length; i++) {
        uint8Array[i] = payload[i] & 0xff;
    }
    var dataView = new DataView(uint8Array.buffer, 0);
    //Convert binary data to the format used for property reporting.
    if (msgType == MSG_TYPE_PROPERTIES_REPORT) {
        //Set the value of serviceId, which corresponds to smokerdector in the product model.
        var serviceId = 'smokerdector';
        //Obtain the level value from the code stream.
        var level = dataView.getInt16(0);
        //Obtain the temperature value from the code stream.
        var temperature = dataView.getInt16(2);
        //Convert the code stream to the JSON format used for property reporting.
        jsonObj = {
            "msg_type": "properties_report",
            "services": [{"service_id": serviceId, "properties": {"level": level, "temperature": temperature}}]
        };
    } else if (msgType == MSG_TYPE_COMMAND_RSP) { //Convert binary data to the format used by a command response.
        //Set the value of serviceId, which corresponds to smokerdector in the product model.
        var serviceId = 'smokerdector';
        var command = dataView.getInt8(0); //Obtain the command name ID from the binary code stream.
        var command_name = '';
        if (2 == command) {
            command_name = 'SET_ALARM';
        }
        var result_code  = dataView.getInt16(1); //Obtain the command execution result from the binary code stream.
        var value = dataView.getInt8(3); //Obtain the returned value of the command execution result from the binary code stream.
       //Convert data to the JSON format used by the command response.
        jsonObj = {
            "msg_type": "command_response",
            "result_code": result_code,
            "command_name": command_name,
            "service_id": serviceId,
            "paras": {"value": value}
        };
    } else if (msgType == MSG_TYPE_PROPERTIES_SET_RSP) {
       //Convert data to the JSON format used by the property setting response.
        //jsonObj = {"msg_type":"properties_set_response","result_code":0,"result_desc":"success"};
    } else if (msgType == MSG_TYPE_PROPERTIES_GET_RSP) {
       //Convert data to the JSON format used by the property query response.
        //jsonObj = {"msg_type":"properties_get_response","services":[{"service_id":"analog","properties":{"PhV_phsA":"1","PhV_phsB":"2"}}]};
    } else if (msgType == MSG_TYPE_MESSAGE_UP) {
        //Convert the code stream to the JSON format used by message reporting.
        //jsonObj = {"msg_type":"message_up","content":"hello"};
    }
    //Convert data to a character string in JSON format.
    return JSON.stringify(jsonObj);
}
/*
Sample data: When a command is delivered, JSON dataon the IoT platform is encoded into binary code streams using the encode method of JavaScript.
Input parameters ->
    {"msg_type":"commands","command_name":"SET_ALARM","service_id":"smokerdector","paras":{"value":1}}
Output parameters->
    [0x01,0x00, 0x00, 0x01]
*/
function encode(json) {
    //Convert data to a JSON object.
    var jsonObj = JSON.parse(json);
   //Obtain the message type.
    var msgType = jsonObj.msg_type;
    var payload = [];
   //Convert data in JSON format to binary data.
    if (msgType == MSG_TYPE_COMMANDS) {//Command delivery
       //Command delivery format example: {"msg_type":"commands","command_name":"SET_ALARM","service_id":"smokerdector","paras":{"value":1}}
        //Convert the format used by command delivery to a binary code stream.
        payload = payload.concat(buffer_uint8(1)); //Identifies the command delivery.
        if (jsonObj.command_name == 'SET_ALARM') {
            payload = payload.concat(buffer_uint8(0)); //Command name.
        }
        var paras_value = jsonObj.paras.value;
        payload = payload.concat(buffer_int16(paras_value)); //Set the command property value.
    } else if (msgType == MSG_TYPE_PROPERTIES_SET) {
        //Property setting format example: {"msg_type":"properties_set","services":[{"service_id":"Temperature","properties":{"value":57}}]}
       //Convert the JSON format to the corresponding binary code streams if the property setting scenario is involved.
    } else if (msgType == MSG_TYPE_PROPERTIES_GET) {
        //Property query format example: {"msg_type":"properties_get","service_id":"Temperature"}
       //Convert the JSON format to the corresponding binary code streams if the property query scenario is involved.
    } else if (msgType == MSG_TYPE_MESSAGE_DOWN) {
       //Message delivery format example: {"msg_type":"messages","content":"hello"}
       //Convert the JSON format to the corresponding binary code streams if the message delivery scenario is involved.
    }
   //Return the encoded binary data.
    return payload;
}
//Parse the message type based on the topic name.
function topicParse(topic) {
    for (var type in TOPIC_REG_EXP) {
        var pattern = TOPIC_REG_EXP[type];
        if (pattern.test(topic)) {
            return type;
        }
    }
    return '';
}
//Convert an 8-bit unsigned integer into a byte array.
function buffer_uint8(value) {
    var uint8Array = new Uint8Array(1);
    var dataView = new DataView(uint8Array.buffer);
    dataView.setUint8(0, value);
    return [].slice.call(uint8Array);
}

//Convert a 16-bit unsigned integer into a byte array.
function buffer_int16(value) {
    var uint8Array = new Uint8Array(2);
    var dataView = new DataView(uint8Array.buffer);
    dataView.setInt16(0, value);
    return [].slice.call(uint8Array);
}
//Convert a 32-bit unsigned integer into a byte array.
function buffer_int32(value) {
    var uint8Array = new Uint8Array(4);
    var dataView = new DataView(uint8Array.buffer);
    dataView.setInt32(0, value);
    return [].slice.call(uint8Array);
}

// Upstream message type
var MSG_TYPE_PROPERTIES_REPORT = 'properties_report'; //Reporting device properties
var MSG_TYPE_COMMAND_RSP = 'command_response'; //Returning a command response
//Downstream message type
var MSG_TYPE_COMMANDS = 'commands'; //Delivering a command
var MSG_TYPE_PROPERTIES_REPORT_REPLY = 'properties_report_reply'; //Response for property reporting
//Message type list
var MSG_TYPE_LIST = {
    0: MSG_TYPE_PROPERTIES_REPORT,         //In the code stream, 0 indicates that the device property is reported.
    1: MSG_TYPE_PROPERTIES_REPORT_REPLY, //In the code stream, 1 indicates the response for property reporting.
    2: MSG_TYPE_COMMANDS,                   //In the code stream, 2 indicates the command delivery from the platform.
    3: MSG_TYPE_COMMAND_RSP                 //In the code stream, 3 indicates the command response from the device.
};
/*
Example: When a smoke detector reports properties and returns a command response, it uses binary code streams. The JavaScript script will decode the binary code streams into JSON data that complies with the product model definition.
Input parameters:
  payload:[0x00, 0x00, 0x50, 0x00, 0x5a]
Output parameters:
  {"msg_type":"properties_report","services":[{"service_id":"smokerdector","properties":{"level":80,"temperature":90}}]}
Input parameters:
  payload: [0x03, 0x01, 0x00, 0x00, 0x01]
Output parameters:
  {"msg_type":"command_response","request_id":1,"result_code":0,"paras":{"value":"1"}}
*/
function decode(payload, topic) {
    var jsonObj = {};
    //Perform the AND operation on the payload by using 0xFF to obtain the corresponding complementary code.
    var uint8Array = new Uint8Array(payload.length);
    for (var i = 0; i < payload.length; i++) {
        uint8Array[i] = payload[i] & 0xff;
    }
    var dataView = new DataView(uint8Array.buffer, 0);
    //Obtain the message type from the first byte of the message code stream.
    var messageId = dataView.getInt8(0);
    //Convert binary data to the format used for property reporting.
    if (MSG_TYPE_LIST[messageId] == MSG_TYPE_PROPERTIES_REPORT) {
        //Set the value of serviceId, which corresponds to smokerdector in the product model.
        var serviceId = 'smokerdector';
        //Obtain the level value from the code stream.
        var level = dataView.getInt16(1);
        //Obtain the temperature value from the code stream.
        var temperature  = dataView.getInt16(3);
        //Convert data to the JSON format used by property reporting.
        jsonObj = {"msg_type":"properties_report","services":[{"service_id":serviceId,"properties":{"level":level,"temperature":temperature}}]};
    }else if (MSG_TYPE_LIST[messageId] == MSG_TYPE_COMMAND_RSP) { //Convert binary data to the format used by the command response.
        var requestId = dataView.getInt8(1);
        var result_code  = dataView.getInt16(2); //Obtain the command execution result from the binary code stream.
        var value = dataView.getInt8(4); //Obtain the returned value of the command execution result from the binary code stream.
       //Convert data to the JSON format used by the command response.
        jsonObj = {"msg_type":"command_response","request_id":requestId,"result_code":result_code,"paras":{"value":value}};
    }
    //Convert data to a character string in JSON format.
    return JSON.stringify(jsonObj);
}
/*
Sample data: When a command is delivered, data in JSON format on the platform is encoded into a binary code stream using the encode method of JavaScript.
Input parameters ->
    {"msg_type":"commands","request_id":1,"command_name":"SET_ALARM","service_id":"smokerdector","paras":{"value":1}}
Output parameters->
    [0x02, 0x00, 0x00, 0x00, 0x01]
Sample data: When a response is returned for property reporting, data in JSON format on the platform is encoded into a binary code stream using the encode method of JavaScript.
Input parameters ->
    {"msg_type":"properties_report_reply","request":"000050005a","result_code":0}
Output parameters->
    [0x01, 0x00]
*/
function encode(json) {
    //Convert data to a JSON object.
    var jsonObj = JSON.parse(json);
   //Obtain the message type.
    var msgType = jsonObj.msg_type;
    var payload = [];
   //Convert data in JSON format to binary data.
    if (msgType == MSG_TYPE_COMMANDS) { //Command delivery
        payload = payload.concat(buffer_uint8(2)); //Identifies the command delivery.
        payload = payload.concat(buffer_uint8(jsonObj.request_id)); //Command ID
        if (jsonObj.command_name == 'SET_ALARM') {
            payload = payload.concat(buffer_uint8(0)); //Command name.
        }
        var paras_value = jsonObj.paras.value;
        payload = payload.concat(buffer_int16(paras_value)); //Set the command property value.
    } else if (msgType == MSG_TYPE_PROPERTIES_REPORT_REPLY) { //Response for device property reporting
        payload = payload.concat(buffer_uint8(1)); //Response to property reporting
        if (0 == jsonObj.result_code) {
            payload = payload.concat(buffer_uint8(0)); //The property reporting message is successfully processed.
        }
    }
   //Return the encoded binary data.
    return payload;
}
//Convert an 8-bit unsigned integer into a byte array.
function buffer_uint8(value) {
    var uint8Array = new Uint8Array(1);
    var dataView = new DataView(uint8Array.buffer);
    dataView.setUint8(0, value);
    return [].slice.call(uint8Array);
}
//Convert a 16-bit unsigned integer into a byte array.
function buffer_int16(value) {
    var uint8Array = new Uint8Array(2);
    var dataView = new DataView(uint8Array.buffer);
    dataView.setInt16(0, value);
    return [].slice.call(uint8Array);
}
//Convert a 32-bit unsigned integer into a byte array.
function buffer_int32(value) {
    var uint8Array = new Uint8Array(4);
    var dataView = new DataView(uint8Array.buffer);
    dataView.setInt32(0, value);
    return [].slice.call(uint8Array);
}