In the second blog Wechat development series 2 – development Q&A service using nodejs of this series, we have developed a kind of Q&A service in Wechat which leverages a free Tuning Restful service so that you could chat with this service:

In this blog, I will show the steps how to store all of those conversation logs via Redis, so that you can review the conversations within Wechat app or delete them if necessary.

Implemented feature

Two new sub menus “Review” and “Delete” are developed under menu “Conversation”:

Once Review menu is pressed, the conversation log will be read out from Redis and displayed in Wechat app:

Delete menu will trigger the deletion of the conversation log belonging to current user who has pressed it. Once conversation is deleted, corresponding notification will be sent out if user has pressed the Review menu again.

Implementation detail

(1) Since as before my WeChat server runs on Heroku, which supports Redis as well.
Redis is an open source (BSD licensed), in-memory data structure store, used as a database, cache and message broker. It supports data structures such as strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperloglogs and geospatial indexes with radius queries.
In this blog I will use Redis to store conversation logs.

It is very easy in Heroku to enable an application with Redis support, just select your application from drop down list and press Continue:

The default plan “Hobby Dev” is completely for free and enough for this prototype development.

Once done, in you application dashboard you can see the Redis as addon:

and the actual url for this Redis instance is automatically set in application variable which could be used in your program:

You don’t need any additional configuration on Redis, which is now ready for development.
(2) follow the steps in blog Wechat development series 5 – embedded your UI5 application to Wechat app to create menu and two submenu.

It is enough to create menu via postman. You’d better first remove the old menu done in previous blog and recreate a new menu from scratch:

the source code of HTTP post payload for the new menu creation:

{
                 "button":[
                     {
                       "name":"UI5",
                       "sub_button":[{
                            "type": "view",
                            "name": "Jerry List",
                            "url": "http://wechatjerry.herokuapp.com/ui5"
                       },{
                            "type": "click",
                            "name": "Other UI5 application",
                             "key": "dataQuery"
                       }]
                     },
                     {
                       "name":"Conversation",
                       "sub_button":[{
                            "type": "click",
                            "name": "Review",
                            "key": "review"
                       },{
                            "type": "click",
                            "name": "Delete",
                             "key": "delete"
                       }]
                     }
                 ]
  }

(3) Now every time when Tuning service receives a query from end user and is ready to send the answer of this query, add logic to record this conversation detail.
Just add one line for logging in tuning.js:

The conversationLogService is implemented in conversationLogService.js, which simply delegates the logging call to Redis service wrapper module.

Date.prototype.today = function () { 
    return ((this.getDate() < 10)?"0":"") + this.getDate() +"/"+(((this.getMonth()+1) < 10)?"0":"") + (this.getMonth()+1) +"/"+ this.getFullYear();
}

Date.prototype.timeNow = function () {
     return ((this.getHours() < 10)?"0":"") + this.getHours() +":"+ ((this.getMinutes() < 10)?"0":"") + this.getMinutes() +":"+ ((this.getSeconds() < 10)?"0":"") + this.getSeconds();
}

function logConversation(wholeContent, question, answer){
    var fromUserId = formattedValue(getXMLNodeValue('FromUserName', wholeContent));
    var toUserId = formattedValue(getXMLNodeValue('ToUserName', wholeContent));
    var fromUserName = config.userMap[fromUserId] || fromUserId;
    var toUserName = config.userMap[toUserId] || toUserId;
    var datetime = "Send Time: " + new Date().today() + "  " + new Date().timeNow();
    redisClient.insert(toUserId, objectToString(fromUserName, toUserName, datetime, question, answer));
};

function objectToString(fromUserName, toUserName, datetime, question, answer){
    var record = {
        "from": fromUserName,
        "to": toUserName,
        "sendTime": datetime,
        "question": question,
        "answer": answer
    };

    return JSON.stringify(record); 
}

function getList(sToUserOpenId){
    return redisClient.getList(sToUserOpenId);
}

function deleteLog(sToUserOpenId){
    return redisClient.clearList(sToUserOpenId);
}

var oService = {
    log: logConversation,
    getLog: getList,
    deleteLog: deleteLog
}

module.exports = oService;

Redis service wrapper module is implemented in file redisClient.js.

This wrapper module is built on top of open source Redis module for nodejs, whose source code could be found from github: https://github.com/NodeRedis/node_redis

var redis = require("redis"),
    client = redis.createClient(process.env.REDIS_URL || "redis://h:p99a8dd0d92871b9ffe7a026e6d70beecd7f2a0e743fa1e2840a58ce048f41c4a@ec2-34-237-158-248.compute-1.amazonaws.com:9479"); // by default localhost will be used!!

client.on("error", function (err) {
    console.log("Trouble......... Redis startup failed: " + err);
});

function insertIntoList(sOpenId, oElement){
    client.lpush(sOpenId, oElement);
}

function clearList(sOpenId){
    return new Promise(function(resolve,reject){
        client.del(sOpenId, function(error, count){
            if(error){
                console.log("error when clear list:" + error);
                reject(error);
            }
            var reply = "list clear successfully";
            console.log(reply);
            resolve(reply); 
        });
    });
}

function getListContent(sOpenId){

    return new Promise(function(resolve,reject){
        client.lrange(sOpenId, 0, -1, function(err, reply) {
            console.log("content for list: " + sOpenId + " **********: " + reply + "***");
            var content = reply;
            if( content == ""){
                content = "no conversation log found.";
                console.log("reject content: " + content);
                reject(content);
            }
            else {
              resolve(formatToWechat(content));
            }
        });
     });
}

function formatToWechat(raw){
    var formatted = "[" + raw + "]";
    var result = "";
    var logs = JSON.parse(formatted);
    for( var i = 0; i < logs.length; i++){
        var record = "record[" + i + "]:" + " [[from]] " + logs[i].from
         + " [[to]] " + logs[i].to + " [[sendTime]] " + logs[i].sendTime + " [[question]] " + logs[i].question
        + " [[answer]] " + logs[i].answer;
        if( i === 0){
            result = record;
        }
        else{
            result = result + "\n" + "\n" + record;
        }
    }
    return result;
}

var oRedisClient = {
    insert: insertIntoList,
    clearList: clearList,
    getList: getListContent
};

module.exports = oRedisClient;

(4) implement event handling logic when menu “review” and “delete” are pressed.

Corresponding API provided by Redis are called to read log records from Redis or just clear the list where the log records are stored.

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