Using PowerAutomate to talk to Tuya devices

[Rookie1]

I am busy with an energy saving applications. In this I need to simply switch power to my geyser to make sure it is switched on when the sun is shining (This is connected to a set of rules, all defined in PowerApps).

I have a Tuya compatible switch, user id and secret code. I studied the API and can execute the switching function both in the Tuya platform and got it working in Postman. There is an amount of pre-processing that needs to happen to get a token (Use usercode, secret, time, etc in a Shifting algorithm to get a token valid for 2 hours, that can be refreshed). I tried powerapps custom connector development (it seems similar to OAuth2.0, but I cannot find a place to add the code (this is defined in Postman as a pre-request script). All of this written in JavaScript.   

Is there a non-obvious place to add the JavaScript? Is there a different way to go aboy

[lbendlin · Accepted solution]

Custom connectors have a place to add code but it needs to be in C#

[Rookie1]

Thanks, I am actually pursuing to build custom connector to calculate the token alone, my c# skills just very low. I am just worried that I am over-complicating things.

There is an option to import a postman script. I imported a working postman script through the import method. 

It created all the flows in the custom connectors, but uses variables setup as pm.environment variables 

like below:

It misses a set of functions used to calculate the variables.

Below Postman Pre-request Java script for info:

I guess I could try and translate this to c#, but this might deceive the object.

(function () {

pm.environment.set("variable_key", "variable_value");

pm.collectionVariables.get("variable_key");

pm.variables.get("variable_key");

pm.globals.get("variable_key");

pm.environment.get("variable_key");

    var timestamp = getTime();

    pm.environment.set("timestamp",timestamp);

    const clientId = pm.environment.get("client_id");

    const secret = pm.environment.get("secret");

    var accessToken = "";

    if(pm.environment.has("easy_access_token")){

        accessToken = pm.environment.get("easy_access_token")

    }

    const httpMethod = pm.request.method.toUpperCase();

    const query = pm.request.url.query;

    const mode = pm.request.body.mode;

    const headers = pm.request.headers;

    // sha256

    var signMap = stringToSign(query, mode, httpMethod, secret)

    var urlStr = signMap["url"]

    var signStr = signMap["signUrl"]

    pm.request.url = pm.request.url.host + urlStr

    var nonce = ""

    if (headers.has("nonce")) {

        var jsonHeaders = JSON.parse(JSON.stringify(headers))

        jsonHeaders.forEach(function(item){

            if (item.key == "nonce" && !item.disabled) {

                nonce = headers.get("nonce")

            }

        })

    }

    var sign = calcSign(clientId, timestamp, nonce, signStr, secret);

    pm.environment.set('easy_sign', sign);

})();

function getTime(){

    var timestamp = new Date().getTime();

    return timestamp;

}

// Token verification calculation

function calcSign(clientId,timestamp,nonce,signStr,secret){

    var str = clientId +timestamp + nonce + signStr;

    var hash = CryptoJS.HmacSHA256(str, secret);

    var hashInBase64 = hash.toString();

    var signUp = hashInBase64.toUpperCase();

    return signUp;

}

// // Business verification calculation

// function calcSign(clientId,accessToken,timestamp,nonce,signStr,secret){

//     var str = clientId + accessToken +timestamp + nonce + signStr;

//     var hash = CryptoJS.HmacSHA256(str, secret);

//     var hashInBase64 = hash.toString();

//     var signUp = hashInBase64.toUpperCase();

//     return signUp;

// }

// Generate signature string

function stringToSign(query, mode, method, secret){

    var sha256 = "";

    var url = "";

    var headersStr = ""

    const headers = pm.request.headers;

    var map = {}

    var arr = []

    var bodyStr = ""

    if(query){

        toJsonObj(query, arr, map)

    }

    if (pm.request.body && mode) {

        if (mode != "formdata" && mode != "urlencoded"){

            bodyStr = replacePostmanParams(pm.request.body.toString())

        } else if (mode == "formdata") {

            // Traversing form key value pairs

            toJsonObj(pm.request.body["formdata"], arr, map)

        } else if (mode == "urlencoded") {

            // Traversing form key value pairs

            toJsonObj(pm.request.body["urlencoded"], arr, map)

        }

    }

    sha256 = CryptoJS.SHA256(bodyStr)

    arr = arr.sort()

    arr.forEach(function(item){

            url += item + "=" + map[item] + "&"

    })

    if (url.length > 0 ) {

        url = url.substring(0, url.length-1)

        url = "/" + pm.request.url.path.join("/") + "?" + url

    } else {

        url = "/" + pm.request.url.path.join("/")

    }

    if (headers.has("Signature-Headers") && headers.get("Signature-Headers")) {

        var jsonHeaders = JSON.parse(JSON.stringify(headers))

        var signHeaderStr = headers.get("Signature-Headers")

        const signHeaderKeys = signHeaderStr.split(":")

        signHeaderKeys.forEach(function(item){

            var val = ""

            if (isSelected(jsonHeaders,item) && headers.get(item)) {

                val = headers.get(item)

            }

            headersStr += item + ":" + val + "\n"

        })

    }

    var map = {}

    url = replacePostmanUrl(url)    

    map["signUrl"] = method + "\n" + sha256 + "\n" + headersStr + "\n" + url

    map["url"] = url

    return map

}

function isSelected(jsonHeaders,key){

    var result = true;

    jsonHeaders.forEach(function(item){

        if (item.key == key && item.disabled) {

            result = false

        }

    })

    return result

}

function replacePostmanParams(str){

    while(str.indexOf("{{")!=-1&&str.indexOf("}}")!=-1){

        const key = str.substring(str.indexOf("{{")+2,str.indexOf("}}"))

        var value = pm.environment.get(key)

        if(!value) value=""

        str = str.replace("{{"+key+"}}", value)

    }

    return str

}

function replacePostmanUrl(str){

    console.log("str:",str)

    while(str.indexOf("{{")!=-1&&str.indexOf("}}")!=-1){

        const key = str.substring(str.indexOf("{{")+2,str.indexOf("}}"))

        var value = pm.environment.get(key)

        if(!value) value=""

        str = str.replace("{{"+key+"}}", value)

    }

    while(str.indexOf(":")!=-1){

        const tempStr = str.substring(str.indexOf(":")+1,str.length);

        var key = "";

        if(tempStr.indexOf("/")!=-1){

            key = tempStr.substring(0,tempStr.indexOf("/"))

        }else if(tempStr.indexOf("?")!=-1){

            key = tempStr.substring(0,tempStr.indexOf("?"))

        }else {

            key = tempStr.substring(0,tempStr.length)

        }

        var value = pm.request.url.variables.get(key)

        if(!value) value=""

        str = str.replace(":"+key, value)

    }

    return str

}

function toJsonObj(params, arr, map){

    var jsonBodyStr = JSON.stringify(params)

    var jsonBody = JSON.parse(jsonBodyStr)

    jsonBody.forEach(function(item){

        if(!item.disabled){

            arr.push(item.key)

            map[item.key] = item.value

        }

    })

}

[Rookie1]

I implemented a combination of Powerautomate and Custom Connectors if anybody is interested.

I created the following:

Custom Connector 1. This only has C# code which I translated from jScript in Postman. This calculates the signstring to be used for the token call

Flow : Execute Custom connector to get parameters, parse JSON,  and then use this to calculate the token

Custom Connector 2. This takes the token and convert it to a signstring for commands (different for on and off)

Depending on on or off parameter set in input to flows.

Flow : Use parameters retrieved above , Parse JSON to perform a command call for on or off.

I previously built a connector to my inverter and can now do multiple calculations in powerapps to optimize powerusage for my geyser.

Project not complete, but learnt a lot. 

[lbendlin]

I would be interested in using this for my thermostat and window blinds. (both for temperature and insolation control).  I guess I have to figure out the JSON for the control calls?

[Rookie1]

I think the first to determine is the API for the manufacturer of your devices. In my case, Tuya provided this platform. Also consider IFFFTT as a platform. Next step is to apply for the API username and password and getting a manual for the calls to be performed. Once there, just a question of figuring out the steps in your flow.

This could be an interesting control project.

The reason why I had to include the coding part was  because Tuya has a very elaborate authentication mechanism. Other connectors that I built was much less complicated (eg to my inverter).

[lbendlin]

Understood. All the devices I mentioned are Tuya based.