st-schema

st-schema-nodejs

ST Schema helper library for NodeJS

Installing the module

npm install st-schema

Connector app structure

const connector = new SchemaConnector()
  .discoveryHandler((accessToken, response) => {
    /**
     * Discovery request. Respond with a list of devices. Called after installation of the
     * connector and every six hours after that.
     * @accessToken External cloud access token
     * @response {DiscoveryResponse} Discovery response object
     */
  })
  .stateRefreshHandler((accessToken, response) => {
    /**
     * State refresh request. Respond with the current states of all devices. Called after
     * device discovery runs.
     * @accessToken External cloud access token
     * @response {StateRefreshResponse} StateRefresh response object
     */
  })
  .commandHandler((accessToken, response, devices) => {
    /**
     * Device command request. Control the devices and respond with new device states
     * @accessToken External cloud access token
     * @response {CommandResponse} CommandResponse response object
     * @devices {array} List of ST device commands
     */
  })
  .callbackAccessHandler((accessToken, callbackAuthentication, callbackUrls) => {
    /**
     * Create access and refresh tokens to allow SmartThings to be informed of device state
     * changes as they happen. 
     * @accessToken External cloud access token
     * @callbackAuthentication ST access and refresh tokens for proactive state callbacks
     * @callbackUrls Callback and refresh token URLs
     */
  })
  .integrationDeletedHandler(accessToken => {
    /**
     * Called when the connector is removed from SmartThings. You may want clean up access
     * tokens and other data when that happend.
     * @accessToken External cloud access token
     */
  });

Minimal loopback connector example

This simple connector creates a one dimmer device named Test Dimmer. There's no physical device involved. The connector command handler simply returns the state value corresponding to the issued command. The current state of the device is stored in memory, so if the server is restarted the states will revert to their initial value. This implementation does not implement proactive state callbacks.

connector.js

const {SchemaConnector, DeviceErrorTypes} = require('st-schema')
const deviceStates = { switch: 'off', level: 100}
const connector = new SchemaConnector()
  .discoveryHandler((accessToken, response) => {
    response.addDevice('external-device-1', 'Test Dimmer', 'c2c-dimmer')
      .manufacturerName('Example Connector')
      .modelName('Virtual Dimmer');
  })
  .stateRefreshHandler((accessToken, response) => {
    response.addDevice('external-device-1', [
      {
        component: 'main',
        capability: 'st.switch',
        attribute: 'switch',
        value: deviceStates.switch
      },
      {
        component: 'main',
        capability: 'st.switchLevel',
        attribute: 'level',
        value: deviceStates.level
      }
    ])
  })
  .commandHandler((accessToken, response, devices) => {
    for (const device of devices) {
      const deviceResponse = response.addDevice(device.externalDeviceId);
      for (cmd of device.commands) {
        const state = {
          component: cmd.component,
          capability: cmd.capability
        };
        if (cmd.capability === 'st.switchLevel' && cmd.command === 'setLevel') {
          state.attribute = 'level';
          state.value = deviceStates.level = cmd.arguments[0];
          deviceResponse.addState(state);

        } else if (cmd.capability === 'st.switch') {
          state.attribute = 'switch';
          state.value = deviceStates.switch = cmd.command === 'on' ? 'on' : 'off';
          deviceResponse.addState(state);

        } else {
          deviceResponse.setError(
            `Command '${cmd.command} of capability '${cmd.capability}' not supported`,
            DeviceErrorTypes.CAPABILITY_NOT_SUPPORTED)
        }
      }
    }
  });

module.exports = connector

Running as a web-service

To run the above connector as a web service using the Express framework create a server like this one. Note that a real application would need to validate the access token passed in each request. This example only checks for the presence of the token.

server.js

const express = require('express');
const connector = require('./connector');
const server = express();
const port = 3000;
server.use(express.json());

server.post('/', (req, res) => {
  if (accessTokenIsValid(req)) {
    connector.handleHttpCallback(req, res)
  }
});

function accessTokenIsValid(req) {
  // Replace with proper validation of issued access token
  if (req.body.authentication.token) {
    return true;
  }
  res.status(401).send('Unauthorized')
  return false;
}

server.listen(port);
console.log(`Server listening on http://127.0.0.1:${port}`);

Running as an AWS Lambda

To run the connector as an AWS lambda use a handler like this one.

index.js

const connector = require('./connector');
exports.handle = async (evt, context, callback) => {
    return connector.handleLambdaCallback(evt, context, callback);
};

Proactive state callbacks

Sensors and devices that can be controlled other than through the SmartThings mobile app can change state at any time. To ensure that the SmartThings platform is made aware of these state changes right away callsbacks can be implemented to call into the SmartThings cloud. These callbacks are secured via a token exchange dependent on the client ID and secret defined for the ST Schema connector in the Developer Workspace. The following example is a minimal implementation of a connector that supports these callback. It builds on the previous example by implementing the callbacks and exposing a web-service endpoint for executing device commands.

app.js

The connector app is now initialized with the ST Schema connector's client ID and secret, which are available from the Developer workspace. It also declares an accessTokens map to contain the list of connectors that need to be called when device state changes. Note that this simple implementation stores the connectors in memory, so restarting the server will cause them to be lost. The app also has new callbackAccessHandler and integrationDeletedHandler handlers defined to add and remove entries from the accessTokens map.

const {SchemaConnector} = require('st-schema');
const deviceStates = {switch: 'off', level: 100};
const accessTokens = {};
const connector = new SchemaConnector()
  .clientId(process.env.ST_CLIENT_ID)
  .clientSecret(process.env.ST_CLIENT_SECRET)
  .discoveryHandler((accessToken, response) => {
    response.addDevice('external-device-1', 'Test Dimmer', 'c2c-dimmer')
      .manufacturerName('Example Connector')
      .modelName('Virtual Dimmer');
  })
  .stateRefreshHandler((accessToken, response) => {
    response.addDevice('external-device-1', [
      {
        component: 'main',
        capability: 'st.switch',
        attribute: 'switch',
        value: deviceStates.switch
      },
      {
        component: 'main',
        capability: 'st.switchLevel',
        attribute: 'level',
        value: deviceStates.level
      }
    ])
  })
  .commandHandler((accessToken, response, devices) => {
    for (const device of devices) {
      const deviceResponse = response.addDevice(device.externalDeviceId);
      for (cmd of device.commands) {
        const state = {
          component: cmd.component,
          capability: cmd.capability
        };
        if (cmd.capability === 'st.switchLevel' && cmd.command === 'setLevel') {
          state.attribute = 'level';
          state.value = deviceStates.level = cmd.arguments[0];
          deviceResponse.addState(state);

        } else if (cmd.capability === 'st.switch') {
          state.attribute = 'switch';
          state.value = deviceStates.switch = cmd.command === 'on' ? 'on' : 'off';
          deviceResponse.addState(state);

        } else {
          deviceResponse.setError(
            `Command '${cmd.command} of capability '${cmd.capability}' not supported`,
            DeviceErrorTypes.CAPABILITY_NOT_SUPPORTED)
        }
      }
    }
  })
  .callbackAccessHandler((accessToken, callbackAuthentication, callbackUrls) => {
    accessTokens[accessToken] = {
      callbackAuthentication,
      callbackUrls
    }
  })

  .integrationDeletedHandler(accessToken => {
    delete accessTokens[accessToken]
  });

module.exports = {
  connector: connector,
  deviceStates: deviceStates,
  accessTokens: accessTokens
};

server.js

The web server is modified to add a new /command endpoint for turning on and off the switch. It expects a JSON body of the form {"attribute": "switch", "value": "on"}.

"use strict";
require('dotenv').config();
const express = require('express');
const {StateUpdateRequest} = require('st-schema');
const {connector, deviceStates, accessTokens} = require('./app');
const server = express();
const port = 3001;
server.use(express.json());

server.post('/', (req, res) => {
  if (accessTokenIsValid(req)) {
    connector.handleHttpCallback(req, res)
  }
});

server.post('/command', (req, res) => {
  deviceStates[req.body.attribute] = req.body.value;
  for (const accessToken of Object.keys(accessTokens)) {
    const item = accessTokens[accessToken];
    const updateRequest = new StateUpdateRequest(process.env.ST_CLIENT_ID, process.env.ST_CLIENT_SECRET);
    const deviceState = [
      {
        externalDeviceId: 'external-device-1',
        states: [
          {
            component: 'main',
            capability: req.body.attribute === 'level' ? 'st.switchLevel' : 'st.switch',
            attribute: req.body.attribute,
            value: req.body.value
          }
        ]
      }
    ];
    updateRequest.updateState(item.callbackUrls, item.callbackAuthentication, deviceState)
  }
  res.send({});
  res.end()
});


function accessTokenIsValid(req) {
  // Replace with proper validation of issued access token
  if (req.body.authentication && req.body.authentication.token) {
    return true;
  }
  res.status(401).send('Unauthorized');
  return false;
}

server.listen(port);
console.log(`Server listening on http://127.0.0.1:${port}`);