Source: org/terraswarm/accessor/accessors/web/devices/PhSensor.js

// Copyright (c) 2016 The Regents of the University of California.
// All rights reserved.

// Permission is hereby granted, without written agreement and without
// license or royalty fees, to use, copy, modify, and distribute this
// software and its documentation for any purpose, provided that the above
// copyright notice and the following two paragraphs appear in all copies
// of this software.

// IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
// FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
// ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
// THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE.

// THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
// PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
// CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
// ENHANCEMENTS, OR MODIFICATIONS.

/**
 *
 *
 *  Retrieves the latest ph measurement from your garden
 *
 *  This accessor does not block waiting for the response, but if any additional
 *  *symbol* input is received before a pending request has received a response
 *  or timed out, then the new request will be queued and sent out only after
 *  the pending request has completed. This strategy ensures that outputs are
 *  produced in the same order as the input requests.
 *
 *  This accessor requires the optional 'httpClient' module, which may or may
 *  not be provided by an accessor host. Most hosts will provide this module.
 *
 *  @accessor devices/PhSensor
 *  @author Matt Weber (matt.weber@eecs.berkeley.edu)
 *  @version $$Id$$
 *  @input trigger An input to trigger data acqusition.
 *  @output {number} ph The latest measured pH value.
 */

// Stop extra messages from jslint and jshint.  Note that there should
// be no space between the / and the * and global. See
// https://chess.eecs.berkeley.edu/ptexternal/wiki/Main/JSHint */
/*globals addInputHandler, get, error, exports, extend, get, input, output, parameter, require, send */
/*jshint globalstrict: true*/
'use strict';

var http = require('@accessors-modules/http-client');

/** Set up the accessor by defining the inputs and outputs.
 */
exports.setup = function () {
    this.extend('net/REST');

    this.output('ph', {
        'type': 'number'
    });

    // Change default values of the base class inputs.
    // Also, hide base class inputs, except trigger.
    this.input('options', {
        'visibility': 'expert',
        'value': '"http://192.168.1.247:8080"'
    });
    this.input('command', {
        'visibility': 'expert',
        'value': 'ph'
    });
    this.input('arguments', {
        'visibility': 'expert'
    });
    //this.input('arguments', {'visibility':'expert', 'value':'{"env":"http://datatables.org/alltables.env", "format":"json"}'});
    this.input('body', {
        'visibility': 'expert'
    });
    //this.input('trigger', {'visibility':'expert'});
    this.output('headers', {
        'visibility': 'expert'
    });
    this.output('status', {
        'visibility': 'expert'
    });
    this.parameter('outputCompleteResponsesOnly', {
        'visibility': 'expert'
    });
};

/** Initialize the accessor by attaching an input handler to the *symbol* input. */
exports.initialize = function () {
    // Be sure to call the superclass so that the trigger input handler gets registered.
    this.exports.ssuper.initialize.call(this);

    // Capture 'this' for use in callback.
    var self = this;


};


/** Filter the response, extracting the ph information. The full response is produced
 *  on the 'response' output.
 */

exports.filterResponse = function (response) {


    if (response) {
        try {
            // Check if response is JSON or stringified JSON.  If stringified, parse.
            var parsed;
            if (typeof response == "object") {
                parsed = response;
            } else {
                parsed = JSON.parse(response);
            }
            // Extract the last ph value from the JSON record.
            if (parsed.type !== 'ph') {
                throw "type of received value is not 'ph'";
            }
            var ph = parseFloat(parsed.value);
            // Send the ph to the 'ph' output.
            this.send('ph', ph);
        } catch (err) {
            error('PhSensor: Unable to parse response: ' + err.message);
            this.send('ph', null);
        }
    } else {
        this.send('ph', null);
    }
    return response;
};