Add IoT Mailbox simulator app specification Resolves: N/a See also: N/apull/73/head
jdmedlock
6 years ago
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# IOT Mailbox Simulator
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**Tier:** 1-Beginner
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The objective of the IOT Mailbox Simulator is to mimic how an Internet of Things
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(IOT) enabled physical mailbox might be used to notify you when "snail" mail
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has arrived. In doing so it will provide you with experience using callbacks
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to communicate state between different components of an app that are dependent
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on one another.
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### Requirements & Constraints
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- Even though this app is specified using Javascript concepts and terminology
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you are free to implement it in the language of your choice.
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- The following Javascript class is provided to start and stop the monitoring
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process, and to signal the app web page with the state of the mailbox door
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(open or closed) at preset intervals. Keep in mind that the interval you specify
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shouldn't exceed the time it normally takes to open or close the door or you
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might miss a delivery!
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```
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/**
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* Monitor the light levels inside an IOT enabled snail mailbox to detect
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* when the mailbox door has been opened and closed.
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* @class IOTMailbox
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*/
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class IOTMailbox {
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/**
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* Creates an instance of IOTMailbox.
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* @param {number} [signalInterval=500] Timer interval for checking mailbox status.
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* @param {function} signalCallback Function to invoke when the timer interval expires.
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* @memberof IOTMailbox
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*/
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constructor(signalInterval = 500, signalCallback) {
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this.signalInterval = signalInterval;
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this.signalCallback = signalCallback;
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this.intervalID = null;
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this.lastLightLevel = 0;
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}
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/**
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* Start monitoring of the mailbox and invoke the caller specified callback
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* function when the interval expires.
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* @memberof IOTMailbox
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*/
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startMonitoring = () => {
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console.log(`Starting monitoring of mailbox...`);
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this.intervalID = window.setInterval(this.signalStateChange, this.signalInterval);
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}
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/**
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* Stop monitoring the mailbox status
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* @memberof IOTMailbox
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*/
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stopMonitoring = () => {
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if (this.intervalID === null) return;
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window.clearInterval(this.intervalID);
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this.intervalID = null;
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console.log(`Mailbox monitoring stopped...`);
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}
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/**
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* Pass the current light level inside the mailbox to the users callback
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* function. The positive light levels indicate the door is open while
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* negative levels indicate it is closed. Depending on the sampling interval
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* the mailbox door could be in any postion from fully closed to fully open.
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* This means the light level varies from interval-to-interval.
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* @memberof IOTMailbox
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*/
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signalStateChange = () => {
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const lightLevel = this.lastLightLevel >= 0
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? Math.random().toFixed(2) * -1
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: Math.random().toFixed(2);
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console.log(`Mailbox state changed - lightLevel: ${lightLevel}`);
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this.signalCallback(this.lightLevel);
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this.lastLightLevel = lightLevel;
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}
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};
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```
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## User Stories
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- [ ] User can see a web page containing a control panel containing three
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buttons - 'Start Monitoring', 'Stop Monitoring', and 'Reset'.
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- [ ] User can see a notification panel where the mailbox status will be posted.
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- [ ] User can see a scrollable log panel where execution details describing
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the apps operation and interface with the IOTMailbox instance will be posted.
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- [ ] User can click the 'Start Monitoring' button to begin receiving state
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notifications from the mailbox.
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- [ ] User can see a message added to the log panel when monitoring starts.
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- [ ] User can see a message added to the log panel for light level passed
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through the callback function. This should include the numerical light level
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and whether the door is open or closed.
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- [ ] User can see a message added to the notification panel when the door has
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been opened.
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- [ ] User can click the 'Stop Monitoring' button to stop receiving state
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notifications from the mailbox.
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- [ ] User can see a message added to the log panel when monitoring stops.
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## Bonus features
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- [ ] User can see the 'Start Monitoring' button disabled until monitoring is
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stopped.
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- [ ] User can see the 'Stop Monitoring' button disabled until monitoring is
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started.
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- [ ] User can see an field in the control panel allowing the length of the
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monitoring interval to be specified.
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- [ ] User can see a message added to the notification panel if the door is
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left open.
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- [ ] User can hear an audible alert when the door is opened.
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## Useful links and resources
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- [Snail Mail (Wikipedia)](https://en.wikipedia.org/wiki/Snail_mail)
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- [Internet of Things (Wikipedia)](https://en.wikipedia.org/wiki/Internet_of_things)
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- [IOT Mailbox: An Introduction](https://iotexpert.com/2018/08/13/iot-mailbox-an-introduction/)
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- [What the Heck is a Callback?](https://codeburst.io/javascript-what-the-heck-is-a-callback-aba4da2deced)
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- [window.setInterval (MDN)](https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/setInterval)
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## Example projects
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N/a
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