techops-recsys-lateral-hiring / developer-joyofenergy-java

Welcome to PowerDale

PowerDale is a small town with around 100 residents. Most houses have a smart meter installed that can save and send information about how much power a house is drawing/using.

There are three major providers of energy in town that charge different amounts for the power they supply.

• Dr Evil's Dark Energy
• The Green Eco
• Power for Everyone

Introducing JOI Energy

JOI Energy is a new start-up in the energy industry. Rather than selling energy they want to differentiate themselves from the market by recording their customers' energy usage from their smart meters and recommending the best supplier to meet their needs.

You have been placed into their development team, whose current goal is to produce an API which their customers and smart meters will interact with.

Unfortunately, two members of the team are on annual leave, and another one has called in sick! You are left with another ThoughtWorker to progress with the current user stories on the story wall. This is your chance to make an impact on the business, improve the code base and deliver value.

Story Wall

At JOI energy the development team use a story wall or Kanban board to keep track of features or "stories" as they are worked on.

The wall you will be working from today has 7 columns:

• Backlog
• Ready for Dev
• In Dev
• Ready for Testing
• In Testing
• Ready for sign off
• Done

Examples can be found here https://leankit.com/learn/kanban/kanban-board/

Users

To trial the new JOI software 5 people from the JOI accounts team have agreed to test the service and share their energy data.

User	Smart Meter ID	Power Supplier
Sarah	smart-meter-0	Dr Evil's Dark Energy
Peter	smart-meter-1	The Green Eco
Charlie	smart-meter-2	Dr Evil's Dark Energy
Andrea	smart-meter-3	Power for Everyone
Alex	smart-meter-4	The Green Eco

These values are used in the code and in the following examples too.

Requirements

The project requires Java 17 or higher.

The project makes use of Gradle and uses the Gradle wrapper, which means you don't need Gradle installed.

Useful Gradle commands

The project makes use of Gradle and uses the Gradle wrapper to help you out carrying some common tasks such as building the project or running it.

List all Gradle tasks

List all the tasks that Gradle can do, such as build and test.

$ ./gradlew tasks

Build the project

Compiles the project, runs the test and then creates an executable JAR file

$ ./gradlew build

Run the application using Java and the executable JAR file produced by the Gradle build task. The application will be listening to port 8080.

$ java -jar build/libs/developer-joyofenergy-java.jar

Run the tests

There are two types of tests, the unit tests and the functional tests. These can be executed as follows.

• Run unit tests only

  $ ./gradlew test

• Run functional tests only

  $ ./gradlew functionalTest

• Run both unit and functional tests

  $ ./gradlew check

Run the application

Run the application which will be listening on port 8080.

$ ./gradlew bootRun

API

Below is a list of API endpoints with their respective input and output. Please note that the application needs to be running for the following endpoints to work. For more information about how to run the application, please refer to run the application section above.

Store Readings

Endpoint

POST /readings/store

Example of body

{
  "smartMeterId": <smartMeterId>,
  "electricityReadings": [
    {
      "time": <time>,
      "reading": <reading>
    }
  ]
}

Parameters

Parameter	Description
smartMeterId	One of the smart meters' id listed above
time	The date/time (as epoch) when the reading was taken
reading	The consumption in kW at the time of the reading

Example readings

Date (GMT)	Epoch timestamp	Reading (kW)
2020-11-29 8:00	1606636800	0.0503
2020-11-29 8:01	1606636860	0.0621
2020-11-29 8:02	1606636920	0.0222
2020-11-29 8:03	1606636980	0.0423
2020-11-29 8:04	1606637040	0.0191

In the above example, the smart meter sampled readings, in kW, every minute. Note that the reading is in kW and not kWH, which means that each reading represents the consumption at the reading time. If no power is being consumed at the time of reading, then the reading value will be 0. Given that 0 may introduce new challenges, we can assume that there is always some consumption, and we will never have a 0 reading value. These readings are then sent by the smart meter to the application using REST. There is a service in the application that calculates the kWH from these readings.

The following POST request, is an example request using CURL, sends the readings shown in the table above.

$ curl \
  -X POST \
  -H "Content-Type: application/json" \
  "http://localhost:8080/readings/store" \
  -d '{"smartMeterId":"smart-meter-0","electricityReadings":[{"time":1606636800,"reading":0.0503},{"time":1606636860,"reading":0.0621},{"time":1606636920,"reading":0.0222},{"time":1606636980,"reading":0.0423},{"time":1606637040,"reading":0.0191}]}'

The above command does not return anything.

Get Stored Readings

Endpoint

GET /readings/read/<smartMeterId>

Parameters

Parameter	Description
smartMeterId	One of the smart meters' id listed above

Retrieving readings using CURL

$ curl "http://localhost:8080/readings/read/smart-meter-0"

Example output

[
  {
    "time": "2020-11-29T08:00:00Z",
    "reading": 0.0503
  },
  {
    "time": "2020-11-29T08:01:00Z",
    "reading": 0.0621
  },
  {
    "time": "2020-11-29T08:02:00Z",
    "reading": 0.0222
  },
  {
    "time": "2020-11-29T08:03:00Z",
    "reading": 0.0423
  },
  {
    "time": "2020-11-29T08:04:00Z",
    "reading": 0.0191
  }
]

View Current Price Plan and Compare Usage Cost Against all Price Plans

Endpoint

GET /price-plans/compare-all/<smartMeterId>

Parameters

Parameter	Description
smartMeterId	One of the smart meters' id listed above

Retrieving readings using CURL

$ curl "http://localhost:8080/price-plans/compare-all/smart-meter-0"

Example output

{
  "pricePlanComparisons": {
    "price-plan-2": 0.0002,
    "price-plan-1": 0.0004,
    "price-plan-0": 0.002
  },
  "pricePlanId": "price-plan-0"
}

View Recommended Price Plans for Usage

Endpoint

GET /price-plans/recommend/<smartMeterId>[?limit=<limit>]

Parameters

Parameter	Description
smartMeterId	One of the smart meters' id listed above
limit	(Optional) limit the number of plans to be displayed

Retrieving readings using CURL

$ curl "http://localhost:8080/price-plans/recommend/smart-meter-0?limit=2"

Example output

[
  {
    "price-plan-2": 0.0002
  },
  {
    "price-plan-1": 0.0004
  }
]

developer-joyofenergy-java's Issues

Query

Dear Devs,
I'm in a dire need of a preparation session. I'm supposed to present at 14:30 ATM but after installing and studying during the weekend, I'm still completely lost. Java wasn't even my language of choice and I'm ashamed to admit I can hardly follow the components.
The best,
Pablo.

Project fails to build on machines with Java 19

Steps to Reproduce

In a machine with Java v19
Checkout out the project clean
Run ./gradlew tasks
Output:

FAILURE: Build failed with an exception.

* Where:
Settings file '/Users/georgioschinis/tw/recruiting/developer-joyofenergy-java/settings.gradle'

* What went wrong:
Could not compile settings file '/Users/georgioschinis/tw/recruiting/developer-joyofenergy-java/settings.gradle'.
> startup failed:
  General error during conversion: Unsupported class file major version 63
  
  java.lang.IllegalArgumentException: Unsupported class file major version 63
        at groovyjarjarasm.asm.ClassReader.<init>(ClassReader.java:199)
        at groovyjarjarasm.asm.ClassReader.<init>(ClassReader.java:180)
        at groovyjarjarasm.asm.ClassReader.<init>(ClassReader.java:166)
        at groovyjarjarasm.asm.ClassReader.<init>(ClassReader.java:287)

This complicates running the code on candidates machines with newer versions of Java.

The issue is that the gradlew wrapper downloads gradle version 7 that does not support Java versions 17,18 and 19.

Upgrade to Java 11+

Hi folks,

Given java 8 's Premier support has expired, shall we migrate this repo to Java 11 or 17 ?

Please suggest your candidates in IntelliJ IDEA with a version after 2021

• I'm glad to receive the interview invitation from your company. I'm unfamiliar with the grandle usage because the popular package managing tool of Java in my country is maven.

• When I try to see the project's details, I found it could not run in my IntelliJ IDEA 2019 version with grandle problems.

• I search the problem in StackOverflow, and I find it cannot run in the IntelliJ IDEA 2019 version. And When I update IntelliJ IDEA to a 2021 version, the problem can be solved.

Does not build on JDKs where version >= 16.

Consider bumping gradle wrapper to version 7 to address this issue (or requiring a JDK version < 16)