coding-challenge-20230104

Stellar IT Coding Challenge

Challenge Request

Coding Challenge: Problem: A retailer offers a rewards program to its customers awarding points based on each recorded purchase as follows:

For every dollar spent over $50 on the transaction, the customer receives one point. In addition, for every dollar spent over $100, the customer receives another point. Ex: for a $120 purchase, the customer receives (120 - 50) x 1 + (120 - 100) x 1 = 90 points

Given a record of every transaction during a three-month period, calculate the reward points earned for each customer per month and total.

• Make up a data set to best demonstrate your solution
• Check solution into GitHub and please share the GitHub URL.

Write a REST API that calculates and returns the reward points in Java using Spring Boot as a microservice.

Additional Notes:

• All of the code should be provided in GitHub. Check-in all the code into master branch and squash and re-order all commits if necessary to have clean purposeful commit messages like you would normally in your job.
• Include a dataset in a table format that shows the customer list, transaction list, monthly total per customer, and 3 months summary it in, and add an image inside the README.md file with this data set and results.
• The client would be assessing your Coding Style and your personality when you join as a developer in their team, not just whether the code runs or logic is correct. So, please follow all of the Best practices that you know and have implemented in the past while doing this exercise.
• Please pay attention to the way you name your variables, classes, name of your project and package structure etc. Do not do silly mistakes like declaring variables but not using your variables anywhere in the code or using something from the Target folder.
• Externalize all the dependencies of your code nicely into property file or resource files in appropriate locations in package layout.
• Do NOT copy paste from GitHub, Stack Overflow or Leetcode. We run a plagiarism check and automatically reject all copy past jobs. Taking inspiration from something online is fine but blatant copy paste or renaming variables after copying and pasting will be very easily flagged by our software. So, please do it on your own.
• You API should contain clear Documentation (a well formatted README.md and comments in code, sample Request Response formats, how to invoke your API by any client), a Health Check Endpoint to check whether the service is running or not by a monitoring tool.
• Write your own Unit Tests and provide instructions on How to run your Tests in your README.md file
• Show your ability to write well maintainable code by including custom Exception Handling (ability to identify problems within code easily by throwing custom Errors), custom Logging (different levels like Verbose etc)
• Additional brownie points if you can containerize your API with Dockerfile and provide instructions on How to run your dockerized API in REAMDE.md

Challenge Response

Configuration

This API requires no external data store for operation, allowing it to be deployed as a microservice.
The Application supports an application properties setting to control the window of months to accumulate reward points. change the months value in the hierarchy to meet the current requirements.

application.properties

rewards.window.months = 3

APIs Exposed

Service Health Check API

A simple service health check is expose as GET and will respond with a 'UP' or "DOWN" body message based on the configuration parameters of the Rewards calcuation being injected into the API Endpoing.

GET http://localhost:8080/actuator/health

Always returns HTTP 200, unless the service is not running at all.

HTTP RESPONSE BODY

VALUE RETURNED	SERVICE STATE
{"status": "UP"}	The Rewards Service is up and configured to service requests
{"status": "DOWN"}	The Rewards Service is down and not properly configured to service requests.

Transaction Set Rewards Calculation API

Swagger UI is enabled at:

http://localhost:8080/swagger-ui/index.html

** RESPONSE EXAMPLE **

POST http://localhost:8080/api/rewards/calculate_period

Given the requirements, the Request Structure to be sent to the API as JSON Body Payload of an array of TransactionSummaryVO records

TransactionSummaryVO

FIELD	TYPE	DESCRIPTION
transactionId	STRING	A Transaction Id
transactionDate	ISO-8601 As 'yyyy-MM-dd'T'hh:mm:ss.sssZ'	The Date/Time of the transation occured
transactionTotal	DOUBLE 2 Decimal Places expected	The transaction total in monetary units

Example JSON request body

[
  {
    "transactionId": "A", 
    "transactionDate": "2023-10-04T12:00:00.000+0000", 
    "transactionTotal": 120.00
  },
  {
    "transactionId": "B", 
    "transactionDate": "2023-10-04T12:00:00.000+0000", 
    "transactionTotal": 2 },
  {
    "transactionId": "C", 
    "transactionDate": "2023-09-04T12:00:00.000+0000", 
    "transactionTotal": 120.00
  },
  {
    "transactionId": "D", 
    "transactionDate": "2023-09-04T12:00:00.000+0000", 
    "transactionTotal": 2
  },
  {
    "transactionId": "E", 
    "transactionDate": "2023-08-04T12:00:00.000+0000", 
    "transactionTotal": 120.00
  },
  {
    "transactionId": "F", 
    "transactionDate": "2023-08-04T12:00:00.000+0000",
    "transactionTotal": 2
  },
  {
    "transactionId": "G", 
    "transactionDate": "2023-07-04T00:00:00.000+0000", 
    "transactionTotal": 120.00
  },
  {
    "transactionId": "H", 
    "transactionDate": "2023-07-04T00:00:00.000+0000", 
    "transactionTotal": 2
  }
]

Reaponse:

HTTP STATUS	DESCRIPTION
200 - OK	Request Accepted, rewards responce enclosed
403 - Input Error	Request Not Accepted

With a Response of JSON as follows for that dataset

RewardsVO

FIELD	TYPE	DESCRIPTION
periodStart	ISO-8601 As 'yyyy-MM-dd'T'hh:mm:ss.sssZ'	The Start Date/Time this Rewards Period Represents.
periodEnd	ISO-8601 As 'yyyy-MM-dd'T'hh:mm:ss.sssZ'	The End Date/Time this Rewards Period Represents.
rewardsPointsTotal	INTEGER	The total Rewards Points accumuated this window
rewardsPointsPeriods	ARRAY of RewardsPeriodVO	A collection of point assesment per month

RewardsPeriodVO

FIELD	TYPE	DESCRIPTION
periodStart	ISO-8601 As 'yyyy-MM-dd'T'hh:mm:ss.sssZ'	The Start Date/Time this Rewards Period Represents.
totalTranslationsAmount	DOUBLE	A sum of eligible transactions for this period
totalTransactions	INTEGER	A count of eligible transactions for this period
accumulatedRewards	INTEGER	The sum of rewards points accumulated for eligible transaction in this period

Example Response

{
"periodStart": "2023-07-04T05:00:00.000+00:00",
"periodEnd": "2023-10-05T04:59:59.999+00:00",
"rewardsPointsTotal": 270,
"rewardsPointsPeriods": [
  {
    "periodStart": "2023-10-01T05:00:00.000+00:00",
    "totalTranslationsAmount": 122.0,
    "totalTransactions": 2,
    "accumulatedRewards": 90
  },
  {
    "periodStart": "2023-09-01T05:00:00.000+00:00",
    "totalTranslationsAmount": 122.0,
    "totalTransactions": 2,
    "accumulatedRewards": 90
  },
  {
    "periodStart": "2023-08-01T05:00:00.000+00:00",
    "totalTranslationsAmount": 122.0,
    "totalTransactions": 2,
    "accumulatedRewards": 90
  }
]
}

Unit Tests

The com.coding.challenge.api.RewardsAPI is validated with JUnit test cases in com.coding.challenge.domain.RewardsCalculatorTest which tests the given example from requirements as well as negative tests and edge case tests.

Run Suite

Run the entire suite in the Maven Lifecycle management by

bash$ mvn test

Which should result in all defined tests being ran as example:

[INFO] Running com.coding.challenge.ChallengeApplicationTests
19:25:43.271 [main] INFO org.springframework.test.context.support.AnnotationConfigContextLoaderUtils -- Could not detect default configuration classes for test class [com.coding.challenge.ChallengeApplicationTests]: ChallengeApplicationTests does not declare any static, non-private, non-final, nested classes annotated with @Configuration.
19:25:43.327 [main] INFO org.springframework.boot.test.context.SpringBootTestContextBootstrapper -- Found @SpringBootConfiguration com.coding.challenge.ChallengeApplication for test class com.coding.challenge.ChallengeApplicationTests

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v3.1.4)

2023-10-04T19:25:43.567-05:00  INFO 1841737 --- [           main] c.c.challenge.ChallengeApplicationTests  : Starting ChallengeApplicationTests using Java 17.0.8.1 with PID 1841737 (started by jlong23 in /home/jlong23/dev/coding-challenge-20230104)
2023-10-04T19:25:43.568-05:00  INFO 1841737 --- [           main] c.c.challenge.ChallengeApplicationTests  : No active profile set, falling back to 1 default profile: "default"
2023-10-04T19:25:44.206-05:00  INFO 1841737 --- [           main] c.c.challenge.ChallengeApplicationTests  : Started ChallengeApplicationTests in 0.804 seconds (process running for 1.356)
OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 1.482 s - in com.coding.challenge.ChallengeApplicationTests
[INFO] Running com.coding.challenge.domain.RewardsCalculatorTest
[INFO] Tests run: 9, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.018 s - in com.coding.challenge.domain.RewardsCalculatorTest
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 10, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  2.601 s
[INFO] Finished at: 2023-10-04T19:25:44-05:00
[INFO] ------------------------------------------------------------------------
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If you use a modern IDE, it gennerally has detection and running facilities for running the unittests in the IDE

UnitTests Validation Scenarios

Rewards Amount Calculation

Validates the expected rewards points for Transactional Amounts

• Positive Validations:

  • com.coding.challenge.domain.RewardsCalculatorTest.testCalculateRewardsForTransactionAmount

    • Tests the given example of 120 Unit transaction resulting in 90 Rewards points

  • com.coding.challenge.domain.RewardsCalculatorTest.testCalculateRewardsForTransactionUnderLowerThreshold

    • Tests the Lower Threshold value of the Rewards Calculation with 52 Unite resulting in 2 Rewards points

• Negative & Edge Validations:

  • com.coding.challenge.domain.RewardsCalculatorTest.testCalculateRewardsForTransactionEqualThreshold

    • Tests the transaction amount equal to the threshold, 50 Units results in 0 Reward points

  • com.coding.challenge.domain.RewardsCalculatorTest.testCalculateRewardsForTransactionNearlyAtThreshold

    • Edge Test for a transaction amount that is fractionally under the lower threshold amount, 50.99 Units results in 0 Reward points

Rewards Period Segment Calculations

• Positive Validations:

  • com.coding.challenge.domain.RewardsCalculatorTest.testCalculateRewardsPeriodSegment

    • Validates the calculation of the rewards points for a period segment (Month) for the expected results

    • Transacion Id	Transaction Date	Transaction Amount
      "A"	TODAY	120

• Negative & Edge Validations:

  • com.coding.challenge.domain.RewardsCalculatorTest.testCalculateRewardsPeriodSegmentEdgeCase

    • Tests with two transaction with one below the lower threshold value of the Rewards Calculation with 2 Unite resulting in 0 Rewards points

    • Transacion Id	Transaction Date	Transaction Amount
      "A"	TODAY	120
      "B"	TODAY	2

Reward Period Calculation

• Positive & Edge Case Validations:

  • com.coding.challenge.domain.RewardsCalculatorTest.testCalculateRewardsForPeriod

    • Validates the calculation of the rewards points for a define period (3 Month) for only 1 month of transactions for the expected results

    • Transacion Id	Transaction Date	Transaction Amount
      "A"	TODAY	120
      "B"	TODAY	2

  • com.coding.challenge.domain.RewardsCalculatorTest.testCalculateRewardsForPeriod_3MonthEdgeCase

    • Validates the calculation of the rewards points for a define period (3 Month) with 3 months of transactions for the expected results

    • Transacion Id	Transaction Date	Transaction Amount
      "A"	TODAY	120
      "B"	TODAY	2
      "C"	TODAY - 1 MONTH	120
      "D"	TODAY - 1 MONTH	2
      "E"	TODAY - 2 MONTH	120
      "F"	TODAY - 2 MONTH	2

  • com.coding.challenge.domain.RewardsCalculatorTest.testCalculateRewardsForPeriod_3MonthEdgeCasePlus

    • Validates the calculation of the rewards points for a define period (3 Month) with 3 months and One Day of transactions for the expected results, the last two translations "G & H" are excluded due to the date window

    • Transacion Id	Transaction Date	Transaction Amount
      "A"	TODAY	120
      "B"	TODAY	2
      "C"	TODAY - 1 MONTH	120
      "D"	TODAY - 1 MONTH	2
      "E"	TODAY - 2 MONTH	120
      "F"	TODAY - 2 MONTH	2
      "G"	TODAY - 3 MONTH	120
      "H"	TODAY - 3 MONTH	2

Validation Tool Configuration

A Postman Project has been provided in the ./Postman folder with sample data to use.

Import the project and change the endpoint to your deployment needs.

REQUEST EXAMPLE

** RESPONSE EXAMPLE **

Code Rationalization

While not provided in the challenge, I saw a need to ensure we can extend the calculation engine to support windowed and recalculation of transaction sets for the windowed total of rewards points. The Calculation is very strict for whole monetary units, for point calculations. Care was also taken for the window to be Start of the Day 3 months from today, a sliding window that would have rewards expire do to the edge conditions of date comparisons.