Price Calculation Service

Small service with functionality to calculate product price based on configured base price and promotions.
Two kinds of promotions are allowed:

• Percent Off Promotion
  • A static percent is subtracted from price, regardless of amount of ordered items.
• Count Based Promotion
  • With every ordered item (of the same kind) applied percent off increases until limit is reached.
  • Note that validation of proper (low to high) percent order is not implemented.

If no promotion is configured for a product, then price will be calculated without discount.

Promotions must have a start and end time configured in order to guarantee a consistent experience for buyers.

Issues

I believe that the approach to pass the configuration via environment variable would be painful in the real world application, requiring a redeployment on every promotion change. Also, environment variables don't really play well with whitespace and newlines, which could be frustrating for operators.

As remedy, an upstream product cache component should be introduced from which price-calculation-service could read product and promotion data.

Nice to have missing things

• Swagger endpoint.
• Upstream product cache component mentioned in the Issues section.
• Configuration validation should be tested.
• More test cases should be added to ensure that edge-cases are covered.
• Request UUID should be sanitized, to reduce attack risk.
• Docker image should be built via Maven and version not hardcoded for future releases.

How to run

Build and package

mvn package

Configuration

Example hardcoded configuration for one product with two types of promotions.
Please keep in mind that the promotionStartTime and promotionEndTime properties are in UTC time.

products:
  {
    d651b6a0-6753-43a3-be55-c7917dce55d6:
      {
        basePrice: 199.99,
        percentOffPromotions: [
          {
            promotionStartTime: '2024-02-03T11:00:00Z',
            promotionEndTime: '2024-02-04T23:00:00Z',
            percentOff: 4
          }
        ],
        countBasedPromotions: [
          {
            promotionStartTime: '2024-02-03T11:00:00Z',
            promotionEndTime: '2024-02-04T23:00:00Z',
            percentOffSequence: [ 3, 5, 7, 10, 15 ]
          }
        ]
      }
  }

Actual configuration file available to the application when Dockerized relies on environment variable.

products: ${PRODUCTS_CONFIGURATION:-}

Export Products section as environment variable

Set below (flattened products section from above) as PRODUCTS_CONFIGURATION (Operating System dependent)

  {     d651b6a0-6753-43a3-be55-c7917dce55d6:       {         basePrice: 199.99,         percentOffPromotions: [           {             promotionStartTime: '2024-02-03T11:00:00Z',             promotionEndTime: '2024-02-04T23:00:00Z',             percentOff: 4           }         ],         countBasedPromotions: [           {             promotionStartTime: '2024-02-03T11:00:00Z',             promotionEndTime: '2024-02-04T23:00:00Z',             percentOffSequence: [ 3, 5, 7, 10, 15 ]           }         ]       }   }

Note that some terminal emulators might alter the copied text when pasted into them. The safest way is to put the config into a temporary file and copy its contents directly.

Export (PowerShell)

$env:PRODUCTS_CONFIGURATION=$(cat temporary_file_with_config)

Export (bash)

PRODUCTS_CONFIGURATION=$(cat temporary_file_with_config)

Run

Java

java -jar target/price-calculation-service-1.0-SNAPSHOT-jar-with-dependencies.jar server config.yaml 

If you prefer not to use environment variables, create a local configuration file next to config.yaml and pass its name to arguments instead.

Docker

Build docker container

Remember to package first!

docker image build -t price-calculation-service:latest .

Run (PowerShell)

docker run -p 8080:8080 -e PRODUCTS_CONFIGURATION=$env:PRODUCTS_CONFIGURATION price-calculation-service:latest

Run (bash)

docker run -p 8080:8080 -e PRODUCTS_CONFIGURATION=$PRODUCTS_CONFIGURATION price-calculation-service:latest

Validate

Send a simple request to validate that the application is working

curl http://localhost:8080/v1/price/d651b6a0-6753-43a3-be55-c7917dce55d6?amount=1


StatusCode        : 200
StatusDescription : OK
Content           : {"price":191.99}
RawContent        : HTTP/1.1 200 OK
                    Vary: Accept-Encoding
                    Content-Length: 16
                    Content-Type: application/json
                    Date: Sat, 03 Feb 2024 17:07:00 GMT

                    {"price":191.99}
Forms             : {}
Headers           : {[Vary, Accept-Encoding], [Content-Length, 16], [Content-Type, application/json], [Date, Sat, 03 Feb 2024 17:07:00 GMT]}
Images            : {}
InputFields       : {}
Links             : {}
ParsedHtml        : System.__ComObject
RawContentLength  : 16