Your Task

Our company has released a beta version of String Reply Service and it has been a huge success. In the current implementation (as part of boilerplate code), the String Reply Service takes in an input string (in the format of [a-z0-9]*) and returns the input in a JSON object.

For example,

GET /reply/kbzw9ru
{
    "data": "kbzw9ru"
}

As the service is widely adopted, there have been increasing feature requests. Our project manager has come back with the following requirement:

The input string will now be comprised of two components, a rule and a string, separated by a dash (-). Rules always contain two numbers. Each number represents a string operation.

The supported numbers are:

• 1: reverse the string

  E.g. kbzw9ru becomes ur9wzbk

• 2: encode the string via MD5 hash algorithm and display as hex

  E.g. kbzw9ru becomes 0fafeaae780954464c1b29f765861fad

The numbers are applied in sequence, i.e. the output of the first rule will serve as the input of the second rule. The numbers can also be repeated, i.e. a rule of 11 would mean reversing the string twice, resulting in no change to the string.

Giving a few examples,

GET /v2/reply/11-kbzw9ru
{
    "data": "kbzw9ru"
}

GET /v2/reply/12-kbzw9ru
{
    "data": "5a8973b3b1fafaeaadf10e195c6e1dd4"
}

GET /v2/reply/22-kbzw9ru
{
    "data": "e8501e64cf0a9fa45e3c25aa9e77ffd5"
}

Note: Additional new rules are expected to be introduced in the future releases. Please make sure all of your change work

What you need to do

Use the boilerplate given and implement the above requirement. Your implementation should also consider:

• Additional rules are expected in the future releases. The change in rule set should have minimal code change and impact to existing functionality.
• Testability for individual rules and the application. Unit tests are highly recommended.
• Endpoint should return correct status code and response message. E.g. For invalid request, such as GET /v2/reply/13-kbzw9ru, it should return status code 400 with message "Invalid input".

Upon completing the task, please feel free to (though not required):

• host your code on Github
• include any readme to explain your setup/environment
• add/implement anything you think would be beneficial

Build project

To build the project, simply run

./gradlew build

Start project

To start the project, simply run

./gradlew bootRun

Once the service started, the endpoint will be available at localhost:8080, so you can make request to the service endpoint

GET localhost:8080/reply/helloworld

{
    message: "helloword"
}