This is a solution for the Yak Shop problem. The solution is written in Go and uses the echo and cobra cli.

• Go
• Git

For the unit tests assertions, I have used both testify and cupaloy. The reason for this is that I wanted to try out cupaloy. It is a snapshot testing library for Go. It is similar to Jest snapshot testing. It is very easy to use and it is very useful for testing the JSON responses.

The solution is divided into 3 parts:

• The Yak Shop CLI
• The Yak Shop API
• The Yak Shop UI

The Yak shop CLI is to query the herd and the stock. It is located in the cmd folder.

The Yak Shop API is a REST API that exposes the following endpoints:

• POST /yak-shop/load
• GET /yak-shop/stock/:T
• GET /yak-shop/herd/:T
• POST /yak-shop/order/:T

The Yak Shop UI is a web interface that allows the user to place an order. It uses the REST API to place the order. The UI is located in the html folder. The URL for the UI is: http://localhost:8080/yak-shop/order-template

Run the following command to install the dependencies:

go mod tidy

go test ./...

go run main.go

By default, the REST API will run on port 8080. You can change the port in the .env file.

PORT=8080

⚠️ Important Note:

• Before running any other APIs, it's crucial to first execute the load API; failing to do so will result in the other APIs returning empty results.

• For easy testing, I have created a POSTMAN collection. You can refer to the postman folder for the same.

YAK-1: As a Yak Shepherd, I want to be able to read in a XML file that contains data about my herd so that I can query it.

Input herd.xml:

<herd>
<labyak name="Betty-1" age="4" sex="f" />
<labyak name="Betty-2" age="8" sex="f" />
<labyak name="Betty-3" age="9.5" sex="f" />
</herd>

N.B. The age is given in standard Yak years. Your program should take 2 parameters: • The XML file to read • An integer T, representing the elapsed time in days

Execute the following command:

go run cmd/main.go -f ./data/herd.xml -T 13

Output

In Stock:
        1104.480 liters of milk
        3 skins of wool
Herd:
        Betty-1 4.13 years old
        Betty-2 8.13 years old
        Betty-3 9.63 years old

YAK-2: As a Yak Shepherd I want to be able to load a new Herd into my webshop using an HTTP REST service so that I can open my webshop.I want to be able to run my webshop and load my herd into it. Once I load a herd, any previous state of my webshop should be reset to the initial state. The following are the HTTP requests I want to make:

POST /yak-shop/load which returns a HTTP Status Code 205 (Reset Content)

Request:

POST http://localhost:8080/yak-shop/load
Content-Type: application/xml

<herd>
<labyak name="Betty-1" age="4" sex="f" />
<labyak name="Betty-2" age="8" sex="f" />
<labyak name="Betty-3" age="9.5" sex="f" />
</herd>

Response:

HTTP/1.1 205 Reset Content
Vary: Origin
Date: Fri, 27 Oct 2023 17:38:02 GMT
Content-Length: 0
Connection: close

YAK-3: As a Yak Shepherd I want to be able to query my herd and my current stock using HTTP REST services which output JSON data.

The following are the requests you wish to make: • GET /yak-shop/stock/T which returns a view of your stock at T days • GET /yak-shop/herd/T which returns a view of your herd at T days

Request:

GET http://localhost:8080/yak-shop/stock/13

Response:

HTTP/1.1 200 OK
Content-Type: application/json; charset=UTF-8
Vary: Origin
Date: Fri, 27 Oct 2023 17:42:04 GMT
Content-Length: 27
Connection: close

{
  "milk": 1104.48,
  "skins": 3
}

Request:

GET http://localhost:8080/yak-shop/herd/13

Response:

HTTP/1.1 200 OK
Content-Type: application/json; charset=UTF-8
Vary: Origin
Date: Fri, 27 Oct 2023 17:42:30 GMT
Content-Length: 163
Connection: close

{
  "herd": [
    {
      "name": "Betty-1",
      "age": 4.13,
      "age-last-shaved": 4
    },
    {
      "name": "Betty-2",
      "age": 8.13,
      "age-last-shaved": 8
    },
    {
      "name": "Betty-3",
      "age": 9.63,
      "age-last-shaved": 9.5
    }
  ]
}

YAK-4: As a Yak Shepherd I want my customers to be able to buy from my stock using my HTTP REST services.

Request: • POST /yak-shop/order/T where T is the day the customer orders, this means that day T has not elapsed

Request:

POST http://localhost:8080/yak-shop/order/14
Content-Type: application/json

{
"customer": "Medvedev",
"order": { "milk": 1100, "skins": 3 }
}

Response:

HTTP/1.1 201 Created
Content-Type: application/json; charset=UTF-8
Vary: Origin
Date: Fri, 27 Oct 2023 17:44:33 GMT
Content-Length: 24
Connection: close

{
  "milk": 1100,
  "skins": 3
}

Request:

POST http://localhost:8080/yak-shop/order/14
Content-Type: application/json

{
"customer": "Medvedev",
"order": { "milk": 1200, "skins": 3 }
}

Response:

HTTP/1.1 206 Partial Content
Content-Type: application/json; charset=UTF-8
Vary: Origin
Date: Fri, 27 Oct 2023 17:45:28 GMT
Content-Length: 12
Connection: close

{
  "skins": 3
}

YAK-5: As a Yak Shepherd I want to have a user interface in my browser which I can use to order goods. The user interface should be able to place an order using the exposed REST services, and provide feedback whether the order was placed successfully, partial successfully, or failed. In case of a partial success it should output what you will get delivered.

I have used go templates to render the HTML. The templates are located in the html folder.

Open the following URL in your browser:

http://localhost:8080/yak-shop/order-template