The Cake is a Lie

Instructions

Problem Statement

CakeStation, a popular bakery that bakes various cakes, has asked you to set up an online order management system for them.

The details of items on the menu are as follows.

The following is expected to be possible.

• Retrieve the menu.
• Place an order.
• Retrieve the status of an order (one of pending, in progress, or completed).
• Update an order. Only allowed if the status is still pending.
• Delete an order. Only allowed if the status is still pending.

Constraints

1. Retrieve the Menu

   • Method - GET
   • Path - /menu
   • Response
     • 200 OK
     • content-type - application/json
     • a JSON object with the item names as the keys and the prices as the values (integer)

       {
          "Butter Cake": 15,
          "Chocolate Cake": 20,
          "Tres Leches": 25
       }
       

2. Place an Order

   • Method - POST

   • Path - /order

   • Request

     • the request payload will be a JSON object with the following fields
       • username - username of the user (string)
       • order_items - an array of JSON objects representing the order items. Each JSON object will contain exactly two fields: a string item field indicating the name of the item and an integer quantity field indicating the order quantity for the particular item.

       {
           "type": "object",
           "properties": {
               "username": {
                   "type": "string"
               },
               "order_items": {
                   "type": "array",
                   "items": {
                       "type": "object",
                       "properties": {
                           "item": {
                               "type": "string"
                           },
                           "quantity": {
                               "type": "integer"
                           }
                       },
                       "required": [
                           "item",
                           "quantity"
                       ]
                   }
               }
           },
           "required": [
               "username",
               "order_items"
           ]
       }
       

   • Response

     • 400 Bad Request if
       • the payload does not match the expected format or
       • the username is empty or
       • the order_items array is empty or
       • the order_items array contains more than one JSON object for a particular type of cake or
       • a member of the order_items array has an item field with a type of cake that is not on the menu or
       • a member of the order_items array has a quantity field that has a value less than 1
     • 201 Created if the order is placed successfully
       • content-type - application/json
       • a JSON object with two fields
         • an order_id containing the randomly generated order ID string. This should be the string representation of a valid numeric value.
         • a total field containing the total value (integer) of the order (i.e., sum of price x quantity for each kind of cake)

         {
             "type": "object",
             "properties": {
                 "order_id": {
                     "type": "string"
                 },
                 "total": {
                     "type": "integer"
                 }
             },
             "required": [
                 "order_id",
                 "total"
             ]
         }
         

3. Retrieve the Status of an Order

   • Method - GET
   • Path - /order/{orderId}
   • Response
     • 404 Not Found if there is no order with the specified orderId
     • 200 OK

       • content-type - application/json

       • a JSON object with two string fields order_id and status, representing the order ID and the status (one of pending, in progress, or completed) respectively

         {
             "type": "object",
             "properties": {
                 "order_id": {
                     "type": "string"
                 },
                 "status": {
                     "type": "string"
                 }
             },
             "required": [
                 "order_id",
                 "status"
             ]
         }
         

4. Update an Order. Only allowed if the status is still pending.

   • Method - PUT

   • Path - /order/{orderId}

   • Request

     • the request payload will be a JSON object with a single field order_items.

       • order_items - an array of JSON objects representing the order items. Each JSON object will contain exactly two fields: a string item field indicating the name of the item and an integer quantity field indicating the order quantity for the particular item.

       {
           "type": "object",
           "properties": {
               "order_items": {
                   "type": "array",
                   "items": {
                       "type": "object",
                       "properties": {
                           "item": {
                               "type": "string"
                           },
                           "quantity": {
                               "type": "integer"
                           }
                       },
                       "required": [
                           "item",
                           "quantity"
                       ]
                   }
               }
           },
           "required": [
               "order_items"
           ]
       }
       

   • Response

     • 404 Not Found if there is no order with the specified orderId
     • 403 Forbidden if the order status is not pending (i.e., in progress or completed)
     • 400 Bad Request if the order_items array doesn't meet the same requirements as that for placing the order (2)
     • 200 OK if the update is successful

       • content-type - application/json

       • a JSON object with two fields

         • an order_id containing the same order ID string as the original order
         • a total field containing the total value of the order (i.e. the sum of price x quantity for each kind of cake)

         {
             "type": "object",
             "properties": {
                 "order_id": {
                     "type": "string"
                 },
                 "total": {
                     "type": "integer"
                 }
             },
             "required": [
                 "order_id",
                 "total"
             ]
         }
         

     Note: if an update attempt fails, no changes should be done to the existing order.

5. Delete an Order. Only allowed if the status is still pending.

   • Method - DELETE
   • Path - /order/{orderId}
   • Response
     • 404 Not Found if there is no order with the specified orderId
     • 403 Forbidden if the order status is not pending (i.e., in progress or completed)
     • 200 OK if the deletion is successful

6. The generated order ID should be unique, should be a string, and should be a string representation of a valid number (e.g., "1", "1234").

Definition

• Use a configurable variable port with the default value of 8080 to specify the port the service listens on.
• Use a module-level orderStatus map to maintain the status of the orders, in which the value is either "pending", "in progress", or "completed" against the randomly generated order ID string.
  • key - randomly generated order ID string
  • value - status of the order ("pending", "in progress", or "completed")
• Update the orderStatus map with the value "pending" for each new order.

Example 1

Retrieving the menu.

$ curl -v http://localhost:8080/menu

< HTTP/1.1 200 OK
< content-type: application/json
{"Butter Cake":15, "Chocolate Cake":20, "Tres Leches":25}

Example 2

Attempting to place the order with a valid payload.

$ curl -v http://localhost:8080/order -d '{"username": "mary", "order_items": [{"item": "Tres Leches", "quantity": 1}, {"item": "Chocolate Cake", "quantity": 2}]}' -H 'Content-Type: application/json'

< HTTP/1.1 201 Created
< content-type: application/json
{"order_id":"7", "total":65}

Note: "order_id" should/will be a randomly generated unique string.

Example 3

Attempting to place the order with payload does not match the expected format.

$ curl -v http://localhost:8080/order -d '{"username": "mary", "order_items": [{"Tres Leches": 1}, {"Chocolate Cake": 2}]}' -H 'Content-Type: application/json'

< HTTP/1.1 400 Bad Request

Hints

• Simple HTTP service
• A quoted identifier ('order) can be used to use order (which is a keyword) as the path.
• Using service data binding will validate that the payload is of the expected structure, and will handle responding with status code 400 (Bad Request) when binding fails.
• Using status code records as return types and returning record values of those types from resource methods will handle setting the relevant status code to the response internally.
• Configurable variables

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Source

This is an exercise to introduce users to using Ballerina HTTP service data binding