Wolt

Opening hours challenge. See requirements for full spec.

Part 1: Implementation

Prerequisites

You should have the following dependencies

• Docker
• SBT

To run the example requests below, you will need the following dependencies:

• Httpie

How to run

The solution can be run as a docker container

sbt clean compile stage && \
    docker build . --no-cache -t wolt:latest && \
    docker run -p 3000:3000 wolt:latest

Exposed endpoints

HealthCheck

${baseUrl}/healthz

When the service is up, this endpoint will return 204 No Content to indicate it is healthy.

If run using the Docker image, this is also used by the Docker HEALTHCHECK.

Example Request

http GET http://localhost:3000/status

Pretty Print

${baseUrl}/hours/pretty_print

This endpoint takes input of Json in the format described (see requirements.)

Example Request

echo '{   "monday":[   ],   "tuesday":[      {         "type":"open",         "value":36000      },      {         "type":"close",         "value":64800      }   ],   "wednesday":[   ],   "thursday":[      {         "type":"open",         "value":36000      },      {         "type":"close",         "value":64800      }   ],   "friday":[      {         "type":"open",         "value":36000      }   ],   "saturday":[      {         "type":"close",         "value":3600      },      {         "type":"open",         "value":36000      }   ],   "sunday":[      {         "type":"close",         "value":3600      },      {         "type":"open",         "value":43200      },      {         "type":"close",         "value":75600      }   ]}' | \
  http POST http://localhost:3000/hours/pretty_print

Part 2: Json Format

Is the current JSON structure the best way to store that kind of data or can you come up with a better version?

Seconds since Epoch for time

It seems to me that there is no benefit to serialising the times as a Unix timestamp in seconds. Though it is trivial to define a Deserialiser for this format, it only serves to obfuscate the data in the Json.

I would suggest a simple representation of hh:mm would be clearer both in the Json and would likely get a Deserialiser in this case "for free" e.g.

{
   "friday":[
      {
         "type":"open",
         "value":"18:00"
      }
   ],
   "saturday":[
      {
         "type":"close",
         "value":"01:00"
      },
      {
         "type":"open",
         "value":"09:00"
      },
      {
         "type":"close",
         "value":"11:00"
      },
      {
         "type":"open",
         "value":"16:00"
      },
      {
         "type":"close",
         "value":"23:00"
      }
   ]
}

There is also a question of whether the TimeZone of the opening hours should be included in the Json. However, I assume that this is explicitly intended to be decoupled and would be based on the restaurant's location - This makes sense - we could also always serialise to UTC. Though it should not be left up to the App/Browser to derive the user's timezone in this case.

Order dependant arrays

In the current structure, we rely on the assumption that the arrays are in order, but there is nothing in the json which enforces or denotes the order explicitly.

I would suggest to modify the structure here in a way which explicitly denotes the order of the elements. e.g.

{
  "friday":{
    "1":{
      "type":"open",
      "value":"18:00"
    }
  },
  "saturday":{
    "1":{
      "type":"close",
      "value":"01:00"
    },
    "2":{
      "type":"open",
      "value":"09:00"
    },
    "3":{
      "type":"close",
      "value":"11:00"
    },
    "4":{
      "type":"open",
      "value":"16:00"
    },
    "5":{
      "type":"close",
      "value":"23:00"
    }
  }
}

Naming

Both type and value have no semantic meaning without the context required. Why not give these meaningful names? e.g.

{
  "friday":{
    "1":{
      "action":"open",
      "time":"18:00"
    }
  },
  "saturday":{
    "1":{
      "action":"close",
      "time":"01:00"
    },
    "2":{
      "action":"open",
      "time":"09:00"
    },
    "3":{
      "action":"close",
      "time":"11:00"
    },
    "4":{
      "action":"open",
      "time":"16:00"
    },
    "5":{
      "action":"close",
      "time":"23:00"
    }
  }
}