Haskell Servant with Event-Sourcing

A very simple but interesing application made using Haskell Servant and Eventful.

It stores a stream of events in-memory that represent an integer counter.

It supports 3 types of events: increment (POST counter/increment), decrement (POST counter/decrement) and reset (POST counter/reset).

Example:

POST counter/increment 123

GET counter/latest
{
    "count": 123
}

GET counter/events
[
    [
        {
            "tag": "CounterIncremented",
            "contents": 123
        },
        {
            "count": 123
        }
    ]
]