HeterogeneousDateDecoding

Heterogeneous Date Decoding

Difficulty: medium

Problem Statement

You are dealing with a JSON response from a legacy API. Unfortunately, various people have worked on the API over the years which has resulted in a quite heterogeneous structure. Among others, there are different formats for timestamps in the responses. Below is an example of a JSON response encoding a time interval of 60 seconds.

{
    "date1": 459125100
    "date2": 459125160000
}

Here date1 is a timestamp in second-based Epoch time while date2 is a timestamp in millisecond-based Epoch time

Your task is to decode such an object into an instance of a type that conforms to the protocol

protocol P {
    var date1: Date { get }
    var date2: Date { get }
}

The particular type you use is entirely arbitrary as long as it conforms to P.

Write a method that takes a Data instance representing a JSON object of the aforementioned format and decodes it into an instance conforming to P.

func decode(_ json: Data) throws -> P {
    // ?    
}

Further Instructions

To start working on this challenge open Challenge.swift and uncomment the code skeleton.

To run unit tests that validate your code, uncomment the body of the test method in ChallengeTests.swift and hit CMD + U in Xcode. On Linux you can run the tests by executing swift test in the package directory.

To view selected solutions open Solutions.swift.