Parse strings according to JSON schema patterns

[dragonwasrobot]

See http://json-schema.org/latest/json-schema-validation.html#format

For example, if we have the node

"datum": {
  "required: ["createdDate"]
  "properties": {
    "createdDate": {
      "type": "string",
      "format": "date-time"
    }
  }
}

we want it to generate the type

type alias Datum =
      { createdDate: Date
      }

rather than

type alias Datum =
      { createdDate: String
      }

Possible decoder for date-time could be:

dateDecoder : Decoder Date
dateDecoder =
    Decode.string
        |> Decode.andThen
            (\dateStr ->
                case Date.fromIsoString dateStr of
                    Ok date ->
                        Decode.succeed date

                    Err err ->
                        Decode.fail err
            )

Possible encoder

encodeDate : Date -> Value
encodeDate date =
    date
        |> Date.toIsoString
        |> Encode.string

However, the implications for the parser has to be checked first.