A partially built advanced Codec.

Starts building an advanced Codec, usually used for a custom type.

This version allows you to control how variants are encoded, but will use Json.Decode.oneOf under the hood, so if two variants have the same shape when encoded, it will always use the first one for decoding.

⚠️ In particular, in the example below swapping the Green and Yellow variants means that Green values will be decoded as Yellow (because Codec.succeed always succeeds). ⚠️

type Semaphore
    = Red Int String
    | Yellow
    | Green Float


semaphoreCodec : Codec Semaphore
semaphoreCodec =
    Codec.Advanced.custom
        (\red green yellow value ->
            case value of
                Red i s ->
                    red ( i, s )


                Yellow ->
                    yellow ()


                Green f ->
                    green f
        )
        |> Codec.Advanced.variant
            (\( i, s ) -> Red i s)
            (Codec.tuple Codec.int Codec.string)
        |> Codec.Advanced.variant
            Green
            Codec.float
        |> Codec.Advanced.variant
            (\() -> Yellow)
            (Codec.succeed ())
        |> Codec.Advanced.build

Define a variant for an advanced codec.

The first argument is a function from the encoded type to your custom type, the second argument is a codec for the encoded type.

Build a Codec from a fully build AdvancedCodec.