Dowser.Client.Codec behaviour (Dowser.Client v0.1.1)

View Source

Behaviour for casting a whole request/response body, wired onto a Dowser.Client.Config/request as :codec_adapter.

Unlike Dowser.Client.Field (which casts one value), a Codec sees the entire decoded body and is responsible for everything that happens to it beyond plain JSON decoding:

  • decode/2 — casts a decoded response body (already key-cast per opts[:key_fn], see below) into whatever richer shape the codec wants.
  • encode/2 — the reverse, casting a request body before it's JSON-encoded.

Both receive opts — the resolved :codec_opts, with two entries always added by Dowser.Client.Request: :key_fn (the key-casting function resolved from :keys) and :config (the resolved Dowser.Client.Config). dowser_client's default (Dowser.Client.Codec.Default) only applies :key_fn to every key of the body and otherwise passes it through unchanged — use it as a reference implementation.

dowser_client has no backend-specific knowledge of its own, so it ships no other implementation. A backend package (e.g. dowser_elasticsearch) that wants per-field value casting (dates, geo points, ...) implements its own Codec that walks the body against its mapping/schema — backend-specific knowledge dowser_client doesn't have — dispatching each field to a Dowser.Client.Codec.Builder-built module's load/2/dump/2. See Dowser.Client.Codec.Builder for that half of the pattern.

Summary

Callbacks

decode(value, opts)
encode(value, opts)

Callbacks

decode(value, opts)

@callback decode(value :: term(), opts :: keyword()) :: {:ok, term()} | {:error, term()}

encode(value, opts)

@callback encode(value :: term(), opts :: keyword()) :: {:ok, term()} | {:error, term()}