Behaviour contract for variant transformers.
Implementations are dispatched by Attached.Processors.Transformers
based on (input_content_type, output_content_type) pairs — an image
transformer declares image/ → image/, a PDF-to-text transformer
declares application/pdf → text/plain, etc.
Summary
Callbacks
Returns true if this transformer can handle the given input/output content-type pair.
Returns true if this transformer's runtime dependencies are present (NIF compiled, CLI tool on PATH, etc.). Unavailable transformers are skipped by the dispatcher, so the next one in the list can try.
Returns a short, actionable string explaining how to satisfy this transformer's runtime dependencies — hex deps to add, system packages to install, binaries to provide on PATH.
Transform the file at input_path, applying transforms in order,
and write the result to output_path.
Callbacks
Returns true if this transformer can handle the given input/output content-type pair.
@callback available?() :: boolean()
Returns true if this transformer's runtime dependencies are present (NIF compiled, CLI tool on PATH, etc.). Unavailable transformers are skipped by the dispatcher, so the next one in the list can try.
@callback install_hint() :: String.t()
Returns a short, actionable string explaining how to satisfy this transformer's runtime dependencies — hex deps to add, system packages to install, binaries to provide on PATH.
Shown in the dashboard for every transformer (not only unavailable ones) so operators can use the list as an install checklist.
@callback transform( input_path :: String.t(), transforms :: keyword(), output_path :: String.t() ) :: :ok | {:error, term()}
Transform the file at input_path, applying transforms in order,
and write the result to output_path.