@spec build(
  Facturx.Invoice.t(),
  keyword()
) :: {:ok, binary()} | {:error, term()}

Build a CII XML binary from an Facturx.Invoice struct.

@spec extract(binary()) ::
  {:ok, %{xml: binary(), profile: profile() | nil, filename: String.t()}}
  | {:error, term()}

Extract the embedded CII XML (and metadata) from a Factur-X PDF.

@spec generate(binary(), Facturx.Invoice.t() | binary(), keyword()) ::
  {:ok, binary()} | {:error, term()}

Build a Factur-X PDF: embed the CII XML for invoice into a PDF/A-3.

pdf_a3 must already be a valid PDF/A-3 (the visual invoice). Pass either an Facturx.Invoice struct or a ready CII XML binary as the payload.

@spec parse(binary()) :: {:ok, Facturx.Invoice.t()} | {:error, term()}

Parse a CII XML binary into an Facturx.Invoice struct.

@spec profiles() :: [profile()]

The supported Factur-X profiles.

@spec validate(
  binary(),
  keyword()
) :: {:ok, :valid} | {:error, {:invalid, [map()]}} | {:error, term()}

Validate CII XML against the EN 16931 Schematron (business rules).

Optional: requires a reachable Saxon endpoint (:endpoint opt) and the req dependency. See Facturx.Validate.

@spec validate_xsd(
  binary(),
  keyword()
) :: {:ok, :valid} | {:error, {:invalid, [String.t()]}} | {:error, term()}

Validate CII XML against the EN 16931 XSD (structure/types).

Pure Elixir, in-process (OTP :xmerl_xsd) — no external tool. See Facturx.XSD.