@spec valid_functions() :: [atom()]

Returns list of valid function codes.

@spec validate(atom()) :: {:ok, atom()} | {:error, String.t()}

Validates function code.

Valid Codes

• :uct - Ukrainian Credit Transfer (default)
• :ict - International Credit Transfer
• :xct - Cross-border Credit Transfer

Examples

iex> QRNBU.Validators.FunctionCode.validate(:uct)
{:ok, :uct}

iex> QRNBU.Validators.FunctionCode.validate(:ict)
{:ok, :ict}

iex> QRNBU.Validators.FunctionCode.validate(:xct)
{:ok, :xct}

iex> QRNBU.Validators.FunctionCode.validate(:invalid)
{:error, "Invalid function code. Must be one of: uct, ict, xct"}

iex> QRNBU.Validators.FunctionCode.validate("uct")
{:error, "Function code must be an atom"}