Return blank strings in responses

lib/iban_ex/commons/commons.ex

@@ -1,6 +1,11 @@
 defmodule IbanEx.Commons do
   @moduledoc false
 
+  @spec blank(nil | binary()) :: nil | binary()
+  def blank(nil), do: nil
+  def blank(""), do: nil
+  def blank(string) when is_binary(string), do: string
+
   @spec normalize(binary()) :: binary()
   def normalize(string) do
     string

lib/iban_ex/country/template.ex

@@ -9,6 +9,7 @@ defmodule IbanEx.Country.Template do
 
   @callback size() :: size()
   @callback rule() :: rule()
+  @callback incomplete_rule() :: rule()
   @callback to_string(Iban.t(), joiner()) :: String.t()
   @callback to_string(Iban.t()) :: String.t()
 
@@ -39,11 +40,33 @@ def to_string(
       @spec size() :: integer()
       def size(), do: @size
 
+      @doc """
+      Return Regex for parsing complete BBAN (part of IBAN string)
+      """
       @impl IbanEx.Country.Template
       @spec rule() :: Regex.t()
       def rule(), do: @rule
 
-      defoverridable to_string: 1, to_string: 2, size: 0, rule: 0
+      @doc """
+      Return Regex without trailing “$” for parsing incomplete BBAN (part of IBAN string) (for partial suggestions)
+      """
+      @impl IbanEx.Country.Template
+      @spec incomplete_rule() :: Regex.t()
+      def incomplete_rule() do
+        source =
+          @rule
+          |> Regex.source()
+          |> String.slice(0..-2//1)
+          |> String.replace("{", "{0,")
+
+        opts =
+          @rule
+          |> Regex.opts()
+
+        Regex.compile!(source, opts)
+      end
+
+      defoverridable to_string: 1, to_string: 2, size: 0, rule: 0, incomplete_rule: 0
     end
   end
 end

lib/iban_ex/parser.ex

@@ -42,11 +42,29 @@ def parse(iban_string) do
   end
 
   @spec parse_bban(binary(), <<_::16>>) :: map()
-  def parse_bban(bban_string, country_code) do
-    regex = Country.country_module(country_code).rule()
-    for {key, val} <- Regex.named_captures(regex, bban_string),
-        into: %{},
-        do: {String.to_atom(key), val}
+  def parse_bban(bban_string, country_code, options \\ [incomplete: false])
+
+  def parse_bban(bban_string, country_code, incomplete: true) do
+    Country.country_module(country_code).incomplete_rule()
+    |> parse_bban_by_regex(bban_string)
+  end
+
+  def parse_bban(bban_string, country_code, _options) do
+    Country.country_module(country_code).rule()
+    |> parse_bban_by_regex(bban_string)
+  end
+
+  defp parse_bban_by_regex(_regex, nil), do: %{}
+  defp parse_bban_by_regex(regex, bban_string) do
+    case Regex.named_captures(regex, bban_string) do
+      map when is_map(map) ->
+        for {key, val} <- map,
+            into: %{},
+            do: {String.to_atom(key), val}
+
+      nil ->
+        %{}
+    end
   end
 
   @spec country_code(iban_string()) :: country_code_string()