Add universal modules page

Author: RoyalIcing

apps/components_guide_web/lib/components_guide_web/controllers/universal_modules_controller.ex

@@ -0,0 +1,103 @@
+defmodule ComponentsGuideWeb.UniversalModulesController do
+  use ComponentsGuideWeb, :controller
+
+  def index(conn, _params) do
+    source = "
+    const pi = 3.14;
+
+    const answer = 42;
+    "
+    decoded = decode_module(source)
+    render(conn, "index.html", source: source, decoded: inspect(decoded))
+  end
+
+  defp decode_module(source) do
+    decode_module(nil, source, [])
+  end
+
+  defp decode_module(nil, <<"\n", rest::bitstring>>, result),
+    do: decode_module(nil, rest, result)
+
+  # Skip semicolons
+  defp decode_module(nil, <<";", rest::bitstring>>, result),
+    do: decode_module(nil, rest, result)
+
+  # Skip semicolons
+  defp decode_module(nil, <<" ", rest::bitstring>>, result),
+    do: decode_module(nil, rest, result)
+
+  defp decode_module(nil, <<"const ", rest::bitstring>>, result) do
+    decode_module({:const, :expect_identifier, []}, rest, result)
+  end
+
+  # Skip whitespace
+  defp decode_module({_, :expect_identifier, []} = context, <<" ", rest::bitstring>>, result),
+    do: decode_module(context, rest, result)
+
+  # Skip whitespace
+  defp decode_module({_, :expect_expression, []} = context, <<" ", rest::bitstring>>, result),
+    do: decode_module(context, rest, result)
+
+  defp decode_module(
+         {:const, :expect_identifier, _} = context,
+         <<" ", rest::bitstring>>,
+         result
+       ) do
+    decode_module(context, rest, result)
+  end
+
+  defp decode_module(
+         {:const, :expect_identifier, reverse_identifier},
+         <<"=", rest::bitstring>>,
+         result
+       ) do
+    identifier = reverse_identifier |> Enum.reverse() |> :binary.list_to_bin()
+    decode_module({{:const, identifier}, :expect_expression, []}, rest, result)
+  end
+
+  defp decode_module(
+         {:const, :expect_identifier, reverse_identifier},
+         <<char::utf8, rest::bitstring>>,
+         result
+       ) do
+    decode_module({:const, :expect_identifier, [char | reverse_identifier]}, rest, result)
+  end
+
+  defp decode_module(
+         {{:const, identifier}, :expect_expression, expression},
+         <<";", rest::bitstring>>,
+         result
+       ),
+       do: decode_module(nil, rest, [{:const, identifier, expression} | result])
+
+  defp decode_module(
+         {{:const, identifier}, :expect_expression, []} = context,
+         <<char::utf8, _::bitstring>> = source,
+         result
+       )
+       when char in [?0, ?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?9] do
+    case Float.parse(source) do
+      :error ->
+        err(context, source, result)
+
+      {f, rest} ->
+        decode_module({{:const, identifier}, :expect_expression, [f]}, rest, result)
+    end
+  end
+
+  defp decode_module(nil, "", result) do
+    {:ok, Enum.reverse(result)}
+  end
+
+  defp decode_module(context, source, result) do
+    err(context, source, result)
+  end
+
+  defp err(context, source, result) do
+    {:err, context, source, result}
+  end
+end
+
+defmodule ComponentsGuideWeb.UniversalModulesView do
+  use ComponentsGuideWeb, :view
+end

apps/components_guide_web/lib/components_guide_web/router.ex

@@ -67,6 +67,8 @@ defmodule ComponentsGuideWeb.Router do
     get("/react+typescript", ReactTypescriptController, :index)
     get("/react+typescript/:article", ReactTypescriptController, :show)
 
+    get("/universal-modules", UniversalModulesController, :index)
+
     resources("/text", TextController)
     get("/text/:id/text/:format", TextController, :show_text_format)
 

apps/components_guide_web/lib/components_guide_web/templates/universal_modules/index.html.eex

@@ -0,0 +1,7 @@
+<pre>
+  <%= @source %>
+</pre>
+
+<pre>
+  <%= @decoded %>
+</pre>