Proof of concept

Author: imranismail

lib/parameters/open_api.ex

@@ -0,0 +1,89 @@
+defmodule Parameters.OAS3 do
+  def type_mapper(:map), do: :object
+  def type_mapper(:integer), do: :number
+  def type_mapper(:float), do: :number
+  def type_mapper(any), do: any
+
+  defmacro __using__(opts) do
+    version = Keyword.fetch!(opts, :version)
+    title = Keyword.fetch!(opts, :title)
+    content_types = Keyword.fetch!(opts, :content_types)
+    accepts = Keyword.fetch!(opts, :accepts)
+
+    quote do
+      def generate do
+        config = Application.get_env(unquote(opts[:otp_app]), __MODULE__)
+        router = Keyword.fetch!(config, :router)
+        routes = router.__routes__()
+        accepts = unquote(accepts)
+        content_types = unquote(content_types)
+
+        spec = %{
+          openapi: "3.0.0",
+          info: %{
+            title: unquote(title),
+            version: unquote(version)
+          }
+        }
+
+        key_fn = fn route -> route.path end
+        val_fn = fn route ->
+          parameters = route.plug.__parameters__()
+          node = Enum.find(parameters, fn node -> node.id == route.plug_opts end)
+
+          key = "#{route.verb}"
+          val = %{
+            requestBody: %{
+              required: true,
+              description: "",
+              content: for pipeline <- route.pipe_through, into: %{} do
+                key = Keyword.fetch!(content_types, pipeline)
+
+                val = %{
+                  schema: %{
+                    required: for field <- node.fields, field.options[:required] do
+                      field.id
+                    end,
+                    properties: for field <- node.fields, into: %{} do
+                      {field.id, %{
+                        type: Parameters.OpenAPI.type_mapper(field.type)
+                      }}
+                    end,
+                  }
+                }
+
+                {key, val}
+              end,
+            },
+            responses: %{
+              default: %{
+                description: "",
+                content: for pipeline <- route.pipe_through, into: %{} do
+                  key = Keyword.fetch!(content_types, pipeline)
+
+                  val = %{
+                    schema: %{
+                      type: :object
+                    }
+                  }
+
+                  {key, val}
+                end,
+              }
+            },
+          }
+
+          {key, val}
+        end
+
+        paths =
+          routes
+          |> Enum.group_by(key_fn, val_fn)
+          |> Enum.map(fn {key, val} -> {key, Enum.into(val, %{})} end)
+          |> Enum.into(%{})
+
+        Map.put(spec, :paths, paths)
+      end
+    end
+  end
+end