defmodule MaruSwagger do
  use Maru.Middleware
  alias Maru.Router.Endpoint

  def init(opts) do
    at = opts |> Keyword.fetch! :at
    pretty = opts |> Keyword.get :pretty, false
    {at |> Maru.Router.Path.split, pretty}
  end

  def call(%Plug.Conn{path_info: path_info}=conn, {path, pretty}) do
    case Maru.Router.Path.lstrip(path_info, path) do
      nil            -> conn
      {:ok, result}  ->
        resp = result |> List.first |> generate |> Poison.encode!(pretty: pretty)
        conn
     |> Plug.Conn.put_resp_header("access-control-allow-origin", "*")
     |> Plug.Conn.send_resp(200, resp)
     |> Plug.Conn.halt
    end
  end

  def generate(version \\ nil) do
    [{module, _}] = Maru.Config.servers
      module
   |> Maru.Builder.Routers.generate
   |> Dict.fetch!(version)
	 |> Enum.sort(&(&1.path > &2.path))
   |> Enum.map(&extract_endpoint/1)
	 |> to_swagger
  end

  defp extract_endpoint(ep) do
    params = ep |> extract_params
    method =
      case ep.method do
        {:_, [], nil} -> "MATCH"
        m -> m
      end
    %{desc: ep.desc, method: method, path: ep.path, params: params, version: ep.version}
  end

  defp extract_params(%Endpoint{method: {:_, [], nil}}=ep) do
    %{ep | method: "MATCH"} |> extract_params
  end

  defp extract_params(%Endpoint{method: "GET"}), do: []
  defp extract_params(%Endpoint{method: "GET", path: path, param_context: params_list}) do
    for param <- params_list do
      if param.attr_name in path do
        %{ in: "path" }
      else
        %{ in: "query" }
      end
   |> Map.merge %{
        name: param.attr_name,
        description: param.desc || "",
        required: param.required,
        type: decode_parser(param.parser)
      }
    end
  end

  defp extract_params(%Endpoint{param_context: []}), do: []
  defp extract_params(%Endpoint{path: path, param_context: params_list}) do
    {file_list, param_list} = Enum.split_while(
      params_list,
      fn(param) ->
        decode_parser(param.parser) == "file"
      end
    )

    p = for param <- param_list do
      {param.attr_name, %{type: decode_parser(param.parser)}}
    end |> Enum.into %{}

    f = for param <- file_list do
      %{ name: param.attr_name,
         in: "formData",
         description: "file",
         required: true,
         type: "file"
       }
    end

    %{ name: "body",
       in: "body",
       description: "desc",
       required: false,
     }
 |> fn r ->
      if p == %{} do r else
        r
     |> put_in([:schema], %{})
     |> put_in([:schema, :properties], p)
      end
    end.()
 |> fn r ->
      if f == [] do [r] else f end
    end.()
 |> fn r ->
      if Enum.any? path, &is_atom/1 do
        r ++ path |> Enum.filter(&is_atom/1) |> Enum.map &(%{name: &1, in: "path", required: true, type: "string"})
      else r end
    end.()
  end


  defp decode_parser(parser) do
      parser |> to_string |> String.split(".") |> List.last |> String.downcase
  end


  defp to_swagger(list) do
    paths = list |> List.foldr %{}, fn (%{desc: desc, method: method, path: url_list, params: params}, result) ->
      url = join_path(url_list)
      if Map.has_key? result, url do
        result
      else
        result |> put_in([url], %{})
      end
			|> put_in([url, String.downcase(method)], %{
        description: desc || "",
        parameters: params,
        responses: %{
          "200" => %{description: "ok"}
        }
      })
    end

    %{version: version} = List.first(list)
    [{mod, _}] = Maru.Config.servers
    v =  version
    %{ swagger: "2.0",
       info: %{ version: v,
                title: mod,
              },
       paths: paths
     }
  end

  defp join_path(path) do
    [ "/" | for i <- path do
      cond do
        is_atom(i) -> "{#{i}}"
        is_binary(i) -> i
        true -> raise "unknow path type"
      end
    end ] |> Path.join
  end
end