defmodule Xcribe.ApiBlueprint.Formatter do
  @moduledoc false

  alias Xcribe.{ContentDecoder, JsonSchema, Request}

  import Xcribe.Helpers.Formatter

  def merge_request(requests, new_request) do
    group_key = object_key(new_request)

    Map.update(
      requests,
      group_key,
      new_request[group_key],
      &merge_group(&1, new_request[group_key])
    )
  end

  def full_request_object(%Request{resource_group: group} = request) do
    %{
      capitalize_all_words(to_string(group)) => %{
        summary: "",
        description: "",
        resources: resource_object(request)
      }
    }
  end

  def resource_object(%Request{} = request) do
    %{
      resource_key(request) => %{
        name: resource_name(request),
        summary: "",
        description: "",
        parameters: resource_parameters(request),
        actions: action_object(request)
      }
    }
  end

  def action_object(%Request{} = request) do
    %{
      action_key(request) => %{
        name: action_name(request),
        summary: "",
        description: "",
        parameters: action_parameters(request),
        requests: request_object(request)
      }
    }
  end

  def request_object(%Request{description: desc, header_params: headers} = request) do
    %{
      desc => %{
        content_type: content_type(headers),
        headers: headers(headers),
        body: request.request_body,
        schema: request_schema(request),
        response: response_object(request)
      }
    }
  end

  def response_object(%Request{resp_headers: headers, status_code: code} = request) do
    %{
      status: code,
      content_type: content_type(headers),
      headers: headers(headers),
      body: response_body(request),
      schema: response_schema(request)
    }
  end

  def action_parameters(%Request{path_params: path_params}) do
    Enum.reduce(path_params, %{}, &reduce_path_params/2)
  end

  def resource_parameters(%Request{path: path, path_params: path_params}) do
    path_params
    |> Map.take(url_params(path))
    |> Enum.reduce(%{}, &reduce_path_params/2)
  end

  def response_schema(%Request{resp_body: body, resp_headers: headers}) do
    headers
    |> content_type()
    |> json_schema_for(body)
  end

  def response_body(%Request{resp_body: body, resp_headers: headers}) do
    case content_type(headers) do
      nil -> %{}
      content_type -> ContentDecoder.decode!(body, content_type)
    end
  end

  def request_schema(%Request{request_body: body}) when body == %{}, do: %{}

  def request_schema(%Request{request_body: body, header_params: headers}) do
    headers
    |> content_type()
    |> json_schema_for(body)
  end

  def action_name(%Request{action: action, resource: resource}),
    do: "#{capitalize_all_words(resource)}#{action}"

  def action_key(%Request{path: path, verb: verb}) do
    Enum.reduce(
      url_params(path),
      "#{String.upcase(verb)} #{path}",
      &String.replace(&2, &1, format_path_parameter(&1))
    )
  end

  def resource_name(%Request{resource: resource}),
    do: resource |> capitalize_all_words() |> String.trim()

  def resource_key(%Request{path: path}) do
    Enum.reduce(
      url_params(path),
      resource_path(path),
      &String.replace(&2, &1, format_path_parameter(&1))
    )
  end

  defp merge_group(group, new_request),
    do: %{group | resources: merge_group_resources(group.resources, new_request.resources)}

  defp merge_group_resources(resources, new_request) do
    resource_key = object_key(new_request)

    Map.update(
      resources,
      resource_key,
      new_request[resource_key],
      &merge_resource(&1, new_request[resource_key])
    )
  end

  defp merge_resource(resource, new_request) do
    %{resource | actions: merge_resource_actions(resource.actions, new_request.actions)}
  end

  defp merge_resource_actions(actions, new_request) do
    action_key = object_key(new_request)

    Map.update(
      actions,
      action_key,
      new_request[action_key],
      &merge_action(&1, new_request[action_key])
    )
  end

  defp merge_action(action, new_request) do
    %{action | requests: Map.merge(action.requests, new_request.requests)}
  end

  defp object_key(%{} = request) do
    request
    |> Map.keys()
    |> List.first()
  end

  defp resource_path(path) do
    ~r/(.*)(?=\/{.*}$)|(.*)/
    |> Regex.run(path, capture: :all_but_first)
    |> List.last()
  end

  defp capitalize_all_words(string),
    do: Enum.reduce(String.split(string, "_"), "", &"#{&2}#{String.capitalize(&1)} ")

  defp json_schema_for("application/json" = type, body) when is_binary(body),
    do: json_schema_for(type, ContentDecoder.decode!(body, type))

  defp json_schema_for("application/json", body) when is_map(body) or is_list(body),
    do: JsonSchema.schema_for(body)

  defp json_schema_for(_content_type, _body), do: %{}

  defp reduce_path_params({param, value}, parameters) do
    Map.put(
      parameters,
      format_path_parameter(param),
      schema_for(value, true)
    )
  end

  defp schema_for(value, required) do
    {nil, value}
    |> JsonSchema.schema_for()
    |> add_required(required)
  end

  defp headers(headers), do: headers |> Enum.into(%{}) |> Map.delete("content-type")

  defp add_required(map, true), do: Map.put(map, :required, true)

  defp url_params(path) do
    case Regex.run(~r/\{(.*?)\}.+/, path, capture: :all_but_first) do
      nil -> []
      result -> result
    end
  end
end