# Pleroma: A lightweight social networking server
# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only

defmodule Pleroma.Web.OAuth.OAuthController do
  use Pleroma.Web, :controller

  alias Pleroma.Helpers.UriHelper
  alias Pleroma.Maps
  alias Pleroma.MFA
  alias Pleroma.Plugs.RateLimiter
  alias Pleroma.Registration
  alias Pleroma.Repo
  alias Pleroma.User
  alias Pleroma.Web.Auth.Authenticator
  alias Pleroma.Web.ControllerHelper
  alias Pleroma.Web.OAuth.App
  alias Pleroma.Web.OAuth.Authorization
  alias Pleroma.Web.OAuth.MFAController
  alias Pleroma.Web.OAuth.MFAView
  alias Pleroma.Web.OAuth.OAuthView
  alias Pleroma.Web.OAuth.Scopes
  alias Pleroma.Web.OAuth.Token
  alias Pleroma.Web.OAuth.Token.Strategy.RefreshToken
  alias Pleroma.Web.OAuth.Token.Strategy.Revoke, as: RevokeToken

  require Logger

  if Pleroma.Config.oauth_consumer_enabled?(), do: plug(Ueberauth)

  plug(:fetch_session)
  plug(:fetch_flash)

  plug(:skip_plug, [Pleroma.Plugs.OAuthScopesPlug, Pleroma.Plugs.EnsurePublicOrAuthenticatedPlug])

  plug(RateLimiter, [name: :authentication] when action == :create_authorization)

  action_fallback(Pleroma.Web.OAuth.FallbackController)

  @oob_token_redirect_uri "urn:ietf:wg:oauth:2.0:oob"

  # Note: this definition is only called from error-handling methods with `conn.params` as 2nd arg
  def authorize(%Plug.Conn{} = conn, %{"authorization" => _} = params) do
    {auth_attrs, params} = Map.pop(params, "authorization")
    authorize(conn, Map.merge(params, auth_attrs))
  end

  def authorize(%Plug.Conn{assigns: %{token: %Token{}}} = conn, %{"force_login" => _} = params) do
    if ControllerHelper.truthy_param?(params["force_login"]) do
      do_authorize(conn, params)
    else
      handle_existing_authorization(conn, params)
    end
  end

  # Note: the token is set in oauth_plug, but the token and client do not always go together.
  # For example, MastodonFE's token is set if user requests with another client,
  # after user already authorized to MastodonFE.
  # So we have to check client and token.
  def authorize(
        %Plug.Conn{assigns: %{token: %Token{} = token}} = conn,
        %{"client_id" => client_id} = params
      ) do
    with %Token{} = t <- Repo.get_by(Token, token: token.token) |> Repo.preload(:app),
         ^client_id <- t.app.client_id do
      handle_existing_authorization(conn, params)
    else
      _ -> do_authorize(conn, params)
    end
  end

  def authorize(%Plug.Conn{} = conn, params), do: do_authorize(conn, params)

  defp do_authorize(%Plug.Conn{} = conn, params) do
    app = Repo.get_by(App, client_id: params["client_id"])
    available_scopes = (app && app.scopes) || []
    scopes = Scopes.fetch_scopes(params, available_scopes)

    scopes =
      if scopes == [] do
        available_scopes
      else
        scopes
      end

    # Note: `params` might differ from `conn.params`; use `@params` not `@conn.params` in template
    render(conn, Authenticator.auth_template(), %{
      response_type: params["response_type"],
      client_id: params["client_id"],
      available_scopes: available_scopes,
      scopes: scopes,
      redirect_uri: params["redirect_uri"],
      state: params["state"],
      params: params
    })
  end

  defp handle_existing_authorization(
         %Plug.Conn{assigns: %{token: %Token{} = token}} = conn,
         %{"redirect_uri" => @oob_token_redirect_uri}
       ) do
    render(conn, "oob_token_exists.html", %{token: token})
  end

  defp handle_existing_authorization(
         %Plug.Conn{assigns: %{token: %Token{} = token}} = conn,
         %{} = params
       ) do
    app = Repo.preload(token, :app).app

    redirect_uri =
      if is_binary(params["redirect_uri"]) do
        params["redirect_uri"]
      else
        default_redirect_uri(app)
      end

    if redirect_uri in String.split(app.redirect_uris) do
      redirect_uri = redirect_uri(conn, redirect_uri)
      url_params = %{access_token: token.token}
      url_params = Maps.put_if_present(url_params, :state, params["state"])
      url = UriHelper.append_uri_params(redirect_uri, url_params)
      redirect(conn, external: url)
    else
      conn
      |> put_flash(:error, dgettext("errors", "Unlisted redirect_uri."))
      |> redirect(external: redirect_uri(conn, redirect_uri))
    end
  end

  def create_authorization(
        %Plug.Conn{} = conn,
        %{"authorization" => _} = params,
        opts \\ []
      ) do
    with {:ok, auth, user} <- do_create_authorization(conn, params, opts[:user]),
         {:mfa_required, _, _, false} <- {:mfa_required, user, auth, MFA.require?(user)} do
      after_create_authorization(conn, auth, params)
    else
      error ->
        handle_create_authorization_error(conn, error, params)
    end
  end

  def after_create_authorization(%Plug.Conn{} = conn, %Authorization{} = auth, %{
        "authorization" => %{"redirect_uri" => @oob_token_redirect_uri}
      }) do
    # Enforcing the view to reuse the template when calling from other controllers
    conn
    |> put_view(OAuthView)
    |> render("oob_authorization_created.html", %{auth: auth})
  end

  def after_create_authorization(%Plug.Conn{} = conn, %Authorization{} = auth, %{
        "authorization" => %{"redirect_uri" => redirect_uri} = auth_attrs
      }) do
    app = Repo.preload(auth, :app).app

    # An extra safety measure before we redirect (also done in `do_create_authorization/2`)
    if redirect_uri in String.split(app.redirect_uris) do
      redirect_uri = redirect_uri(conn, redirect_uri)
      url_params = %{code: auth.token}
      url_params = Maps.put_if_present(url_params, :state, auth_attrs["state"])
      url = UriHelper.append_uri_params(redirect_uri, url_params)
      redirect(conn, external: url)
    else
      conn
      |> put_flash(:error, dgettext("errors", "Unlisted redirect_uri."))
      |> redirect(external: redirect_uri(conn, redirect_uri))
    end
  end

  defp handle_create_authorization_error(
         %Plug.Conn{} = conn,
         {:error, scopes_issue},
         %{"authorization" => _} = params
       )
       when scopes_issue in [:unsupported_scopes, :missing_scopes] do
    # Per https://github.com/tootsuite/mastodon/blob/
    #   51e154f5e87968d6bb115e053689767ab33e80cd/app/controllers/api/base_controller.rb#L39
    conn
    |> put_flash(:error, dgettext("errors", "This action is outside the authorized scopes"))
    |> put_status(:unauthorized)
    |> authorize(params)
  end

  defp handle_create_authorization_error(
         %Plug.Conn{} = conn,
         {:account_status, :confirmation_pending},
         %{"authorization" => _} = params
       ) do
    conn
    |> put_flash(:error, dgettext("errors", "Your login is missing a confirmed e-mail address"))
    |> put_status(:forbidden)
    |> authorize(params)
  end

  defp handle_create_authorization_error(
         %Plug.Conn{} = conn,
         {:mfa_required, user, auth, _},
         params
       ) do
    {:ok, token} = MFA.Token.create_token(user, auth)

    data = %{
      "mfa_token" => token.token,
      "redirect_uri" => params["authorization"]["redirect_uri"],
      "state" => params["authorization"]["state"]
    }

    MFAController.show(conn, data)
  end

  defp handle_create_authorization_error(
         %Plug.Conn{} = conn,
         {:account_status, :password_reset_pending},
         %{"authorization" => _} = params
       ) do
    conn
    |> put_flash(:error, dgettext("errors", "Password reset is required"))
    |> put_status(:forbidden)
    |> authorize(params)
  end

  defp handle_create_authorization_error(
         %Plug.Conn{} = conn,
         {:account_status, :deactivated},
         %{"authorization" => _} = params
       ) do
    conn
    |> put_flash(:error, dgettext("errors", "Your account is currently disabled"))
    |> put_status(:forbidden)
    |> authorize(params)
  end

  defp handle_create_authorization_error(%Plug.Conn{} = conn, error, %{"authorization" => _}) do
    Authenticator.handle_error(conn, error)
  end

  @doc "Renew access_token with refresh_token"
  def token_exchange(
        %Plug.Conn{} = conn,
        %{"grant_type" => "refresh_token", "refresh_token" => token} = _params
      ) do
    with {:ok, app} <- Token.Utils.fetch_app(conn),
         {:ok, %{user: user} = token} <- Token.get_by_refresh_token(app, token),
         {:ok, token} <- RefreshToken.grant(token) do
      json(conn, OAuthView.render("token.json", %{user: user, token: token}))
    else
      _error -> render_invalid_credentials_error(conn)
    end
  end

  def token_exchange(%Plug.Conn{} = conn, %{"grant_type" => "authorization_code"} = params) do
    with {:ok, app} <- Token.Utils.fetch_app(conn),
         fixed_token = Token.Utils.fix_padding(params["code"]),
         {:ok, auth} <- Authorization.get_by_token(app, fixed_token),
         %User{} = user <- User.get_cached_by_id(auth.user_id),
         {:ok, token} <- Token.exchange_token(app, auth) do
      json(conn, OAuthView.render("token.json", %{user: user, token: token}))
    else
      error ->
        handle_token_exchange_error(conn, error)
    end
  end

  def token_exchange(
        %Plug.Conn{} = conn,
        %{"grant_type" => "password"} = params
      ) do
    with {:ok, %User{} = user} <- Authenticator.get_user(conn),
         {:ok, app} <- Token.Utils.fetch_app(conn),
         requested_scopes <- Scopes.fetch_scopes(params, app.scopes),
         {:ok, token} <- login(user, app, requested_scopes) do
      json(conn, OAuthView.render("token.json", %{user: user, token: token}))
    else
      error ->
        handle_token_exchange_error(conn, error)
    end
  end

  def token_exchange(
        %Plug.Conn{} = conn,
        %{"grant_type" => "password", "name" => name, "password" => _password} = params
      ) do
    params =
      params
      |> Map.delete("name")
      |> Map.put("username", name)

    token_exchange(conn, params)
  end

  def token_exchange(%Plug.Conn{} = conn, %{"grant_type" => "client_credentials"} = _params) do
    with {:ok, app} <- Token.Utils.fetch_app(conn),
         {:ok, auth} <- Authorization.create_authorization(app, %User{}),
         {:ok, token} <- Token.exchange_token(app, auth) do
      json(conn, OAuthView.render("token.json", %{token: token}))
    else
      _error ->
        handle_token_exchange_error(conn, :invalid_credentails)
    end
  end

  # Bad request
  def token_exchange(%Plug.Conn{} = conn, params), do: bad_request(conn, params)

  defp handle_token_exchange_error(%Plug.Conn{} = conn, {:mfa_required, user, auth, _}) do
    conn
    |> put_status(:forbidden)
    |> json(build_and_response_mfa_token(user, auth))
  end

  defp handle_token_exchange_error(%Plug.Conn{} = conn, {:account_status, :deactivated}) do
    render_error(
      conn,
      :forbidden,
      "Your account is currently disabled",
      %{},
      "account_is_disabled"
    )
  end

  defp handle_token_exchange_error(
         %Plug.Conn{} = conn,
         {:account_status, :password_reset_pending}
       ) do
    render_error(
      conn,
      :forbidden,
      "Password reset is required",
      %{},
      "password_reset_required"
    )
  end

  defp handle_token_exchange_error(%Plug.Conn{} = conn, {:account_status, :confirmation_pending}) do
    render_error(
      conn,
      :forbidden,
      "Your login is missing a confirmed e-mail address",
      %{},
      "missing_confirmed_email"
    )
  end

  defp handle_token_exchange_error(%Plug.Conn{} = conn, {:account_status, :approval_pending}) do
    render_error(
      conn,
      :forbidden,
      "Your account is awaiting approval.",
      %{},
      "awaiting_approval"
    )
  end

  defp handle_token_exchange_error(%Plug.Conn{} = conn, _error) do
    render_invalid_credentials_error(conn)
  end

  def token_revoke(%Plug.Conn{} = conn, %{"token" => _token} = params) do
    with {:ok, app} <- Token.Utils.fetch_app(conn),
         {:ok, _token} <- RevokeToken.revoke(app, params) do
      json(conn, %{})
    else
      _error ->
        # RFC 7009: invalid tokens [in the request] do not cause an error response
        json(conn, %{})
    end
  end

  def token_revoke(%Plug.Conn{} = conn, params), do: bad_request(conn, params)

  # Response for bad request
  defp bad_request(%Plug.Conn{} = conn, _) do
    render_error(conn, :internal_server_error, "Bad request")
  end

  @doc "Prepares OAuth request to provider for Ueberauth"
  def prepare_request(%Plug.Conn{} = conn, %{
        "provider" => provider,
        "authorization" => auth_attrs
      }) do
    scope =
      auth_attrs
      |> Scopes.fetch_scopes([])
      |> Scopes.to_string()

    state =
      auth_attrs
      |> Map.delete("scopes")
      |> Map.put("scope", scope)
      |> Jason.encode!()

    params =
      auth_attrs
      |> Map.drop(~w(scope scopes client_id redirect_uri))
      |> Map.put("state", state)

    # Handing the request to Ueberauth
    redirect(conn, to: o_auth_path(conn, :request, provider, params))
  end

  def request(%Plug.Conn{} = conn, params) do
    message =
      if params["provider"] do
        dgettext("errors", "Unsupported OAuth provider: %{provider}.",
          provider: params["provider"]
        )
      else
        dgettext("errors", "Bad OAuth request.")
      end

    conn
    |> put_flash(:error, message)
    |> redirect(to: "/")
  end

  def callback(%Plug.Conn{assigns: %{ueberauth_failure: failure}} = conn, params) do
    params = callback_params(params)
    messages = for e <- Map.get(failure, :errors, []), do: e.message
    message = Enum.join(messages, "; ")

    conn
    |> put_flash(
      :error,
      dgettext("errors", "Failed to authenticate: %{message}.", message: message)
    )
    |> redirect(external: redirect_uri(conn, params["redirect_uri"]))
  end

  def callback(%Plug.Conn{} = conn, params) do
    params = callback_params(params)

    with {:ok, registration} <- Authenticator.get_registration(conn) do
      auth_attrs = Map.take(params, ~w(client_id redirect_uri scope scopes state))

      case Repo.get_assoc(registration, :user) do
        {:ok, user} ->
          create_authorization(conn, %{"authorization" => auth_attrs}, user: user)

        _ ->
          registration_params =
            Map.merge(auth_attrs, %{
              "nickname" => Registration.nickname(registration),
              "email" => Registration.email(registration)
            })

          conn
          |> put_session_registration_id(registration.id)
          |> registration_details(%{"authorization" => registration_params})
      end
    else
      error ->
        Logger.debug(inspect(["OAUTH_ERROR", error, conn.assigns]))

        conn
        |> put_flash(:error, dgettext("errors", "Failed to set up user account."))
        |> redirect(external: redirect_uri(conn, params["redirect_uri"]))
    end
  end

  defp callback_params(%{"state" => state} = params) do
    Map.merge(params, Jason.decode!(state))
  end

  def registration_details(%Plug.Conn{} = conn, %{"authorization" => auth_attrs}) do
    render(conn, "register.html", %{
      client_id: auth_attrs["client_id"],
      redirect_uri: auth_attrs["redirect_uri"],
      state: auth_attrs["state"],
      scopes: Scopes.fetch_scopes(auth_attrs, []),
      nickname: auth_attrs["nickname"],
      email: auth_attrs["email"]
    })
  end

  def register(%Plug.Conn{} = conn, %{"authorization" => _, "op" => "connect"} = params) do
    with registration_id when not is_nil(registration_id) <- get_session_registration_id(conn),
         %Registration{} = registration <- Repo.get(Registration, registration_id),
         {_, {:ok, auth, _user}} <-
           {:create_authorization, do_create_authorization(conn, params)},
         %User{} = user <- Repo.preload(auth, :user).user,
         {:ok, _updated_registration} <- Registration.bind_to_user(registration, user) do
      conn
      |> put_session_registration_id(nil)
      |> after_create_authorization(auth, params)
    else
      {:create_authorization, error} ->
        {:register, handle_create_authorization_error(conn, error, params)}

      _ ->
        {:register, :generic_error}
    end
  end

  def register(%Plug.Conn{} = conn, %{"authorization" => _, "op" => "register"} = params) do
    with registration_id when not is_nil(registration_id) <- get_session_registration_id(conn),
         %Registration{} = registration <- Repo.get(Registration, registration_id),
         {:ok, user} <- Authenticator.create_from_registration(conn, registration) do
      conn
      |> put_session_registration_id(nil)
      |> create_authorization(
        params,
        user: user
      )
    else
      {:error, changeset} ->
        message =
          Enum.map(changeset.errors, fn {field, {error, _}} ->
            "#{field} #{error}"
          end)
          |> Enum.join("; ")

        message =
          String.replace(
            message,
            "ap_id has already been taken",
            "nickname has already been taken"
          )

        conn
        |> put_status(:forbidden)
        |> put_flash(:error, "Error: #{message}.")
        |> registration_details(params)

      _ ->
        {:register, :generic_error}
    end
  end

  defp do_create_authorization(conn, auth_attrs, user \\ nil)

  defp do_create_authorization(
         %Plug.Conn{} = conn,
         %{
           "authorization" =>
             %{
               "client_id" => client_id,
               "redirect_uri" => redirect_uri
             } = auth_attrs
         },
         user
       ) do
    with {_, {:ok, %User{} = user}} <-
           {:get_user, (user && {:ok, user}) || Authenticator.get_user(conn)},
         %App{} = app <- Repo.get_by(App, client_id: client_id),
         true <- redirect_uri in String.split(app.redirect_uris),
         requested_scopes <- Scopes.fetch_scopes(auth_attrs, app.scopes),
         {:ok, auth} <- do_create_authorization(user, app, requested_scopes) do
      {:ok, auth, user}
    end
  end

  defp do_create_authorization(%User{} = user, %App{} = app, requested_scopes)
       when is_list(requested_scopes) do
    with {:account_status, :active} <- {:account_status, User.account_status(user)},
         {:ok, scopes} <- validate_scopes(app, requested_scopes),
         {:ok, auth} <- Authorization.create_authorization(app, user, scopes) do
      {:ok, auth}
    end
  end

  # Note: intended to be a private function but opened for AccountController that logs in on signup
  @doc "If checks pass, creates authorization and token for given user, app and requested scopes."
  def login(%User{} = user, %App{} = app, requested_scopes) when is_list(requested_scopes) do
    with {:ok, auth} <- do_create_authorization(user, app, requested_scopes),
         {:mfa_required, _, _, false} <- {:mfa_required, user, auth, MFA.require?(user)},
         {:ok, token} <- Token.exchange_token(app, auth) do
      {:ok, token}
    end
  end

  # Special case: Local MastodonFE
  defp redirect_uri(%Plug.Conn{} = conn, "."), do: auth_url(conn, :login)

  defp redirect_uri(%Plug.Conn{}, redirect_uri), do: redirect_uri

  defp get_session_registration_id(%Plug.Conn{} = conn), do: get_session(conn, :registration_id)

  defp put_session_registration_id(%Plug.Conn{} = conn, registration_id),
    do: put_session(conn, :registration_id, registration_id)

  defp build_and_response_mfa_token(user, auth) do
    with {:ok, token} <- MFA.Token.create_token(user, auth) do
      MFAView.render("mfa_response.json", %{token: token, user: user})
    end
  end

  @spec validate_scopes(App.t(), map() | list()) ::
          {:ok, list()} | {:error, :missing_scopes | :unsupported_scopes}
  defp validate_scopes(%App{} = app, params) when is_map(params) do
    requested_scopes = Scopes.fetch_scopes(params, app.scopes)
    validate_scopes(app, requested_scopes)
  end

  defp validate_scopes(%App{} = app, requested_scopes) when is_list(requested_scopes) do
    Scopes.validate(requested_scopes, app.scopes)
  end

  def default_redirect_uri(%App{} = app) do
    app.redirect_uris
    |> String.split()
    |> Enum.at(0)
  end

  defp render_invalid_credentials_error(conn) do
    render_error(conn, :bad_request, "Invalid credentials")
  end
end