defmodule PhoenixKitWeb.Users.Auth do
  @moduledoc """
  Authentication and authorization plugs for PhoenixKit user management.

  This module provides plugs and functions for handling user authentication,
  session management, and access control in Phoenix applications using PhoenixKit.

  ## Key Features

  - User authentication with email and password
  - Remember me functionality with secure cookies
  - Session-based authentication
  - Route protection and access control
  - Integration with Phoenix LiveView on_mount callbacks

  ## Usage

  The plugs in this module are automatically configured when using
  `PhoenixKitWeb.Integration.phoenix_kit_routes/1` macro in your router.
  """
  use PhoenixKitWeb, :verified_routes

  import Plug.Conn
  import Phoenix.Controller

  alias PhoenixKit.Utils.Routes
  alias PhoenixKit.Admin.Events
  alias PhoenixKit.Users.Auth
  alias PhoenixKit.Users.Auth.Scope

  # Make the remember me cookie valid for 60 days.
  # If you want bump or reduce this value, also change
  # the token expiry itself in UserToken.
  @max_age 60 * 60 * 24 * 60
  @remember_me_cookie "_phoenix_kit_web_user_remember_me"
  @remember_me_options [sign: true, max_age: @max_age, same_site: "Lax"]

  @doc """
  Logs the user in.

  It renews the session ID and clears the whole session
  to avoid fixation attacks. See the renew_session
  function to customize this behaviour.

  It also sets a `:live_socket_id` key in the session,
  so LiveView sessions are identified and automatically
  disconnected on log out. The line can be safely removed
  if you are not using LiveView.
  """
  def log_in_user(conn, user, params \\ %{}) do
    token = Auth.generate_user_session_token(user)
    user_return_to = get_session(conn, :user_return_to)

    conn
    |> renew_session()
    |> put_token_in_session(token)
    |> maybe_write_remember_me_cookie(token, params)
    |> redirect(to: user_return_to || signed_in_path(conn))
  end

  defp maybe_write_remember_me_cookie(conn, token, %{"remember_me" => "true"}) do
    put_resp_cookie(conn, @remember_me_cookie, token, @remember_me_options)
  end

  defp maybe_write_remember_me_cookie(conn, _token, _params) do
    conn
  end

  # This function renews the session ID and erases the whole
  # session to avoid fixation attacks. If there is any data
  # in the session you may want to preserve after log in/log out,
  # you must explicitly fetch the session data before clearing
  # and then immediately set it after clearing, for example:
  #
  #     defp renew_session(conn) do
  #       preferred_locale = get_session(conn, :preferred_locale)
  #
  #       conn
  #       |> configure_session(renew: true)
  #       |> clear_session()
  #       |> put_session(:preferred_locale, preferred_locale)
  #     end
  #
  defp renew_session(conn) do
    delete_csrf_token()

    conn
    |> configure_session(renew: true)
    |> clear_session()
  end

  @doc """
  Logs the user out.

  It clears all session data for safety. See renew_session.
  """
  def log_out_user(conn) do
    user_token = get_session(conn, :user_token)

    # Get user info before deleting token for admin notification
    user = user_token && Auth.get_user_by_session_token(user_token)

    user_token && Auth.delete_user_session_token(user_token)

    if live_socket_id = get_session(conn, :live_socket_id) do
      broadcast_disconnect(live_socket_id)
    end

    # Notify admin panel about user logout
    if user do
      session_id = extract_session_id_from_live_socket_id(get_session(conn, :live_socket_id))
      Events.broadcast_user_session_disconnected(user.id, session_id)
    end

    conn
    |> renew_session()
    |> delete_resp_cookie(@remember_me_cookie)
    |> redirect(to: "/")
  end

  @doc """
  Logs out a specific user by invalidating all their session tokens and broadcasting disconnect to their LiveView sessions.

  This function is useful when user roles or permissions change and you need to force re-authentication
  to ensure the user gets updated permissions in their session.

  ## Parameters

  - `user`: The user to log out from all sessions

  ## Examples

      iex> log_out_user_from_all_sessions(user)
      :ok
  """
  def log_out_user_from_all_sessions(user) do
    # Get all session tokens before deleting them
    user_tokens = Auth.get_all_user_session_tokens(user)

    # Broadcast disconnect to all LiveView sessions for this user
    # Each session token creates a unique live_socket_id
    Enum.each(user_tokens, fn token ->
      live_socket_id = "phoenix_kit_sessions:#{Base.url_encode64(token.token)}"
      broadcast_disconnect(live_socket_id)
    end)

    # Delete all session tokens for this user
    Auth.delete_all_user_session_tokens(user)

    :ok
  end

  @doc """
  Authenticates the user by looking into the session
  and remember me token.
  """
  def fetch_phoenix_kit_current_user(conn, _opts) do
    {user_token, conn} = ensure_user_token(conn)
    user = user_token && Auth.get_user_by_session_token(user_token)

    # Check if user is active, log out inactive users
    active_user =
      case user do
        %{is_active: false} = inactive_user ->
          require Logger

          Logger.warning(
            "PhoenixKit: Inactive user #{inactive_user.id} attempted access, logging out"
          )

          # Don't assign inactive user, effectively logging them out
          nil

        active_user ->
          active_user
      end

    assign(conn, :phoenix_kit_current_user, active_user)
  end

  @doc """
  Fetches the current user and creates a scope for authentication context.

  This plug combines user fetching with scope creation, providing a
  structured way to handle authentication state in your application.

  The scope is assigned to `:phoenix_kit_current_scope` and includes
  both the user and authentication status.
  """
  def fetch_phoenix_kit_current_scope(conn, _opts) do
    {user_token, conn} = ensure_user_token(conn)
    user = user_token && Auth.get_user_by_session_token(user_token)

    # Check if user is active, log out inactive users
    active_user =
      case user do
        %{is_active: false} = inactive_user ->
          require Logger

          Logger.warning(
            "PhoenixKit: Inactive user #{inactive_user.id} attempted scope access, logging out"
          )

          # Don't assign inactive user, effectively logging them out
          nil

        active_user ->
          active_user
      end

    scope = Scope.for_user(active_user)

    conn
    |> assign(:phoenix_kit_current_user, active_user)
    |> assign(:phoenix_kit_current_scope, scope)
  end

  defp ensure_user_token(conn) do
    if token = get_session(conn, :user_token) do
      {token, conn}
    else
      conn = fetch_cookies(conn, signed: [@remember_me_cookie])

      if token = conn.cookies[@remember_me_cookie] do
        {token, put_token_in_session(conn, token)}
      else
        {nil, conn}
      end
    end
  end

  @doc """
  Handles mounting and authenticating the phoenix_kit_current_user in LiveViews.

  ## `on_mount` arguments

    * `:phoenix_kit_mount_current_user` - Assigns phoenix_kit_current_user
      to socket assigns based on user_token, or nil if
      there's no user_token or no matching user.

    * `:phoenix_kit_mount_current_scope` - Assigns both phoenix_kit_current_user
      and phoenix_kit_current_scope to socket assigns. The scope provides
      structured access to authentication state.

    * `:phoenix_kit_ensure_authenticated` - Authenticates the user from the session,
      and assigns the phoenix_kit_current_user to socket assigns based
      on user_token.
      Redirects to login page if there's no logged user.

    * `:phoenix_kit_ensure_authenticated_scope` - Authenticates the user via scope system,
      assigns both phoenix_kit_current_user and phoenix_kit_current_scope.

    * `:phoenix_kit_ensure_owner` - Ensures the user has owner role,
      and redirects to the home page if not.

    * `:phoenix_kit_ensure_admin` - Ensures the user has admin or owner role,
      and redirects to the home page if not.
      Redirects to login page if there's no logged user.

    * `:phoenix_kit_redirect_if_user_is_authenticated` - Authenticates the user from the session.
      Redirects to signed_in_path if there's a logged user.

    * `:phoenix_kit_redirect_if_authenticated_scope` - Checks authentication via scope system.
      Redirects to signed_in_path if there's a logged user.

  ## Examples

  Use the `on_mount` lifecycle macro in LiveViews to mount or authenticate
  the current_user:

      defmodule PhoenixKitWeb.PageLive do
        use PhoenixKitWeb, :live_view

        on_mount {PhoenixKitWeb.Users.Auth, :phoenix_kit_mount_current_user}
        ...
      end

  Or use the scope system for better encapsulation:

      defmodule PhoenixKitWeb.PageLive do
        use PhoenixKitWeb, :live_view

        on_mount {PhoenixKitWeb.Users.Auth, :phoenix_kit_mount_current_scope}
        ...
      end

  Or use the `live_session` of your router to invoke the on_mount callback:

      live_session :authenticated, on_mount: [{PhoenixKitWeb.Users.Auth, :phoenix_kit_ensure_authenticated_scope}] do
        live "/profile", ProfileLive, :index
      end
  """
  def on_mount(:phoenix_kit_mount_current_user, _params, session, socket) do
    {:cont, mount_phoenix_kit_current_user(socket, session)}
  end

  def on_mount(:phoenix_kit_mount_current_scope, _params, session, socket) do
    {:cont, mount_phoenix_kit_current_scope(socket, session)}
  end

  def on_mount(:phoenix_kit_ensure_authenticated, _params, session, socket) do
    socket = mount_phoenix_kit_current_user(socket, session)

    if socket.assigns.phoenix_kit_current_user do
      {:cont, socket}
    else
      socket =
        socket
        |> Phoenix.LiveView.put_flash(:error, "You must log in to access this page.")
        |> Phoenix.LiveView.redirect(to: Routes.path("/users/log-in"))

      {:halt, socket}
    end
  end

  def on_mount(:phoenix_kit_ensure_authenticated_scope, _params, session, socket) do
    socket = mount_phoenix_kit_current_scope(socket, session)

    if Scope.authenticated?(socket.assigns.phoenix_kit_current_scope) do
      {:cont, socket}
    else
      socket =
        socket
        |> Phoenix.LiveView.put_flash(:error, "You must log in to access this page.")
        |> Phoenix.LiveView.redirect(to: Routes.path("/users/log-in"))

      {:halt, socket}
    end
  end

  def on_mount(:phoenix_kit_redirect_if_user_is_authenticated, _params, session, socket) do
    socket = mount_phoenix_kit_current_user(socket, session)

    if socket.assigns.phoenix_kit_current_user do
      {:halt, Phoenix.LiveView.redirect(socket, to: signed_in_path(socket))}
    else
      {:cont, socket}
    end
  end

  def on_mount(:phoenix_kit_redirect_if_authenticated_scope, _params, session, socket) do
    socket = mount_phoenix_kit_current_scope(socket, session)

    if Scope.authenticated?(socket.assigns.phoenix_kit_current_scope) do
      {:halt, Phoenix.LiveView.redirect(socket, to: signed_in_path(socket))}
    else
      {:cont, socket}
    end
  end

  def on_mount(:phoenix_kit_ensure_owner, _params, session, socket) do
    socket = mount_phoenix_kit_current_scope(socket, session)
    scope = socket.assigns.phoenix_kit_current_scope

    if Scope.owner?(scope) do
      {:cont, socket}
    else
      socket =
        socket
        |> Phoenix.LiveView.put_flash(:error, "You must be an owner to access this page.")
        |> Phoenix.LiveView.redirect(to: "/")

      {:halt, socket}
    end
  end

  def on_mount(:phoenix_kit_ensure_admin, _params, session, socket) do
    socket = mount_phoenix_kit_current_scope(socket, session)
    scope = socket.assigns.phoenix_kit_current_scope

    if Scope.admin?(scope) do
      {:cont, socket}
    else
      socket =
        socket
        |> Phoenix.LiveView.put_flash(:error, "You must be an admin to access this page.")
        |> Phoenix.LiveView.redirect(to: "/")

      {:halt, socket}
    end
  end

  defp mount_phoenix_kit_current_user(socket, session) do
    Phoenix.Component.assign_new(socket, :phoenix_kit_current_user, fn ->
      case session["user_token"] do
        nil -> nil
        user_token -> get_active_user_from_token(user_token)
      end
    end)
  end

  defp get_active_user_from_token(user_token) do
    user = Auth.get_user_by_session_token(user_token)

    case user do
      %{is_active: false} = inactive_user ->
        require Logger

        Logger.warning(
          "PhoenixKit: Inactive user #{inactive_user.id} attempted LiveView mount, blocking access"
        )

        nil

      active_user ->
        active_user
    end
  end

  defp mount_phoenix_kit_current_scope(socket, session) do
    socket = mount_phoenix_kit_current_user(socket, session)
    user = socket.assigns.phoenix_kit_current_user
    scope = Scope.for_user(user)

    Phoenix.Component.assign(socket, :phoenix_kit_current_scope, scope)
  end

  @doc false
  def init(opts), do: opts

  @doc false
  def call(conn, :fetch_phoenix_kit_current_user),
    do: fetch_phoenix_kit_current_user(conn, [])

  @doc false
  def call(conn, :fetch_phoenix_kit_current_scope),
    do: fetch_phoenix_kit_current_scope(conn, [])

  @doc false
  def call(conn, :phoenix_kit_redirect_if_user_is_authenticated),
    do: redirect_if_user_is_authenticated(conn, [])

  @doc false
  def call(conn, :phoenix_kit_require_authenticated_user),
    do: require_authenticated_user(conn, [])

  @doc false
  def call(conn, :phoenix_kit_require_authenticated_scope),
    do: require_authenticated_scope(conn, [])

  @doc """
  Used for routes that require the user to not be authenticated.
  """
  def redirect_if_user_is_authenticated(conn, _opts) do
    if conn.assigns[:phoenix_kit_current_user] do
      conn
      |> redirect(to: signed_in_path(conn))
      |> halt()
    else
      conn
    end
  end

  @doc """
  Used for routes that require the user to be authenticated.

  If you want to enforce the user email is confirmed before
  they use the application at all, here would be a good place.
  """
  def require_authenticated_user(conn, _opts) do
    if conn.assigns[:phoenix_kit_current_user] do
      conn
    else
      conn
      |> put_flash(:error, "You must log in to access this page.")
      |> maybe_store_return_to()
      |> redirect(to: Routes.path("/users/log-in"))
      |> halt()
    end
  end

  @doc """
  Used for routes that require the user to be authenticated via scope.

  This function checks authentication status through the scope system,
  providing a more structured approach to authentication checks.

  If you want to enforce the user email is confirmed before
  they use the application at all, here would be a good place.
  """
  def require_authenticated_scope(conn, _opts) do
    case conn.assigns[:phoenix_kit_current_scope] do
      %Scope{} = scope ->
        if Scope.authenticated?(scope) do
          conn
        else
          conn
          |> put_flash(:error, "You must log in to access this page.")
          |> maybe_store_return_to()
          |> redirect(to: Routes.path("/users/log-in"))
          |> halt()
        end

      _ ->
        # Scope not found, try to create it from current_user
        conn
        |> fetch_phoenix_kit_current_scope([])
        |> require_authenticated_scope([])
    end
  end

  @doc """
  Used for routes that require the user to be an owner.

  If you want to enforce the owner requirement without
  redirecting to the login page, consider using
  `:phoenix_kit_require_authenticated_scope` instead.
  """
  def require_owner(conn, _opts) do
    case conn.assigns[:phoenix_kit_current_scope] do
      %Scope{} = scope ->
        if Scope.owner?(scope) do
          conn
        else
          conn
          |> put_flash(:error, "You must be an owner to access this page.")
          |> redirect(to: "/")
          |> halt()
        end

      _ ->
        # Scope not found, try to create it from current_user
        conn
        |> fetch_phoenix_kit_current_scope([])
        |> require_owner([])
    end
  end

  @doc """
  Used for routes that require the user to be an admin or owner.

  If you want to enforce the admin requirement without
  redirecting to the login page, consider using
  `:phoenix_kit_require_authenticated_scope` instead.
  """
  def require_admin(conn, _opts) do
    case conn.assigns[:phoenix_kit_current_scope] do
      %Scope{} = scope ->
        if Scope.admin?(scope) do
          conn
        else
          conn
          |> put_flash(:error, "You must be an admin to access this page.")
          |> redirect(to: "/")
          |> halt()
        end

      _ ->
        # Scope not found, try to create it from current_user
        conn
        |> fetch_phoenix_kit_current_scope([])
        |> require_admin([])
    end
  end

  @doc """
  Used for routes that require the user to have a specific role.
  """
  def require_role(conn, role_name) when is_binary(role_name) do
    case conn.assigns[:phoenix_kit_current_scope] do
      %Scope{} = scope ->
        if Scope.has_role?(scope, role_name) do
          conn
        else
          conn
          |> put_flash(:error, "You must have the #{role_name} role to access this page.")
          |> redirect(to: "/")
          |> halt()
        end

      _ ->
        # Scope not found, try to create it from current_user
        conn
        |> fetch_phoenix_kit_current_scope([])
        |> require_role(role_name)
    end
  end

  defp put_token_in_session(conn, token) do
    conn
    |> put_session(:user_token, token)
    |> put_session(:live_socket_id, "phoenix_kit_sessions:#{Base.url_encode64(token)}")
  end

  defp maybe_store_return_to(%{method: "GET"} = conn) do
    put_session(conn, :user_return_to, current_path(conn))
  end

  defp maybe_store_return_to(conn), do: conn

  defp signed_in_path(_conn), do: "/"

  defp extract_session_id_from_live_socket_id(live_socket_id) do
    case live_socket_id do
      "phoenix_kit_sessions:" <> encoded_token ->
        # Use first 8 chars of encoded token as session_id for admin display
        String.slice(encoded_token, 0, 8)

      _ ->
        "unknown"
    end
  end

  defp broadcast_disconnect(live_socket_id) do
    case get_parent_endpoint() do
      {:ok, endpoint} ->
        try do
          endpoint.broadcast(live_socket_id, "disconnect", %{})
        rescue
          error ->
            require Logger
            Logger.warning("[PhoenixKit] Failed to broadcast disconnect: #{inspect(error)}")
        end

      {:error, reason} ->
        require Logger
        Logger.warning("[PhoenixKit] Could not find parent endpoint for broadcast: #{reason}")
    end
  end

  defp get_parent_endpoint do
    # Simple endpoint detection without external dependencies
    app_name = Application.get_application(__MODULE__)
    base_module = app_name |> to_string() |> Macro.camelize()

    potential_endpoints = [
      Module.concat([base_module <> "Web", "Endpoint"]),
      Module.concat([base_module, "Endpoint"])
    ]

    Enum.reduce_while(potential_endpoints, {:error, "No endpoint found"}, fn endpoint, _acc ->
      if Code.ensure_loaded?(endpoint) and function_exported?(endpoint, :broadcast, 3) do
        {:halt, {:ok, endpoint}}
      else
        {:cont, {:error, "No endpoint found"}}
      end
    end)
  end
end