##
# If OPENPROJECT_AUTH__SOURCE__SSO_HEADER and OPENPROJECT_AUTH__SOURCE__SSO_SECRET are
# configured OpenProject will login the user given in the HTTP header with the given name
# together with the secret in the form of `login:$secret`.
module AuthSourceSSO
  def find_current_user
    user = super

    # Do nothing if sso disabled
    return user unless auth_source_sso_enabled?
    # Return super auth if SSO already in progress
    return user if sso_in_progress!

    # Get the header-provided login value
    login = read_sso_login

    if login.present?
      perform_header_sso login, user
    elsif header_optional?
      user
    else
      handle_sso_failure!
      nil
    end
  end

  def perform_header_sso(login, user)
    # Log out the current user if the login does not match
    logged_user = match_sso_with_logged_user(login, user)

    # Return the logged in user if matches
    return logged_user if logged_user.present?

    Rails.logger.debug { "Starting header-based auth source SSO for #{header_name}='#{op_auth_header_value}'" }

    user = find_or_create_sso_user(login, save: true)
    handle_sso_for! user, login
  end

  def match_sso_with_logged_user(login, user)
    return if user.nil?
    return user if user.login.casecmp?(login)

    Rails.logger.warn { "Header-based auth source SSO user changed from #{user.login} to #{login}. Re-authenticating" }
    ::Users::LogoutService.new(controller: self).call(user)

    nil
  end

  def read_sso_login
    get_validated_login! op_auth_header_value
  end

  def sso_config
    @sso_config ||= OpenProject::Configuration.auth_source_sso.try(:with_indifferent_access)
  end

  def auth_source_sso_enabled?
    header_name.present?
  end

  def op_auth_header_value
    String(request.headers[header_name])
  end

  def header_name
    sso_config && sso_config[:header].to_s
  end

  def header_secret
    sso_config && sso_config[:secret].to_s
  end

  def header_optional?
    sso_config && sso_config[:optional]
  end

  def header_slo_url
    sso_config && sso_config[:logout_url]
  end

  def get_validated_login!(value)
    login, valid_secret = extract_from_header(value)

    unless valid_secret
      Rails.logger.error("Secret contained in auth source SSO header #{header_name} is not valid.")
      return nil
    end

    unless login.present?
      Rails.logger.error("Provided SSO header #{header_name} is empty or not valid.")
      return nil
    end

    login
  end

  def extract_from_header(value)
    if header_secret.present?
      valid_secret = value.end_with?(":#{header_secret}")
      login = value.gsub(/:#{Regexp.escape(header_secret)}\z/, '')

      [login, valid_secret]
    else
      [value, true]
    end
  end

  def find_or_create_sso_user(login, save: false)
    find_user_from_auth_source(login) || create_user_from_auth_source(login, save: save)
  end

  def find_user_from_auth_source(login)
    User
      .by_login(login)
      .where.not(auth_source_id: nil)
      .first
  end

  def create_user_from_auth_source(login, save:)
    attrs = AuthSource.find_user(login)
    return unless attrs

    attrs[:login] = login

    call =
      if save
        Users::CreateService
          .new(user: User.system)
          .call(attrs)
      else
        Users::SetAttributesService
          .new(model: User.new, user: User.system, contract_class: Users::CreateContract)
          .call(attrs)
      end

    user = call.result

    call.on_success do
      logger.info(
        "User '#{user.login}' created from external auth source: " +
          "#{user.auth_source.type} - #{user.auth_source.name}"
      )
    end

    call.on_failure do
      logger.error "Tried to create user '#{login}' from external auth source but failed: #{call.message}"
    end

    user
  end

  def sso_in_progress!
    sso_failure_in_progress! || session[:auth_source_registration] || session[:authenticated_user_id]
  end

  def sso_failure_in_progress!
    failure = session[:auth_source_sso_failure]

    if failure
      if failure[:ttl] > 0
        session[:auth_source_sso_failure] = failure.merge(ttl: failure[:ttl] - 1)
      else
        session.delete :auth_source_sso_failure

        nil
      end
    end
  end

  def sso_login_failed?(user)
    user.nil? || user.new_record? || !(user.active? || user.invited?)
  end

  def handle_sso_for!(user, login)
    if sso_login_failed?(user)
      handle_sso_failure!(login: login)
    else
      # valid user
      # If a user is invited, ensure it gets activated
      activated = user.invited?
      activate_user_if_invited! user

      handle_sso_success user, activated
    end
  end

  def handle_sso_success(user, just_activated)
    session[:user_from_auth_header] = true
    # remember the back_url so we can redirect to the original request
    session[:back_url] = request.fullpath
    successful_authentication(user, reset_stages: true, just_registered: just_activated)
  end

  def activate_user_if_invited!(user)
    return unless user.invited?

    user.active!
  end

  def perform_post_logout(prev_session, previous_user)
    if prev_session[:user_from_auth_header] && header_slo_url.present?
      redirect_to header_slo_url
    else
      super
    end
  end

  def handle_sso_failure!(login: nil)
    session[:auth_source_sso_failure] = {
      login: login,
      back_url: request.base_url + request.original_fullpath,
      ttl: 1
    }

    redirect_to sso_failure_path
  end
end