# Load a specific server configuration
module Gitlab
  module Auth
    module LDAP
      class Config
        NET_LDAP_ENCRYPTION_METHOD = {
          simple_tls: :simple_tls,
          start_tls:  :start_tls,
          plain:      nil
        }.freeze

        attr_accessor :provider, :options

        InvalidProvider = Class.new(StandardError)

        def self.enabled?
          Gitlab.config.ldap.enabled
        end

        def self.servers
          Gitlab.config.ldap['servers']&.values || []
        end

        def self.available_servers
          return [] unless enabled?

          _available_servers
        end

        def self._available_servers
          Array.wrap(servers.first)
        end

        def self.providers
          servers.map { |server| server['provider_name'] }
        end

        def self.valid_provider?(provider)
          providers.include?(provider)
        end

        def self.invalid_provider(provider)
          raise InvalidProvider.new("Unknown provider (#{provider}). Available providers: #{providers}")
        end

        def initialize(provider)
          if self.class.valid_provider?(provider)
            @provider = provider
          else
            self.class.invalid_provider(provider)
          end

          @options = config_for(@provider) # Use @provider, not provider
        end

        def enabled?
          base_config.enabled
        end

        def adapter_options
          opts = base_options.merge(
            encryption: encryption_options
          )

          opts.merge!(auth_options) if has_auth?

          opts
        end

        def omniauth_options
          opts = base_options.merge(
            base: base,
            encryption: options['encryption'],
            filter: omniauth_user_filter,
            name_proc: name_proc,
            disable_verify_certificates: !options['verify_certificates']
          )

          if has_auth?
            opts.merge!(
              bind_dn: options['bind_dn'],
              password: options['password']
            )
          end

          opts[:ca_file] = options['ca_file'] if options['ca_file'].present?
          opts[:ssl_version] = options['ssl_version'] if options['ssl_version'].present?

          opts
        end

        def base
          @base ||= Person.normalize_dn(options['base'])
        end

        def uid
          options['uid']
        end

        def label
          options['label']
        end

        def sync_ssh_keys?
          sync_ssh_keys.present?
        end

        # The LDAP attribute in which the ssh keys are stored
        def sync_ssh_keys
          options['sync_ssh_keys']
        end

        def user_filter
          options['user_filter']
        end

        def constructed_user_filter
          @constructed_user_filter ||= Net::LDAP::Filter.construct(user_filter)
        end

        def group_base
          options['group_base']
        end

        def admin_group
          options['admin_group']
        end

        def active_directory
          options['active_directory']
        end

        def block_auto_created_users
          options['block_auto_created_users']
        end

        def attributes
          default_attributes.merge(options['attributes'])
        end

        def timeout
          options['timeout'].to_i
        end

        def external_groups
          options['external_groups'] || []
        end

        def has_auth?
          options['password'] || options['bind_dn']
        end

        def allow_username_or_email_login
          options['allow_username_or_email_login']
        end

        def lowercase_usernames
          options['lowercase_usernames']
        end

        def name_proc
          if allow_username_or_email_login
            proc { |name| name.gsub(/@.*\z/, '') }
          else
            proc { |name| name }
          end
        end

        def default_attributes
          {
            'username'    => %w(uid sAMAccountName userid),
            'email'       => %w(mail email userPrincipalName),
            'name'        => 'cn',
            'first_name'  => 'givenName',
            'last_name'   => 'sn'
          }
        end

        protected

        def base_options
          {
            host: options['host'],
            port: options['port']
          }
        end

        def base_config
          Gitlab.config.ldap
        end

        def config_for(provider)
          base_config.servers.values.find { |server| server['provider_name'] == provider }
        end

        def encryption_options
          method = translate_method(options['encryption'])
          return nil unless method

          {
            method: method,
            tls_options: tls_options(method)
          }
        end

        def translate_method(method_from_config)
          NET_LDAP_ENCRYPTION_METHOD[method_from_config.to_sym]
        end

        def tls_options(method)
          return { verify_mode: OpenSSL::SSL::VERIFY_NONE } unless method

          opts = if options['verify_certificates']
                   OpenSSL::SSL::SSLContext::DEFAULT_PARAMS
                 else
                   # It is important to explicitly set verify_mode for two reasons:
                   # 1. The behavior of OpenSSL is undefined when verify_mode is not set.
                   # 2. The net-ldap gem implementation verifies the certificate hostname
                   #    unless verify_mode is set to VERIFY_NONE.
                   { verify_mode: OpenSSL::SSL::VERIFY_NONE }
                 end

          opts[:ca_file] = options['ca_file'] if options['ca_file'].present?
          opts[:ssl_version] = options['ssl_version'] if options['ssl_version'].present?

          opts
        end

        def auth_options
          {
            auth: {
              method: :simple,
              username: options['bind_dn'],
              password: options['password']
            }
          }
        end

        def omniauth_user_filter
          uid_filter = Net::LDAP::Filter.eq(uid, '%{username}')

          if user_filter.present?
            Net::LDAP::Filter.join(uid_filter, constructed_user_filter).to_s
          else
            uid_filter.to_s
          end
        end
      end
    end
  end
end