module RemoteDb
  module Concerns
    module Configurable
      extend ActiveSupport::Concern

      class ForbiddenActionException < Exception; end

      module ClassMethods
        def configure(config_hash = nil)
          if config_hash
            config_hash.each do |k,v|
              setter = "#{k}="
              if configuration.respond_to?(setter )
                configuration.send(setter , v)
              end
            end
          end

          yield(configuration) if block_given?
        end

        def configuration
          @configuration ||= RemoteDb::Configuration.new
        end

        def without_readonly
          raise ForbiddenActionException unless configuration.environment == :test

          load_models!(readonly: false)
          yield
          load_models!(readonly: true)
        end

        def load_models!(options = { readonly: true })
          clear_old_models
          define_base_record(options)
          send(:require_models) if respond_to?(:require_models)
        end

        private
        
        def clear_old_models
          if self.const_defined? 'BaseRecord'
            self.const_get('BaseRecord').clear_all_connections!
          end
          (self.constants - [:VERSION, :ClassMethods, :ForbiddenActionException]).each do |const|
            self.send :remove_const, const
          end
        end

        def define_base_record(options)
          module_name = self.name
          connection_spec = configuration.connection_spec
          klass = Class.new(ActiveRecord::Base) do
            self.abstract_class = true

            # AR 4 requires AR models to be named.
            define_singleton_method(:name) { "#{module_name}::BaseRecord" }

            # Connect via custom db settings
            establish_connection(connection_spec)

            # Force model to be ready-only
            if options[:readonly]
              include Concerns::ReadOnlyModel
            end

            # Scope which columns are exposed
            include Concerns::RestrictedColumns
          end

          self.const_set 'BaseRecord', klass
        end
      end
    end
  end
end