require 'active_record'
require 'merb-core/dispatch/session'
require 'base64'

module Merb

  # Sessions stored in ActiveRecord model.
  #
  # To use ActiveRecord based sessions add the following to config/init.rb:
  #
  # Merb::Config[:session_store] = 'activerecord'

  class ActiveRecordSessionStore < ::ActiveRecord::Base

    table_name = (Merb::Plugins.config[:merb_active_record][:session_table_name] || "sessions")

    set_table_name table_name

    # Customizable data column name. Defaults to 'data'.
    cattr_accessor :data_column_name
    self.data_column_name = 'data'

    before_save :marshal_data!
    before_save :raise_on_session_data_overflow!

    class << self

      # ==== Parameters
      # session_id<String>:: ID of the session to retrieve.
      #
      # ==== Returns
      # ContainerSession:: The session corresponding to the ID.
      def retrieve_session(session_id)
        if item = find_by_session_id(session_id)
          item.data
        end
      end

      # ==== Parameters
      # session_id<String>:: ID of the session to set.
      # data<ContainerSession>:: The session to set.
      def store_session(session_id, data)
        if item = find_by_session_id(session_id)
          item.update_attributes!(:data => data)
        else
          create(:session_id => session_id, :data => data)
        end
      end

      # ==== Parameters
      # session_id<String>:: ID of the session to delete.
      def delete_session(session_id)
        delete_all(["#{connection.quote_column_name('session_id')} IN (?)", session_id])
      end

      # ==== Returns
      # Integer:: The maximum length of the 'data' column.
      def data_column_size_limit
        @data_column_size_limit ||= columns_hash[@@data_column_name].limit
      end

      def marshal(data)
        Base64.encode64(Marshal.dump(data)) if data
      end

      def unmarshal(data)
        Marshal.load(Base64.decode64(data)) if data
      end

    end

    # Lazy-unmarshal session state.
    def data
      @data ||= self.class.unmarshal(read_attribute(@@data_column_name)) || {}
    end

    # Virtual attribute writer - override.
    def data=(hsh)
      @data = hsh if hsh.is_a?(Hash)
    end

    # Has the session been loaded yet?
    def loaded?
      !!@data
    end

    private

    # Marshals data before saving.
    def marshal_data!
      return false if !loaded?
      write_attribute(@@data_column_name, self.class.marshal(self.data))
    end

    # Ensures that the data about to be stored in the database is not
    # larger than the data storage column.
    #
    # ==== Raises
    # Merb::SessionMixin::SessionOverflow:: raised if there's too much data.
    def raise_on_session_data_overflow!
      return false if !loaded?
      limit = self.class.data_column_size_limit
      if loaded? && limit && read_attribute(@@data_column_name).size > limit
        raise Merb::SessionMixin::SessionOverflow
      end
    end

  end

  class ActiveRecordSession < SessionStoreContainer

    # The session store type
    self.session_store_type = :activerecord

    # The store object is the model class itself
    self.store = ActiveRecordSessionStore

  end

end