module ActsAsArchive
  module Base
    module Table

      def self.included(base)
        unless base.included_modules.include?(InstanceMethods)
          base.send :extend, ClassMethods
          base.send :include, InstanceMethods

          if base.connection.class.to_s.include?('Mysql')
            base.send :extend, ActsAsArchive::Base::Adapters::MySQL
          elsif base.connection.class.to_s.include?('PostgreSQL')
            base.send :extend, ActsAsArchive::Base::Adapters::PostgreSQL
          else
            raise 'acts_as_archive does not support this database adapter'
          end
        end
      end

      module ClassMethods

        def archive_table_exists?
          connection.table_exists?("archived_#{table_name}")
        end

        def create_archive_table
          if table_exists? && !archive_table_exists?
            connection.execute(%{
              CREATE TABLE archived_#{table_name}
                #{"ENGINE=InnoDB" if connection.class.to_s.include?('Mysql')}
                AS SELECT * from #{table_name}
                WHERE false;
            })
            columns = connection.columns("archived_#{table_name}").collect(&:name)
            unless columns.include?('deleted_at')
              connection.add_column("archived_#{table_name}", :deleted_at, :datetime)
            end
          end
        end

        def create_archive_indexes
          if archive_table_exists?
            indexes = archive_table_indexed_columns

            (archive_indexes - indexes).each do |index|
              begin
                connection.add_index("archived_#{table_name}", index)
              rescue ActiveRecord::StatementInvalid => e
                Rails.logger.warn "Can't add index : #{index.inspect} on #{table_name} (#{e.to_s})"
              end
            end
            (indexes - archive_indexes).each do |index|
              begin 
                connection.remove_index("archived_#{table_name}", index)
              rescue ActiveRecord::StatementInvalid => e
                Rails.logger.warn "Can't remove index : #{index.inspect} on #{table_name} (#{e.to_s})"
              end
            end
          end
        end


        def migrate_from_acts_as_paranoid
          if column_names.include?('deleted_at')
            if table_exists? && archive_table_exists?
              condition = "deleted_at IS NOT NULL"
              if self.count_by_sql("SELECT COUNT(*) FROM #{table_name} WHERE #{condition}") > 0
                # Base::Destroy.copy_to_archive
                copy_to_archive(condition, true)
              end
            end
          end
        end

        private

        def archive_table_indexed_columns
          case connection.class.to_s
          when "ActiveRecord::ConnectionAdapters::MysqlAdapter"
            index_query = "SHOW INDEX FROM archived_#{table_name}"
            indexes = connection.select_all(index_query).collect do |r|
              r["Column_name"]
            end
          when "ActiveRecord::ConnectionAdapters::PostgreSQLAdapter"
            index_query = "SELECT indexname FROM pg_indexes WHERE tablename = '#{table_name}'"
            indexes = connection.select_all(index_query).collect do |r|
              r["indexname"].split("_on_").last.split("_and_")
            end
          else
            raise "Unsupported Database"
          end
        end
      end

      module InstanceMethods
      end
    end
  end
end