module DirectiveRecord
  module Query
    class BigQuery < SQL

    private

      def aggregate_delimiter
        "__"
      end

      def group_by_all_sql
        "all_rows"
      end

      def normalize_from!(options)
        period = options[:period]

        options[:where].delete_if do |statement|
          if statement.match(/^#{period} = '(\d{4}-\d{2}-\d{2})'$/)
            begin_date, end_date = $1, $1
          elsif statement.match(/^#{period} >= '(\d{4}-\d{2}-\d{2})' AND #{period} <= '(\d{4}-\d{2}-\d{2})'$/)
            begin_date, end_date = $1, $2
          end
          if begin_date
            dataset = ::BigQuery.connection.instance_variable_get(:@dataset) # TODO: fix this
            options[:from] = (Date.parse(begin_date)..Date.parse(end_date)).collect do |date|
              "[#{dataset}.#{base.table_name}_#{date.strftime("%Y%m%d")}]"
            end
            options[:from] = "\n  #{options[:from].join(",\n  ")}"
          end
        end
      end

      def prepend_base_alias!(options); end

      def finalize_options!(options)
        aliases = options[:aliases] || {}

        options[:select].collect! do |string|
          expression, select_alias = string.match(/^(.*) AS (.*)$/).try(:captures)
          if select_alias
            aliases[expression] = select_alias
            options[:group_by].to_s.include?(expression) || !expression.match(/^\w+(\.\w+)*$/) ? string : "MAX(#{expression}) AS #{select_alias}"
          else
            string.match(/^\w+(\.\w+)*$/) ? "MAX(#{string})" : string
          end
        end if options[:group_by]

        [:group_by, :having, :order_by].each do |key|
          if value = options[key]
            value = value.join ", "
            aliases.each{|pattern, replacement| value.gsub! pattern, replacement}
            options[key] = value
          end
        end
      end

    end
  end
end