ActiveRecord::Base.select_values

class ActiveRecord::Base

  class << self

    def select_values(*args)
      options = args.extract_options!
      validate_find_options(options)
      set_readonly_option!(options)
      raise "select_values does not support the :include option" if options[:include]

      sql = construct_finder_sql(options)
      select_values_by_sql(options[:select].to_s, sql)
    end

    def select_value(*args)
      options = args.extract_options!
      validate_find_options(options)
      set_readonly_option!(options)
      raise "select_values does not support the :include option" if options[:include]

      sql = construct_finder_sql(options.update(:limit => 1))
      select_values_by_sql(options[:select].to_s, sql).first
    end

    def select_all(*args)
      options = args.extract_options!
      validate_find_options(options)
      set_readonly_option!(options)
      raise "select_values does not support the :include option" if options[:include]

      sql = construct_finder_sql(options)
      select_all_by_sql(sql)
    end

    def select_rows(*args)
      options = args.extract_options!
      validate_find_options(options)
      set_readonly_option!(options)
      raise "select_rows does not support the :include option" if options[:include]

      sql = construct_finder_sql(options)
      columns = options[:select].split(',').map(&:strip)
      columns = columns.map do |column|
        column.include?(" AS ") ? column[/AS (.+)/][3..-1] : column
      end
      select_rows_by_sql(columns, sql)
    end

    private

    def select_values_by_sql(column_name, sql)
      result = connection.select_values(sanitize_sql(sql))
      column = columns_hash[column_name]
      column ? result.map {|val| column.type_cast(val) } : result
    end

    def select_all_by_sql(sql)
      result = connection.select_all(sanitize_sql(sql))
      result.collect do |record|
        record.inject({}) do |memo, kv|
          column = self.columns_hash[kv[0]]
          memo[kv[0]] = column ? column.type_cast(kv[1]) : kv[1]
          memo
        end
      end
    end

    def select_rows_by_sql(columns, sql)
      result = connection.select_rows(sanitize_sql(sql))
      result.collect do |record|
        row = []
        record.each_with_index do |value, index|
          column = self.columns_hash[columns[index]]
          row << (column ? column.type_cast(value) : value)
        end
        row
      end
    end

  end

end