require "groupdate/order_hack"
require "groupdate/series"
require "active_record"

module Groupdate
  module Scopes
    time_fields = %w(second minute hour day week month year)
    number_fields = %w(day_of_week hour_of_day)
    (time_fields + number_fields).each do |field|
      define_method :"group_by_#{field}" do |*args|
        args = args.dup
        options = args[-1].is_a?(Hash) ? args.pop : {}
        column = connection.quote_table_name(args[0])
        time_zone = args[1] || Groupdate.time_zone || Time.zone || "Etc/UTC"
        if time_zone.is_a?(ActiveSupport::TimeZone) or time_zone = ActiveSupport::TimeZone[time_zone]
          time_zone = time_zone.tzinfo.name
        else
          raise "Unrecognized time zone"
        end

        # for week
        week_start = [:mon, :tue, :wed, :thu, :fri, :sat, :sun].index((options[:start] || Groupdate.week_start).to_sym)
        if field == "week" and !week_start
          raise "Unrecognized :start option"
        end

        query =
          case connection.adapter_name
          when "MySQL", "Mysql2"
            case field
            when "day_of_week" # Sunday = 0, Monday = 1, etc
              # use CONCAT for consistent return type (String)
              ["DAYOFWEEK(CONVERT_TZ(#{column}, '+00:00', ?)) - 1", time_zone]
            when "hour_of_day"
              ["EXTRACT(HOUR from CONVERT_TZ(#{column}, '+00:00', ?))", time_zone]
            when "week"
              ["CONVERT_TZ(DATE_FORMAT(CONVERT_TZ(DATE_SUB(#{column}, INTERVAL ((#{7 - week_start} + WEEKDAY(CONVERT_TZ(#{column}, '+00:00', ?))) % 7) DAY), '+00:00', ?), '%Y-%m-%d 00:00:00'), ?, '+00:00')", time_zone, time_zone, time_zone]
            else
              format =
                case field
                when "second"
                  "%Y-%m-%d %H:%i:%S"
                when "minute"
                  "%Y-%m-%d %H:%i:00"
                when "hour"
                  "%Y-%m-%d %H:00:00"
                when "day"
                  "%Y-%m-%d 00:00:00"
                when "month"
                  "%Y-%m-01 00:00:00"
                else # year
                  "%Y-01-01 00:00:00"
                end

              ["CONVERT_TZ(DATE_FORMAT(CONVERT_TZ(#{column}, '+00:00', ?), '#{format}'), ?, '+00:00')", time_zone, time_zone]
            end
          when "PostgreSQL", "PostGIS"
            case field
            when "day_of_week"
              ["EXTRACT(DOW from #{column}::timestamptz AT TIME ZONE ?)::integer", time_zone]
            when "hour_of_day"
              ["EXTRACT(HOUR from #{column}::timestamptz AT TIME ZONE ?)::integer", time_zone]
            when "week" # start on Sunday, not PostgreSQL default Monday
              ["(DATE_TRUNC('#{field}', (#{column}::timestamptz - INTERVAL '#{week_start} day') AT TIME ZONE ?) + INTERVAL '#{week_start} day') AT TIME ZONE ?", time_zone, time_zone]
            else
              ["DATE_TRUNC('#{field}', #{column}::timestamptz AT TIME ZONE ?) AT TIME ZONE ?", time_zone, time_zone]
            end
          else
            raise "Connection adapter not supported: #{connection.adapter_name}"
          end

        group = group(Groupdate::OrderHack.new(sanitize_sql_array(query), field, time_zone))
        if args[2]
          Series.new(group, field, column, time_zone, args[2], week_start)
        else
          group
        end
      end
    end
  end
end