module Wikidata
  module Property
    class Time < Wikidata::Property::Base
      DATE_PRECISION = {
        0 => { key: nil, value: 1_000_000_000 * 365 * 24 * 3600 },
        1 => { key: nil, value: 100_000_000 * 365 * 24 * 3600 },
        2 => { key: nil, value: 10_000_000 * 365 * 24 * 3600 },
        3 => { key: nil, value: 1_000_000 * 365 * 24 * 3600 },
        4 => { key: nil, value: 100_000 * 365 * 24 * 3600 },
        5 => { key: nil, value: 10_000 * 365 * 24 * 3600 },
        6 => { key: nil, value: 1000 * 365 * 24 * 3600 },
        7 => { key: :century, value: 100 * 365 * 24 * 3600 },
        8 => { key: :decade, value: 10 * 365 * 24 * 3600 },
        9 => { key: :year, value: 365 * 24 * 3600 },
        10 => { key: :month, value: 30 * 24 * 3600 },
        11 => { key: :day, value: 24 * 3600 },
        12 => { key: nil, value: 3600 },
        13 => { key: nil, value: 60 },
        14 => { key: nil, value: 1 }
      }.freeze

      DAYS_IN_MONTH = {
        1 => 31,
        2 => 28,
        3 => 31,
        4 => 30,
        5 => 31,
        6 => 30,
        7 => 31,
        8 => 31,
        9 => 30,
        10 => 31,
        11 => 30,
        12 => 31
      }

      def date
        return @_date if @_date

        d = ::Hash[%i[year month day hour min sec].zip(
          value.time.scan(/(-?\d+)-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2})/).first.map(&:to_i)
        )]
        %i[month day].each do |k|
          d[k] = (d[k] == 0 ? 1 : d[k])
        end
        @_date ||= DateTime.new(*d.values)
      end

      def timestamp
        date.to_time.utc.to_i
      end

      def precision
        DATE_PRECISION[value.precision.to_i][:value]
      end

      def precision_key
        DATE_PRECISION[value.precision.to_i][:key]
      end

      def after
        value.after
      end

      def before
        value.before
      end

      def range
        return @_range if @_range

        if before.to_i == 0 && after.to_i == 0 && precision_key
          send(:"#{precision_key}_range")
        else
          generic_range
        end
      end

      protected

      def generic_range
        from = if before > 0
                 timestamp - (before.to_i * precision)
               else
                 timestamp
               end
        to = if after > 0
               timestamp + (after.to_i * precision)
             else
               timestamp
             end

        @_range ||= (to_datetime ::Time.at(from).utc)..(to_datetime ::Time.at(to).utc)
      end

      def century_range
        century = date.year / 100
        if date.year > 0
          from = DateTime.new((century - 1) * 100 + 1, 1, 1, 0, 0, 0)
          to = DateTime.new(century * 100, 12, 31, 23, 59, 59)
        else
          from = DateTime.new(century * 100, 1, 1, 0, 0, 0)
          to = DateTime.new((century + 1) * 100 - 1, 12, 31, 23, 59, 59)
        end
        @_range ||= (from..to)
      end

      def year_range
        from = DateTime.new(date.year, 1, 1, 0, 0, 0)
        to = DateTime.new(date.year, 12, 31, 23, 59, 59)
        @_range ||= (from..to)
      end

      def decade_range
        decade = date.year.round(-1)
        if decade > 0
          from = DateTime.new(decade, 1, 1, 0, 0, 0)
          to = DateTime.new(decade + 9, 12, 31, 23, 59, 59)
        else
          from = DateTime.new(decade - 9, 1, 1, 0, 0, 0)
          to = DateTime.new(decade, 12, 31, 23, 59, 59)
        end
        @_range ||= (from..to)
      end

      def month_range
        last_day = if date.month == 2 && self.class.leap_year?(date.year)
                     29
                   else
                     DAYS_IN_MONTH[date.month]
                   end
        from = DateTime.new(date.year, date.month, 1, 0, 0, 0)
        to = DateTime.new(date.year, date.month, last_day, 23, 59, 59)
        @_range ||= (from..to)
      end

      def day_range
        from = DateTime.new(date.year, date.month, date.day, 0, 0, 0)
        to = DateTime.new(date.year, date.month, date.day, 23, 59, 59)
        @_range ||= (from..to)
      end

      def to_datetime(t)
        DateTime.new t.year, t.month, t.day, t.hour, t.min, t.sec
      end

      def self.leap_year?(year)
        (year % 4 == 0) && !(year % 100 == 0) || (year % 400 == 0)
      end
    end
  end
end