# encoding: utf-8
#
# This file is part of the lazier gem. Copyright (C) 2013 and above Shogun <shogun_panda@cowtech.it>.
# Licensed under the MIT license, which can be found at http://www.opensource.org/licenses/mit-license.php.
#

module Lazier
  # Extensions for date and time objects.
  module DateTime
    extend ::ActiveSupport::Concern

    # General methods.
    module ClassMethods
      # Returns strings representations of days.
      # @see Settings#setup_date_names
      #
      # @param short [Boolean] If return the abbreviated representations.
      # @return [Array] Return string representations of days.
      def days(short = true)
        ::Lazier.settings.date_names[short ? :short_days : :long_days].collect.with_index {|label, index|
          {value: (index + 1).to_s, label: label}
        }
      end

      # Returns strings representations of months.
      # @see Settings#setup_date_names
      #
      # @param short [Boolean] If return the abbreviated representations.
      # @return [Array] Return string representations of months.
      def months(short = true)
        ::Lazier.settings.date_names[short ? :short_months : :long_months].collect.with_index {|label, index|
          {value: (index + 1).to_s.rjust(2, "0"), label: label}
        }
      end

      # Returns a range of years.
      #
      # ```ruby
      # Date.years(3, false, 2010)
      # # => [2007, 2008, 2009, 2010]
      # ```
      #
      # ```ruby
      # Date.years(1, true, 2010, true)
      # # => [{:value=>2009, :label=>2009}, {:value=>2010, :label=>2010}, {:value=>2011, :label=>2011}]
      # ```
      #
      #
      # @param offset [Fixnum] The width of the range.
      # @param also_future [Boolean] If return also future years.
      # @param reference [Fixnum] The ending (or middle, if `also_future` is `true`) value of the range. Defaults to the current year.
      # @param as_objects [Boolean] If to return years in hashes with `:value` and `label` keys.
      # @return [Array] A range of years. Every entry is
      def years(offset = 10, also_future = true, reference = nil, as_objects = false)
        y = reference || ::Date.today.year
        (y - offset..(also_future ? y + offset : y)).collect { |year| as_objects ? {value: year, label: year} : year }
      end

      # Returns all the availabe timezones.
      #
      # @return [Array]All the zone available.
      def timezones
        ::ActiveSupport::TimeZone.all
      end

      # Returns a list of names of all timezones.
      #
      # @param with_dst [Boolean] If include DST version of the zones.
      # @param dst_label [String] Label for the DST indication. Defaults to `(DST)`.
      # @return [Array] A list of names of timezones.
      def list_timezones(with_dst = true, dst_label = nil)
        ::ActiveSupport::TimeZone.list_all(with_dst, dst_label)
      end

      # Find a zone by its name.
      #
      # @param name [String] The zone name.
      # @param dst_label [String] Label for the DST indication. Defaults to `(DST)`.
      # @return [TimeZone] A timezone or `nil` if no zone was found.
      def find_timezone(name = true, dst_label = nil)
        ::ActiveSupport::TimeZone.find(name, dst_label)
      end

      # Returns a string representation of a timezone.
      #
      # ```ruby
      # DateTime.parameterize_zone(ActiveSupport::TimeZone["Pacific Time (US & Canada)"])
      # # => "-0800@pacific-time-us-canada"
      # ```
      # @param tz [TimeZone] The zone to represent.
      # @param with_offset [Boolean] If to include offset into the representation.
      # @return [String] A string representation which can be used for searches.
      def parameterize_zone(tz, with_offset = true)
        ::ActiveSupport::TimeZone::parameterize_zone(tz, with_offset)
      end

      # Finds a parameterized timezone.
      # @see DateTime#parameterize_zone
      #
      # @param tz [String] The zone to unparameterize.
      # @param as_string [Boolean] If return just the zone name.
      # @param dst_label [String] Label for the DST indication. Defaults to `(DST)`.
      # @return [String|TimeZone] The found timezone or `nil` if the zone is not valid.
      def unparameterize_zone(tz, as_string = false, dst_label = nil)
        ::ActiveSupport::TimeZone::unparameterize_zone(tz, as_string, dst_label)
      end

      # Returns an offset in rational value.
      #
      # @param offset [Fixnum] The offset to convert.
      # @return [Rational] The converted offset.
      def rationalize_offset(offset)
        ::ActiveSupport::TimeZone.rationalize_offset(offset)
      end

      # Returns the Easter (according to Gregorian calendar) date for the year.
      # @see http://en.wikipedia.org/wiki/Computus#Anonymous_Gregorian_algorithm
      #
      # @param year [Fixnum] The year to compute the date for. Defaults to the current year.
      # @return [Date] The Easter date for the year.
      def easter(year = nil)
        year = ::Date.today.year if !year.is_integer?

        # Compute using Anonymous Gregorian Algorithm: http://en.wikipedia.org/wiki/Computus#Anonymous_Gregorian_algorithm
        data = easter_start(year)
        data = easter_part_1(data)
        data = easter_part_2(year, data)
        data = easter_part_3(year, data)
        day, month = easter_end(data)

        ::Date.civil(year, month, day)
      end

      # Lookups a custom datetime format.
      # @see Settings#setup_date_formats
      #
      # @param key [Symbol] The name of the format to search.
      # @return [String] The format or the name itself (if the format has not been found).
      def custom_format(key)
        ::Lazier.settings.date_formats.fetch(key, key)
      end

      # Checks if the date is valid against to a specific format.
      # @see DateTime#custom_format
      #
      # @param value [String] The value to check.
      # @param format [String] The format to check the value against.
      # @return [Boolean] `true` if the value is valid against the format, `false` otherwise.
      def is_valid?(value, format = "%F %T")
        !(::DateTime.strptime(value, self.custom_format(format)) rescue nil).nil?
      end

      private
        # Part one of Easter calculation.
        #
        # @param year [Fixnum] The year to compute the date for.
        # @return [Array] Partial variables for #easter_part_1.
        def easter_start(year)
          [year % 19, (year / 100.0).floor, year % 100]
        end

        # Part two of Easter calculation.
        # @param data [Fixnum] Partial variables from #easter_start.
        # @return [Array] Partial variables for #easter_part_2.
        def easter_part_1(data)
          _, b, c = data

          [
            b - (b / 4.0).floor - ((b - ((b + 8) / 25.0).floor + 1) / 3.0).floor,
            b % 4,
            (c / 4.0).floor,
            c % 4
          ]
        end

        # Part three of Easter calculation.
        #
        # @param data [Fixnum] Partial variables from #easter_part_1.
        # @return [Array] Partial variables for #easter_part_3.
        def easter_part_2(year, data)
          a = year % 19
          x, e, i, k = data
          h = ((19 * a) + x + 15) % 30
          [h, (32 + (2 * e) + (2 * i) - h - k) % 7]
        end

        # Part four of Easter calculation
        # @param data [Arrays] Partial variables from #easter_part_2.
        # @return [Array] Partial variables for #easter_end.
        def easter_part_3(year, data)
          a = year % 19
          h, l = data
          [h, l, ((a + (11 * h) + (22 * l)) / 451.0).floor]
        end

        # Final part of Easter calculation.
        #
        # @param data [Fixnum] Variable from #easter_part_3.
        # @return [Array] Day and month of Easter day.
        def easter_end(data)
          h, l, m = data
          [((h + l - (7 * m) + 114) % 31) + 1, ((h + l - (7 * m) + 114) / 31.0).floor]
        end
    end

    # Returns the UTC::Time representation of the current datetime.
    #
    # @return [UTC::Time] The UTC::Time representation of the current datetime.
    def utc_time
      utc.to_time
    end

    # Returns the number of months passed between the beginning of the base year and the current date.
    #
    # ```ruby
    # DateTime.civil(2013, 6, 1).in_months(2011)
    # # => 18
    # ```
    #
    # @param base [DateTime] The base year to start computation from. Default to current year.
    # @return [Fixnum] Returns the number of months passed between the beginning of the base year and the current date.
    def in_months(base = nil)
      (year - (base || ::Date.today.year)) * 12 + month
    end

    # Returns the current month number with leading 0.
    #
    # @return [String] The current month number with leading 0.
    def padded_month
      month.indexize
    end

    # Formats a datetime, looking up also custom formats.
    # @see Settings#setup_date_formats
    #
    # @param format [String] A format or a custom format name to use for formatting.
    # @return [String] The formatted date.
    def lstrftime(format = nil)
      strftime(::DateTime.custom_format(format.to_s).gsub(/(?<!%)(%[ab])/i) {|mo| localize_time_component(mo) })
    end

    # Formats a datetime in the current timezone.
    #
    # @param format [String] The format to use for formatting.
    # @return [String] The formatted date.
    def local_strftime(format = nil)
      (respond_to?(:in_time_zone) ? in_time_zone : self).strftime(::DateTime.custom_format(format))
    end

    # Formats a datetime in the current timezone, looking up also custom formats.
    # @see Settings#setup_date_formats
    #
    # @param format [String] A format or a custom format name.
    # @return [String] The formatted date.
    def local_lstrftime(format = nil)
      (respond_to?(:in_time_zone) ? in_time_zone : self).lstrftime(format)
    end

    private
      # Returns a component of the date in the current locale.
      #
      # @param component [String] The component to localize.
      # @return [String] The localized component.
      def localize_time_component(component)
        type = {"%a" => :short_days, "%A" => :long_days, "%b" => :short_months, "%B" => :long_months}.fetch(component, "")
        index = component =~ /%a/i ? wday : month - 1
        ::Lazier.settings.date_names[type][index]
      end
  end

  # Extensions for timezone objects.
  module TimeZone
    extend ::ActiveSupport::Concern

    # General methods.
    module ClassMethods
      # Returns an offset in rational value.
      #
      # @param offset [Fixnum] The offset to convert.
      # @return [Rational] The converted offset.
      def rationalize_offset(offset)
        ::TZInfo::OffsetRationals.rational_for_offset(offset.is_a?(::Fixnum) ? offset : offset.offset)
      end

      # Returns a +HH:MM formatted representation of the offset.
      #
      # @param offset [Rational|Fixnum] The offset to represent, in seconds or as a rational.
      # @param colon [Boolean] If to put the colon in the output string.
      # @return [String] The formatted offset.
      def format_offset(offset, colon = true)
        self.seconds_to_utc_offset(offset.is_a?(::Rational) ? (offset * 86400).to_i : offset, colon)
      end

      # Find a zone by its name.
      #
      # @param name [String] The zone name.
      # @param dst_label [String] Label for the DST indication. Defaults to `(DST)`.
      # @return [TimeZone] A timezone or `nil` if no zone was found.
      def find(name, dst_label = nil)
        catch(:zone) do
          ::ActiveSupport::TimeZone.all.each do |zone|
            zone.aliases.each do |zone_alias|
              throw(:zone, zone) if [zone.to_str(zone_alias), zone.to_str_with_dst(dst_label, nil, zone_alias)].include?(name)
            end
          end

          nil
        end
      end

      # Returns a list of names of all timezones.
      #
      # @param with_dst [Boolean] If include DST version of the zones.
      # @param dst_label [String] Label for the DST indication. Defaults to `(DST)`.
      # @return [Array] A list of names of timezones.
      def list_all(with_dst = true, dst_label = nil)
        dst_label ||= "(DST)"

        @zones_names ||= { "STANDARD" => ::ActiveSupport::TimeZone.all.collect(&:to_s) }
        @zones_names["DST[#{dst_label}]-STANDARD"] ||= ::ActiveSupport::TimeZone.all.collect { |zone| fetch_aliases(zone, dst_label) }.flatten.compact.uniq.sort { |a,b| ::ActiveSupport::TimeZone.compare(a, b) } # Sort by name

        @zones_names["#{with_dst ? "DST[#{dst_label}]-" : ""}STANDARD"]
      end

      # Returns a string representation of a timezone.
      #
      # ```ruby
      # DateTime.parameterize_zone(ActiveSupport::TimeZone["Pacific Time (US & Canada)"])
      # # => "-0800@pacific-time-us-canada"
      # ```
      # @param tz [TimeZone] The zone to represent.
      # @param with_offset [Boolean] If to include offset into the representation.
      # @return [String] A string representation which can be used for searches.
      def parameterize_zone(tz, with_offset = true)
        tz = tz.to_s if !tz.is_a?(::String)

        if tz =~ /^(\([a-z]+([+-])(\d{2})(:?)(\d{2})\)\s(.+))$/i then
          with_offset ? "#{$2}#{$3}#{$5}@#{$6.parameterize}" : $6.parameterize
        elsif !with_offset then
          tz.gsub(/^([+-]?(\d{2})(:?)(\d{2})@)/, "")
        else
          tz.parameterize
        end
      end

      # Finds a parameterized timezone.
      # @see DateTime#parameterize_zone
      #
      # @param tz [String] The zone to unparameterize.
      # @param as_string [Boolean] If return just the zone name.
      # @param dst_label [String] Label for the DST indication. Defaults to `(DST)`.
      # @return [String|TimeZone] The found timezone or `nil` if the zone is not valid.
      def unparameterize_zone(tz, as_string = false, dst_label = nil)
        tz = parameterize_zone(tz, false)
        matcher = /(#{Regexp.quote(tz)})$/

        rv = catch(:zone) do
          list_all(true, dst_label).each do |zone|
            throw(:zone, zone) if parameterize_zone(zone, false) =~ matcher
          end

          nil
        end

        rv ? (as_string ? rv : self.find(rv, dst_label)) : nil
      end

      # Compares two timezones. They are sorted by the location name.
      #
      # @param left [String|TimeZone] The first zone name to compare.
      # @param right [String|TimeZone] The second zone name to compare.
      # @return [Fixnum] The result of comparison, like Ruby's operator `<=>`.
      def compare(left, right)
        left = left.to_str if left.is_a?(::ActiveSupport::TimeZone)
        right = right.to_str if right.is_a?(::ActiveSupport::TimeZone)
        left.ensure_string.split(" ", 2)[1] <=> right.ensure_string.split(" ", 2)[1]
      end

      private
        # Returns a list of aliases for a given time zone.
        #
        # @param zone [ActiveSupport::TimeZone] The zone.
        # @param dst_label [String] Label for the DST indication. Defaults to `(DST)`.
        def fetch_aliases(zone, dst_label = "(DST)")
          matcher = /(#{Regexp.quote(dst_label)})$/

          zone.aliases.collect { |zone_alias|
            [zone.to_str(zone_alias), (zone.uses_dst? && zone_alias !~ matcher) ? zone.to_str_with_dst(dst_label, nil, zone_alias) : nil]
          }
        end
    end

    # Returns a list of valid aliases (city names) for this timezone (basing on offset).
    # @return [Array] A list of aliases for this timezone
    def aliases
      reference = self.class::MAPPING.fetch(name, name).gsub("_", " ")
      @aliases ||= ([reference] + self.class::MAPPING.collect { |name, zone| format_alias(name, zone, reference) }).uniq.compact.sort
    end

    # Returns the current offset for this timezone, taking care of Daylight Saving Time (DST).
    #
    # @param rational [Boolean] If to return the offset as a Rational.
    # @param date [DateTime] The date to consider. Defaults to now.
    # @return [Fixnum|Rational] The offset of this timezone.
    def current_offset(rational = false, date = nil)
      date ||= ::DateTime.now
      rv = (period_for_utc(date.utc).dst? ? dst_offset : offset)
      rational ? self.class.rationalize_offset(rv) : rv
    end

    # Returns the current alias for this timezone.
    #
    # @return [String] The current alias or the first alias of the current timezone.
    def current_alias
      identifier = tzinfo.identifier

      catch(:alias) do
        aliases.each do |a|
          throw(:alias, a) if a == identifier
        end

        aliases.first
      end
    end

    # Returns the standard offset for this timezone.
    #
    # @param rational [Boolean] If to return the offset as a Rational.
    # @return [Fixnum|Rational] The offset of this timezone.
    def offset(rational = false)
      rational ? self.class.rationalize_offset(utc_offset) : utc_offset
    end

    # Gets a period for this timezone when the Daylight Saving Time (DST) is active (it takes care of different hemispheres).
    #
    # @param year [Fixnum] The year to which refer to. Defaults to the current year.
    # @return [TimezonePeriod] A period when the Daylight Saving Time (DST) is active or `nil` if the timezone doesn't use DST for that year.
    def dst_period(year = nil)
      year ||= ::Date.today.year

      northern_summer = ::DateTime.civil(year, 7, 15).utc # This is a representation of a summer period in the Northern Hemisphere.
      southern_summer = ::DateTime.civil(year, 1, 15).utc # This is a representation of a summer period in the Southern Hemisphere.

      period = self.period_for_utc(northern_summer)
      period = self.period_for_utc(southern_summer) if !period.dst?
      period.dst? ? period : nil
    end

    # Checks if the timezone uses Daylight Saving Time (DST) for that date or year.
    #
    # @param reference [Object] The date or year to check. Defaults to the current year.
    # @return [Boolean] `true` if the zone uses DST for that date or year, `false` otherwise.
    def uses_dst?(reference = nil)
      if reference.respond_to?(:year) && reference.respond_to?(:utc) then # This is a date like object
        dst_period(reference.year).present? && period_for_utc(reference.utc).dst?
      else
        dst_period(reference).present?
      end
    end

    # Return the correction applied to the standard offset the timezone when the Daylight Saving Time (DST) is active.
    #
    # @param rational [Boolean] If to return the offset as a Rational.
    # @param year [Fixnum] The year to which refer to. Defaults to the current year.
    # @return [Fixnum|Rational] The correction for dst.
    def dst_correction(rational = false, year = nil)
      dst_offset(rational, year, :std_offset)
    end

    # Returns the standard offset for this timezone timezone when the Daylight Saving Time (DST) is active.
    #
    # @param rational [Boolean] If to return the offset as a Rational.
    # @param year [Fixnum] The year to which refer to. Defaults to the current year.
    # @param method [Symbol] The method to use for getting the offset. Default is total offset from UTC.
    # @return [Fixnum|Rational] The DST offset for this timezone or `0`, if the timezone doesn't use DST for that year.
    def dst_offset(rational = false, year = nil, method = :utc_total_offset)
      period = dst_period(year)
      rv = period ? period.send(method) : 0
      rational ? self.class.rationalize_offset(rv) : rv
    end

    # Returns the name for this zone with Daylight Saving Time (DST) active.
    #
    # @param dst_label [String] Label for the DST indication. Defaults to `(DST)`.
    # @param year [Fixnum] The year to which refer to. Defaults to the current year.
    # @param name [String] The name to use for this zone. Defaults to the zone name.
    # @return [String] The name for the zone with DST or `nil`, if the timezone doesn't use DST for that year.
    def dst_name(dst_label = nil, year = nil, name = nil)
      uses_dst?(year) ? "#{name || self.name} #{dst_label || "(DST)"}" : nil
    end

    # Returns the name for this zone with Daylight Saving Time (DST) active.
    #
    # @param name [String] The name to use for this zone. Defaults to the zone name.
    # @param colon [Boolean] If to put the colon in the output string.
    # @return [String] The name for this zone.
    def to_str(name = nil, colon = true)
      "(GMT#{self.formatted_offset(colon)}) #{name || current_alias}"
    end

    # Returns a string representation for this zone with Daylight Saving Time (DST) active.
    #
    # @param dst_label [String] Label for the DST indication. Defaults to `(DST)`.
    # @param year [Fixnum] The year to which refer to. Defaults to the current year.
    # @param name [String] The name to use for this zone. Defaults to the zone name.
    # @return [String] The string representation for the zone with DST or `nil`, if the timezone doesn't use DST for that year.
    def to_str_with_dst(dst_label = nil, year = nil, name = nil)
      self.uses_dst?(year) ? "(GMT#{self.class.seconds_to_utc_offset(dst_period(year).utc_total_offset)}) #{name || current_alias} #{dst_label || "(DST)"}" : nil
    end

    # Returns a parameterized string representation for this zone.
    #
    # @param with_offset [Boolean] If to include offset into the representation.
    # @param name [String] The name to use for this zone. Defaults to the zone name.
    # @return [String] The parameterized string representation for this zone.
    def to_str_parameterized(with_offset = true, name = nil)
      ::ActiveSupport::TimeZone.parameterize_zone(name || to_str, with_offset)
    end

    # Returns a parameterized string representation for this zone with Daylight Saving Time (DST) active.
    #
    # @param dst_label [String] Label for the DST indication. Defaults to `(DST)`.
    # @param year [Fixnum] The year to which refer to. Defaults to the current year.
    # @param name [String] The name to use for this zone. Defaults to the zone name.
    # @return [String] The parameterized string representation for this zone with DST or `nil`, if the timezone doesn't use DST for that year.
    def to_str_with_dst_parameterized(dst_label = nil, year = nil, name = nil)
      rv = to_str_with_dst(dst_label, year, name)
      rv ? ::ActiveSupport::TimeZone.parameterize_zone(rv) : nil
    end

    private
      # Formats a time zone alias.
      #
      # @param name [String] The zone name.
      # @param zone [String] The zone.
      # @param reference [String] The main name for the zone.
      # @return [String|nil] The formatted alias.
      def format_alias(name, zone, reference)
        zone.gsub("_", " ") == reference ? (["International Date Line West", "UTC"].include?(name) || name.include?("(US & Canada)")) ? name : reference.gsub(/\/.*/, "/#{name}") : nil
      end
  end
end