#--
# Copyright (c) 2005-2010 Philip Ross
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#++

module TZInfo
  # A period of time in a timezone where the same offset from UTC applies.
  #
  # All the methods that take times accept instances of Time, DateTime or
  # integer timestamps.
  class TimezonePeriod
    # The TimezoneTransitionInfo that defines the start of this TimezonePeriod 
    # (may be nil if unbounded).
    attr_reader :start_transition
    
    # The TimezoneTransitionInfo that defines the end of this TimezonePeriod
    # (may be nil if unbounded).
    attr_reader :end_transition
    
    # The TimezoneOffsetInfo for this period.
    attr_reader :offset    
    
    # Initializes a new TimezonePeriod.
    def initialize(start_transition, end_transition, offset = nil)
      @start_transition = start_transition
      @end_transition = end_transition
      
      if offset
        raise ArgumentError, 'Offset specified with transitions' if @start_transition || @end_transition
        @offset = offset
      else
        if @start_transition 
          @offset = @start_transition.offset
        elsif @end_transition
          @offset = @end_transition.previous_offset
        else
          raise ArgumentError, 'No offset specified and no transitions to determine it from'
        end
      end
      
      @utc_total_offset_rational = nil      
    end
            
    # Base offset of the timezone from UTC (seconds).
    def utc_offset
      @offset.utc_offset
    end
    
    # Offset from the local time where daylight savings is in effect (seconds).
    # E.g.: utc_offset could be -5 hours. Normally, std_offset would be 0. 
    # During daylight savings, std_offset would typically become +1 hours.
    def std_offset
      @offset.std_offset
    end
    
    # The identifier of this period, e.g. "GMT" (Greenwich Mean Time) or "BST"
    # (British Summer Time) for "Europe/London". The returned identifier is a 
    # symbol.
    def abbreviation
      @offset.abbreviation
    end
    alias :zone_identifier :abbreviation
    
    # Total offset from UTC (seconds). Equal to utc_offset + std_offset.
    def utc_total_offset
      @offset.utc_total_offset
    end
    
    # Total offset from UTC (days). Result is a Rational.
    def utc_total_offset_rational
      unless @utc_total_offset_rational
        @utc_total_offset_rational = OffsetRationals.rational_for_offset(utc_total_offset) 
      end
      @utc_total_offset_rational
    end
    
    # The start time of the period in UTC as a DateTime. May be nil if unbounded.
    def utc_start
      @start_transition ? @start_transition.at.to_datetime : nil
    end
    
    # The end time of the period in UTC as a DateTime. May be nil if unbounded.
    def utc_end
      @end_transition ? @end_transition.at.to_datetime : nil
    end
    
    # The start time of the period in local time as a DateTime. May be nil if 
    # unbounded.
    def local_start
      @start_transition ? @start_transition.local_start.to_datetime : nil
    end
    
    # The end time of the period in local time as a DateTime. May be nil if 
    # unbounded.
    def local_end
      @end_transition ? @end_transition.local_end.to_datetime : nil
    end
    
    # true if daylight savings is in effect for this period; otherwise false.
    def dst?
      @offset.dst?
    end
    
    # true if this period is valid for the given UTC DateTime; otherwise false.
    def valid_for_utc?(utc)
      utc_after_start?(utc) && utc_before_end?(utc) 
    end
    
    # true if the given UTC DateTime is after the start of the period 
    # (inclusive); otherwise false.
    def utc_after_start?(utc)
      !@start_transition || @start_transition.at <= utc
    end
    
    # true if the given UTC DateTime is before the end of the period 
    # (exclusive); otherwise false.
    def utc_before_end?(utc)
      !@end_transition || @end_transition.at > utc
    end
    
    # true if this period is valid for the given local DateTime; otherwise false.
    def valid_for_local?(local)      
      local_after_start?(local) && local_before_end?(local) 
    end
    
    # true if the given local DateTime is after the start of the period 
    # (inclusive); otherwise false.
    def local_after_start?(local)
      !@start_transition || @start_transition.local_start <= local
    end
    
    # true if the given local DateTime is before the end of the period 
    # (exclusive); otherwise false.
    def local_before_end?(local)
      !@end_transition || @end_transition.local_end > local
    end
    
    # Converts a UTC DateTime to local time based on the offset of this period.
    def to_local(utc)
      @offset.to_local(utc)
    end
    
    # Converts a local DateTime to UTC based on the offset of this period.
    def to_utc(local)
      @offset.to_utc(local)
    end
    
    # Returns true if this TimezonePeriod is equal to p. This compares the 
    # start_transition, end_transition and offset using ==.
    def ==(p)
      p.respond_to?(:start_transition) && p.respond_to?(:end_transition) &&
        p.respond_to?(:offset) && start_transition == p.start_transition &&
        end_transition == p.end_transition && offset == p.offset
    end
    
    # Returns true if this TimezonePeriods is equal to p. This compares the
    # start_transition, end_transition and offset using eql?
    def eql?(p)
      p.respond_to?(:start_transition) && p.respond_to?(:end_transition) &&
        p.respond_to?(:offset) && start_transition.eql?(p.start_transition) &&
        end_transition.eql?(p.end_transition) && offset.eql?(p.offset)
    end
    
    # Returns a hash of this TimezonePeriod.
    def hash
      result = @start_transition.hash ^ @end_transition.hash
      result ^= @offset.hash unless @start_transition || @end_transition
      result       
    end
    
    # Returns internal object state as a programmer-readable string.
    def inspect
      result = "#<#{self.class}: #{@start_transition.inspect},#{@end_transition.inspect}"
      result << ",#{@offset.inspect}>" unless @start_transition || @end_transition
      result + '>'
    end
  end
end