class TZInfo::TZDataZone

def add_observance(observance)      
  @observances << observance
end                

def find_transitions
  transitions = TZDataTransitions.new
  
  # algorithm from zic.c outzone
  
  start_time = nil
  until_time = nil
  
  
  @observances.each_with_index {|observance, i|
    std_offset = 0
    use_start = i > 0
    use_until = i < @observances.length - 1
    utc_offset = observance.utc_offset
    start_zone_id = nil
    start_utc_offset = observance.utc_offset
    start_std_offset = 0
    
    if observance.rule_set.count == 0
      std_offset = observance.std_offset
      start_zone_id = observance.format.expand(std_offset, nil)
      
      if use_start
        transitions << TZDataTransition.new(start_time, utc_offset, std_offset, start_zone_id)
        use_start = false
      else
        # zic algorithm only outputs this if std_offset is non-zero
        # to get the initial LMT range, we output this regardless
        transitions << TZDataTransition.new(nil, utc_offset, std_offset, start_zone_id)
      end  
    else
      (TZDataParser::MIN_YEAR..TZDataParser::MAX_YEAR).each {|year|
        if use_until && year > observance.valid_until.year
          break
        end
        
        activated_rules = []
        
        observance.rule_set.each {|rule|
          activated_rule = rule.activate(year)
          activated_rules << activated_rule unless activated_rule.nil?
        }
        
        while true 
          # turn until_time into UTC using the current utc_offset and std_offset
          until_time = observance.valid_until.to_utc(utc_offset, std_offset) if use_until
          
          earliest = nil
          activated_rules.each {|activated_rule| 
            # recalculate the time using the current std_offset
            activated_rule.calculate_time(utc_offset, std_offset) 
            earliest = activated_rule if earliest.nil? || activated_rule.at < earliest.at                   
          }
          
          break if earliest.nil?                
          activated_rules.delete(earliest)                               
          break if use_until && earliest.at >= until_time                
          std_offset = earliest.rule.save                   
          use_start = false if use_start && earliest.at == start_time
          
          if use_start
            if earliest.at < start_time
              start_utc_offset = observance.utc_offset
              start_std_offset = std_offset
              start_zone_id = observance.format.expand(earliest.rule.save, earliest.rule.letter)                    
              next
            end
            
            if start_zone_id.nil? && start_utc_offset + start_std_offset == observance.utc_offset + std_offset
              start_zone_id = observance.format.expand(earliest.rule.save, earliest.rule.letter)
            end
          end
          
          zone_id = observance.format.expand(earliest.rule.save, earliest.rule.letter)
          transitions << TZDataTransition.new(earliest.at, observance.utc_offset, earliest.rule.save, zone_id)
        end              
      }
    end
  
    if use_start
      start_zone_id = observance.format.expand(nil, nil) if start_zone_id.nil? && observance.format.fixed?            
      raise 'Could not determine time zone abbreviation to use just after until time' if start_zone_id.nil?            
      transitions << TZDataTransition.new(start_time, start_utc_offset, start_std_offset, start_zone_id)
    end
              
    start_time = observance.valid_until.to_utc(utc_offset, std_offset) if use_until 
  }
  
  transitions
end

def initialize(name)
  super
  @observances = []
end

def write_index_record(file)
  file.puts("      timezone #{TZDataParser.quote_str(@name)}")
end

def write_module(output_dir) 
  puts "writing zone #{name}"
  
  create_file(output_dir) {|file|        
    
    file.puts("timezone #{TZDataParser.quote_str(@name)} do |tz|")
    file.indent(2)
          
    transitions = find_transitions
    transitions.output_module(file)
    
    file.indent(-2)
    file.puts('end')
  }      
end