class Chronic::RepeaterWeekday < Chronic::Repeater #:nodoc:
  WEEK_WEEKDAYS = 5
  DAY_SECONDS = 86400 # (24 * 60 * 60)
  
  def initialize(type)
    super
    @current_weekday_start = nil
  end
  
  def next(pointer)
    super
    
    direction = pointer == :future ? 1 : -1
    
    if !@current_weekday_start
      @current_weekday_start = Time.construct(@now.year, @now.month, @now.day)
      @current_weekday_start += direction * DAY_SECONDS
      
      until is_weekday?(@current_weekday_start.wday)
        @current_weekday_start += direction * DAY_SECONDS
      end
    else
      loop do
        @current_weekday_start += direction * DAY_SECONDS
        break if is_weekday?(@current_weekday_start.wday)
      end
    end

    Chronic::Span.new(@current_weekday_start, @current_weekday_start + DAY_SECONDS)
  end
  
  def this(pointer = :future)
    super
    
    case pointer
    when :past
      self.next(:past)
    when :future, :none
      self.next(:future)
    end
  end

  def offset(span, amount, pointer)
    direction = pointer == :future ? 1 : -1
    
    num_weekdays_passed = 0; offset = 0
    until num_weekdays_passed == amount
      offset += direction * DAY_SECONDS
      num_weekdays_passed += 1 if is_weekday?((span.begin+offset).wday)
    end
    
    span + offset
  end
  
  def width
    DAY_SECONDS
  end
  
  def to_s
    super << '-weekday'
  end
  
  private
  
  def is_weekend?(day)
    day == symbol_to_number(:saturday) || day == symbol_to_number(:sunday)
  end
  
  def is_weekday?(day)
    !is_weekend?(day)
  end
    
  def symbol_to_number(sym)
    lookup = {:sunday => 0, :monday => 1, :tuesday => 2, :wednesday => 3, :thursday => 4, :friday => 5, :saturday => 6}
    lookup[sym] || raise("Invalid symbol specified")
  end
end