# encoding: utf-8
#
# Implements graphics state saving and restoring
#
# Copyright January 2010, Michael Witrant. All Rights Reserved.
#
# This is free software. Please see the LICENSE and COPYING files for details
#


module PDF
  module Core
    class GraphicStateStack
      attr_accessor :stack

      def initialize(previous_state = nil)
        self.stack = [GraphicState.new(previous_state)]
      end

      def save_graphic_state(graphic_state = nil)
        stack.push(GraphicState.new(graphic_state || current_state))
      end

      def restore_graphic_state
        if stack.empty?
          raise PDF::Core::Errors::EmptyGraphicStateStack,
            "\n You have reached the end of the graphic state stack"
        end
        stack.pop
      end

      def current_state
        stack.last
      end

      def present?
        stack.size > 0
      end

      def empty?
        stack.empty?
      end

    end

    # NOTE: This class may be a good candidate for a copy-on-write hash.
    class GraphicState
      attr_accessor :color_space, :dash, :cap_style, :join_style, :line_width, 
                    :fill_color, :stroke_color

      def initialize(previous_state = nil)
        if previous_state
          initialize_copy(previous_state)
        else
          @color_space  = {}
          @fill_color   = "000000"
          @stroke_color = "000000"
          @dash         = { :dash => nil, :space => nil, :phase => 0 }
          @cap_style    = :butt
          @join_style   = :miter
          @line_width   = 1
        end
      end

      def dash_setting
        if @dash[:dash].kind_of?(Array)
          "[#{@dash[:dash].join(' ')}] #{@dash[:phase]} d"
        else
          "[#{@dash[:dash]} #{@dash[:space]}] #{@dash[:phase]} d"
        end
      end

      private

      def initialize_copy(other)
        # mutable state
        @color_space  = other.color_space.dup
        @fill_color   = other.fill_color.dup
        @stroke_color = other.stroke_color.dup
        @dash         = other.dash.dup

        # immutable state that doesn't need to be duped
        @cap_style    = other.cap_style
        @join_style   = other.join_style
        @line_width   = other.line_width
      end
    end
  end
end