# encoding: utf-8

# graphics.rb : Implements PDF drawing primitives
#
# Copyright April 2008, Gregory Brown.  All Rights Reserved.
#
# This is free software. Please see the LICENSE and COPYING files for details.


require_relative "graphics/color"
require_relative "graphics/dash"
require_relative "graphics/cap_style"
require_relative "graphics/join_style"
require_relative "graphics/transparency"
require_relative "graphics/transformation"
require_relative "graphics/patterns"

module Prawn

  # Implements the drawing facilities for Prawn::Document.
  # Use this to draw the most beautiful imaginable things.
  #
  # This file lifts and modifies several of PDF::Writer's graphics functions
  # ruby-pdf.rubyforge.org
  #
  module Graphics

    include Color
    include Dash
    include CapStyle
    include JoinStyle
    include Transparency
    include Transformation
    include Patterns

    # @group Stable API

    #######################################################################
    # Low level drawing operations must map the point to absolute coords! #
    #######################################################################

    # Moves the drawing position to a given point.  The point can be
    # specified as a tuple or a flattened argument list
    #
    #   pdf.move_to [100,50]
    #   pdf.move_to(100,50)
    #
    def move_to(*point)
      xy = PDF::Core.real_params(map_to_absolute(point))
      renderer.add_content("#{xy} m")
    end

    # Draws a line from the current drawing position to the specified point.
    # The destination may be described as a tuple or a flattened list:
    #
    #   pdf.line_to [50,50]
    #   pdf.line_to(50,50)
    #
    def line_to(*point)
      xy = PDF::Core.real_params(map_to_absolute(point))
      renderer.add_content("#{xy} l")
    end

    # Draws a Bezier curve from the current drawing position to the
    # specified point, bounded by two additional points.
    #
    #   pdf.curve_to [100,100], :bounds => [[90,90],[75,75]]
    #
    def curve_to(dest,options={})
       options[:bounds] or raise Prawn::Errors::InvalidGraphicsPath,
         "Bounding points for bezier curve must be specified "+
         "as :bounds => [[x1,y1],[x2,y2]]"

       curve_points = PDF::Core.real_params(
        (options[:bounds] << dest).flat_map { |e| map_to_absolute(e) })

       renderer.add_content("#{curve_points} c")
    end

    # Draws a rectangle given <tt>point</tt>, <tt>width</tt> and
    # <tt>height</tt>.  The rectangle is bounded by its upper-left corner.
    #
    #    pdf.rectangle [300,300], 100, 200
    #
    def rectangle(point,width,height)
      x,y = map_to_absolute(point)
      box = PDF::Core.real_params([x, y - height, width, height])

      renderer.add_content("#{box} re")
    end

    # Draws a rounded rectangle given <tt>point</tt>, <tt>width</tt> and
    # <tt>height</tt> and <tt>radius</tt> for the rounded corner. The rectangle
    # is bounded by its upper-left corner.
    #
    #    pdf.rounded_rectangle [300,300], 100, 200, 10
    #
    def rounded_rectangle(point,width,height,radius)
      x, y = point
      rounded_polygon(radius, point, [x + width, y], [x + width, y - height], [x, y - height])
    end


    ###########################################################
    #  Higher level functions: May use relative coords        #
    ###########################################################

    # Sets line thickness to the <tt>width</tt> specified.
    #
    def line_width=(width)
      self.current_line_width = width
      write_line_width
    end

    # When called without an argument, returns the current line thickness.
    # When called with an argument, sets the line thickness to the specified
    # value (in PDF points)
    #
    #   pdf.line_width #=> 1
    #   pdf.line_width(5)
    #   pdf.line_width #=> 5
    #
    def line_width(width=nil)
      if width
        self.line_width = width
      else
        current_line_width
      end
    end

    # Draws a line from one point to another. Points may be specified as
    # tuples or flattened argument list:
    #
    #   pdf.line [100,100], [200,250]
    #   pdf.line(100,100,200,250)
    #
    def line(*points)
      x0,y0,x1,y1 = points.flatten
      move_to(x0, y0)
      line_to(x1, y1)
    end

    # Draws a horizontal line from <tt>x1</tt> to <tt>x2</tt> at the
    # current <tt>y</tt> position, or the position specified by the :at option.
    #
    #  # draw a line from [25, 75] to [100, 75]
    #  horizontal_line 25, 100, :at => 75
    #
    def horizontal_line(x1,x2,options={})
      if options[:at]
        y1 = options[:at]
      else
        y1 = y - bounds.absolute_bottom
      end

      line(x1,y1,x2,y1)
    end

    # Draws a horizontal line from the left border to the right border of the
    # bounding box at the current <tt>y</tt> position.
    #
    def horizontal_rule
      horizontal_line(bounds.left, bounds.right)
    end

    # Draws a vertical line at the x cooordinate given by :at from y1 to y2.
    #
    #   # draw a line from [25, 100] to [25, 300]
    #   vertical_line 100, 300, :at => 25
    #
    def vertical_line(y1,y2,params)
      line(params[:at],y1,params[:at],y2)
    end

    # Draws a Bezier curve between two points, bounded by two additional
    # points
    #
    #    pdf.curve [50,100], [100,100], :bounds => [[90,90],[75,75]]
    #
    def curve(origin,dest, options={})
      move_to(*origin)
      curve_to(dest,options)
    end

    # This constant is used to approximate a symmetrical arc using a cubic
    # Bezier curve.
    #
    KAPPA = 4.0 * ((Math.sqrt(2) - 1.0) / 3.0)

    # Draws a circle of radius <tt>radius</tt> with the centre-point at <tt>point</tt>
    # as a complete subpath. The drawing point will be moved to the
    # centre-point upon completion of the drawing the circle.
    #
    #    pdf.circle [100,100], 25
    #
    def circle(center, radius)
      ellipse(center, radius, radius)
    end

    # Draws an ellipse of +x+ radius <tt>r1</tt> and +y+ radius <tt>r2</tt>
    # with the centre-point at <tt>point</tt> as a complete subpath. The
    # drawing point will be moved to the centre-point upon completion of the
    # drawing the ellipse.
    #
    #    # draws an ellipse with x-radius 25 and y-radius 50
    #    pdf.ellipse [100,100], 25, 50
    #
    def ellipse(point, r1, r2 = r1)
      x, y = point
      l1 = r1 * KAPPA
      l2 = r2 * KAPPA

      move_to(x + r1, y)

      # Upper right hand corner
      curve_to [x,  y + r2],
        :bounds => [[x + r1, y + l2], [x + l1, y + r2]]

      # Upper left hand corner
      curve_to [x - r1, y],
        :bounds => [[x - l1, y + r2], [x - r1, y + l2]]

      # Lower left hand corner
      curve_to [x, y - r2],
        :bounds => [[x - r1, y - l2], [x - l1, y - r2]]

      # Lower right hand corner
      curve_to [x + r1, y],
        :bounds => [[x + l1, y - r2], [x + r1, y - l2]]

      move_to(x, y)
    end

    # Draws a polygon from the specified points.
    #
    #    # draws a snazzy triangle
    #    pdf.polygon [100,100], [100,200], [200,200]
    #
    def polygon(*points)
      move_to points[0]
      (points[1..-1] << points[0]).each do |point|
        line_to(*point)
      end
      # close the path
      renderer.add_content "h"
    end

    # Draws a rounded polygon from specified points using the radius to define bezier curves
    #
    #  # draws a rounded filled in polygon
    #   pdf.fill_and_stroke_rounded_polygon(10, [100, 250], [200, 300], [300, 250],
    #                 [300, 150], [200, 100], [100, 150])
    def rounded_polygon(radius, *points)
      move_to point_on_line(radius, points[1], points[0])
      sides = points.size
      points << points[0] << points[1]
      (sides).times do |i|
        rounded_vertex(radius, points[i], points[i + 1], points[i + 2])
      end
      # close the path
      renderer.add_content "h"
    end


    # Creates a rounded vertex for a line segment used for building a rounded polygon
    # requires a radius to define bezier curve and three points. The first two points define
    # the line segment and the third point helps define the curve for the vertex.
    def rounded_vertex(radius, *points)
      radial_point_1 = point_on_line(radius, points[0], points[1])
      bezier_point_1 = point_on_line((radius - radius*KAPPA), points[0], points[1] )
      radial_point_2 = point_on_line(radius, points[2], points[1])
      bezier_point_2 = point_on_line((radius - radius*KAPPA), points[2], points[1])
      line_to(radial_point_1)
      curve_to(radial_point_2, :bounds => [bezier_point_1, bezier_point_2])
    end

    # Strokes the current path. If a block is provided, yields to the block
    # before closing the path. See Graphics::Color for color details.
    #
    def stroke
      yield if block_given?
      renderer.add_content "S"
    end

    # Closes and strokes the current path. If a block is provided, yields to
    # the block before closing the path. See Graphics::Color for color details.
    #
    def close_and_stroke
      yield if block_given?
      renderer.add_content "s"
    end

    # Draws and strokes a rectangle represented by the current bounding box
    #
    def stroke_bounds
      stroke_rectangle bounds.top_left, bounds.width, bounds.height
    end

    # Draws and strokes X and Y axes rulers beginning at the current bounding
    # box origin (or at a custom location).
    #
    # == Options
    #
    # +:at+::
    #   Origin of the X and Y axes (default: [0, 0] = origin of the bounding
    #   box)
    #
    # +:width+::
    #   Length of the X axis (default: width of the bounding box)
    #
    # +:height+::
    #   Length of the Y axis (default: height of the bounding box)
    #
    # +:step_length+::
    #   Length of the step between markers (default: 100)
    #
    # +:negative_axes_length+::
    #   Length of the negative parts of the axes (default: 20)
    #
    # +:color+:
    #   The color of the axes and the text.
    #
    def stroke_axis(options = {})
      options = {
        :at => [0,0],
        :height => bounds.height.to_i - (options[:at] || [0,0])[1],
        :width => bounds.width.to_i - (options[:at] || [0,0])[0],
        :step_length => 100,
        :negative_axes_length => 20,
        :color => "000000",
      }.merge(options)

      Prawn.verify_options([:at, :width, :height, :step_length,
                            :negative_axes_length, :color], options)

      save_graphics_state do
        fill_color(options[:color])
        stroke_color(options[:color])

        dash(1, :space => 4)
        stroke_horizontal_line(options[:at][0] - options[:negative_axes_length],
                               options[:at][0] + options[:width], :at => options[:at][1])
        stroke_vertical_line(options[:at][1] - options[:negative_axes_length],
                             options[:at][1] + options[:height], :at => options[:at][0])
        undash

        fill_circle(options[:at], 1)

        (options[:step_length]..options[:width]).step(options[:step_length]) do |point|
          fill_circle([options[:at][0] + point, options[:at][1]], 1)
          draw_text(point, :at => [options[:at][0] + point - 5, options[:at][1] - 10], :size => 7)
        end

        (options[:step_length]..options[:height]).step(options[:step_length]) do |point|
          fill_circle([options[:at][0], options[:at][1] + point], 1)
          draw_text(point, :at => [options[:at][0] - 17, options[:at][1] + point - 2], :size => 7)
        end
      end
    end

    # Closes and fills the current path. See Graphics::Color for color details.
    #
    # If the option :fill_rule => :even_odd is specified, Prawn will use the
    # even-odd rule to fill the path. Otherwise, the nonzero winding number rule
    # will be used. See the PDF reference, "Graphics -> Path Construction and
    # Painting -> Clipping Path Operators" for details on the difference.
    #
    def fill(options={})
      yield if block_given?
      renderer.add_content(options[:fill_rule] == :even_odd ? "f*" : "f")
    end

    # Closes, fills, and strokes the current path. If a block is provided,
    # yields to the block before closing the path. See Graphics::Color for
    # color details.
    #
    # If the option :fill_rule => :even_odd is specified, Prawn will use the
    # even-odd rule to fill the path. Otherwise, the nonzero winding number rule
    # will be used. See the PDF reference, "Graphics -> Path Construction and
    # Painting -> Clipping Path Operators" for details on the difference.
    #
    def fill_and_stroke(options={})
      yield if block_given?
      renderer.add_content(options[:fill_rule] == :even_odd ? "b*" : "b")
    end

    # Closes the current path.
    #
    def close_path
      renderer.add_content "h"
    end

    ##
    # :method: stroke_rectangle
    #
    # Draws and strokes a rectangle given +point+, +width+ and +height+. The
    # rectangle is bounded by its upper-left corner.
    #
    # :call-seq:
    #   stroke_rectangle(point,width,height)

    ##
    # :method: fill_rectangle
    #
    # Draws and fills ills a rectangle given +point+, +width+ and +height+. The
    # rectangle is bounded by its upper-left corner.
    #
    # :call-seq:
    #   fill_rectangle(point,width,height)

    ##
    # :method: fill_and_stroke_rectangle
    #
    # Draws, fills, and strokes a rectangle given +point+, +width+ and +height+.
    # The rectangle is bounded by its upper-left corner.
    #
    # :call-seq:
    #   fill_and_stroke_rectangle(point,width,height)

    ##
    # :method: stroke_rounded_rectangle
    #
    # Draws and strokes a rounded rectangle given +point+, +width+ and +height+
    # and +radius+ for the rounded corner. The rectangle is bounded by its
    # upper-left corner.
    #
    # :call-seq:
    #   stroke_rounded_rectangle(point,width,height,radius)

    ##
    # :method: fill_rounded_rectangle
    #
    # Draws and fills a rounded rectangle given +point+, +width+ and +height+
    # and +radius+ for the rounded corner. The rectangle is bounded by its
    # upper-left corner.
    #
    # :call-seq:
    #   fill_rounded_rectangle(point,width,height,radius)

    ##
    # :method: stroke_and_fill_rounded_rectangle
    #
    # Draws, fills, and strokes a rounded rectangle given +point+, +width+ and
    # +height+ and +radius+ for the rounded corner. The rectangle is bounded by
    # its upper-left corner.
    #
    # :call-seq:
    #   stroke_and_fill_rounded_rectangle(point,width,height,radius)

    ##
    # :method: stroke_line
    #
    # Strokes a line from one point to another. Points may be specified as
    # tuples or flattened argument list.
    #
    # :call-seq:
    #   stroke_line(*points)

    ##
    # :method: stroke_horizontal_line
    #
    # Strokes a horizontal line from +x1+ to +x2+ at the current y position, or
    # the position specified by the :at option.
    #
    # :call-seq:
    #   stroke_horizontal_line(x1,x2,options={})

    ##
    # :method: stroke_horizontal_rule
    #
    # Strokes a horizontal line from the left border to the right border of the
    # bounding box at the current y position.
    #
    # :call-seq:
    #   stroke_horizontal_rule

    ##
    # :method: stroke_vertical_line
    #
    # Strokes a vertical line at the x coordinate given by :at from y1 to y2.
    #
    # :call-seq:
    #   stroke_vertical_line(y1,y2,params)

    ##
    # :method: stroke_curve
    #
    # Strokes a Bezier curve between two points, bounded by two additional
    # points.
    #
    # :call-seq:
    #   stroke_curve(origin,dest,options={})

    ##
    # :method: stroke_circle
    #
    # Draws and strokes a circle of radius +radius+ with the centre-point at
    # +point+.
    #
    # :call-seq:
    #   stroke_circle(center,radius)

    ##
    # :method: fill_circle
    #
    # Draws and fills a circle of radius +radius+ with the centre-point at
    # +point+.
    #
    # :call-seq:
    #   fill_circle(center,radius)

    ##
    # :method: fill_and_stroke_circle
    #
    # Draws, strokes, and fills a circle of radius +radius+ with the
    # centre-point at +point+.
    #
    # :call-seq:
    #   fill_and_stroke_circle(center,radius)

    ##
    # :method: stroke_ellipse
    #
    # Draws and strokes an ellipse of x radius +r1+ and y radius +r2+ with the
    # centre-point at +point+.
    #
    # :call-seq:
    #   stroke_ellipse(point, r1, r2 = r1)

    ##
    # :method: fill_ellipse
    #
    # Draws and fills an ellipse of x radius +r1+ and y radius +r2+ with the
    # centre-point at +point+.
    #
    # :call-seq:
    #   fill_ellipse(point, r1, r2 = r1)

    ##
    # :method: fill_and_stroke_ellipse
    #
    # Draws, strokes, and fills an ellipse of x radius +r1+ and y radius +r2+
    # with the centre-point at +point+.
    #
    # :call-seq:
    #   fill_and_stroke_ellipse(point, r1, r2 = r1)

    ##
    # :method: stroke_polygon
    #
    # Draws and strokes a polygon from the specified points.
    #
    # :call-seq:
    #   stroke_polygon(*points)

    ##
    # :method: fill_polygon
    #
    # Draws and fills a polygon from the specified points.
    #
    # :call-seq:
    #   fill_polygon(*points)

    ##
    # :method: fill_and_stroke_polygon
    #
    # Draws, strokes, and fills a polygon from the specified points.
    #
    # :call-seq:
    #   fill_and_stroke_polygon(*points)

    ##
    # :method: stroke_rounded_polygon
    #
    # Draws and strokes a rounded polygon from specified points, using +radius+
    # to define Bezier curves.
    #
    # :call-seq:
    #   stroke_rounded_polygon(radius, *points)

    ##
    # :method: fill_rounded_polygon
    #
    # Draws and fills a rounded polygon from specified points, using +radius+ to
    # define Bezier curves.
    #
    # :call-seq:
    #   fill_rounded_polygon(radius, *points)

    ##
    # :method: fill_and_stroke_rounded_polygon
    #
    # Draws, strokes, and fills a rounded polygon from specified points, using
    # +radius+ to define Bezier curves.
    #
    # :call-seq:
    #   fill_and_stroke_rounded_polygon(radius, *points)

    ops    = %w{fill stroke fill_and_stroke}
    shapes = %w{line_to curve_to rectangle rounded_rectangle line horizontal_line horizontal_rule vertical_line
                curve circle_at circle ellipse_at ellipse polygon rounded_polygon rounded_vertex}

    ops.product(shapes).each do |operation,shape|
      class_eval "def #{operation}_#{shape}(*args); #{shape}(*args); #{operation}; end"
    end

    private

    def current_line_width
      graphic_state.line_width
    end

    def current_line_width=(width)
      graphic_state.line_width = width
    end

    def write_line_width
      renderer.add_content("#{current_line_width} w")
    end

    def map_to_absolute(*point)
      x,y = point.flatten
      [@bounding_box.absolute_left + x, @bounding_box.absolute_bottom + y]
    end

    def map_to_absolute!(point)
      point.replace(map_to_absolute(point))
    end

    def degree_to_rad(angle)
       angle * Math::PI / 180
    end

    # Returns the coordinates for a point on a line that is a given distance away from the second
    # point defining the line segement
    def point_on_line(distance_from_end, *points)
      x0,y0,x1,y1 = points.flatten
      length = Math.sqrt((x1 - x0)**2 + (y1 - y0)**2)
      p = (length - distance_from_end) / length
      xr = x0 + p*(x1 - x0)
      yr = y0 + p*(y1 - y0)
      [xr, yr]
    end

  end
end