require 'rubygems'
require 'gbarcode'
require 'dl'
require 'rbconfig'

module GBC
  VERSION = '1.0'.freeze
  class Printer

    def self.cairo_library_name
      case Config::CONFIG['arch']
      when /darwin/
        'libcairo.2.dylib'
      when /mswin32/, /cygwin/
        'cairo.dll'
      else
        'libcairo.so.2'
      end
    end
    def self.name_for_symbol(symbol, signature)
      case Config::CONFIG['arch']
      when /mswin32/, /cygwin/
        sum = -4
        signature.each_byte do |char|
          sum += case char
          when ?D: 8
          else     4
          end
        end
        "#{symbol}@#{sum}"
      else
        symbol.to_s
      end
    end

    private_class_method :cairo_library_name, :name_for_symbol

    LIB = DL.dlopen(cairo_library_name)
    SYM = {:cairo_image_surface_create   => 'PIII',
      :cairo_create    => 'PP',
      :cairo_get_target    => 'PP',
      :cairo_destroy    => '0P',
      :cairo_surface_destroy    => '0P',
      :cairo_surface_write_to_png    => '0PS',    
      :cairo_set_source_rgb    => '0PDDD',
      :cairo_move_to    => '0PDD',
      :cairo_line_to    => '0PDD',
      :cairo_set_line_width    => '0PD',
      :cairo_stroke    => '0P',
      :cairo_select_font_face    => '0PSII',
      :cairo_set_font_size    => '0PD',
      :cairo_show_text    => '0PS'}.inject({}) { |x, (k, v)| x[k] = LIB[name_for_symbol(k, v), v]; x }

      def self.surface w,h
        r, rs = SYM[:cairo_image_surface_create].call(0,w,h)
        # puts "R#{r} #{r.class}:: RS #{rs} #{rs.class}"
        return r
      end

      def self.context(s)
        r,rs = SYM[:cairo_create].call(s)
        # puts "S [#{s} => #{s.class}] :: R[#{r} =>  #{r.class}] :: RS[#{rs} =>  #{rs.class}]"
        SYM[:cairo_set_source_rgb].call(r,0.0,0.0,0.0)
        # puts "S [#{s} => #{s.class}] :: R[#{r} =>  #{r.class}] :: RS[#{rs} =>  #{rs.class}]"
        return r
      end

      def self.ctx w,h
        context(surface(w,h))
      end

      def self.ctx_destroy(c)
        r,rs = SYM[:cairo_destroy].call(c)
      end

      def self.add_bar(c,x,y,w,h)
        # cairo_move_to(cr,11.0,20.5);
        # cairo_line_to(cr,11.0,70.5);
        # cairo_set_line_width(cr,1.85);
        # cairo_stroke(cr);
        SYM[:cairo_move_to].call(c,x,y)
        SYM[:cairo_line_to].call(c,x,h)
        SYM[:cairo_set_line_width].call(c,w)
        SYM[:cairo_stroke].call(c)
      end

      def self.add_text(c,txt,x,y)
        # cairo_select_font_face (cr, "serif", CAIRO_FONT_SLANT_NORMAL = 0, CAIRO_FONT_WEIGHT_BOLD = 1);
        # cairo_set_font_size (cr, 12.0);
        # cairo_move_to (cr, 21.0, 90.0);
        # cairo_show_text (cr, "TEST1234");      
        SYM[:cairo_select_font_face].call(c,"serif",0,1)
        SYM[:cairo_set_font_size].call(c,12.0)
        SYM[:cairo_move_to].call(c,x,y)
        SYM[:cairo_show_text].call(c,txt)
      end

      def self.draw(c,fname)
        # surface = cairo_get_target(cr)
        # cairo_destroy(cr);
        # cairo_surface_write_to_png (surface, "hello.png");
        # cairo_surface_destroy (surface);
        r,rs = SYM[:cairo_get_target].call(c)
        SYM[:cairo_destroy].call(c);
        SYM[:cairo_surface_write_to_png].call(r,fname)
        SYM[:cairo_surface_destroy].call(r);
      end

      def self.bc2png(bc,fname)
        partial = bc.partial.split(//).map {|e| e.to_i }
        len = 0
        partial.map {|e| len += e }      
        # if no height given, use default
        h= 150
        # width = length * 2 pixels + margins (30 px)
        w = len * 2 + 30
        ct = self.ctx(w,h)
        # divide up the width into chunks to use for bars
        bw = (w - 30).to_f / len.to_f
        # start the box encoding
        x = margin = 15.0
        y = 20.0
        bh  = (h - y - (margin * 2) ) 
        # puts w,h,len,bw,bh
        partial.each_index do |idx|
          #draw a bar if index is even
          if (idx % 2 != 0)
            self.add_bar(ct,x,y,(bw * partial[idx]), bh)
          end
          x += bw * partial[idx]
        end
        # add the text
        self.add_text(ct,bc.ascii, (margin + 10).to_f, (h - margin).to_f )
        # draw png & destroy ctx
        self.draw(ct,fname)
        fname
      end
    end
    class Barcode
      include Gbarcode
      def initialize(text,enc = nil)
        @ascii = text
        enc = enc ? enc : BARCODE_ANY
        @bc = barcode_create(text)
        r = barcode_encode(@bc,enc)
        if r != 0 
          raise Exception.new("INVALID ENCODING #{enc.class} FOR TEXT #{text}")
        end
        @encoding = @bc.encoding
        @partial = @bc.partial()
      end

      attr_accessor :ascii, :encoding, :partial

      def to_png(fname)
        return Printer.bc2png(self,fname)
      end
    end
  end