# encoding: utf-8

# text.rb : Implements PDF text primitives
#
# Copyright May 2008, Gregory Brown. All Rights Reserved.
#
# This is free software. Please see the LICENSE and COPYING files for details.
require "zlib"

module Prawn
  class Document
    module Text
      DEFAULT_FONT_SIZE = 12
      
      # The built in fonts specified by the Adobe PDF spec.
      BUILT_INS = %w[ Courier Courier-Bold Courier-Oblique Courier-BoldOblique
                      Helvetica Helvetica-Bold Helvetica-Oblique
                      Helvetica-BoldOblique Times-Roman Times-Bold Times-Italic
                      Times-BoldItalic Symbol ZapfDingbats ]

      # Draws text on the page. If a point is specified via the <tt>:at</tt>
      # option the text will begin exactly at that point, and the string is
      # assumed to be pre-formatted to properly fit the page.
      #
      # When <tt>:at</tt> is not specified, Prawn attempts to wrap the text to
      # fit within your current bounding box (or margin box if no bounding box
      # is being used ). Text will flow onto the next page when it reaches
      # the bottom of the margin_box. Text wrap in Prawn does not re-flow
      # linebreaks, so if you want fully automated text wrapping, be sure to
      # remove newlines before attempting to draw your string.  
      #
      #   pdf.text "Hello World", :at => [100,100]
      #   pdf.text "Goodbye World", :at => [50,50], :size => 16
      #   pdf.text "Will be wrapped when it hits the edge of your bounding box"
      #
      # If your font contains kerning pairs data that Prawn can parse, the 
      # text will be kerned by default.  You can disable this feature by passing
      # <tt>:kerning => false</tt>.
      #
      # == Encoding
      #
      # Note that strings passed to this function should be encoded as UTF-8.
      # If you get unexpected characters appearing in your rendered document, 
      # check this.
      #
      # If the current font is a built-in one, although the string must be
      # encoded as UTF-8, only characters that are available in ISO-8859-1
      # are allowed.
      #
      # If an empty box is rendered to your PDF instead of the character you 
      # wanted it usually means the current font doesn't include that character.
      #
      def text(text,options={})
        # ensure a valid font is selected
        font "Helvetica" unless fonts[@font]

        # we'll be messing with the strings encoding, don't change the users
        # original string
        text = text.dup

        # check the string is encoded sanely
        # - UTF-8 for TTF fonts
        # - ISO-8859-1 for Built-In fonts
        if using_builtin_font?
          normalize_builtin_encoding(text)
        else
          normalize_ttf_encoding(text)
        end

        if options.key?(:kerning)
          options[:kerning] = false unless font_metrics.has_kerning_data?
        else
          options[:kerning] = true if font_metrics.has_kerning_data?
        end

        return wrapped_text(text,options) unless options[:at]
        
        x,y = translate(options[:at])
        font_size(options[:size] || current_font_size) do
          font_name = font_registry[fonts[@font]]          
          
          text = @font_metrics.convert_text(text,options)    

          add_content %Q{
            BT
            /#{font_name} #{current_font_size} Tf
            #{x} #{y} Td
          }
          
          add_content Prawn::PdfObject(text, true) << 
            " #{options[:kerning] ? 'TJ' : 'Tj'}\n"
          
          add_content %Q{
            ET
          }
        end
      end
                       
      # Access to low-level font metrics data. This is only necessary for those
      # who require direct access to font attributes, and can be safely ignored
      # otherwise.
      #                 
      def font_metrics 
        @font_metrics ||= Prawn::Font::Metrics["Helvetica"]
      end

      # Sets the current font.
      #
      # The single parameter must be a string. It can be one of the 14 built-in
      # fonts supported by PDF, or the location of a TTF file. The BUILT_INS
      # array specifies the valid built in font values.
      #
      #   pdf.font "Times-Roman"
      #   pdf.font "Chalkboard.ttf"
      #
      # If a ttf font is specified, the full file will be embedded in the 
      # rendered PDF. This should be your preferred option in most cases. 
      # It will increase the size of the resulting file, but also make it 
      # more portable.
      #
      def font(name)
        proc_set :PDF, :Text
        @font_metrics = Prawn::Font::Metrics[name]
        case(name)
        when /\.ttf$/
          @font = embed_ttf_font(name)
        else
          @font = register_builtin_font(name)
        end
        set_current_font
      end
      
      # Sets the default font size for use within a block.  Individual overrides
      # can be used as desired.  The previous font size will be restored after the
      # block.
      #
      #  Prawn::Document.generate("font_size.pdf") do
      #   font_size!(16) 
      #   text "At size 16"
      #
      #   font_size(10) do
      #     text "At size 10"
      #     text "At size 6", :size => 6
      #     text "At size 10"
      #   end
      #
      #   text "At size 16"
      #  end   
      #
      # When called without an argument, this method returns the current font
      # size.
      #
      def font_size(size=nil)
        return current_font_size unless size
        font_size_before_block = @font_size || DEFAULT_FONT_SIZE
        font_size!(size)
        yield
        font_size!(font_size_before_block)
      end
      
      # Sets the default font size. See example in font_size
      #
      def font_size!(size)
        @font_size = size unless size == nil
      end     
      
      alias_method :font_size=, :font_size!

      private 


      # The current font_size being used in the document.
      #
      def current_font_size
        @font_size || DEFAULT_FONT_SIZE
      end

      def move_text_position(dy)
         (y - dy) < @margin_box.absolute_bottom ? start_new_page : self.y -= dy       
      end

      def text_width(text,size)
        @font_metrics.string_width(text,size)
      end

      # TODO: Get kerning working with wrapped text
      def wrapped_text(text,options) 
        options[:align] ||= :left
        font_size(options[:size] || current_font_size) do
          font_name = font_registry[fonts[@font]]

          text = @font_metrics.naive_wrap(text, bounds.right, current_font_size, 
            :kerning => options[:kerning]) 

          lines = text.lines

          lines.each do |e|    
            
            move_text_position(@font_metrics.font_height(current_font_size) +
                           @font_metrics.descender / 1000.0 * current_font_size)  
                               
                           
            line_width = text_width(e,font_size)
            case(options[:align]) 
            when :left
              x = @bounding_box.absolute_left
            when :center
              x = @bounding_box.absolute_left + 
                (@bounding_box.width - line_width) / 2.0
            when :right
              x = @bounding_box.absolute_right - line_width
            end
                               
            add_content %Q{
              BT
              /#{font_name} #{current_font_size} Tf
              #{x} #{y} Td
            }    
             
           add_content Prawn::PdfObject(@font_metrics.convert_text(e,options), true) << 
             " #{options[:kerning] ? 'TJ' : 'Tj'}\n"   

            add_content %Q{
              ET
            }                
            
            ds = -@font_metrics.descender / 1000.0 * current_font_size 
            move_text_position(options[:spacing] || ds )
          end
        end
      end

      def embed_ttf_font(file) #:nodoc:

        ttf_metrics = Prawn::Font::Metrics::TTF.new(file)

        unless File.file?(file)
          raise ArgumentError, "file #{file} does not exist"
        end

        basename = @font_metrics.basename

        raise "Can't detect a postscript name for #{file}" if basename.nil?

        enctables[basename] = @font_metrics.enc_table

        if enctables[basename].nil?
          raise "#{file} missing the required encoding table" 
        end

        font_content    = File.open(file,"rb") { |f| f.read }
        compressed_font = Zlib::Deflate.deflate(font_content)

        fontfile = ref(:Length  => compressed_font.size,
                       :Length1 => font_content.size,
                       :Filter => :FlateDecode )
        fontfile << compressed_font

        # TODO: Not sure what to do about CapHeight, as ttf2afm doesn't
        #       pick it up. Missing proper StemV and flags
        #
        descriptor = ref(:Type        => :FontDescriptor,
                         :FontName    => basename,
                         :FontFile2   => fontfile,
                         :FontBBox    => @font_metrics.bbox,
                         :Flags       => 32, # FIXME: additional flags
                         :StemV       => 0,
                         :ItalicAngle => 0,
                         :Ascent      => @font_metrics.ascender,
                         :Descent     => @font_metrics.descender
                         )

        descendant = ref(:Type           => :Font,
                         :Subtype        => :CIDFontType2, # CID, TTF
                         :BaseFont       => basename,
                         :CIDSystemInfo  => { :Registry   => "Adobe", 
                                              :Ordering   => "Identity", 
                                              :Supplement => 0 },
                         :FontDescriptor => descriptor,
                         :W              => @font_metrics.glyph_widths,
                         :CIDToGIDMap    => :Identity
                        )

        to_unicode_content = @font_metrics.to_unicode_cmap.to_s
        compressed_to_unicode = Zlib::Deflate.deflate(to_unicode_content)
        to_unicode = ref(:Length  => compressed_to_unicode.size,
                         :Length1 => to_unicode_content.size,
                         :Filter => :FlateDecode )
        to_unicode << compressed_to_unicode

        # TODO: Needs ToUnicode (at least)
        fonts[basename] ||= ref(:Type            => :Font,
                                :Subtype         => :Type0,
                                :BaseFont        => basename,
                                :DescendantFonts => [descendant],
                                :Encoding        => :"Identity-H",
                                :ToUnicode       => to_unicode)
        return basename
      end

      # built-in fonts only work with latin encoding, so translate the string
      def normalize_builtin_encoding(text)
        if text.respond_to?(:encode!)
          text.encode!("ISO-8859-1")
        else
          require 'iconv'
          text.replace Iconv.conv('ISO-8859-1', 'utf-8', text)
        end
      rescue
        raise Prawn::Errors::IncompatibleStringEncoding, "When using a " +
            "builtin font, only characters that exist in " +
            "WinAnsi/ISO-8859-1 are allowed."
      end

      def normalize_ttf_encoding(text)
        # TODO: if the current font is a built in one, we can't use the utf-8
        # string provided by the user. We should convert it to WinAnsi or
        # MacRoman or some such.
        if text.respond_to?(:encode!)
          # if we're running under a M17n aware VM, ensure the string provided is
          # UTF-8 (by converting it if necessary)
          begin
            text.encode!("UTF-8")
          rescue
            raise Prawn::Errors::IncompatibleStringEncoding, "Encoding " +
            "#{text.encoding} can not be transparently converted to UTF-8. " +
            "Please ensure the encoding of the string you are attempting " +
            "to use is set correctly"
          end
        else
          # on a non M17N aware VM, use unpack as a hackish way to verify the
          # string is valid utf-8. I thought it was better than loading iconv
          # though.
          begin
            text.unpack("U*")
          rescue
            raise Prawn::Errors::IncompatibleStringEncoding, "The string you " +
            "are attempting to render is not encoded in valid UTF-8."
          end
        end
      end

      def register_builtin_font(name) #:nodoc:
        unless BUILT_INS.include?(name)
          raise Prawn::Errors::UnknownFont, "#{name} is not a known font."
        end
        fonts[name] ||= ref(:Type => :Font,
                            :Subtype => :Type1,
                            :BaseFont => name.to_sym,
                            :Encoding => :WinAnsiEncoding)
        return name
      end

      def set_current_font #:nodoc:
        return if @font.nil?
        font_registry[fonts[@font]] ||= :"F#{font_registry.size + 1}"

        page_fonts.merge!(
          font_registry[fonts[@font]] => fonts[@font]
        )
      end

      def enctables #:nodoc
        @enctables ||= {}
      end 
      
      def font_registry #:nodoc:
        @font_registry ||= {}
      end

      def fonts #:nodoc:
        @fonts ||= {}
      end

      def using_builtin_font?
        fonts[@font].data[:Subtype] == :Type1
      end
    end
  end
end