# encoding: utf-8

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

require "stringio"
require "prawn/document/page_geometry"
require "prawn/document/bounding_box"
require "prawn/document/column_box"
require "prawn/document/internals"
require "prawn/document/span"
require "prawn/document/snapshot"
require "prawn/document/graphics_state"

module Prawn

  # The Prawn::Document class is how you start creating a PDF document.
  #
  # There are three basic ways you can instantiate PDF Documents in Prawn, they
  # are through assignment, implicit block or explicit block.  Below is an exmple
  # of each type, each example does exactly the same thing, makes a PDF document
  # with all the defaults and puts in the default font "Hello There" and then
  # saves it to the current directory as "example.pdf"
  #
  # For example, assignment can be like this:
  #
  #   pdf = Prawn::Document.new
  #   pdf.text "Hello There"
  #   pdf.render_file "example.pdf"
  #
  # Or you can do an implied block form:
  #
  #   Prawn::Document.generate "example.pdf" do
  #     text "Hello There"
  #   end
  #
  # Or if you need to access a variable outside the scope of the block, the
  # explicit block form:
  #
  #   words = "Hello There"
  #   Prawn::Document.generate "example.pdf" do |pdf|
  #     pdf.text words
  #   end
  #
  # Usually, the block forms are used when you are simply creating a PDF document
  # that you want to immediately save or render out.
  #
  # See the new and generate methods for further details on the above.
  #
  class Document
    include Prawn::Document::Internals
    include Prawn::Core::Annotations
    include Prawn::Core::Destinations
    include Prawn::Document::Snapshot
    include Prawn::Document::GraphicsState
    include Prawn::Document::Security
    include Prawn::Text
    include Prawn::Graphics
    include Prawn::Images
    include Prawn::Stamp
    include Prawn::SoftMask

    # Any module added to this array will be included into instances of
    # Prawn::Document at the per-object level.  These will also be inherited by
    # any subclasses.
    #
    # Example:
    #
    #   module MyFancyModule
    #
    #     def party!
    #       text "It's a big party!"
    #     end
    #
    #   end
    #
    #   Prawn::Document.extensions << MyFancyModule
    #
    #   Prawn::Document.generate("foo.pdf") do
    #     party!
    #   end
    #
    def self.extensions
      @extensions ||= []
    end

    def self.inherited(base) #:nodoc:
      extensions.each { |e| base.extensions << e }
    end

    # Creates and renders a PDF document.
    #
    # When using the implicit block form, Prawn will evaluate the block
    # within an instance of Prawn::Document, simplifying your syntax.
    # However, please note that you will not be able to reference variables
    # from the enclosing scope within this block.
    #
    #   # Using implicit block form and rendering to a file
    #   Prawn::Document.generate "example.pdf" do
    #     # self here is set to the newly instantiated Prawn::Document
    #     # and so any variables in the outside scope are unavailable
    #     font "Times-Roman"
    #     draw_text "Hello World", :at => [200,720], :size => 32
    #   end
    #
    # If you need to access your local and instance variables, use the explicit
    # block form shown below.  In this case, Prawn yields an instance of
    # PDF::Document and the block is an ordinary closure:
    #
    #   # Using explicit block form and rendering to a file
    #   content = "Hello World"
    #   Prawn::Document.generate "example.pdf" do |pdf|
    #     # self here is left alone
    #     pdf.font "Times-Roman"
    #     pdf.draw_text content, :at => [200,720], :size => 32
    #   end
    #
    def self.generate(filename,options={},&block)
      pdf = new(options,&block)
      pdf.render_file(filename)
    end

    # Creates a new PDF Document.  The following options are available (with
    # the default values marked in [])
    #
    # <tt>:page_size</tt>:: One of the Document::PageGeometry sizes [LETTER]
    # <tt>:page_layout</tt>:: Either <tt>:portrait</tt> or <tt>:landscape</tt>
    # <tt>:margin</tt>:: Sets the margin on all sides in points [0.5 inch]
    # <tt>:left_margin</tt>:: Sets the left margin in points [0.5 inch]
    # <tt>:right_margin</tt>:: Sets the right margin in points [0.5 inch]
    # <tt>:top_margin</tt>:: Sets the top margin in points [0.5 inch]
    # <tt>:bottom_margin</tt>:: Sets the bottom margin in points [0.5 inch]
    # <tt>:skip_page_creation</tt>:: Creates a document without starting the first page [false]
    # <tt>:compress</tt>:: Compresses content streams before rendering them [false]
    # <tt>:optimize_objects</tt>:: Reduce number of PDF objects in output, at expense of render time [false]
    # <tt>:background</tt>:: An image path to be used as background on all pages [nil]
    # <tt>:background_scale</tt>:: Backgound image scale [1] [nil]
    # <tt>:info</tt>:: Generic hash allowing for custom metadata properties [nil]
    # <tt>:template</tt>:: The path to an existing PDF file to use as a template [nil]
    #
    # Setting e.g. the :margin to 100 points and the :left_margin to 50 will result in margins
    # of 100 points on every side except for the left, where it will be 50.
    #
    # The :margin can also be an array much like CSS shorthand:
    #
    #   # Top and bottom are 20, left and right are 100.
    #   :margin => [20, 100]
    #   # Top is 50, left and right are 100, bottom is 20.
    #   :margin => [50, 100, 20]
    #   # Top is 10, right is 20, bottom is 30, left is 40.
    #   :margin => [10, 20, 30, 40]
    #
    # Additionally, :page_size can be specified as a simple two value array giving
    # the width and height of the document you need in PDF Points.
    #
    # Usage:
    #
    #   # New document, US Letter paper, portrait orientation
    #   pdf = Prawn::Document.new
    #
    #   # New document, A4 paper, landscaped
    #   pdf = Prawn::Document.new(:page_size => "A4", :page_layout => :landscape)
    #
    #   # New document, Custom size
    #   pdf = Prawn::Document.new(:page_size => [200, 300])
    #
    #   # New document, with background
    #   pdf = Prawn::Document.new(:background => "#{Prawn::DATADIR}/images/pigs.jpg")
    #
    def initialize(options={},&block)
      options = options.dup

      Prawn.verify_options [:page_size, :page_layout, :margin, :left_margin,
        :right_margin, :top_margin, :bottom_margin, :skip_page_creation,
        :compress, :skip_encoding, :background, :info,
        :optimize_objects, :template], options

      # need to fix, as the refactoring breaks this
      # raise NotImplementedError if options[:skip_page_creation]

      self.class.extensions.reverse_each { |e| extend e }
      @internal_state = Prawn::Core::DocumentState.new(options)
      @internal_state.populate_pages_from_store(self)
      min_version(state.store.min_version) if state.store.min_version

      @background = options[:background]
      @background_scale = options[:background_scale] || 1
      @font_size  = 12

      @bounding_box  = nil
      @margin_box    = nil

      @page_number = 0

      options[:size] = options.delete(:page_size)
      options[:layout] = options.delete(:page_layout)

      if options[:template]
        fresh_content_streams(options)
        go_to_page(1)
      else
        if options[:skip_page_creation] || options[:template]
          start_new_page(options.merge(:orphan => true))
        else
          start_new_page(options)
        end
      end

      @bounding_box = @margin_box

      if block
        block.arity < 1 ? instance_eval(&block) : block[self]
      end
    end

    attr_accessor :margin_box
    attr_reader   :margins, :y
    attr_writer   :font_size
    attr_accessor :page_number

    def state
      @internal_state
    end

    def page
      state.page
    end

    # Creates and advances to a new page in the document.
    #
    # Page size, margins, and layout can also be set when generating a
    # new page. These values will become the new defaults for page creation
    #
    #   pdf.start_new_page #=> Starts new page keeping current values
    #   pdf.start_new_page(:size => "LEGAL", :layout => :landscape)
    #   pdf.start_new_page(:left_margin => 50, :right_margin => 50)
    #   pdf.start_new_page(:margin => 100)
    #
    # A template for a page can be specified by pointing to the path of and existing pdf.
    # One can also specify which page of the template which defaults otherwise to 1.
    #
    #  pdf.start_new_page(:template => multipage_template.pdf, :template_page => 2)
    #
    # Note: templates get indexed by either the object_id of the filename or stream
    # entered so that if you reuse the same template multiple times be sure to use the
    # same instance for more efficient use of resources and smaller rendered pdfs.
    def start_new_page(options = {})
      if last_page = state.page
        last_page_size    = last_page.size
        last_page_layout  = last_page.layout
        last_page_margins = last_page.margins
      end

      page_options = {:size => options[:size] || last_page_size,
                      :layout  => options[:layout] || last_page_layout,
                      :margins => last_page_margins}
      if last_page
        new_graphic_state = last_page.graphic_state.dup
        #erase the color space so that it gets reset on new page for fussy pdf-readers
        new_graphic_state.color_space = {}
        page_options.merge!(:graphic_state => new_graphic_state)
      end
      merge_template_options(page_options, options) if options[:template]

      state.page = Prawn::Core::Page.new(self, page_options)

      apply_margin_options(options)
      generate_margin_box

      # Reset the bounding box if the new page has different size or layout
      if last_page && (last_page.size != state.page.size ||
                       last_page.layout != state.page.layout)
        @bounding_box = @margin_box
      end

      state.page.new_content_stream if options[:template]
      use_graphic_settings(options[:template])

      unless options[:orphan]
        state.insert_page(state.page, @page_number)
        @page_number += 1

        canvas { image(@background, :scale => @background_scale, :at => bounds.top_left) } if @background
        @y = @bounding_box.absolute_top

        float do
          state.on_page_create_action(self)
        end
      end
    end

    # Returns the number of pages in the document
    #
    #   pdf = Prawn::Document.new
    #   pdf.page_count #=> 1
    #   3.times { pdf.start_new_page }
    #   pdf.page_count #=> 4
    #
    def page_count
      state.page_count
    end

    # Re-opens the page with the given (1-based) page number so that you can
    # draw on it.
    #
    # See Prawn::Document#number_pages for a sample usage of this capability.
    #
    def go_to_page(k)
      @page_number = k
      state.page = state.pages[k-1]
      generate_margin_box
      @y = @bounding_box.absolute_top
    end

    def y=(new_y)
      @y = new_y
      bounds.update_height
    end

    # The current y drawing position relative to the innermost bounding box,
    # or to the page margins at the top level.
    #
    def cursor
      y - bounds.absolute_bottom
    end

    # Moves to the specified y position in relative terms to the bottom margin.
    #
    def move_cursor_to(new_y)
      self.y = new_y + bounds.absolute_bottom
    end

    # Executes a block and then restores the original y position. If new pages
    # were created during this block, it will teleport back to the original
    # page when done.
    #
    #   pdf.text "A"
    #
    #   pdf.float do
    #     pdf.move_down 100
    #     pdf.text "C"
    #   end
    #
    #   pdf.text "B"
    #
    def float
      original_page = page_number
      original_y = y
      yield
      go_to_page(original_page) unless page_number == original_page
      self.y = original_y
    end

    # Renders the PDF document to string
    #
    def render
      output = StringIO.new
      finalize_all_page_contents

      render_header(output)
      render_body(output)
      render_xref(output)
      render_trailer(output)
      str = output.string
      str.force_encoding("ASCII-8BIT") if str.respond_to?(:force_encoding)
      str
    end

    # Renders the PDF document to file.
    #
    #   pdf.render_file "foo.pdf"
    #
    def render_file(filename)
      Kernel.const_defined?("Encoding") ? mode = "wb:ASCII-8BIT" : mode = "wb"
      File.open(filename,mode) { |f| f << render }
    end

    # The bounds method returns the current bounding box you are currently in,
    # which is by default the box represented by the margin box on the
    # document itself.  When called from within a created <tt>bounding_box</tt>
    # block, the box defined by that call will be returned instead of the
    # document margin box.
    #
    # Another important point about bounding boxes is that all x and y measurements
    # within a bounding box code block are relative to the bottom left corner of the
    # bounding box.
    #
    # For example:
    #
    #  Prawn::Document.new do
    #    # In the default "margin box" of a Prawn document of 0.5in along each edge
    #
    #    # Draw a border around the page (the manual way)
    #    stroke do
    #      line(bounds.bottom_left, bounds.bottom_right)
    #      line(bounds.bottom_right, bounds.top_right)
    #      line(bounds.top_right, bounds.top_left)
    #      line(bounds.top_left, bounds.bottom_left)
    #    end
    #
    #    # Draw a border around the page (the easy way)
    #    stroke_bounds
    #  end
    #
    def bounds
      @bounding_box
    end

    # Returns the innermost non-stretchy bounding box.
    #
    def reference_bounds
      @bounding_box.reference_bounds
    end

    # Sets Document#bounds to the BoundingBox provided.  See above for a brief
    # description of what a bounding box is.  This function is useful if you
    # really need to change the bounding box manually, but usually, just entering
    # and exiting bounding box code blocks is good enough.
    #
    def bounds=(bounding_box)
      @bounding_box = bounding_box
    end

    # Moves up the document by n points relative to the current position inside
    # the current bounding box.
    #
    def move_up(n)
      self.y += n
    end

    # Moves down the document by n points relative to the current position inside
    # the current bounding box.
    #
    def move_down(n)
      self.y -= n
    end

    # Moves down the document and then executes a block.
    #
    #   pdf.text "some text"
    #   pdf.pad_top(100) do
    #     pdf.text "This is 100 points below the previous line of text"
    #   end
    #   pdf.text "This text appears right below the previous line of text"
    #
    def pad_top(y)
      move_down(y)
      yield
    end

    # Executes a block then moves down the document
    #
    #   pdf.text "some text"
    #   pdf.pad_bottom(100) do
    #     pdf.text "This text appears right below the previous line of text"
    #   end
    #   pdf.text "This is 100 points below the previous line of text"
    #
    def pad_bottom(y)
      yield
      move_down(y)
    end

    # Moves down the document by y, executes a block, then moves down the
    # document by y again.
    #
    #   pdf.text "some text"
    #   pdf.pad(100) do
    #     pdf.text "This is 100 points below the previous line of text"
    #   end
    #   pdf.text "This is 100 points below the previous line of text"
    #
    def pad(y)
      move_down(y)
      yield
      move_down(y)
    end


    # Indents the specified number of PDF points for the duration of the block
    #
    #  pdf.text "some text"
    #  pdf.indent(20) do
    #    pdf.text "This is indented 20 points"
    #  end
    #  pdf.text "This starts 20 points left of the above line " +
    #           "and is flush with the first line"
    #  pdf.indent 20, 20 do
    #    pdf.text "This line is indented on both sides."
    #  end
    #
    def indent(left, right = 0, &block)
      bounds.indent(left, right, &block)
    end


    def mask(*fields) # :nodoc:
     # Stores the current state of the named attributes, executes the block, and
     # then restores the original values after the block has executed.
     # -- I will remove the nodoc if/when this feature is a little less hacky
      stored = {}
      fields.each { |f| stored[f] = send(f) }
      yield
      fields.each { |f| send("#{f}=", stored[f]) }
    end

    # Attempts to group the given block vertically within the current context.
    # First attempts to render it in the current position on the current page.
    # If that attempt overflows, it is tried anew after starting a new context
    # (page or column). Returns a logically true value if the content fits in
    # one page/column, false if a new page or column was needed.
    #
    # Raises CannotGroup if the provided content is too large to fit alone in
    # the current page or column.
    #
    def group(second_attempt=false)
      old_bounding_box = @bounding_box
      @bounding_box = SimpleDelegator.new(@bounding_box)

      def @bounding_box.move_past_bottom
        raise RollbackTransaction
      end

      success = transaction { yield }

      @bounding_box = old_bounding_box

      unless success
        raise Prawn::Errors::CannotGroup if second_attempt
        old_bounding_box.move_past_bottom
        group(second_attempt=true) { yield }
      end

      success
    end

    # Places a text box on specified pages for page numbering.  This should be called
    # towards the end of document creation, after all your content is already in
    # place.  In your template string, <page> refers to the current page, and
    # <total> refers to the total amount of pages in the document.  Page numbering should
    # occur at the end of your Prawn::Document.generate block because the method iterates
    # through existing pages after they are created.
    #
    # Parameters are:
    #
    # <tt>string</tt>:: Template string for page number wording.
    #                   Should include '<page>' and, optionally, '<total>'.
    # <tt>options</tt>:: A hash for page numbering and text box options.
    #     <tt>:page_filter</tt>:: A filter to specify which pages to place page numbers on.
    #                             Refer to the method 'page_match?'
    #     <tt>:start_count_at</tt>:: The starting count to increment pages from.
    #     <tt>:total_pages</tt>:: If provided, will replace <total> with the value given.
    #                             Useful to override the total number of pages when using
    #                             the start_count_at option.
    #     <tt>:color</tt>:: Text fill color.
    #
    #     Please refer to Prawn::Text::text_box for additional options concerning text
    #     formatting and placement.
    #
    # Example: Print page numbers on every page except for the first.  Start counting from
    #          five.
    #
    #   Prawn::Document.generate("page_with_numbering.pdf") do
    #     number_pages "<page> in a total of <total>",
    #                                          {:start_count_at => 5,
    #                                           :page_filter => lambda{ |pg| pg != 1 },
    #                                           :at => [bounds.right - 50, 0],
    #                                           :align => :right,
    #                                           :size => 14}
    #   end
    #
    def number_pages(string, options={})
      opts = options.dup
      start_count_at = opts.delete(:start_count_at).to_i
      page_filter = if opts.has_key?(:page_filter)
        opts.delete(:page_filter)
      else
        :all
      end
      total_pages = opts.delete(:total_pages)
      txtcolor = opts.delete(:color)
      # An explicit height so that we can draw page numbers in the margins
      opts[:height] = 50 unless opts.has_key?(:height)

      start_count = false
      pseudopage = 0
      (1..page_count).each do |p|
        unless start_count
          pseudopage = case start_count_at
                       when 0
                         1
                       else
                         start_count_at.to_i
                       end
        end
        if page_match?(page_filter, p)
          go_to_page(p)
          # have to use fill_color here otherwise text reverts back to default fill color
          fill_color txtcolor unless txtcolor.nil?
          total_pages = total_pages.nil? ? page_count : total_pages
          str = string.gsub("<page>","#{pseudopage}").gsub("<total>","#{total_pages}")
          text_box str, opts
          start_count = true  # increment page count as soon as first match found
        end
        pseudopage += 1 if start_count
      end
    end

    # Provides a way to execute a block of code repeatedly based on a
    # page_filter.
    #
    # Available page filters are:
    #   :all         repeats on every page
    #   :odd         repeats on odd pages
    #   :even        repeats on even pages
    #   some_array   repeats on every page listed in the array
    #   some_range   repeats on every page included in the range
    #   some_lambda  yields page number and repeats for true return values
    def page_match?(page_filter, page_number)
      case page_filter
      when :all
        true
      when :odd
        page_number % 2 == 1
      when :even
        page_number % 2 == 0
      when Range, Array
        page_filter.include?(page_number)
      when Proc
        page_filter.call(page_number)
      end
    end


    # Returns true if content streams will be compressed before rendering,
    # false otherwise
    #
    def compression_enabled?
      !!state.compress
    end

    private

    def merge_template_options(page_options, options)
      object_id = state.store.import_page(options[:template], options[:template_page] || 1)
      page_options.merge!(:object_id => object_id, :page_template => true)
    end

    # setting override_settings to true ensures that a new graphic state does not end up using
    # previous settings especially from imported template streams
    def use_graphic_settings(override_settings = false)
      set_fill_color if current_fill_color != "000000" || override_settings
      set_stroke_color if current_stroke_color != "000000" || override_settings
      write_line_width if line_width != 1 || override_settings
      write_stroke_cap_style if cap_style != :butt || override_settings
      write_stroke_join_style if join_style != :miter || override_settings
      write_stroke_dash if dashed? || override_settings
    end

    def generate_margin_box
      old_margin_box = @margin_box
      page           = state.page

      @margin_box = BoundingBox.new(
        self,
        nil,  # margin box has no parent
        [ page.margins[:left], page.dimensions[-1] - page.margins[:top] ] ,
        :width => page.dimensions[-2] - (page.margins[:left] + page.margins[:right]),
        :height => page.dimensions[-1] - (page.margins[:top] + page.margins[:bottom])
      )

      # This check maintains indentation settings across page breaks
      if old_margin_box
        @margin_box.add_left_padding(old_margin_box.total_left_padding)
        @margin_box.add_right_padding(old_margin_box.total_right_padding)
      end

      # we must update bounding box if not flowing from the previous page
      #
      # FIXME: This may have a bug where the old margin is restored
      # when the bounding box exits.
      @bounding_box = @margin_box if old_margin_box == @bounding_box
    end

    def apply_margin_options(options)
      if options[:margin]
        # Treat :margin as CSS shorthand with 1-4 values.
        margin = Array(options[:margin])
        positions = { 4 => [0,1,2,3], 3 => [0,1,2,1],
                      2 => [0,1,0,1], 1 => [0,0,0,0] }[margin.length]

        [:top, :right, :bottom, :left].zip(positions).each do |p,i|
          options[:"#{p}_margin"] ||= margin[i]
        end
      end

      [:left,:right,:top,:bottom].each do |side|
         if margin = options[:"#{side}_margin"]
           state.page.margins[side] = margin
         end
      end
    end
  end
end
