require 'rdoc/markup/formatter'
require 'rdoc/markup/fragments'
require 'rdoc/markup/inline'

require 'cgi'

##
# Convert SimpleMarkup to basic LaTeX report format.

class RDoc::Markup::ToLaTeX < RDoc::Markup::Formatter

  BS = "\020"   # \
  OB = "\021"   # {
  CB = "\022"   # }
  DL = "\023"   # Dollar

  BACKSLASH   = "#{BS}symbol#{OB}92#{CB}"
  HAT         = "#{BS}symbol#{OB}94#{CB}"
  BACKQUOTE   = "#{BS}symbol#{OB}0#{CB}"
  TILDE       = "#{DL}#{BS}sim#{DL}"
  LESSTHAN    = "#{DL}<#{DL}"
  GREATERTHAN = "#{DL}>#{DL}"

  def self.l(str)
    str.tr('\\', BS).tr('{', OB).tr('}', CB).tr('$', DL)
  end

  def l(arg)
    RDoc::Markup::ToLaTeX.l(arg)
  end

  LIST_TYPE_TO_LATEX = {
    :BULLET =>  [ l("\\begin{itemize}"), l("\\end{itemize}") ],
    :NUMBER =>  [ l("\\begin{enumerate}"), l("\\end{enumerate}"), "\\arabic" ],
    :UPPERALPHA =>  [ l("\\begin{enumerate}"), l("\\end{enumerate}"), "\\Alph" ],
    :LOWERALPHA =>  [ l("\\begin{enumerate}"), l("\\end{enumerate}"), "\\alph" ],
    :LABELED => [ l("\\begin{description}"), l("\\end{description}") ],
    :NOTE    => [
      l("\\begin{tabularx}{\\linewidth}{@{} l X @{}}"),
      l("\\end{tabularx}") ],
  }

  InlineTag = Struct.new(:bit, :on, :off)

  def initialize
    init_tags
    @list_depth = 0
    @prev_list_types = []
  end

  ##
  # Set up the standard mapping of attributes to LaTeX

  def init_tags
    @attr_tags = [
      InlineTag.new(RDoc::Markup::Attribute.bitmap_for(:BOLD), l("\\textbf{"), l("}")),
      InlineTag.new(RDoc::Markup::Attribute.bitmap_for(:TT),   l("\\texttt{"), l("}")),
      InlineTag.new(RDoc::Markup::Attribute.bitmap_for(:EM),   l("\\emph{"), l("}")),
    ]
  end

  ##
  # Escape a LaTeX string

  def escape(str)
    $stderr.print "FE: ", str if $DEBUG_RDOC
    s = str.
       sub(/\s+$/, '').
      gsub(/([_\${}&%#])/, "#{BS}\\1").
      gsub(/\\/, BACKSLASH).
      gsub(/\^/, HAT).
      gsub(/~/,  TILDE).
      gsub(/</,  LESSTHAN).
      gsub(/>/,  GREATERTHAN).
      gsub(/,,/, ",{},").
      gsub(/\`/,  BACKQUOTE)
    $stderr.print "-> ", s, "\n" if $DEBUG_RDOC
    s
  end

  ##
  # Add a new set of LaTeX tags for an attribute. We allow
  # separate start and end tags for flexibility

  def add_tag(name, start, stop)
    @attr_tags << InlineTag.new(RDoc::Markup::Attribute.bitmap_for(name), start, stop)
  end

  ##
  # Here's the client side of the visitor pattern

  def start_accepting
    @res = ""
    @in_list_entry = []
  end

  def end_accepting
    @res.tr(BS, '\\').tr(OB, '{').tr(CB, '}').tr(DL, '$')
  end

  def accept_paragraph(am, fragment)
    @res << wrap(convert_flow(am.flow(fragment.txt)))
    @res << "\n"
  end

  def accept_verbatim(am, fragment)
    @res << "\n\\begin{code}\n"
    @res << fragment.txt.sub(/[\n\s]+\Z/, '')
    @res << "\n\\end{code}\n\n"
  end

  def accept_rule(am, fragment)
    size = fragment.param
    size = 10 if size > 10
    @res << "\n\n\\rule{\\linewidth}{#{size}pt}\n\n"
  end

  def accept_list_start(am, fragment)
    @res << list_name(fragment.type, true) << "\n"
    @in_list_entry.push false
  end

  def accept_list_end(am, fragment)
    if tag = @in_list_entry.pop
      @res << tag << "\n"
    end
    @res << list_name(fragment.type, false) << "\n"
  end

  def accept_list_item(am, fragment)
    if tag = @in_list_entry.last
      @res << tag << "\n"
    end
    @res << list_item_start(am, fragment)
    @res << wrap(convert_flow(am.flow(fragment.txt))) << "\n"
    @in_list_entry[-1] = list_end_for(fragment.type)
  end

  def accept_blank_line(am, fragment)
    # @res << "\n"
  end

  def accept_heading(am, fragment)
    @res << convert_heading(fragment.head_level, am.flow(fragment.txt))
  end

  ##
  # This is a higher speed (if messier) version of wrap

  def wrap(txt, line_len = 76)
    res = ""
    sp = 0
    ep = txt.length
    while sp < ep
      # scan back for a space
      p = sp + line_len - 1
      if p >= ep
        p = ep
      else
        while p > sp and txt[p] != ?\s
          p -= 1
        end
        if p <= sp
          p = sp + line_len
          while p < ep and txt[p] != ?\s
            p += 1
          end
        end
      end
      res << txt[sp...p] << "\n"
      sp = p
      sp += 1 while sp < ep and txt[sp] == ?\s
    end
    res
  end

  private

  def on_tags(res, item)
    attr_mask = item.turn_on
    return if attr_mask.zero?

    @attr_tags.each do |tag|
      if attr_mask & tag.bit != 0
        res << tag.on
      end
    end
  end

  def off_tags(res, item)
    attr_mask = item.turn_off
    return if attr_mask.zero?

    @attr_tags.reverse_each do |tag|
      if attr_mask & tag.bit != 0
        res << tag.off
      end
    end
  end

  def convert_flow(flow)
    res = ""
    flow.each do |item|
      case item
      when String
        $stderr.puts "Converting '#{item}'" if $DEBUG_RDOC
        res << convert_string(item)
      when AttrChanger
        off_tags(res, item)
        on_tags(res,  item)
      when Special
        res << convert_special(item)
      else
        raise "Unknown flow element: #{item.inspect}"
      end
    end
    res
  end

  ##
  # some of these patterns are taken from SmartyPants...

  def convert_string(item)
    escape(item).

    # convert ... to elipsis (and make sure .... becomes .<elipsis>)
      gsub(/\.\.\.\./, '.\ldots{}').gsub(/\.\.\./, '\ldots{}').

    # convert single closing quote
      gsub(%r{([^ \t\r\n\[\{\(])\'}) { "#$1'" }.
      gsub(%r{\'(?=\W|s\b)}) { "'" }.

    # convert single opening quote
      gsub(/'/, '`').

    # convert double closing quote
      gsub(%r{([^ \t\r\n\[\{\(])\"(?=\W)}) { "#$1''" }.

    # convert double opening quote
      gsub(/"/, "``").

    # convert copyright
      gsub(/\(c\)/, '\copyright{}')

  end

  def convert_special(special)
    handled = false
    Attribute.each_name_of(special.type) do |name|
      method_name = "handle_special_#{name}"
      if self.respond_to? method_name
        special.text = send(method_name, special)
        handled = true
      end
    end
    raise "Unhandled special: #{special}" unless handled
    special.text
  end

  def convert_heading(level, flow)
    res =
      case level
      when 1 then "\\chapter{"
      when 2 then "\\section{"
      when 3 then "\\subsection{"
      when 4 then "\\subsubsection{"
      else  "\\paragraph{"
      end +
      convert_flow(flow) +
      "}\n"
  end

  def list_name(list_type, is_open_tag)
    tags = LIST_TYPE_TO_LATEX[list_type] || raise("Invalid list type: #{list_type.inspect}")
    if tags[2] # enumerate
      if is_open_tag
        @list_depth += 1
        if @prev_list_types[@list_depth] != tags[2]
          case @list_depth
          when 1
            roman = "i"
          when 2
            roman = "ii"
          when 3
            roman = "iii"
          when 4
            roman = "iv"
          else
            raise("Too deep list: level #{@list_depth}")
          end
          @prev_list_types[@list_depth] = tags[2]
          return l("\\renewcommand{\\labelenum#{roman}}{#{tags[2]}{enum#{roman}}}") + "\n" + tags[0]
        end
      else
        @list_depth -= 1
      end
    end
    tags[ is_open_tag ? 0 : 1]
  end

  def list_item_start(am, fragment)
    case fragment.type
    when :BULLET, :NUMBER, :UPPERALPHA, :LOWERALPHA then
      "\\item "

    when :LABELED then
      "\\item[" + convert_flow(am.flow(fragment.param)) + "] "

    when :NOTE then
        convert_flow(am.flow(fragment.param)) + " & "
    else
      raise "Invalid list type"
    end
  end

  def list_end_for(fragment_type)
    case fragment_type
    when :BULLET, :NUMBER, :UPPERALPHA, :LOWERALPHA, :LABELED then
      ""
    when :NOTE
      "\\\\\n"
    else
      raise "Invalid list type"
    end
  end

end