# -*- coding: utf-8 -*-
#
#--
# Copyright (C) 2009 Thomas Leitner <t_leitner@gmx.at>
#
# This file is part of kramdown.
#
# kramdown is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#++
#

require 'set'

module Kramdown

  module Converter

    # Converts a Kramdown::Document to LaTeX. This converter uses ideas from other Markdown-to-LaTeX
    # converters like Pandoc and Maruku.
    class Latex < Base

      # :stopdoc:

      # Initialize the LaTeX converter with the given Kramdown document +doc+.
      def initialize(doc)
        super
        #TODO: set the footnote counter at the beginning of the document
        @doc.options[:footnote_nr]
        @doc.conversion_infos[:packages] = Set.new
      end

      def convert(el, opts = {})
        send("convert_#{el.type}", el, opts)
      end

      def inner(el, opts)
        result = ''
        el.children.each do |inner_el|
          result << send("convert_#{inner_el.type}", inner_el, opts)
        end
        result
      end

      def convert_root(el, opts)
        inner(el, opts)
      end

      def convert_blank(el, opts)
        ""
      end

      def convert_text(el, opts)
        escape(el.value)
      end

      def convert_eob(el, opts)
        ''
      end

      def convert_p(el, opts)
        "#{inner(el, opts)}\n\n"
      end

      def convert_codeblock(el, opts)
        show_whitespace = el.options[:attr] && el.options[:attr]['class'].to_s =~ /\bshow-whitespaces\b/
        lang = el.options[:attr] && el.options[:attr]['lang']
        if show_whitespace || lang
          result = "\\lstset{showspaces=%s,showtabs=%s}\n" % (show_whitespace ? ['true', 'true'] : ['false', 'false'])
          result += "\\lstset{language=#{lang}}\n" if lang
          result += "\\lstset{basicstyle=\\ttfamily\\footnotesize}\\lstset{columns=fixed,frame=tlbr}\n"
          "#{result}\\begin{lstlisting}\n#{el.value}\n\\end{lstlisting}"
        else
          "\\begin{verbatim}#{el.value}\\end{verbatim}\n"
        end
      end

      def latex_environment(type, text)
        "\\begin{#{type}}\n#{text}\n\\end{#{type}}\n"
      end

      def convert_blockquote(el, opts)
        latex_environment('quote', inner(el, opts))
      end

      HEADER_TYPES = {
        1 => 'section',
        2 => 'subsection',
        3 => 'subsubsection',
        4 => 'paragraph',
        5 => 'subparagraph',
        6 => 'subparagraph'
      }
      def convert_header(el, opts)
        type = HEADER_TYPES[el.options[:level]]
        if (el.options[:attr] && (id = el.options[:attr]['id'])) ||
            (@doc.options[:auto_ids] && (id = generate_id(el.options[:raw_text])))
          "\\hypertarget{#{id}}{}\\#{type}{#{inner(el, opts)}}\\label{#{id}}\n\n"
        else
          "\\#{type}*{#{inner(el, opts)}}\n\n"
        end
      end

      def convert_hr(el, opts)
        "\\begin{center}\\rule{3in}{0.4pt}\\end{center}\n"
      end

      def convert_ul(el, opts)
        if !@doc.conversion_infos[:has_toc] && (el.options[:ial][:refs].include?('toc') rescue nil)
          @doc.conversion_infos[:has_toc] = true
          '\tableofcontents'
        else
          latex_environment(el.type == :ul ? 'itemize' : 'enumerate', inner(el, opts))
        end
      end
      alias :convert_ol :convert_ul

      def convert_dl(el, opts)
        latex_environment('description', inner(el, opts))
      end

      def convert_li(el, opts)
        "\\item #{inner(el, opts)}\n"
      end

      def convert_dt(el, opts)
        "\\item[#{inner(el, opts)}] "
      end

      def convert_dd(el, opts)
        "#{inner(el, opts)}\n\n"
      end

      def convert_html_element(el, opts)
        @doc.warnings << "Can't convert HTML element"
        ''
      end

      def convert_html_text(el, opts)
        @doc.warnings << "Can't convert HTML text"
        ''
      end

      def convert_xml_comment(el, opts)
        @doc.warnings << "Can't convert XML comment/PI"
        ''
      end
      alias :convert_xml_pi :convert_xml_comment

      TABLE_ALIGNMENT_CHAR = {:default => 'l', :left => 'l', :center => 'c', :right => 'r'}

      def convert_table(el, opts)
        align = el.options[:alignment].map {|a| TABLE_ALIGNMENT_CHAR[a]}.join('|')
        "\\begin{tabular}{|#{align}|}\n\\hline\n#{inner(el, opts)}\\hline\n\\end{tabular}\n\n"
      end

      def convert_thead(el, opts)
        "#{inner(el, opts)}\\hline\n"
      end

      def convert_tbody(el, opts)
        inner(el, opts)
      end

      def convert_tfoot(el, opts)
        "\\hline \\hline \n#{inner(el, opts)}"
      end

      def convert_tr(el, opts)
        el.children.map {|c| send("convert_#{c.type}", c, opts)}.join(' & ') + "\\\\\n"
      end

      def convert_td(el, opts)
        inner(el, opts)
      end

      def convert_br(el, opts)
        "\\newline\n"
      end

      def convert_a(el, opts)
        url = el.options[:attr]['href']
        if url =~ /^#/
          "\\hyperlink{#{url[1..-1]}}{#{inner(el, opts)}}"
        else
          "\\href{#{url}}{#{inner(el, opts)}}"
        end
      end

      def convert_img(el, opts)
        if el.options[:attr]['src'] =~ /^(https?|ftps?):\/\//
          @doc.warnings << "Cannot include non-local image"
          ''
        else
          @doc.conversion_infos[:packages] << 'graphicx'
          "\\includegraphics{#{el.options[:attr]['src']}}"
        end
      end

      def convert_codespan(el, opts)
        "{\\tt #{escape(el.value)}}"
      end

      def convert_footnote(el, opts)
        "\\footnote{#{inner(@doc.parse_infos[:footnotes][el.options[:name]])}}"
      end

      def convert_raw(el, opts)
        escape(el.value)
      end

      def convert_em(el, opts)
        "\\emph{#{inner(el, opts)}}"
      end

      def convert_strong(el, opts)
        "\\textbf{#{inner(el, opts)}}"
      end

      # Inspired by Maruku: entity conversion table taken from htmltolatex
      # (http://sourceforge.net/projects/htmltolatex/), with some small adjustments as noted
      ENTITY_CONV_TABLE = <<'EOF'
    <char num='913' name='Alpha' convertTo='$A$' />
    <char num='914' name='Beta' convertTo='$B$' />
    <char num='915' name='Gamma' convertTo='$\Gamma$' />
    <char num='916' name='Delta' convertTo='$\Delta$' />
    <char num='917' name='Epsilon' convertTo='$E$' />
    <char num='918' name='Zeta' convertTo='$Z$' />
    <char num='919' name='Eta' convertTo='$H$' />
    <char num='920' name='Theta' convertTo='$\Theta$' />
    <char num='921' name='Iota' convertTo='$I$' />
    <char num='922' name='Kappa' convertTo='$K$' />
    <char num='923' name='Lambda' convertTo='$\Lambda$' />
    <char num='924' name='Mu' convertTo='$M$' />
    <char num='925' name='Nu' convertTo='$N$' />
    <char num='926' name='Xi' convertTo='$\Xi$' />
    <char num='927' name='Omicron' convertTo='$O$' />
    <char num='928' name='Pi' convertTo='$\Pi$' />
    <char num='929' name='Rho' convertTo='$P$' />
    <char num='931' name='Sigma' convertTo='$\Sigma$' />
    <char num='932' name='Tau' convertTo='$T$' />
    <char num='933' name='Upsilon' convertTo='$Y$' />
    <char num='934' name='Phi' convertTo='$\Phi$' />
    <char num='935' name='Chi' convertTo='$X$' />
    <char num='936' name='Psi' convertTo='$\Psi$' />
    <char num='937' name='Omega' convertTo='$\Omega$' />
    <char num='945' name='alpha' convertTo='$\alpha$' />
    <char num='946' name='beta' convertTo='$\beta$' />
    <char num='947' name='gamma' convertTo='$\gamma$' />
    <char num='948' name='delta' convertTo='$\delta$' />
    <char num='949' name='epsilon' convertTo='$\epsilon$' />
    <char num='950' name='zeta' convertTo='$\zeta$' />
    <char num='951' name='eta' convertTo='$\eta$' />
    <char num='952' name='theta' convertTo='$\theta$' />
    <char num='953' name='iota' convertTo='$\iota$' />
    <char num='954' name='kappa' convertTo='$\kappa$' />
    <char num='955' name='lambda' convertTo='$\lambda$' />
    <char num='956' name='mu' convertTo='$\mu$' />
    <char num='957' name='nu' convertTo='$\nu$' />
    <char num='958' name='xi' convertTo='$\xi$' />
    <char num='959' name='omicron' convertTo='$o$' />
    <char num='960' name='pi' convertTo='$\pi$' />
    <char num='961' name='rho' convertTo='$\rho$' />
    <char num='963' name='sigma' convertTo='$\sigma$' />
    <char num='964' name='tau' convertTo='$\tau$' />
    <char num='965' name='upsilon' convertTo='$\upsilon$' />
    <char num='966' name='phi' convertTo='$\phi$' />
    <char num='967' name='chi' convertTo='$\chi$' />
    <char num='968' name='psi' convertTo='$\psi$' />
    <char num='969' name='omega' convertTo='$\omega$' />
    <char num='962' name='sigmaf' convertTo='$\varsigma$' />
    <char num='977' name='thetasym' convertTo='$\vartheta$' />
    <char num='982' name='piv' convertTo='$\varpi$' />
    <char num='8230' name='hellip' convertTo='\ldots' />
    <char num='8242' name='prime' convertTo='$\prime$' />
    <char num='8254' name='oline' convertTo='-' />
    <char num='8260' name='frasl' convertTo='/' />
    <char num='8472' name='weierp' convertTo='$\wp$' />
    <char num='8465' name='image' convertTo='$\Im$' />
    <char num='8476' name='real' convertTo='$\Re$' />
    <char num='8501' name='alefsym' convertTo='$\aleph$' />
    <char num='8226' name='bull' convertTo='$\bullet$' />
    <char num='8482' name='trade' convertTo='$^{\rm TM}$' /> <!-- \texttrademark -->
    <char num='8592' name='larr' convertTo='$\leftarrow$' />
    <char num='8594' name='rarr' convertTo='$\rightarrow$' />
    <char num='8593' name='uarr' convertTo='$\uparrow$' />
    <char num='8595' name='darr' convertTo='$\downarrow$' />
    <char num='8596' name='harr' convertTo='$\leftrightarrow$' />
    <char num='8629' name='crarr' convertTo='$\hookleftarrow$' />
    <char num='8657' name='uArr' convertTo='$\Uparrow$' />
    <char num='8659' name='dArr' convertTo='$\Downarrow$' />
    <char num='8656' name='lArr' convertTo='$\Leftarrow$' />
    <char num='8658' name='rArr' convertTo='$\Rightarrow$' />
    <char num='8660' name='hArr' convertTo='$\Leftrightarrow$' />
    <char num='8704' name='forall' convertTo='$\forall$' />
    <char num='8706' name='part' convertTo='$\partial$' />
    <char num='8707' name='exist' convertTo='$\exists$' />
    <char num='8709' name='empty' convertTo='$\emptyset$' />
    <char num='8711' name='nabla' convertTo='$\nabla$' />
    <char num='8712' name='isin' convertTo='$\in$' />
    <char num='8715' name='ni' convertTo='$\ni$' />
    <char num='8713' name='notin' convertTo='$\notin$' />
    <char num='8721' name='sum' convertTo='$\sum$' />
    <char num='8719' name='prod' convertTo='$\prod$' />
    <char num='8722' name='minus' convertTo='$-$' />
    <char num='8727' name='lowast' convertTo='$\ast$' />
    <char num='8730' name='radic' convertTo='$\surd$' />
    <char num='8733' name='prop' convertTo='$\propto$' />
    <char num='8734' name='infin' convertTo='$\infty$' />
    <char num='8736' name='ang' convertTo='$\angle$' />
    <char num='8743' name='and' convertTo='$\wedge$' />
    <char num='8744' name='or' convertTo='$\vee$' />
    <char num='8745' name='cup' convertTo='$\cup$' />
    <char num='8746' name='cap' convertTo='$\cap$' />
    <char num='8747' name='int' convertTo='$\int$' />
    <char num='8756' name='there4' convertTo='$\therefore$' /> <!-- amssymb --> --CHANGED!!!
    <char num='8764' name='sim' convertTo='$\sim$' />
    <char num='8776' name='asymp' convertTo='$\approx$' />
    <char num='8773' name='cong' convertTo='$\cong$' />
    <char num='8800' name='ne' convertTo='$\neq$' />
    <char num='8801' name='equiv' convertTo='$\equiv$' />
    <char num='8804' name='le' convertTo='$\leq$' />
    <char num='8805' name='ge' convertTo='$\geq$' />
    <char num='8834' name='sub' convertTo='$\subset$' />
    <char num='8835' name='sup' convertTo='$\supset$' />
    <char num='8838' name='sube' convertTo='$\subseteq$' />
    <char num='8839' name='supe' convertTo='$\supseteq$' />
    <char num='8836' name='nsub' convertTo='$\nsubset$' /> <!-- amssymb --> --CHANGED!!!
    <char num='8853' name='oplus' convertTo='$\oplus$' />
    <char num='8855' name='otimes' convertTo='$\otimes$' />
    <char num='8869' name='perp' convertTo='$\perp$' />
    <char num='8901' name='sdot' convertTo='$\cdot$' />
    <char num='8968' name='rceil' convertTo='$\rceil$' />
    <char num='8969' name='lceil' convertTo='$\lceil$' />
    <char num='8970' name='lfloor' convertTo='$\lfloor$' />
    <char num='8971' name='rfloor' convertTo='$\rfloor$' />
    <char num='9001' name='rang' convertTo='$\rangle$' />
    <char num='9002' name='lang' convertTo='$\langle$' />
    <char num='9674' name='loz' convertTo='$\lozenge$' /> <!-- amssymb --> --CHANGED!!!
    <char num='9824' name='spades' convertTo='$\spadesuit$' />
    <char num='9827' name='clubs' convertTo='$\clubsuit$' />
    <char num='9829' name='hearts' convertTo='$\heartsuit$' />
    <char num='9830' name='diams' convertTo='$\diamondsuit$' />
    <char num='38' name='amp' convertTo='\@AMP' />
    <char num='34' name='quot' convertTo='@DOUBLEQUOT' />
    <char num='39' name='apos' convertTo='@QUOT' />     -- ADDED!!!
    <char num='169' name='copy' convertTo='\copyright' />
    <char num='60' name='lt' convertTo='\textless{}' />       -- CHANGED!!!
    <char num='62' name='gt' convertTo='\textgreater{}' />    -- CHANGED!!!
    <char num='338' name='OElig' convertTo='\OE' />
    <char num='339' name='oelig' convertTo='\oe' />
    <char num='352' name='Scaron' convertTo='\v{S}' />
    <char num='353' name='scaron' convertTo='\v{s}' />
    <char num='376' name='Yuml' convertTo='\"Y' />
    <char num='710' name='circ' convertTo='\textasciicircum' />
    <char num='732' name='tilde' convertTo='\textasciitilde' />
    <char num='8211' name='ndash' convertTo='--' />
    <char num='8212' name='mdash' convertTo='---' />
    <char num='8216' name='lsquo' convertTo='`' />
    <char num='8217' name='rsquo' convertTo='@QUOT' />
    <char num='8220' name='ldquo' convertTo='``' />
    <char num='8221' name='rdquo' convertTo='@QUOT@QUOT' />
    <char num='8224' name='dagger' convertTo='\dag' />
    <char num='8225' name='Dagger' convertTo='\ddag' />
    <char num='8240' name='permil' convertTo='\permil' /> <!-- wasysym package -->
    <char num='8364' name='euro' convertTo='\euro' /> <!-- eurosym package -->
    <char num='8249' name='lsaquo' convertTo='\guilsinglleft' />
    <char num='8250' name='rsaquo' convertTo='\guilsinglright' />
    <char num='160' name='nbsp' convertTo='\nolinebreak' />
    <char num='161' name='iexcl' convertTo='\textexclamdown' />
    <char num='163' name='pound' convertTo='\pounds' />
    <char num='164' name='curren' convertTo='\currency' /> <!-- wasysym package -->
    <char num='165' name='yen' convertTo='\textyen' /> <!-- textcomp -->
    <char num='166' name='brvbar' convertTo='\brokenvert' /> <!-- wasysym -->
    <char num='167' name='sect' convertTo='\S' />
    <char num='171' name='laquo' convertTo='\guillemotleft' />
    <char num='187' name='raquo' convertTo='\guillemotright' />
    <char num='174' name='reg' convertTo='\textregistered' />
    <char num='170' name='ordf' convertTo='\textordfeminine' />
    <char num='172' name='not' convertTo='$\neg$' />
    <char num='176' name='deg' convertTo='$\degree$' /> <!-- mathabx -->
    <char num='177' name='plusmn' convertTo='$\pm$' />
    <char num='180' name='acute' convertTo='@QUOT' />
    <char num='181' name='micro' convertTo='$\mu$' />
    <char num='182' name='para' convertTo='\P' />
    <char num='183' name='middot' convertTo='$\cdot$' />
    <char num='186' name='ordm' convertTo='\textordmasculine' />
    <char num='162' name='cent' convertTo='\cent' /> <!-- wasysym -->
    <char num='185' name='sup1' convertTo='$^1$' />
    <char num='178' name='sup2' convertTo='$^2$' />
    <char num='179' name='sup3' convertTo='$^3$' />
    <char num='189' name='frac12' convertTo='$\frac{1}{2}$' />
    <char num='188' name='frac14' convertTo='$\frac{1}{4}$' />
    <char num='190' name='frac34' convertTo='$\frac{3}{4}' />
    <char num='192' name='Agrave' convertTo='\`A' />
    <char num='193' name='Aacute' convertTo='\@QUOTA' />
    <char num='194' name='Acirc' convertTo='\^A' />
    <char num='195' name='Atilde' convertTo='\~A' />
    <char num='196' name='Auml' convertTo='\@DOUBLEQUOTA' />
    <char num='197' name='Aring' convertTo='\AA' />
    <char num='198' name='AElig' convertTo='\AE' />
    <char num='199' name='Ccedil' convertTo='\cC' />
    <char num='200' name='Egrave' convertTo='\`E' />
    <char num='201' name='Eacute' convertTo='\@QUOTE' />
    <char num='202' name='Ecirc' convertTo='\^E' />
    <char num='203' name='Euml' convertTo='\@DOUBLEQUOTE' />
    <char num='204' name='Igrave' convertTo='\`I' />
    <char num='205' name='Iacute' convertTo='\@QUOTI' />
    <char num='206' name='Icirc' convertTo='\^I' />
    <char num='207' name='Iuml' convertTo='\"I' />
    <char num='208' name='ETH' convertTo='$\eth$' /> <!-- amssymb --> --CHANGED!!!
    <char num='209' name='Ntilde' convertTo='\~N' />
    <char num='210' name='Ograve' convertTo='\`O' />
    <char num='211' name='Oacute' convertTo='\@QUOTO' />
    <char num='212' name='Ocirc' convertTo='\^O' />
    <char num='213' name='Otilde' convertTo='\~O' />
    <char num='214' name='Ouml' convertTo='\@DOUBLEQUOTO' />
    <char num='215' name='times' convertTo='$\times$' />
    <char num='216' name='Oslash' convertTo='\O' />
    <char num='217' name='Ugrave' convertTo='\`U' />
    <char num='218' name='Uacute' convertTo='\@QUOTU' />
    <char num='219' name='Ucirc' convertTo='\^U' />
    <char num='220' name='Uuml' convertTo='\@DOUBLEQUOTU' />
    <char num='221' name='Yacute' convertTo='\@QUOTY' />
    <char num='222' name='THORN' convertTo='\Thorn' />    <!-- wasysym -->
    <char num='223' name='szlig' convertTo='\ss' />
    <char num='224' name='agrave' convertTo='\`a' />
    <char num='225' name='aacute' convertTo='\@QUOTa' />
    <char num='226' name='acirc' convertTo='\^a' />
    <char num='227' name='atilde' convertTo='\~a' />
    <char num='228' name='auml' convertTo='\@DOUBLEQUOTa' />
    <char num='229' name='aring' convertTo='\aa' />
    <char num='230' name='aelig' convertTo='\ae' />
    <char num='231' name='ccedil' convertTo='\cc' />
    <char num='232' name='egrave' convertTo='\`e' />
    <char num='233' name='eacute' convertTo='\@QUOTe' />
    <char num='234' name='ecirc' convertTo='\^e' />
    <char num='235' name='euml' convertTo='\@DOUBLEQUOTe' />
    <char num='236' name='igrave' convertTo='\`i' />
    <char num='237' name='iacute' convertTo='\@QUOTi' />
    <char num='238' name='icirc' convertTo='\^i' />
    <char num='239' name='iuml' convertTo='\@DOUBLEQUOTi' />
    <char num='240' name='eth' convertTo='$\eth$' /> <!-- -->
    <char num='241' name='ntilde' convertTo='\~n' />
    <char num='242' name='ograve' convertTo='\`o' />
    <char num='243' name='oacute' convertTo='\@QUOTo' />
    <char num='244' name='ocirc' convertTo='\^o' />
    <char num='245' name='otilde' convertTo='\~o' />
    <char num='246' name='ouml' convertTo='\@DOUBLEQUOTo' />
    <char num='247' name='divide' convertTo='$\divide$' />
    <char num='248' name='oslash' convertTo='\o' />
    <char num='249' name='ugrave' convertTo='\`u' />
    <char num='250' name='uacute' convertTo='\@QUOTu' />
    <char num='251' name='ucirc' convertTo='\^u' />
    <char num='252' name='uuml' convertTo='\@DOUBLEQUOTu' />
    <char num='253' name='yacute' convertTo='\@QUOTy' />
    <char num='254' name='thorn' convertTo='\thorn' /> <!-- wasysym -->
    <char num='255' name='yuml' convertTo='\@DOUBLEQUOTy' />
EOF
      ENTITY_MAP = {}
      ENTITY_CONV_TABLE.split(/\n/).each do |line|
        num = line.scan(/num='(\d+)'/).first.first.to_i
        name = line.scan(/name='(.*?)'/).first.first
        latex = line.scan(/convertTo='(.*?)'/).first.first.gsub(/@AMP/, '&').
          gsub(/@QUOT/, '\'').gsub(/@DOUBLEQUOT/, '"').gsub(/@LT/, '<').gsub(/@GT/, '>') + '{}'
        package = line.scan(/<!--\s*(\w+)/).first
        package = package.first unless package.nil?
        ENTITY_MAP[num] = [latex, package]
        ENTITY_MAP[name] = [latex, package]
      end

      def convert_entity(el, opts)
        result = ENTITY_MAP[el.value]
        if result
          @doc.conversion_infos[:packages] << result[1] if result[1]
          result[0]
        else
          @doc.warnings << "Couldn't find entity in substitution table!"
          ''
        end
      end

      TYPOGRAPHIC_SYMS = {
        :mdash => '---', :ndash => '--', :ellipsis => '\ldots{}',
        :laquo_space => '\guillemotleft{}~', :raquo_space => '~\guillemotright{}',
        :laquo => '\guillemotleft{}', :raquo => '\guillemotright{}'
      }
      def convert_typographic_sym(el, opts)
        TYPOGRAPHIC_SYMS[el.value]
      end

      SMART_QUOTE_SYMS = {:lsquo => '`', :rsquo => '\'', :ldquo => '``', :rdquo => '\'\''}
      def convert_smart_quote(el, opts)
        SMART_QUOTE_SYMS[el.value]
      end

      def convert_math(el, opts)
        @doc.conversion_infos[:packages] += %w[amssymb amsmath amsthm amsfonts]
        if el.options[:type] == :block
          if el.value =~ /\A\s*\\begin\{/
            el.value
          else
            latex_environment('displaymath', el.value)
          end
        else
          "$#{el.value}$"
        end
      end

      def convert_abbreviation(el, indent, opts)
        el.value
      end

      ESCAPE_MAP = {
        "^"  => "\\^{}",
        "\\" => "\\textbackslash{}",
        "~"  => "\\ensuremath{\\sim}",
        "|"  => "\\textbar{}",
        "<"  => "\\textless{}",
        ">"  => "\\textgreater{}"
      }.merge(Hash[*("{}$%&_#".scan(/./).map {|c| [c, "\\#{c}"]}.flatten)])
      ESCAPE_RE = Regexp.union(*ESCAPE_MAP.collect {|k,v| k})

      def escape(str)
        str.gsub(ESCAPE_RE) {|m| ESCAPE_MAP[m]}
      end

    end

  end
end