module Latex

  @@replacements = [
    [ /\&/, '\\\&'],
    [ / "/, " ``"],
    [ /\$/, "\\\$"],
    [ /\%/, "\\\%"],
    [ /#/, "\\\#"],
    [ /\~/, "$\\sim$"],
    [ /…/, "\\ldots"],
    [ /ö/, "\\\"o"],
    [ /ò/, '\\\`o']
  ]
  def Latex.replacements
    @@replacements
  end

  class Builder

    def initialize(out)
      @out = out
      @commands = {}

      latex_command(:section)
      latex_command(:subsection)
      latex_command(:subsubsection)
      latex_command(:section!)
      latex_command(:subsection!)
      latex_command(:subsubsection!)
      latex_command(:renewcommand)
      latex_command(:textbf, yield_arg: true)
      latex_command(:textit, yield_arg: true)
      latex_command(:texttt, yield_arg: true)
      latex_command(:textsf, yield_arg: true)
      latex_command(:emph, yield_arg: true)
      latex_command(:huge)
      latex_command(:Huge)
      latex_command(:large)
      latex_command(:Large)
      latex_command(:small)
      latex_command(:Small)
      latex_command(:tiny)
      latex_command(:footnotesize)
      latex_command(:verbatim, environment: true)
      latex_command(:pagestyle)
      latex_command(:documentclass, arg_optional:[true,false])
      latex_command(:usepackage)
      latex_command(:vspace)
      latex_command(:vspace!)
      latex_command(:fullpage)
      latex_command(:document, environment: true)
      latex_command(:hrule)
      latex_command(:nopagebreak)
      latex_command(:noindent)
      latex_command(:hfill)
      latex_command(:smallskip)
      latex_command(:medskip)
      latex_command(:bigskip)
      latex_command(:itemize , arg_optional:[true], environment: true)
      latex_command(:enumerate , arg_optional:[true], environment: true)
      latex_command(:item)
      latex_command(:tabular, environment: true)
      latex_command(:parbox, yield_arg: true)
      latex_command(:url)
      latex_command(:center, environment: true)
    end

    def puts_direct(data)
      @out.puts data
    end

    def print_direct(data)
      @out.print(data)
    end
  
    def safe_text(txt)
      Latex.replacements.fold(txt.to_s) { |t, s| t.gsub(*s) }
    end

    def puts(data)
      puts_direct(safe_text(data))
    end

    def print(data)
      print_direct(safe_text(data))
    end

    def latex_command(command, options = {})
      @commands[command.to_sym] = ({
        arg_optional: [],
        yield_arg: false,
        environment: false,
        literal: command.to_s.gsub(/!/, "*")
      }.merge(options))
    end

    def method_missing(m, *args, &block)

      raise "Method Missing: #{m}" unless @commands.has_key?(m)
      options = @commands[m]

      if options[:environment] 
        print_direct "\\begin{#{options[:literal]}}"
      else
        print_direct "\\#{options[:literal]}"
      end

      args.zip(options[:arg_optional]).each { |a,at|
          case at
          when nil,false then print_direct "{#{safe_text a}}"
          when true      then print_direct "[#{safe_text a}]"
          end
        }

      if options[:environment] 
        puts_direct ""
        yield
        puts_direct "\\end{#{options[:literal]}}"
      else
        if options[:yield_arg]
          print_direct "{"
          yield
          print_direct "}"
        end
        puts_direct ""
      end
    end

    def build_itemize(array, *args)

      config = {}
      if args[-1].is_a? Hash
        config = args.pop()
      end

      if(array.length > 0)
        if config.fetch(:enumerate, false) then 
          enumerate(*args) do 
            array.each do |r|
              item
              yield r
            end
          end
        else 
          itemize(*args) do 
            array.each do |r|
              item
              yield r
            end
          end
        end
      end
    end
  
    def endl(size = nil)
      puts_direct "\\\\#{if size.nil? then "" else "[#{size}]" end}"
    end

    def wrap
      print_direct "{"
      yield
      print_direct "}"
    end

    def em_dash
      print_direct "---"
    end
  end

end