class CommandParser
  def self.snippet(str)
    self.parse(self.lex(str))
  end
  def self.lex(str)
    tokens = []
    while !(str.nil? || str.empty?)
      case str
      when /\A(?:\w|\.)+\(/
        tokens << [:fun_begin,$&]
      when /\A[\w.]+\s*<?=\s*/
        tokens << [:assignment,$&]
      when /\A[$\w.]+(?=,|)/
        tokens << [:term,$&]
      when /\A\.\.\./
        tokens << [:term,$&]
      when /\A,\s*/
        tokens << [:comma,$&]
      when /\A\)/
        tokens << [:fun_end,$&]
      when /\A".*?(?!\\)"/
        tokens << [:quoted,$&]
      when /\A\s*([\+\-\*\/!^]|&&|\|\|)\s*/
        tokens << [:operator,$&]
      when /\A\d+(\.\d+)?/
        tokens << [:number,$&]
      when /\A\{/
        tokens << [:brace_begin,$&]
      when /\A\}/
        tokens << [:brace_end,$&]
      when /\A\[/
        tokens << [:bracket_begin,$&]
      when /\A\]/
        tokens << [:bracket_end,$&]
      when /\A:/
        tokens << [:list_separator,$&]
      when /\s+/
      else
        pp str
        raise "Could not process: " + str
      end
      str = $'
    end
    tokens
  end
  def self.parse(datum)
    str = ""
    snippet_counter = -1
    datum.each do |type,match|
      # pp type,match
      case type
      when :fun_begin, :brace_begin, :bracket_begin
        str << ("${#{snippet_counter+=1}:#{match}${#{snippet_counter+=1}:")
      when :assignment
        str << match << "${#{snippet_counter+=1}:"
      when :comma
        str << "}${#{snippet_counter+=1}:" << match
      when :brace_end, :bracket_end, :fun_end
        str << "}" << match << "}"
      when :quoted
        str << "${#{snippet_counter+=1}:\"${#{snippet_counter+=1}:#{match[1..-2].gsub("}","\\}")}}\"}"
      else
        str << match
      end
    end
    str[4..-2]
  end
end