class Byebug::TraceCommand

def description
  %{tr[ace] (on|off)\tset trace mode
    tr[ace] var(iable) VARNAME [stop|nostop]\tset trace variable on VARNAME}
end

def execute
  if @match[1] =~ /on|off/
    onoff = 'on' == @match[1]
    Byebug.tracing = onoff
    print "#{show_setting('linetrace')}\n"
  elsif @match[1] =~ /var(?:iable)?/
    varname = @match[2]
    if debug_eval("defined?(#{varname})")
      if @match[3] && @match[3] !~ /(:?no)?stop/
        errmsg "expecting \"stop\" or \"nostop\"; got \"#{@match[3]}\"\n"
      else
        dbg_cmd = (@match[3] && @match[3] !~ /nostop/) ? 'byebug(1,0)' : ''
      end
      eval("trace_var(:\"#{varname}\") do |val|
              print \"traced variable \#{varname} has value \#{val}\n\"
              #{dbg_cmd}
            end")
      print "Tracing variable \"#{varname}\".\n"
    else
      errmsg "#{varname} is not a global variable.\n"
    end
  else
    errmsg "expecting \"on\", \"off\", \"var\" or \"variable\"; got: " \
           "\"#{@match[1]}\"\n"
  end
end

def names
  %w(trace)
end

def regexp
  /^\s* tr(?:ace)? (?: \s+ (\S+))   # on | off | var(iable)
                   (?: \s+ (\S+))?  # (variable-name)?
                   (?: \s+ (\S+))?  # (stop | nostop)?
   \s*$/x
end