switch_color(frag)

--?   print('before', '^'..frag..'$', Current_state)
  switch_color_based_on_prefix(frag)

  switch_color_based_on_suffix(frag)
--?   print('state after suffix', Current_state)

function switch_color(frag)
--?   print('switch', frag, Current_state, Next_state[Current_state])

function switch_color_based_on_prefix(frag)

  frag = rtrim(frag)

--?     print(Current_state, 'checking for transition', frag, edge.prefix)

--?       print('switching to', Current_state)

    elseif edge.suffix and rfind(frag, edge.suffix, nil, --[[plain]] true) == #frag then

    end
  end
end
function switch_color_based_on_suffix(frag)
  if Next_state[Current_state] == nil then
    return
  end
  frag = rtrim(frag)
  for _,edge in pairs(Next_state[Current_state]) do
    if edge.suffix and rfind(frag, edge.suffix, nil, --[[plain]] true) == #frag then

--?       print('switching to', Current_state)

end
function trim(s)
  return s:gsub('^%s+', ''):gsub('%s+$', '')

function ltrim(s)
  return s:gsub('^%s+', '')
end
function rtrim(s)
  return s:gsub('%s+$', '')
end