local errorStack = {}
local mFinally = nil

local patt = { { ".* attempt to call nil", "NIL_FUNCTION_EXCEPTION" } }
function errorToException(err)
  for k,v in pairs( patt ) do
    if string.find( err, v[1] ) then return v[2] end
  end
  return "UNHANDLED_EXCEPTION"
end

local function doFinally()
  if mFinally == nil or mFinally == "" then return end
  func,err = loadstring(mFinally)
  if func == nil then error(err) end
  setfenv(func,getfenv())
  local myErrorStack = errorStack
  local mmFinally = mFinally
  errorStack = {}
  mFinally = ""
  if func then pcall(func) end
  errorStack = myErrorStack
  mFinally = mmFinally
end

function sFinally(str)
  mFinally = str
end


function try(str)
  func,err = loadstring(str)
  errorStack = {}
  if func then
    setfenv(func,getfenv())
    local myErrorStack = errorStack
    errorStack = {}
    local arg = {pcall(func)}
    errorStack = myErrorStack
    local errVal = table.remove(arg,1)
    if not errVal then
      table.insert(errorStack,errorToException(arg[1]))
    else
      doFinally()
    end

  else
    table.insert(errorStack,errorToException(err))
  end
end

function catch(err, str)
  if #errorStack == 0 then return end
  local lErr = table.remove(errorStack)
  if lErr == err then
    func,err = loadstring(str)
    if func == nil then doFinally() error(err) end
    setfenv(func,getfenv())
    local myErrorStack = errorStack
    errorStack = {}
    if func then
      pcall(func)
    end
    errorStack = myErrorStack
    doFinally()
  end
end