local function copyObject(o)
  local obj = {}
  for k,v in pairs(o) do
    obj[k] = v
  end
  setmetatable(obj, getmetatable(o))
  return obj
end

local function execDebug(env)
  local input = io.input()
  local result = { pcall(input.read, input, "*l") }
  if not result[1] then
    return false, result[2]
  end

  local func = load("return " .. result[2], "debug", "bt", env)
  if type(func) ~= "function" then
    func = load(result[2], "debug", "bt", env)
    if type(func) ~= "function" then
      return false, func
    end
  end

  return pcall(func)
end

local function debugREPL(onResult, debugArgs)
  local globalEnv = copyObject(_ENV)
  globalEnv._debug = debugArgs
  local result, retval
  repeat
    result, retval = execDebug(globalEnv)
    if result and type(onResult) == "function" then
      onResult(retval)
    end
  until not result
  return retval
end

return { debugREPL = debugREPL, execDebug = execDebug }