local fs = require 'fs'
local timer = require 'timer'
local coroutine = require 'coroutine'

local function fiber(block, callback)
  local paused
  local co = coroutine.create(block)
  local function check(success, ...)
    if not success then
      return callback(...)
    end
    if not paused then
      return callback(nil, ...)
    end
    paused = false
  end
  local function async_wrap(fn)
    return function(...)
      local args = {...}
      args[#args + 1] = function (err, result)
        if err then
          check(coroutine.resume(co, false, err))
        else
          check(coroutine.resume(co, result))
        end
      end
      fn(unpack(args))
      paused = true
      return coroutine.yield()
    end
  end
  check(coroutine.resume(co, wait))
end


print "Starting fiber."
fiber(function (async_wrap)
  local open = async_wrap(fs.open)
  local sleep = async_wrap(timer.setTimeout)

  print "Opening file"
  local fd = assert(open(__dirname .. "/../LICENSE.txt", "r", "0644"))
  print("file opened at " .. fd)
  sleep(1000)
  error("Oops")
  return 5,6

end, function (err, ...)
  p({err=err,...})
  if err then error(err) end
  print "Fiber finished"
end)
print "started."