local timer = require("hs.timer")
local eventtap = require("hs.eventtap")

local events = eventtap.event.types

local module = {}

module.timeFrame = 1

module.action = function()
  hs.alert("You double tapped ctrl!")
end

local timeFirstControl = 0
local firstDown = false
local secondDown = false

local noFlags = function(ev)
  local result = true
  for k,v in pairs(ev:getFlags()) do
    if v then
      result = false
      break
    end
  end
  return result
end

local onlyCtrl = function(ev)
  local result = ev:getFlags().ctrl
  for k,v in pairs(ev:getFlags()) do
    if k ~= "ctrl" and v then
      result = false
      break
    end
  end
  return result
end

local reset = function()
  timeFirstControl = 0
  firstDown = false
  secondDown = false
end

module.eventWatcher = eventtap.new({events.flagsChanged, events.keyDown}, function(ev)
  if(timer.secondsSinceEpoch() - timeFirstControl) > module.timeFrame then
    reset()
  end

  if ev:getType() == events.flagsChanged then
    if noFlags(ev) and firstDown and secondDown then
      if module.action then module.action() end
      reset()
    elseif onlyCtrl(ev) and not firstDown then
      firstDown = true
      timeFirstControl = timer.secondsSinceEpoch()
    elseif onlyCtrl(ev) and firstDown then
      secondDown = true
    elseif not noFlags(ev) then
      reset()
    end
  else
    reset()
  end
  return false
end):start()

return module