EventSystem 1.0

os.loadAPI('es')

local ox = -1
local oy = -1

local function onClick(_,_,x,y)
  ox = x
  oy = y
end

local function onDrag(_,_,x,y)
  paintutils.drawLine(ox,oy,x,y,2^14)
  ox = x
  oy = y
end

local function onEnd()
  term.setBackgroundColor(2^15)
  term.clear()
  term.setCursorPos(1,1)
end

term.clear()
es.setTerminate(true)
es.addHandler('mouse_drag',onDrag)
es.addHandler('mouse_click',onClick)
es.addHandler('end',onEnd)

es.start()

	os.pullEvent = os.pullEventRaw

	local running = false

	local handlers = {}
	local handlerkeys = {}

	local eventWaiting = {}
	local terminate = true

	local function tickloop()
	  while true do
		triggerEvent('tick')
		sleep(0.05)
	  end
	end

	local function eventloop()
	  while true do
		local ev, a, b, c = os.pullEventRaw()

		if (ev == 'terminate' and terminate) or ev == 'internal-terminate' then
		  triggerEvent('end')
		  exit()
		  return
		else
		  triggerEvent(ev,a,b,c)
		  triggerEvent('general',a,b,c)
		end
	  end
	end

	function triggerEvent(ev,a,b,c)

	  if eventWaiting[1] ~= nil then
		if ev ~= eventWaiting[1] then return false end
		local argtable = {a,b,c}

		for i = 2,#eventWaiting do
		  if eventWaiting[i] == nil then break end
		  if eventWaiting[i] ~= argtable[i-1] then
			return false
		  end
		end
		eventWaiting = {}
	  end

	  if ev == nil or handlers == nil then return false end

	  if handlers[ev] == nil then return false end


	  if type(handlers[ev]) ~= 'table' and handlers[ev] ~= nil then
		handlers[ev] = nil
	  end

	  if #handlers[ev] == 0 then return false end

	  for i = 1,#handlers[ev] do
		handlers[ev][i](ev,a,b,c)
	  end

	  return true
	end

	function addHandler(etype, func)
	  if func == nil then
		func = etype
		etype = "general"
	  end

	  if type(func) ~= 'function' or type(etype) ~= 'string' then
		if (not type(func) == 'string') and (not type(etype) == 'function') then
		  return false
		end

		if type(func) == 'string' and type(etype) == 'function' then
		  local inter = func
		  func = etype
		  etype = inter
		end
	  end


	  if handlers[etype] == nil then
		handlers[etype] = {}
		table.insert(handlerkeys,etype)
	  end
	  for i = 1,#handlers[etype] do
		if func == handlers[etype][i] then
		  return false
		end
	  end
	  table.insert(handlers[etype],func)  
	  return true
	end

	function removeHandler(func)
	  while true do
		local found = false
		for i = 1,#handlerkeys do
		  local k = handlerkeys[i]
		  for j = 1,#handlers[k] do
			if handlers[k][j] == func then
			  handlers[k][j] = nil
			  found = true
			  break
			end
		  end

		  if found then break end
		end  
		if not found then return false end
	  end

	  local rmi = {}

	  for i = 1,#handlerkeys do
		local k = handlerkeys[i]
		if #handlers[k] == 0 then
		  handlers[k] = nil
		  table.insert(rmi,i)
		end
	  end
	  for i = 1,#rmi do
		table.remove(handlerkeys,rmi[i])
	  end

	end

	function exit()
	  handlers = nil
	  os.queueEvent('internal-terminate')
	end

	function waitForEvent(ev,a,b,c)
	  if ev == nil then return false end
	  eventWaiting = {ev,a,b,c}
	  return true
	end

	function start()
	  if not running then
		running = true
		triggerEvent('begin')
		parallel.waitForAny(eventloop,tickloop)
	  end
	end

	function setTerminate(bool)
	  if type(bool) ~= 'boolean' then
		return false
	  end
	  terminate = bool
	end