import math
import os
import sys
import collections
from datetime import datetime


def spawn_daemon(fun):
	# do the UNIX double-fork magic, see Stevens' "Advanced
	# Programming in the UNIX Environment" for details (ISBN 0201563177)
	try:
		pid = os.fork()
		if pid > 0:
			# parent process, return and keep running
			return
	except OSError as e:
		print("fork #1 failed: {0} ({1})".format(e.errno, e.strerror), file=sys.stderr)
		sys.exit(1)

	os.setsid()

	# do second fork
	try:
		pid = os.fork()
		if pid > 0:
			# exit from second parent
			print("[{0}] server running".format(pid))
			sys.exit(0)
	except OSError as e:
		print("fork #2 failed: {0} ({1})".format(e.errno, e.strerror), file=sys.stderr)
		sys.exit(1)

	fun()

	# all done
	os._exit(os.EX_OK)


def split_host(host, default_port=0):
	address, _, port = host.partition(":")
	if not port: port = default_port
	return (address, port)


class Progress:
	def __init__(self, n, i0=0):
		self._n = n
		self._i0 = i0
		self._i = i0
		self._last = ""
		self._past = collections.deque()

	def p(self, i):
		i0 = self._i0
		n = self._n
		now = datetime.now()

		assert i0<=i<n or n<i<=i0, (i0, i, n)
		percentage = Progress._p(i, n, i0)
		res = "{0}%".format(percentage)
		if len(self._past)==0 or (now-self._past[-1][0]).total_seconds()>1:
			self._past.append((now, i))
		if res!=self._last or (now-self._past[0][0]).total_seconds()>5:
			eta = format_seconds(self.eta(i))
			self._print("{0} (ETA {1})".format(res, eta))
			self._last = res
			while (now-self._past[0][0]).total_seconds()>5:
				self._past.popleft()

	def done(self):
		self._print("100%", end="\n")

	def eta(self, i2):
		t2 = datetime.now()
		(t1, i1) = self._past[0]
		if i2==i1: return float("nan")
		return (self._n-i2)/(i2-i1)*(t2-t1).total_seconds()

	@staticmethod
	def _p(i, n, i0):
		_1=1 if n>=i0 else -1
		return 100*(i+_1-i0)//(n-i0)

	def _print(self, s, end=""):
		print("\r"+" "*80, end="")
		print("\r"+s, end=end)


def format_seconds(secs):
	if math.isnan(secs): return "?"
	secs = round(secs)
	if secs<60: return "{0}s".format(secs)
	mins = secs//60
	secs %= 60
	if mins<60: return "{0:02}:{1:02}".format(mins, secs)
	hours = mins//60
	mins %= 60
	return "{0:02}:{1:02}:{2:02}".format(hours, mins, secs)


if __name__=="__main__":
	import random
	import time
	progress = Progress(100)
	for i in range(1, 100):
		progress.p(i)
		time.sleep(random.random()*2)
	progress.done()