#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Author: Andreas Büsching <crunchy@bitkipper.net>
#
# generic notifier implementation
#
# Copyright (C) 2004, 2005, 2006
#	Andreas Büsching <crunchy@bitkipper.net>
#
# This library is free software; you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License version
# 2.1 as published by the Free Software Foundation.
#
# This library is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301 USA

"""Simple mainloop that watches sockets and timers."""

# python core packages
from copy import copy
from select import select
from select import error as select_error
from time import time
import os, sys

import socket

# internal packages
import log
import dispatch

IO_READ = 1
IO_WRITE = 2
IO_EXCEPT = 4

__sockets = {}
__sockets[ IO_READ ] = {}
__sockets[ IO_WRITE ] = {}
__sockets[ IO_EXCEPT ] = {}
__timers = {}
__timer_id = 0
__min_timer = None
__in_step = False
__step_depth = 0
__step_depth_max = 0

_options = {
	'recursive_depth' : 2,
}

def socket_add( id, method, condition = IO_READ ):
	"""The first argument specifies a socket, the second argument has to be a
	function that is called whenever there is data ready in the socket.
	The callback function gets the socket back as only argument."""
	global __sockets
	__sockets[ condition ][ id ] = method

def socket_remove( id, condition = IO_READ ):
	"""Removes the given socket from scheduler. If no condition is specified the
	default is IO_READ."""
	global __sockets
	if __sockets[ condition ].has_key( id ):
		del __sockets[ condition ][ id ]

def timer_add( interval, method ):
	"""The first argument specifies an interval in milliseconds, the second
	argument a function. This is function is called after interval
	seconds. If it returns true it's called again after interval
	seconds, otherwise it is removed from the scheduler. The third
	(optional) argument is a parameter given to the called
	function. This function returns an unique identifer which can be
	used to remove this timer"""
	global __timer_id

	try:
		__timer_id += 1
	except OverflowError:
		__timer_id = 0

	__timers[ __timer_id ] = \
	[ interval, int( time() * 1000 ) + interval, method ]

	return __timer_id

def timer_remove( id ):
	"""Removes the timer identifed by the unique ID from the main loop."""
	if __timers.has_key( id ):
		del __timers[ id ]

def dispatcher_add( method ):
	global __min_timer
	__min_timer = dispatch.MIN_TIMER
	dispatch.dispatcher_add( method )

dispatcher_remove = dispatch.dispatcher_remove

__current_sockets = {}
__current_sockets[ IO_READ ] = []
__current_sockets[ IO_WRITE ] = []
__current_sockets[ IO_EXCEPT ] = []

( INTERVAL, TIMESTAMP, CALLBACK ) = range( 3 )

def step( sleep = True, external = True ):
	"""Do one step forward in the main loop. First all timers are checked for
	expiration and if necessary the accociated callback function is called.
	After that the timer list is searched for the next timer that will expire.
	This will define the maximum timeout for the following select statement
	evaluating the registered sockets. Returning from the select statement the
	callback functions from the sockets reported by the select system call are
	invoked. As a final task in a notifier step all registered external
	dispatcher functions are invoked."""

	global __in_step, __step_depth, __step_depth_max

	__in_step = True
	__step_depth += 1

	try:
		if __step_depth > __step_depth_max:
			log.exception( 'maximum recursion depth reached' )
			__step_depth -= 1
			__in_step = False
			return

		# handle timers
		_copy = __timers.copy()
		for i, timer in _copy.items():
			timestamp = timer[ TIMESTAMP ]
			if not timestamp:
				# prevert recursion, ignore this timer
				continue
			now = int( time() * 1000 )
			if timestamp <= now:
				# Update timestamp on timer before calling the callback to
				# prevent infinite recursion in case the callback calls
				# step().
				timer[ TIMESTAMP ] = 0
				try:
					if not timer[ CALLBACK ]():
						if __timers.has_key( i ):
							del __timers[ i ]
					else:
						# Find a moment in the future. If interval is 0, we
							# just reuse the old timestamp, doesn't matter.
						now = int( time() * 1000 )
						if timer[ INTERVAL ]:
							timestamp += timer[ INTERVAL ]
							while timestamp <= now:
								timestamp += timer[ INTERVAL ]
						timer[ TIMESTAMP ] = timestamp
				except ( KeyboardInterrupt, SystemExit ), e:
					__step_depth -= 1
					__in_step = False
					raise e
				except:
					log.exception( 'removed timer %d' % i )
					if __timers.has_key( i ):
						del __timers[ i ]

			# if it causes problems to iterate over probably non-existing
			# timers, I think about adding the following code:
			# if not __in_step:
			#	  break

		# get minInterval for max timeout
		timeout = None
		if not sleep:
			timeout = 0
		else:
			now = int( time() * 1000 )
			for t in __timers:
				interval, timestamp, callback = __timers[ t ]
				if not timestamp:
					# timer is blocked (recursion), ignore it
					continue
				nextCall = timestamp - now
				if timeout == None or nextCall < timeout:
					if nextCall > 0:
						timeout = nextCall
					else:
						timeout = 0
						break
			if timeout == None: timeout = dispatch.MIN_TIMER
			if __min_timer and __min_timer < timeout: timeout = __min_timer

		r = w = e = ()
		try:
			r, w, e = select( __sockets[ IO_READ ].keys(),
							  __sockets[ IO_WRITE ].keys(),
							  __sockets[ IO_EXCEPT ].keys(), timeout / 1000.0 )
		except ( ValueError, select_error ):
			log.exception( 'error in select' )
			sys.exit( 1 )

		for sl in ( ( r, IO_READ ), ( w, IO_WRITE ), ( e, IO_EXCEPT ) ):
			sockets, condition = sl
			# append all unknown sockets to check list
			for s in sockets:
				if not s in __current_sockets[ condition ]:
					__current_sockets[ condition ].append( s )
			while len( __current_sockets[ condition ] ):
				sock = __current_sockets[ condition ].pop( 0 )
				is_socket = isinstance( sock, ( socket.socket, file,
												socket._socketobject ) )
				if ( is_socket and sock.fileno() != -1 ) or \
					   ( isinstance( sock, int ) and sock != -1 ):
					if __sockets[ condition ].has_key( sock ):
						try:
							if not __sockets[ condition ][ sock ]( sock ):
								socket_remove( sock, condition )
						except ( KeyboardInterrupt, SystemExit ), e:
							raise e
						except:
							log.exception( 'error in socket callback' )
							sys.exit( 1 )

		# handle external dispatchers
		if external:
			try:
				dispatch.dispatcher_run()
			except ( KeyboardInterrupt, SystemExit ), e:
				raise e
			except Exception, e:
				__step_depth -= 1
				__in_step = False
				log.exception( 'error in dispatcher function' )
				raise e
	except ( KeyboardInterrupt, SystemExit ), e:
		__step_depth -= 1
		__in_step = False
		raise e

	__step_depth -= 1
	__in_step = False

def loop():
	"""Executes the 'main loop' forever by calling step in an endless loop"""
	while 1:
		step()

def _init():
	global __step_depth_max

	__step_depth_max = _options[ 'recursive_depth' ]