# -*- coding: utf-8 -*-
#
# AWL simulator - SFBs
#
# Copyright 2014-2015 Michael Buesch <m@bues.ch>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#

from __future__ import division, absolute_import, print_function, unicode_literals
from awlsim.common.compat import *

from awlsim.core.systemblocks.systemblocks import *
from awlsim.core.util import *


class SFB1(SFB):
	name = (1, "CTD", "IEC 1131-3 down counter")

	interfaceFields = {
		BlockInterfaceField.FTYPE_IN	: (
			BlockInterfaceField(name = "CD",
					    dataType = AwlDataType.makeByName("BOOL")),
			BlockInterfaceField(name = "LOAD",
					    dataType = AwlDataType.makeByName("BOOL")),
			BlockInterfaceField(name = "PV",
					    dataType = AwlDataType.makeByName("INT")),
		),
		BlockInterfaceField.FTYPE_OUT	: (
			BlockInterfaceField(name = "Q",
					    dataType = AwlDataType.makeByName("BOOL")),
			BlockInterfaceField(name = "CV",
					    dataType = AwlDataType.makeByName("INT")),
		),
		BlockInterfaceField.FTYPE_STAT	: (
			BlockInterfaceField(name = "CDO",
					    dataType = AwlDataType.makeByName("BOOL")),
		),
	}

	def run(self):
		s = self.cpu.statusWord

		# CD pos-edge detection
		CD = self.fetchInterfaceFieldByName("CD")
		CD_pos_edge = CD & ~self.fetchInterfaceFieldByName("CDO") & 1
		self.storeInterfaceFieldByName("CDO", CD)

		CV = wordToSignedPyInt(self.fetchInterfaceFieldByName("CV"))
		if self.fetchInterfaceFieldByName("LOAD"): # Counter load
			CV = wordToSignedPyInt(self.fetchInterfaceFieldByName("PV"))
			self.storeInterfaceFieldByName("CV", CV)
		elif CD_pos_edge and CV > -32768: # Count down
			CV -= 1
			self.storeInterfaceFieldByName("CV", CV)

		# Update Q-status
		self.storeInterfaceFieldByName("Q", 1 if CV <= 0 else 0)

		s.BIE = 1
