# -*- coding: utf-8 -*-
#
# AWL simulator - utility functions
# Copyright 2012 Michael Buesch <m@bues.ch>
#
# Licensed under the terms of the GNU General Public License version 2.
#

import os
import random
import struct


class AwlSimError(Exception):
	pass

class AwlParserError(Exception):
	pass

def awlFileRead(filename):
	try:
		fd = open(filename, "r", encoding="latin_1")
		data = fd.read()
		fd.close()
	except IOError as e:
		raise AwlParserError("Failed to read '%s': %s" %\
			(filename, str(e)))
	return data

def awlFileWrite(filename, data):
	data = "\r\n".join(data.splitlines()) + "\r\n"
	for count in range(1000):
		tmpFile = "%s-%d-%d.tmp" %\
			(filename, random.randint(0, 0xFFFF), count)
		if not os.path.exists(tmpFile):
			break
	else:
		raise AwlParserError("Could not create temporary file")
	try:
		fd = open(tmpFile, "w", encoding="latin_1")
		fd.write(data)
		fd.flush()
		fd.close()
		if os.name.lower() != "posix":
			# Can't use safe rename on non-POSIX.
			# Must unlink first.
			os.unlink(filename)
		os.rename(tmpFile, filename)
	except (IOError, OSError) as e:
		raise AwlParserError("Failed to write file:\n" + str(e))
	finally:
		try:
			os.unlink(tmpFile)
		except (IOError, OSError):
			pass

def byteToSignedPyInt(byte):
	if byte & 0x80:
		return -((~byte + 1) & 0xFF)
	return byte & 0xFF

def wordToSignedPyInt(word):
	if word & 0x8000:
		return -((~word + 1) & 0xFFFF)
	return word & 0xFFFF

def dwordToSignedPyInt(dword):
	if dword & 0x80000000:
		return -((~dword + 1) & 0xFFFFFFFF)
	return dword & 0xFFFFFFFF

def pyFloatToDWord(pyfl):
	buf = struct.pack('>f', pyfl)
	dword = (buf[0] << 24) |\
		(buf[1] << 16) |\
		(buf[2] << 8) |\
		buf[3]
	if isDenormalPyFloat(pyfl):
		# Denormal floats are equal to zero on the S7 CPU.
		# OV and OS flags are set in the StatusWord handler.
		dword = 0x00000000
	elif (dword & 0x7FFFFFFF) > 0x7F800000:
		# NaNs are always all-ones on the S7 CPU.
		dword = 0xFFFFFFFF
	return dword

def dwordToPyFloat(dword):
	return struct.unpack('>f',
		bytes( ((dword >> 24) & 0xFF,
			(dword >> 16) & 0xFF,
			(dword >> 8) & 0xFF,
			dword & 0xFF)
		)
	)[0]

# The smallest normalized positive 32-bit float.
minNormPosFloat32 = dwordToPyFloat(0x00000001)
# The smallest normalized negative 32-bit float.
minNormNegFloat32 = dwordToPyFloat(0xFF7FFFFF)
# The biggest normalized negative 32-bit float.
maxNormNegFloat32 = dwordToPyFloat(0x80000001)
# The biggest normalized positive 32-bit float.
maxNormPosFloat32 = dwordToPyFloat(0x7F7FFFFF)

# Positive infinity as a python float
posInfFloat = dwordToPyFloat(0x7F800000)
# Negative infinity as a python float
negInfFloat = dwordToPyFloat(0xFF800000)
# NaN as a python float
nanFloat = dwordToPyFloat(0xFFFFFFFF)

def isDenormalPyFloat(pyfl):
	return (pyfl > 0.0 and pyfl < minNormPosFloat32) or\
	       (pyfl < 0.0 and pyfl > maxNormNegFloat32)

def pyFloatEqual(pyfl0, pyfl1):
	return abs(pyfl0 - pyfl1) < 0.000001

def floatEqual(fl0, fl1):
	if not isinstance(fl0, float):
		fl0 = dwordToPyFloat(fl0)
	if not isinstance(fl1, float):
		fl1 = dwordToPyFloat(fl1)
	return pyFloatEqual(fl0, fl1)