#!/usr/bin/env python
# -*- coding: utf-8 -*-

""" pySim: various utilities
"""

#
# Copyright (C) 2009-2010  Sylvain Munaut <tnt@246tNt.com>
#
# 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, see <http://www.gnu.org/licenses/>.
#


def h2b(s):
	return ''.join([chr((int(x,16)<<4)+int(y,16)) for x,y in zip(s[0::2], s[1::2])])

def b2h(s):
	return ''.join(['%02x'%ord(x) for x in s])

def h2i(s):
	return [(int(x,16)<<4)+int(y,16) for x,y in zip(s[0::2], s[1::2])]

def i2h(s):
	return ''.join(['%02x'%(x) for x in s])

def h2s(s):
	return ''.join([chr((int(x,16)<<4)+int(y,16)) for x,y in zip(s[0::2], s[1::2]) if not (x == 'f' and y == 'f') ])

def s2h(s):
	return b2h(s)

def swap_nibbles(s):
	return ''.join([x+y for x,y in zip(s[1::2], s[0::2])])

def rpad(s, l, c='f'):
	return s + c * (l - len(s))

def lpad(s, l, c='f'):
	return c * (l - len(s)) + s

def half_round_up(n):
	return (n + 1)//2

# IMSI encoded format:
# For IMSI 0123456789ABCDE:
#
# |     byte 1      | 2 upper | 2 lower  | 3 upper | 3 lower | ... | 9 upper | 9 lower |
# | length in bytes |    0    | odd/even |    2    |    1    | ... |    E    |    D    |
#
# If the IMSI is less than 15 characters, it should be padded with 'f' from the end.
#
# The length is the total number of bytes used to encoded the IMSI. This includes the odd/even
# parity bit. E.g. an IMSI of length 14 is 8 bytes long, not 7, as it uses bytes 2 to 9 to
# encode itself.
#
# Because of this, an odd length IMSI fits exactly into len(imsi) + 1 // 2 bytes, whereas an
# even length IMSI only uses half of the last byte.

def enc_imsi(imsi):
	"""Converts a string imsi into the value of the EF"""
	l = half_round_up(len(imsi) + 1)	# Required bytes - include space for odd/even indicator
	oe = len(imsi) & 1			# Odd (1) / Even (0)
	ei = '%02x' % l + swap_nibbles('%01x%s' % ((oe<<3)|1, rpad(imsi, 15)))
	return ei

def dec_imsi(ef):
	"""Converts an EF value to the imsi string representation"""
	if len(ef) < 4:
		return None
	l = int(ef[0:2], 16) * 2		# Length of the IMSI string
	l = l - 1						# Encoded length byte includes oe nibble
	swapped = swap_nibbles(ef[2:]).rstrip('f')
	oe = (int(swapped[0])>>3) & 1	# Odd (1) / Even (0)
	if not oe:
		# if even, only half of last byte was used
		l = l-1
	if l != len(swapped) - 1:
		return None
	imsi = swapped[1:]
	return imsi

def dec_iccid(ef):
	return swap_nibbles(ef).strip('f')

def enc_iccid(iccid):
	return swap_nibbles(rpad(iccid, 20))

def enc_plmn(mcc, mnc):
	"""Converts integer MCC/MNC into 3 bytes for EF"""
	return swap_nibbles(lpad('%d' % int(mcc), 3) + lpad('%d' % int(mnc), 3))

def dec_spn(ef):
	byte1 = int(ef[0:2])
	hplmn_disp = (byte1&0x01 == 0x01)
	oplmn_disp = (byte1&0x02 == 0x02)
	name = h2s(ef[2:])
	return (name, hplmn_disp, oplmn_disp)

def enc_spn(name, hplmn_disp=False, oplmn_disp=False):
	byte1 = 0x00
	if hplmn_disp: byte1 = byte1|0x01
	if oplmn_disp: byte1 = byte1|0x02
	return i2h([byte1])+s2h(name)

def hexstr_to_fivebytearr(s):
	return [s[i:i+10] for i in range(0, len(s), 10) ]

# Accepts hex string representing three bytes
def dec_mcc_from_plmn(plmn):
	ia = h2i(plmn)
	digit1 = ia[0] & 0x0F		# 1st byte, LSB
	digit2 = (ia[0] & 0xF0) >> 4	# 1st byte, MSB
	digit3 = ia[1] & 0x0F		# 2nd byte, LSB
	if digit3 == 0xF and digit2 == 0xF and digit1 == 0xF:
		return 0xFFF # 4095
	return derive_mcc(digit1, digit2, digit3)

def dec_mnc_from_plmn(plmn):
	ia = h2i(plmn)
	digit1 = ia[2] & 0x0F		# 3rd byte, LSB
	digit2 = (ia[2] & 0xF0) >> 4	# 3rd byte, MSB
	digit3 = (ia[1] & 0xF0) >> 4	# 2nd byte, MSB
	if digit3 == 0xF and digit2 == 0xF and digit1 == 0xF:
		return 0xFFF # 4095
	return derive_mnc(digit1, digit2, digit3)

def dec_act(twohexbytes):
	act_list = [
		{'bit': 15, 'name': "UTRAN"},
		{'bit': 14, 'name': "E-UTRAN"},
		{'bit':  7, 'name': "GSM"},
		{'bit':  6, 'name': "GSM COMPACT"},
		{'bit':  5, 'name': "cdma2000 HRPD"},
		{'bit':  4, 'name': "cdma2000 1xRTT"},
	]
	ia = h2i(twohexbytes)
	u16t = (ia[0] << 8)|ia[1]
	sel = []
	for a in act_list:
		if u16t & (1 << a['bit']):
			sel.append(a['name'])
	return sel

def dec_xplmn_w_act(fivehexbytes):
	res = {'mcc': 0, 'mnc': 0, 'act': []}
	plmn_chars = 6
	act_chars = 4
	plmn_str = fivehexbytes[:plmn_chars]				# first three bytes (six ascii hex chars)
	act_str = fivehexbytes[plmn_chars:plmn_chars + act_chars]	# two bytes after first three bytes
	res['mcc'] = dec_mcc_from_plmn(plmn_str)
	res['mnc'] = dec_mnc_from_plmn(plmn_str)
	res['act'] = dec_act(act_str)
	return res

def format_xplmn_w_act(hexstr):
	s = ""
	for rec_data in hexstr_to_fivebytearr(hexstr):
		rec_info = dec_xplmn_w_act(rec_data)
		if rec_info['mcc'] == 0xFFF and rec_info['mnc'] == 0xFFF:
			rec_str = "unused"
		else:
			rec_str = "MCC: %03d MNC: %03d AcT: %s" % (rec_info['mcc'], rec_info['mnc'], ", ".join(rec_info['act']))
		s += "\t%s # %s\n" % (rec_data, rec_str)
	return s

def derive_milenage_opc(ki_hex, op_hex):
	"""
	Run the milenage algorithm to calculate OPC from Ki and OP
	"""
	from Crypto.Cipher import AES
	from Crypto.Util.strxor import strxor
	from pySim.utils import b2h

	# We pass in hex string and now need to work on bytes
	aes = AES.new(h2b(ki_hex))
	opc_bytes = aes.encrypt(h2b(op_hex))
	return b2h(strxor(opc_bytes, h2b(op_hex)))

def calculate_luhn(cc):
	"""
	Calculate Luhn checksum used in e.g. ICCID and IMEI
	"""
	num = map(int, str(cc))
	check_digit = 10 - sum(num[-2::-2] + [sum(divmod(d * 2, 10)) for d in num[::-2]]) % 10
	return 0 if check_digit == 10 else check_digit

def mcc_from_imsi(imsi):
	"""
	Derive the MCC (Mobile Country Code) from the first three digits of an IMSI
	"""
	if imsi == None:
		return None

	if len(imsi) > 3:
		return imsi[:3]
	else:
		return None

def mnc_from_imsi(imsi, long=False):
	"""
	Derive the MNC (Mobile Country Code) from the 4th to 6th digit of an IMSI
	"""
	if imsi == None:
		return None

	if len(imsi) > 3:
		if long:
			return imsi[3:6]
		else:
			return imsi[3:5]
	else:
		return None

def derive_mcc(digit1, digit2, digit3):
	"""
	Derive decimal representation of the MCC (Mobile Country Code)
	from three given digits.
	"""

	mcc = 0

	if digit1 != 0x0f:
		mcc += digit1 * 100
	if digit2 != 0x0f:
		mcc += digit2 * 10
	if digit3 != 0x0f:
		mcc += digit3

	return mcc

def derive_mnc(digit1, digit2, digit3=0x0f):
	"""
	Derive decimal representation of the MNC (Mobile Network Code)
	from two or (optionally) three given digits.
	"""

	mnc = 0

	# 3-rd digit is optional for the MNC. If present
	# the algorythm is the same as for the MCC.
	if digit3 != 0x0f:
		return derive_mcc(digit1, digit2, digit3)

	if digit1 != 0x0f:
		mnc += digit1 * 10
	if digit2 != 0x0f:
		mnc += digit2

	return mnc

def dec_msisdn(ef_msisdn):
	"""
	Decode MSISDN from EF.MSISDN or EF.ADN (same structure).
	See 3GPP TS 31.102, section 4.2.26 and 4.4.2.3.
	"""

	# Convert from str to (kind of) 'bytes'
	ef_msisdn = h2b(ef_msisdn)

	# Make sure mandatory fields are present
	if len(ef_msisdn) < 14:
		raise ValueError("EF.MSISDN is too short")

	# Skip optional Alpha Identifier
	xlen = len(ef_msisdn) - 14
	msisdn_lhv = ef_msisdn[xlen:]

	# Parse the length (in bytes) of the BCD encoded number
	bcd_len = ord(msisdn_lhv[0])
	# BCD length = length of dial num (max. 10 bytes) + 1 byte ToN and NPI
	if bcd_len == 0xff:
		return None
	elif bcd_len > 11 or bcd_len < 1:
		raise ValueError("Length of MSISDN (%d bytes) is out of range" % bcd_len)

	# Parse ToN / NPI
	ton = (ord(msisdn_lhv[1]) >> 4) & 0x07
	npi = ord(msisdn_lhv[1]) & 0x0f
	bcd_len -= 1

	# No MSISDN?
	if not bcd_len:
		return (npi, ton, None)

	msisdn = swap_nibbles(b2h(msisdn_lhv[2:][:bcd_len])).rstrip('f')
	# International number 10.5.118/3GPP TS 24.008
	if (ton & 0x01) == 0x01:
		msisdn = '+' + msisdn

	return (npi, ton, msisdn)

def enc_msisdn(msisdn, npi=0x01, ton=0x03):
	"""
	Encode MSISDN as LHV so it can be stored to EF.MSISDN.
	See 3GPP TS 31.102, section 4.2.26 and 4.4.2.3.

	Default NPI / ToN values:
	  - NPI: ISDN / telephony numbering plan (E.164 / E.163),
	  - ToN: network specific or international number (if starts with '+').
	"""

	# Leading '+' indicates International Number
	if msisdn[0] == '+':
		msisdn = msisdn[1:]
		ton = 0x01

	# Append 'f' padding if number of digits is odd
	if len(msisdn) % 2 > 0:
		msisdn += 'f'

	# BCD length also includes NPI/ToN header
	bcd_len = len(msisdn) // 2 + 1
	npi_ton = (npi & 0x0f) | ((ton & 0x07) << 4) | 0x80
	bcd = rpad(swap_nibbles(msisdn), 10 * 2) # pad to 10 octets

	return ('%02x' % bcd_len) + ('%02x' % npi_ton) + bcd