######################## BEGIN LICENSE BLOCK ########################
# The Original Code is Mozilla Communicator client code.
#
# The Initial Developer of the Original Code is
# Netscape Communications Corporation.
# Portions created by the Initial Developer are Copyright (C) 1998
# the Initial Developer. All Rights Reserved.
#
# Contributor(s):
#   Mark Pilgrim - port to Python
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# 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 St, Fifth Floor, Boston, MA
# 02110-1301  USA
######################### END LICENSE BLOCK #########################

import constants
from euctwfreq import EUCTWCharToFreqOrder, EUCTW_TABLE_SIZE, EUCTW_TYPICAL_DISTRIBUTION_RATIO
from euckrfreq import EUCKRCharToFreqOrder, EUCKR_TABLE_SIZE, EUCKR_TYPICAL_DISTRIBUTION_RATIO
from gb2312freq import GB2312CharToFreqOrder, GB2312_TABLE_SIZE, GB2312_TYPICAL_DISTRIBUTION_RATIO
from big5freq import Big5CharToFreqOrder, BIG5_TABLE_SIZE, BIG5_TYPICAL_DISTRIBUTION_RATIO
from jisfreq import JISCharToFreqOrder, JIS_TABLE_SIZE, JIS_TYPICAL_DISTRIBUTION_RATIO

ENOUGH_DATA_THRESHOLD = 1024
SURE_YES = 0.99
SURE_NO = 0.01

class CharDistributionAnalysis:
	def __init__(self):
		self._mCharToFreqOrder = None # Mapping table to get frequency order from char order (get from GetOrder())
		self._mTableSize = None # Size of above table
		self._mTypicalDistributionRatio = None # This is a constant value which varies from language to language, used in calculating confidence.  See http://www.mozilla.org/projects/intl/UniversalCharsetDetection.html for further detail.
		self.reset()

	def reset(self):
		"""reset analyser, clear any state"""
		self._mDone = constants.False # If this flag is set to constants.True, detection is done and conclusion has been made
		self._mTotalChars = 0 # Total characters encountered
		self._mFreqChars = 0 # The number of characters whose frequency order is less than 512

	def feed(self, aStr, aCharLen):
		"""feed a character with known length"""
		if aCharLen == 2:
			# we only care about 2-bytes character in our distribution analysis
			order = self.get_order(aStr)
		else:
			order = -1
		if order >= 0:
			self._mTotalChars += 1
			# order is valid
			if order < self._mTableSize:
				if 512 > self._mCharToFreqOrder[order]:
					self._mFreqChars += 1

	def get_confidence(self):
		"""return confidence based on existing data"""
		# if we didn't receive any character in our consideration range, return negative answer
		if self._mTotalChars <= 0:
			return SURE_NO

		if self._mTotalChars != self._mFreqChars:
			r = self._mFreqChars / ((self._mTotalChars - self._mFreqChars) * self._mTypicalDistributionRatio)
			if r < SURE_YES:
				return r

		# normalize confidence (we don't want to be 100% sure)
		return SURE_YES

	def got_enough_data(self):
		# It is not necessary to receive all data to draw conclusion. For charset detection,
		# certain amount of data is enough
		return self._mTotalChars > ENOUGH_DATA_THRESHOLD

	def get_order(self, aStr):
		# We do not handle characters based on the original encoding string, but
		# convert this encoding string to a number, here called order.
		# This allows multiple encodings of a language to share one frequency table.
		return -1

class EUCTWDistributionAnalysis(CharDistributionAnalysis):
	def __init__(self):
		CharDistributionAnalysis.__init__(self)
		self._mCharToFreqOrder = EUCTWCharToFreqOrder
		self._mTableSize = EUCTW_TABLE_SIZE
		self._mTypicalDistributionRatio = EUCTW_TYPICAL_DISTRIBUTION_RATIO

	def get_order(self, aStr):
		# for euc-TW encoding, we are interested
		#   first  byte range: 0xc4 -- 0xfe
		#   second byte range: 0xa1 -- 0xfe
		# no validation needed here. State machine has done that
		if aStr[0] >= '\xC4':
			return 94 * (ord(aStr[0]) - 0xC4) + ord(aStr[1]) - 0xA1
		else:
			return -1

class EUCKRDistributionAnalysis(CharDistributionAnalysis):
	def __init__(self):
		CharDistributionAnalysis.__init__(self)
		self._mCharToFreqOrder = EUCKRCharToFreqOrder
		self._mTableSize = EUCKR_TABLE_SIZE
		self._mTypicalDistributionRatio = EUCKR_TYPICAL_DISTRIBUTION_RATIO

	def get_order(self, aStr):
		# for euc-KR encoding, we are interested
		#   first  byte range: 0xb0 -- 0xfe
		#   second byte range: 0xa1 -- 0xfe
		# no validation needed here. State machine has done that
		if aStr[0] >= '\xB0':
			return 94 * (ord(aStr[0]) - 0xB0) + ord(aStr[1]) - 0xA1
		else:
			return -1;

class GB2312DistributionAnalysis(CharDistributionAnalysis):
	def __init__(self):
		CharDistributionAnalysis.__init__(self)
		self._mCharToFreqOrder = GB2312CharToFreqOrder
		self._mTableSize = GB2312_TABLE_SIZE
		self._mTypicalDistributionRatio = GB2312_TYPICAL_DISTRIBUTION_RATIO

	def get_order(self, aStr):
		# for GB2312 encoding, we are interested
		#  first  byte range: 0xb0 -- 0xfe
		#  second byte range: 0xa1 -- 0xfe
		# no validation needed here. State machine has done that
		if (aStr[0] >= '\xB0') and (aStr[1] >= '\xA1'):
			return 94 * (ord(aStr[0]) - 0xB0) + ord(aStr[1]) - 0xA1
		else:
			return -1;

class Big5DistributionAnalysis(CharDistributionAnalysis):
	def __init__(self):
		CharDistributionAnalysis.__init__(self)
		self._mCharToFreqOrder = Big5CharToFreqOrder
		self._mTableSize = BIG5_TABLE_SIZE
		self._mTypicalDistributionRatio = BIG5_TYPICAL_DISTRIBUTION_RATIO

	def get_order(self, aStr):
		# for big5 encoding, we are interested
		#   first  byte range: 0xa4 -- 0xfe
		#   second byte range: 0x40 -- 0x7e , 0xa1 -- 0xfe
		# no validation needed here. State machine has done that
		if aStr[0] >= '\xA4':
			if aStr[1] >= '\xA1':
				return 157 * (ord(aStr[0]) - 0xA4) + ord(aStr[1]) - 0xA1 + 63
			else:
				return 157 * (ord(aStr[0]) - 0xA4) + ord(aStr[1]) - 0x40
		else:
			return -1

class SJISDistributionAnalysis(CharDistributionAnalysis):
	def __init__(self):
		CharDistributionAnalysis.__init__(self)
		self._mCharToFreqOrder = JISCharToFreqOrder
		self._mTableSize = JIS_TABLE_SIZE
		self._mTypicalDistributionRatio = JIS_TYPICAL_DISTRIBUTION_RATIO

	def get_order(self, aStr):
		# for sjis encoding, we are interested
		#   first  byte range: 0x81 -- 0x9f , 0xe0 -- 0xfe
		#   second byte range: 0x40 -- 0x7e,  0x81 -- oxfe
		# no validation needed here. State machine has done that
		if (aStr[0] >= '\x81') and (aStr[0] <= '\x9F'):
			order = 188 * (ord(aStr[0]) - 0x81)
		elif (aStr[0] >= '\xE0') and (aStr[0] <= '\xEF'):
			order = 188 * (ord(aStr[0]) - 0xE0 + 31)
		else:
			return -1;
		order = order + ord(aStr[1]) - 0x40
		if aStr[1] > '\x7F':
			order =- 1
		return order

class EUCJPDistributionAnalysis(CharDistributionAnalysis):
	def __init__(self):
		CharDistributionAnalysis.__init__(self)
		self._mCharToFreqOrder = JISCharToFreqOrder
		self._mTableSize = JIS_TABLE_SIZE
		self._mTypicalDistributionRatio = JIS_TYPICAL_DISTRIBUTION_RATIO

	def get_order(self, aStr):
		# for euc-JP encoding, we are interested
		#   first  byte range: 0xa0 -- 0xfe
		#   second byte range: 0xa1 -- 0xfe
		# no validation needed here. State machine has done that
		if aStr[0] >= '\xA0':
			return 94 * (ord(aStr[0]) - 0xA1) + ord(aStr[1]) - 0xa1
		else:
			return -1