######################## BEGIN LICENSE BLOCK ########################
# The Original Code is Mozilla Universal charset detector code.
#
# The Initial Developer of the Original Code is
# Netscape Communications Corporation.
# Portions created by the Initial Developer are Copyright (C) 2001
# the Initial Developer. All Rights Reserved.
#
# Contributor(s):
#   Mark Pilgrim - port to Python
#   Shy Shalom - original C code
#
# 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, sys
from charsetprober import CharSetProber

SAMPLE_SIZE = 64
SB_ENOUGH_REL_THRESHOLD = 1024
POSITIVE_SHORTCUT_THRESHOLD = 0.95
NEGATIVE_SHORTCUT_THRESHOLD = 0.05
SYMBOL_CAT_ORDER = 250
NUMBER_OF_SEQ_CAT = 4
POSITIVE_CAT = NUMBER_OF_SEQ_CAT - 1
#NEGATIVE_CAT = 0

class SingleByteCharSetProber(CharSetProber):
	def __init__(self, model, reversed=constants.False, nameProber=None):
		CharSetProber.__init__(self)
		self._mModel = model
		self._mReversed = reversed # TRUE if we need to reverse every pair in the model lookup
		self._mNameProber = nameProber # Optional auxiliary prober for name decision
		self.reset()

	def reset(self):
		CharSetProber.reset(self)
		self._mLastOrder = 255 # char order of last character
		self._mSeqCounters = [0] * NUMBER_OF_SEQ_CAT
		self._mTotalSeqs = 0
		self._mTotalChar = 0
		self._mFreqChar = 0 # characters that fall in our sampling range

	def get_charset_name(self):
		if self._mNameProber:
			return self._mNameProber.get_charset_name()
		else:
			return self._mModel['charsetName']

	def feed(self, aBuf):
		if not self._mModel['keepEnglishLetter']:
			aBuf = self.filter_without_english_letters(aBuf)
		aLen = len(aBuf)
		if not aLen:
			return self.get_state()
		for c in aBuf:
			order = self._mModel['charToOrderMap'][ord(c)]
			if order < SYMBOL_CAT_ORDER:
				self._mTotalChar += 1
			if order < SAMPLE_SIZE:
				self._mFreqChar += 1
				if self._mLastOrder < SAMPLE_SIZE:
					self._mTotalSeqs += 1
					if not self._mReversed:
						self._mSeqCounters[self._mModel['precedenceMatrix'][(self._mLastOrder * SAMPLE_SIZE) + order]] += 1
					else: # reverse the order of the letters in the lookup
						self._mSeqCounters[self._mModel['precedenceMatrix'][(order * SAMPLE_SIZE) + self._mLastOrder]] += 1
			self._mLastOrder = order

		if self.get_state() == constants.eDetecting:
			if self._mTotalSeqs > SB_ENOUGH_REL_THRESHOLD:
				cf = self.get_confidence()
				if cf > POSITIVE_SHORTCUT_THRESHOLD:
					if constants._debug:
						sys.stderr.write('%s confidence = %s, we have a winner\n' % (self._mModel['charsetName'], cf))
					self._mState = constants.eFoundIt
				elif cf < NEGATIVE_SHORTCUT_THRESHOLD:
					if constants._debug:
						sys.stderr.write('%s confidence = %s, below negative shortcut threshhold %s\n' % (self._mModel['charsetName'], cf, NEGATIVE_SHORTCUT_THRESHOLD))
					self._mState = constants.eNotMe

		return self.get_state()

	def get_confidence(self):
		r = 0.01
		if self._mTotalSeqs > 0:
#			print self._mSeqCounters[POSITIVE_CAT], self._mTotalSeqs, self._mModel['mTypicalPositiveRatio']
			r = (1.0 * self._mSeqCounters[POSITIVE_CAT]) / self._mTotalSeqs / self._mModel['mTypicalPositiveRatio']
#			print r, self._mFreqChar, self._mTotalChar
			r = r * self._mFreqChar / self._mTotalChar
			if r >= 1.0:
				r = 0.99
		return r
