######################## BEGIN LICENSE BLOCK ########################
# The Original Code is mozilla.org 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, sys
from constants import eStart, eError, eItsMe
from charsetprober import CharSetProber
from codingstatemachine import CodingStateMachine
from mbcssm import UTF8SMModel

ONE_CHAR_PROB = 0.5

class UTF8Prober(CharSetProber):
	def __init__(self):
		CharSetProber.__init__(self)
		self._mCodingSM = CodingStateMachine(UTF8SMModel)
		self.reset()

	def reset(self):
		CharSetProber.reset(self)
		self._mCodingSM.reset()
		self._mNumOfMBChar = 0

	def get_charset_name(self):
		return "utf-8"

	def feed(self, aBuf):
		for c in aBuf:
			codingState = self._mCodingSM.next_state(c)
			if codingState == eError:
				self._mState = constants.eNotMe
				break
			elif codingState == eItsMe:
				self._mState = constants.eFoundIt
				break
			elif codingState == eStart:
				if self._mCodingSM.get_current_charlen() >= 2:
					self._mNumOfMBChar += 1

		if self.get_state() == constants.eDetecting:
			if self.get_confidence() > constants.SHORTCUT_THRESHOLD:
				self._mState = constants.eFoundIt

		return self.get_state()

	def get_confidence(self):
		unlike = 0.99
		if self._mNumOfMBChar < 6:
			for i in range(0, self._mNumOfMBChar):
				unlike = unlike * ONE_CHAR_PROB
			return 1.0 - unlike
		else:
			return unlike