#!/usr/bin/python
#-*- coding: utf-8 -*-
# ---------------------------------------------------------------------------
# This file is a plugin for Anki flashcard application http://ichi2.net/anki/
# ---------------------------------------------------------------------------
# File:        passwords.py
# Description: This plugin uses PyMe and hashlib to attempt to securely allow
#              you to learn your passwords using Anki. The plaintext is stored
#              GPG encrypted so that it cannot be accessed. Your guesses are
#              checked against the SHA1 sum, and if you get it wrong you get
#              the option to decrypt and display the real password.
#
#              You can add passwords using a menu option in the Tools menu.
#
#              Note that I neither know Python, PyMe, anki /nor/ Hashlib, so
#              almost certainly something I've done here is stupid. The code
#              is basically based on the encrypt-to-all PyMe example with the
#              Anki stuff taken from the Go Problem, yesno and two step answer
#              plugins. Feel free to fix it and mail me the result. I certainly
#              won't be offended if you tell me my code is awful!
#
#              You will want to alter the constants at the start - at the least
#              because you don't want to encrypt your passwords to be read only
#              by me.
#
# Author:      David Buckley <isreal-anki-passwords@bucko.me.uk>
# Version:     0.01 (2009-04-28)
# License:     GNU GPL, version 3 or later; http://www.gnu.org/copyleft/gpl.html
# ---------------------------------------------------------------------------
# Changelog:
# ---- 0.02 -- 2009-04-28 -- David Buckley ----
#   fixed bug which meant password entries were corrupted on edit
# ---- 0.01 -- 2009-04-28 -- David Buckley ----
#   initial release
# ---------------------------------------------------------------------------

from PyQt4.QtCore import *
from PyQt4.QtGui import *
from ankiqt import mw
from anki.cards import Card
from anki.models import Model, FieldModel, CardModel
from anki.errors import FactInvalidError
from anki.hooks import wrap
from ankiqt.ui import view
from ankiqt.ui import main
from pyme import core
from pyme.core import Data, Context
from pyme.constants import validity
from pyme.errors import GPGMEError
import re
import hashlib

""" You may wish to change these. """
MODEL="Password Model"
SHOW_PASS_KEY=Qt.Key_S
GPG_USER_NAME="David Buckley"
SALT=u'My Anki Password salt'

""" This routine is called after showAnswerButton, and fixes the edit box to
    hide typed text. """
def afterShowAnswerButton(self):
	if self.currentCard.fact.model.name == MODEL:
		self.typeAnswerField.setEchoMode(QLineEdit.Password)
		self.typeAnswerField.setText("")
	else:
		self.typeAnswerField.setEchoMode(QLineEdit.Normal)

""" This routine is called instead of drawAnswer, and removes the ugly SHA1
    sum, replacing it with a status message. """
def aroundDrawAnswer(self, _old=''):
	if self.main.currentCard.fact.model.name == MODEL:
		sha1 = self.main.currentCard.fact['SHA1']
		d = hashlib.new('sha1')
		salted = SALT + unicode(self.main.typeAnswerField.text())
		d.update(salted.encode('utf-8').encode('base64'))

		if (d.hexdigest() == sha1):
			self.write(self.center('<span id=answer />' + self.mungeQA(self.main.deck, "Correct!")))
		else:
			self.write(self.center('<span id=answer />' + self.mungeQA(self.main.deck, "Wrong! Press S to decrypt and show password.")))
	else:
		_old(self)

""" Ask for a GPG password using a QInputDialog. """
def passCallback(hint='', desc='', prev_bad='', hook=''):
	extra = ''
	if prev_bad:
		extra = "\nYou got it wrong; try again."
	passphrase = str(QInputDialog.getText(mw, "GPG Passphrase", "I need your passphrase.\nKey: " + desc + "\nHint: " + hint + extra, QLineEdit.Password)[0])
	return passphrase

""" Steal presses of the SHOW_PASS_KEY to make them show the password. """
def aroundKeyPressEvent(self, evt, _old=''):
	if self.state == "showAnswer":
		key = unicode(evt.text())
		if evt.key() == SHOW_PASS_KEY:
			if self.currentCard.fact.model.name == MODEL:
				mf = self.mainWin.mainText.page().mainFrame()

				""" Set up the PyMe stuff """
				c = Context();
				c.set_passphrase_cb(passCallback)
				c.set_armor(1);
				cipher = Data(re.sub("<br[^>]*>","\n",self.currentCard.fact['GPG'].encode('ascii')))
				cipher.seek(0,0)

				""" Try to decrypt the password """
				try:
					plain = Data();
					c.op_decrypt(cipher, plain);
					plain.seek(0,0);
					QMessageBox.information(mw, "Password", "Your password is %s" % unicode(plain.read(), 'utf-8'))
				except GPGMEError, e:
					QMessageBox.information(mw, "Error", "Could not decrypt your password.\nError: " + str(e))
					

				evt.accept()
				return
	
	_old(self, evt)

""" Display a sequence of dialog boxes then add a new entry to the deck """
def addPassword():
	ret = QInputDialog.getText(mw, "Description", "Enter a description for the password")
	if ret[1]:
		desc = unicode(ret[0])
	else:
		return

	ret = QInputDialog.getText(mw, "Password", "Enter the password", QLineEdit.Password)
	if ret[1]:
		pass1 = unicode(ret[0])
	else:
		return

	ret = QInputDialog.getText(mw, "Confirm", "Confirm the password", QLineEdit.Password)
	if ret[1]:
		pass2 = unicode(ret[0])
	else:
		return

	if pass1 != pass2:
		QMessageBox.information(mw, "Mismatch", "Your passwords didn't match")
		return

	""" Model's not there? Fix it before we get into worse trouble. """
	if not [m for m in mw.deck.models if m.name == MODEL]:
		m = Model(unicode(MODEL))
		m.addFieldModel(FieldModel(u'Description', True, True))
		m.addFieldModel(FieldModel(u'SHA1', True, True))
		m.addFieldModel(FieldModel(u'GPG', True, True))
		cm=CardModel(u'Password',u'%(Description)s',u'%(SHA1)s')
		cm.typeAnswer = u'SHA1'
		m.addCardModel(cm)
		mw.deck.addModel(m)

	""" Attempt to add the card. """
	try:
		fact = mw.deck.newFact()
		"TODO Is this a hack?"
		for m in mw.deck.models:
			if m.name == 'Password Model':
				fact.model = m

		fact['Description'] = desc

		""" hashlib stuff for SHA1 hashing """
		sha1 = hashlib.new('sha1')
		salted = SALT + pass1
		sha1.update(salted.encode('utf-8').encode('base64'))
		fact['SHA1'] = unicode(sha1.hexdigest())

		""" PyMe setup """
		c = Context();
		c.set_armor(1);
		c.op_keylist_start(GPG_USER_NAME, 0)
		key = c.op_keylist_next()

		if not key:
			QMessageBox.information(mw, "Error", "Could not find your key. Check you've set it up in the plugin file.")
			return

		print "Encrypting with key: " + key.uids[0].uid

		""" Do the encryption, or try to """
		plain = Data(pass1.encode('utf-8'))
		cipher = Data()
		try:
			c.op_encrypt([key], 1, plain, cipher)
			cipher.seek(0,0)
			fact['GPG'] = unicode(re.sub("\n","<br>",cipher.read()), 'ascii')
			mw.deck.addFact(fact)
		except GPGMEError, e:
			QMessageBox.information(mw, "Error", "Could not encrypt your password.\nError: " + str(e))

	except FactInvalidError:
		pass


""" Set up all the stuff we need initialising. """
def initPlugin():
	main.AnkiQt.showAnswerButton = wrap(main.AnkiQt.showAnswerButton, afterShowAnswerButton, "after")
	main.AnkiQt.keyPressEvent = wrap(main.AnkiQt.keyPressEvent, aroundKeyPressEvent, "around")
	view.View.drawAnswer = wrap(view.View.drawAnswer, aroundDrawAnswer, "around")
	menu = QAction(mw)
	menu.setText("Add Password")
	mw.connect(menu, SIGNAL("triggered()"), addPassword)
	mw.mainWin.menuTools.addSeparator()
	mw.mainWin.menuTools.addAction(menu)

""" Ensure we can be set up. """
mw.addHook("init", initPlugin)