text: #!/usr/bin/env python
  #
  # Electrum - lightweight Bitcoin client
  # Copyright (C) 2013 ecdsa@github
  #
  # Permission is hereby granted, free of charge, to any person
  # obtaining a copy of this software and associated documentation files
  # (the "Software"), to deal in the Software without restriction,
  # including without limitation the rights to use, copy, modify, merge,
  # publish, distribute, sublicense, and/or sell copies of the Software,
  # and to permit persons to whom the Software is furnished to do so,
  # subject to the following conditions:
  #
  # The above copyright notice and this permission notice shall be
  # included in all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  # EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  # NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  # BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  # ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  # SOFTWARE.
  
  from PyQt5.QtCore import Qt
  from PyQt5.QtGui import *
  from PyQt5.QtWidgets import *
  from electrum.i18n import _
  from .util import *
  import re
  import math
  
  from electrum.plugins import run_hook
  
  def check_password_strength(password):
  
      '''
      Check the strength of the password entered by the user and return back the same
      :param password: password entered by user in New Password
      :return: password strength Weak or Medium or Strong
      '''
      password = password
      n = math.log(len(set(password)))
      num = re.search("[0-9]", password) is not None and re.match("^[0-9]*$", password) is None
      caps = password != password.upper() and password != password.lower()
      extra = re.match("^[a-zA-Z0-9]*$", password) is None
      score = len(password)*( n + caps + num + extra)/20
      password_strength = {0:"Weak",1:"Medium",2:"Strong",3:"Very Strong"}
      return password_strength[min(3, int(score))]
  
  
  PW_NEW, PW_CHANGE, PW_PASSPHRASE = range(0, 3)
  
  
  class PasswordLayout(object):
  
      titles = [_("Enter Password"), _("Change Password"), _("Enter Passphrase")]
  
      def __init__(self, wallet, msg, kind, OK_button, force_disable_encrypt_cb=False):
          self.wallet = wallet
  
          self.pw = QLineEdit()
          self.pw.setEchoMode(2)
          self.new_pw = QLineEdit()
          self.new_pw.setEchoMode(2)
          self.conf_pw = QLineEdit()
          self.conf_pw.setEchoMode(2)
          self.kind = kind
          self.OK_button = OK_button
  
          vbox = QVBoxLayout()
          label = QLabel(msg + "\n")
          label.setWordWrap(True)
  
          grid = QGridLayout()
          grid.setSpacing(8)
          grid.setColumnMinimumWidth(0, 150)
          grid.setColumnMinimumWidth(1, 100)
          grid.setColumnStretch(1,1)
  
          if kind == PW_PASSPHRASE:
              vbox.addWidget(label)
              msgs = [_('Passphrase:'), _('Confirm Passphrase:')]
          else:
              logo_grid = QGridLayout()
              logo_grid.setSpacing(8)
              logo_grid.setColumnMinimumWidth(0, 70)
              logo_grid.setColumnStretch(1,1)
  
              logo = QLabel()
              logo.setAlignment(Qt.AlignCenter)
  
              logo_grid.addWidget(logo,  0, 0)
              logo_grid.addWidget(label, 0, 1, 1, 2)
              vbox.addLayout(logo_grid)
  
              m1 = _('New Password:') if kind == PW_CHANGE else _('Password:')
              msgs = [m1, _('Confirm Password:')]
              if wallet and wallet.has_password():
                  grid.addWidget(QLabel(_('Current Password:')), 0, 0)
                  grid.addWidget(self.pw, 0, 1)
                  lockfile = ":icons/lock.png"
              else:
                  lockfile = ":icons/unlock.png"
              logo.setPixmap(QPixmap(lockfile).scaledToWidth(36, mode=Qt.SmoothTransformation))
  
          grid.addWidget(QLabel(msgs[0]), 1, 0)
          grid.addWidget(self.new_pw, 1, 1)
  
          grid.addWidget(QLabel(msgs[1]), 2, 0)
          grid.addWidget(self.conf_pw, 2, 1)
          vbox.addLayout(grid)
  
          # Password Strength Label
          if kind != PW_PASSPHRASE:
              self.pw_strength = QLabel()
              grid.addWidget(self.pw_strength, 3, 0, 1, 2)
              self.new_pw.textChanged.connect(self.pw_changed)
  
          self.encrypt_cb = QCheckBox(_('Encrypt wallet file'))
          self.encrypt_cb.setEnabled(False)
          grid.addWidget(self.encrypt_cb, 4, 0, 1, 2)
          self.encrypt_cb.setVisible(kind != PW_PASSPHRASE)
  
          def enable_OK():
              ok = self.new_pw.text() == self.conf_pw.text()
              OK_button.setEnabled(ok)
              self.encrypt_cb.setEnabled(ok and bool(self.new_pw.text())
                                         and not force_disable_encrypt_cb)
          self.new_pw.textChanged.connect(enable_OK)
          self.conf_pw.textChanged.connect(enable_OK)
  
          self.vbox = vbox
  
      def title(self):
          return self.titles[self.kind]
  
      def layout(self):
          return self.vbox
  
      def pw_changed(self):
          password = self.new_pw.text()
          if password:
              colors = {"Weak":"Red", "Medium":"Blue", "Strong":"Green",
                        "Very Strong":"Green"}
              strength = check_password_strength(password)
              label = (_("Password Strength") + ": " + "<font color="
                       + colors[strength] + ">" + strength + "</font>")
          else:
              label = ""
          self.pw_strength.setText(label)
  
      def old_password(self):
          if self.kind == PW_CHANGE:
              return self.pw.text() or None
          return None
  
      def new_password(self):
          pw = self.new_pw.text()
          # Empty passphrases are fine and returned empty.
          if pw == "" and self.kind != PW_PASSPHRASE:
              pw = None
          return pw
  
  
  class PasswordLayoutForHW(object):
  
      def __init__(self, wallet, msg, kind, OK_button):
          self.wallet = wallet
  
          self.kind = kind
          self.OK_button = OK_button
  
          vbox = QVBoxLayout()
          label = QLabel(msg + "\n")
          label.setWordWrap(True)
  
          grid = QGridLayout()
          grid.setSpacing(8)
          grid.setColumnMinimumWidth(0, 150)
          grid.setColumnMinimumWidth(1, 100)
          grid.setColumnStretch(1,1)
  
          logo_grid = QGridLayout()
          logo_grid.setSpacing(8)
          logo_grid.setColumnMinimumWidth(0, 70)
          logo_grid.setColumnStretch(1,1)
  
          logo = QLabel()
          logo.setAlignment(Qt.AlignCenter)
  
          logo_grid.addWidget(logo,  0, 0)
          logo_grid.addWidget(label, 0, 1, 1, 2)
          vbox.addLayout(logo_grid)
  
          if wallet and wallet.has_storage_encryption():
              lockfile = ":icons/lock.png"
          else:
              lockfile = ":icons/unlock.png"
          logo.setPixmap(QPixmap(lockfile).scaledToWidth(36, mode=Qt.SmoothTransformation))
  
          vbox.addLayout(grid)
  
          self.encrypt_cb = QCheckBox(_('Encrypt wallet file'))
          grid.addWidget(self.encrypt_cb, 1, 0, 1, 2)
  
          self.vbox = vbox
  
      def title(self):
          return _("Toggle Encryption")
  
      def layout(self):
          return self.vbox
  
  
  class ChangePasswordDialogBase(WindowModalDialog):
  
      def __init__(self, parent, wallet):
          WindowModalDialog.__init__(self, parent)
          is_encrypted = wallet.has_storage_encryption()
          OK_button = OkButton(self)
  
          self.create_password_layout(wallet, is_encrypted, OK_button)
  
          self.setWindowTitle(self.playout.title())
          vbox = QVBoxLayout(self)
          vbox.addLayout(self.playout.layout())
          vbox.addStretch(1)
          vbox.addLayout(Buttons(CancelButton(self), OK_button))
          self.playout.encrypt_cb.setChecked(is_encrypted)
  
      def create_password_layout(self, wallet, is_encrypted, OK_button):
          raise NotImplementedError()
  
  
  class ChangePasswordDialogForSW(ChangePasswordDialogBase):
  
      def __init__(self, parent, wallet):
          ChangePasswordDialogBase.__init__(self, parent, wallet)
          if not wallet.has_password():
              self.playout.encrypt_cb.setChecked(True)
  
      def create_password_layout(self, wallet, is_encrypted, OK_button):
          if not wallet.has_password():
              msg = _('Your wallet is not protected.')
              msg += ' ' + _('Use this dialog to add a password to your wallet.')
          else:
              if not is_encrypted:
                  msg = _('Your bitcoins are password protected. However, your wallet file is not encrypted.')
              else:
                  msg = _('Your wallet is password protected and encrypted.')
              msg += ' ' + _('Use this dialog to change your password.')
          self.playout = PasswordLayout(
              wallet, msg, PW_CHANGE, OK_button,
              force_disable_encrypt_cb=not wallet.can_have_keystore_encryption())
  
      def run(self):
          if not self.exec_():
              return False, None, None, None
          return True, self.playout.old_password(), self.playout.new_password(), self.playout.encrypt_cb.isChecked()
  
  
  class ChangePasswordDialogForHW(ChangePasswordDialogBase):
  
      def __init__(self, parent, wallet):
          ChangePasswordDialogBase.__init__(self, parent, wallet)
  
      def create_password_layout(self, wallet, is_encrypted, OK_button):
          if not is_encrypted:
              msg = _('Your wallet file is NOT encrypted.')
          else:
              msg = _('Your wallet file is encrypted.')
          msg += '\n' + _('Note: If you enable this setting, you will need your hardware device to open your wallet.')
          msg += '\n' + _('Use this dialog to toggle encryption.')
          self.playout = PasswordLayoutForHW(wallet, msg, PW_CHANGE, OK_button)
  
      def run(self):
          if not self.exec_():
              return False, None
          return True, self.playout.encrypt_cb.isChecked()
  
  
  class PasswordDialog(WindowModalDialog):
  
      def __init__(self, parent=None, msg=None):
          msg = msg or _('Please enter your password')
          WindowModalDialog.__init__(self, parent, _("Enter Password"))
          self.pw = pw = QLineEdit()
          pw.setEchoMode(2)
          vbox = QVBoxLayout()
          vbox.addWidget(QLabel(msg))
          grid = QGridLayout()
          grid.setSpacing(8)
          grid.addWidget(QLabel(_('Password')), 1, 0)
          grid.addWidget(pw, 1, 1)
          vbox.addLayout(grid)
          vbox.addLayout(Buttons(CancelButton(self), OkButton(self)))
          self.setLayout(vbox)
          run_hook('password_dialog', pw, grid, 1)
  
      def run(self):
          if not self.exec_():
              return
          return self.pw.text()
  