text: #!/usr/bin/env python
  #
  # Electrum - Lightweight Bitcoin Client
  # Copyright (C) 2015 Thomas Voegtlin
  #
  # 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.
  import random
  import time
  import threading
  import base64
  from functools import partial
  import traceback
  import sys
  
  import smtplib
  import imaplib
  import email
  from email.mime.multipart import MIMEMultipart
  from email.mime.base import MIMEBase
  from email.encoders import encode_base64
  
  from PyQt5.QtCore import QObject, pyqtSignal, QThread
  from PyQt5.QtWidgets import (QVBoxLayout, QLabel, QGridLayout, QLineEdit,
                               QInputDialog)
  
  from electrum_sum.gui.qt.util import (EnterButton, Buttons, CloseButton, OkButton,
                                        WindowModalDialog, get_parent_main_window)
  
  from electrum_sum.plugin import BasePlugin, hook
  from electrum_sum.paymentrequest import PaymentRequest
  from electrum_sum.i18n import _
  from electrum_sum.logging import Logger
  
  
  class Processor(threading.Thread, Logger):
      polling_interval = 5*60
  
      def __init__(self, imap_server, username, password, callback):
          threading.Thread.__init__(self)
          Logger.__init__(self)
          self.daemon = True
          self.username = username
          self.password = password
          self.imap_server = imap_server
          self.on_receive = callback
          self.M = None
          self.reset_connect_wait()
  
      def reset_connect_wait(self):
          self.connect_wait = 100  # ms, between failed connection attempts
  
      def poll(self):
          try:
              self.M.select()
          except:
              return
          typ, data = self.M.search(None, 'ALL')
          for num in str(data[0], 'utf8').split():
              typ, msg_data = self.M.fetch(num, '(RFC822)')
              msg = email.message_from_bytes(msg_data[0][1])
              p = msg.get_payload()
              if not msg.is_multipart():
                  p = [p]
                  continue
              for item in p:
                  if item.get_content_type() == "application/sumcoin-paymentrequest":
                      pr_str = item.get_payload()
                      pr_str = base64.b64decode(pr_str)
                      self.on_receive(pr_str)
  
      def run(self):
          while True:
              try:
                  self.M = imaplib.IMAP4_SSL(self.imap_server)
                  self.M.login(self.username, self.password)
              except BaseException as e:
                  self.logger.info(f'connecting failed: {repr(e)}')
                  self.connect_wait *= 2
              else:
                  self.reset_connect_wait()
              # Reconnect when host changes
              while self.M and self.M.host == self.imap_server:
                  try:
                      self.poll()
                  except BaseException as e:
                      self.logger.info(f'polling failed: {repr(e)}')
                      break
                  time.sleep(self.polling_interval)
              time.sleep(random.randint(0, self.connect_wait))
  
      def send(self, recipient, message, payment_request):
          msg = MIMEMultipart()
          msg['Subject'] = message
          msg['To'] = recipient
          msg['From'] = self.username
          part = MIMEBase('application', "sumcoin-paymentrequest")
          part.set_payload(payment_request)
          encode_base64(part)
          part.add_header('Content-Disposition', 'attachment; filename="payreq.sum"')
          msg.attach(part)
          try:
              s = smtplib.SMTP_SSL(self.imap_server, timeout=2)
              s.login(self.username, self.password)
              s.sendmail(self.username, [recipient], msg.as_string())
              s.quit()
          except BaseException as e:
              self.logger.info(e)
  
  
  class QEmailSignalObject(QObject):
      email_new_invoice_signal = pyqtSignal()
  
  
  class Plugin(BasePlugin):
  
      def fullname(self):
          return 'Email'
  
      def description(self):
          return _("Send and receive payment requests via email")
  
      def is_available(self):
          return True
  
      def __init__(self, parent, config, name):
          BasePlugin.__init__(self, parent, config, name)
          self.imap_server = self.config.get('email_server', '')
          self.username = self.config.get('email_username', '')
          self.password = self.config.get('email_password', '')
          if self.imap_server and self.username and self.password:
              self.processor = Processor(self.imap_server, self.username, self.password, self.on_receive)
              self.processor.start()
          self.obj = QEmailSignalObject()
          self.obj.email_new_invoice_signal.connect(self.new_invoice)
          self.wallets = set()
  
      def on_receive(self, pr_str):
          self.logger.info('received payment request')
          self.pr = PaymentRequest(pr_str)
          self.obj.email_new_invoice_signal.emit()
  
      @hook
      def load_wallet(self, wallet, main_window):
          self.wallets |= {wallet}
  
      @hook
      def close_wallet(self, wallet):
          self.wallets -= {wallet}
  
      def new_invoice(self):
          for wallet in self.wallets:
              wallet.invoices.add(self.pr)
          #main_window.invoice_list.update()
  
      @hook
      def receive_list_menu(self, menu, addr):
          window = get_parent_main_window(menu)
          menu.addAction(_("Send via e-mail"), lambda: self.send(window, addr))
  
      def send(self, window, addr):
          from electrum_sum import paymentrequest
          r = window.wallet.receive_requests.get(addr)
          message = r.get('memo', '')
          if r.get('signature'):
              pr = paymentrequest.serialize_request(r)
          else:
              pr = paymentrequest.make_request(self.config, r)
          if not pr:
              return
          recipient, ok = QInputDialog.getText(window, 'Send request', 'Email invoice to:')
          if not ok:
              return
          recipient = str(recipient)
          payload = pr.SerializeToString()
          self.logger.info(f'sending mail to {recipient}')
          try:
              # FIXME this runs in the GUI thread and blocks it...
              self.processor.send(recipient, message, payload)
          except BaseException as e:
              self.logger.exception('')
              window.show_message(str(e))
          else:
              window.show_message(_('Request sent.'))
  
      def requires_settings(self):
          return True
  
      def settings_widget(self, window):
          return EnterButton(_('Settings'), partial(self.settings_dialog, window))
  
      def settings_dialog(self, window):
          d = WindowModalDialog(window, _("Email settings"))
          d.setMinimumSize(500, 200)
  
          vbox = QVBoxLayout(d)
          vbox.addWidget(QLabel(_('Server hosting your email account')))
          grid = QGridLayout()
          vbox.addLayout(grid)
          grid.addWidget(QLabel('Server (IMAP)'), 0, 0)
          server_e = QLineEdit()
          server_e.setText(self.imap_server)
          grid.addWidget(server_e, 0, 1)
  
          grid.addWidget(QLabel('Username'), 1, 0)
          username_e = QLineEdit()
          username_e.setText(self.username)
          grid.addWidget(username_e, 1, 1)
  
          grid.addWidget(QLabel('Password'), 2, 0)
          password_e = QLineEdit()
          password_e.setText(self.password)
          grid.addWidget(password_e, 2, 1)
  
          vbox.addStretch()
          vbox.addLayout(Buttons(CloseButton(d), OkButton(d)))
  
          if not d.exec_():
              return
  
          server = str(server_e.text())
          self.config.set_key('email_server', server)
          self.imap_server = server
  
          username = str(username_e.text())
          self.config.set_key('email_username', username)
          self.username = username
  
          password = str(password_e.text())
          self.config.set_key('email_password', password)
          self.password = password
  
          check_connection = CheckConnectionThread(server, username, password)
          check_connection.connection_error_signal.connect(lambda e: window.show_message(
              _("Unable to connect to mail server:\n {}").format(e) + "\n" +
              _("Please check your connection and credentials.")
          ))
          check_connection.start()
  
  
  class CheckConnectionThread(QThread):
      connection_error_signal = pyqtSignal(str)
  
      def __init__(self, server, username, password):
          super().__init__()
          self.server = server
          self.username = username
          self.password = password
  
      def run(self):
          try:
              conn = imaplib.IMAP4_SSL(self.server)
              conn.login(self.username, self.password)
          except BaseException as e:
              self.connection_error_signal.emit(str(e))
  