Add mail backend for Exchange account (#636)

* Add mail backend for Exchange account

* Rename backend class, clean code

docs/conf.py

@@ -54,6 +54,14 @@ MOCK_MODULES = [
     "khal",
     "khal.cli",
     "khal.settings",
+    "requests.auth",
+    "requests.sessions",
+    "requests.packages",
+    "requests.packages.urllib3",
+    "requests.packages.urllib3.response",
+    "lxml.etree",
+    "requests.adapters",
+    "exchangelib"
 ]
 
 for mod_name in MOCK_MODULES:

i3pystatus/mail/ews.py

@@ -0,0 +1,71 @@
+import exchangelib
+import contextlib
+import time
+
+from i3pystatus.mail import Backend
+
+
+class ExchangeMailAccount(Backend):
+    """
+    Checks for mail on an Exchange account.
+
+    Requires the python exchangelib library - https://github.com/ecederstrand/exchangelib.
+    """
+
+    settings = (
+        ("host", 'The url to connect to. If unset, autodiscover is tried with the email address domain. If set, autodiscover is disabled.'),
+        "username", "password", "email_address",
+        ('keyring_backend', 'alternative keyring backend for retrieving credentials'),
+    )
+    required = ("username", "password", "email_address")
+    keyring_backend = None
+
+    host = None
+
+    account = None
+    last = 0
+
+    @contextlib.contextmanager
+    def ensure_connection(self):
+        try:
+            if not self.account:
+                credentials = exchangelib.ServiceAccount(
+                    username=self.username,
+                    password=self.password)
+                if self.host:
+                    config = exchangelib.Configuration(
+                        server=self.host,
+                        credentials=credentials)
+                    self.account = exchangelib.Account(
+                        primary_smtp_address=self.email_address,
+                        config=config,
+                        autodiscover=False,
+                        access_type=exchangelib.DELEGATE)
+                else:
+                    self.account = exchangelib.Account(
+                        primary_smtp_address=self.email_address,
+                        credentials=credentials,
+                        autodiscover=True,
+                        access_type=exchangelib.DELEGATE)
+            yield
+        except Exception as e:
+            # NOTE(sileht): retry just once if the connection have been
+            # broken to ensure this is not a sporadic connection lost.
+            # Like wifi reconnect, sleep wake up
+            # Wait a bit when disconnection occurs to not hog the cpu
+            self.logger.warn(e)
+            time.sleep(1)
+            self.connection = None
+
+    def count_new_mail(self):
+        self.account.inbox.refresh()
+        self.last = self.account.inbox.unread_count
+
+    @property
+    def unread(self):
+        with self.ensure_connection():
+            self.count_new_mail()
+        return self.last
+
+
+Backend = ExchangeMailAccount