From 0e1f6b24f3a543140dc97928a50cdf69ffab61a7 Mon Sep 17 00:00:00 2001
From: Brad Warren <bradmw@umich.edu>
Date: Wed, 27 May 2015 19:29:06 -0400
Subject: [PATCH] Added basic notifier

---
 letsencrypt/cli.py        |  7 +++++
 letsencrypt/interfaces.py | 27 +++++++++++++++++++
 letsencrypt/notifier.py   | 57 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+)
 create mode 100644 letsencrypt/notifier.py

diff --git a/letsencrypt/cli.py b/letsencrypt/cli.py
index defa7633d..8cb8ec84f 100644
--- a/letsencrypt/cli.py
+++ b/letsencrypt/cli.py
@@ -1,5 +1,6 @@
 """Let's Encrypt CLI."""
 # TODO: Sanity check all input.  Be sure to avoid shell code etc...
+import atexit
 import argparse
 import logging
 import os
@@ -20,6 +21,7 @@ from letsencrypt import errors
 from letsencrypt import interfaces
 from letsencrypt import le_util
 from letsencrypt import log
+from letsencrypt import notifier
 
 from letsencrypt.display import util as display_util
 from letsencrypt.display import ops as display_ops
@@ -347,6 +349,11 @@ def main(args=sys.argv[1:]):
         displayer = display_util.NcursesDisplay()
     zope.component.provideUtility(displayer)
 
+    # Notifier
+    notify = notifier.Notifier()
+    zope.component.provideUtility(notify)
+    atexit.register(notify.print_messages)
+
     # Logging
     level = -args.verbose_count * 10
     logger = logging.getLogger()
diff --git a/letsencrypt/interfaces.py b/letsencrypt/interfaces.py
index 609b9410a..b39737070 100644
--- a/letsencrypt/interfaces.py
+++ b/letsencrypt/interfaces.py
@@ -346,3 +346,30 @@ class IValidator(zope.interface.Interface):
 
     def hsts(name):
         """Verify HSTS header is enabled."""
+
+
+class INotify(zope.interface.Interface):
+    """Interface to collect and display information to the user."""
+
+    HIGH_PRIORITY = zope.interface.Attribute(
+        "Used to denote high priority messages")
+    MEDIUM_PRIORITY = zope.interface.Attribute(
+        "Used to denote medium priority messages")
+    LOW_PRIORITY = zope.interface.Attribute(
+        "Used to denote low priority messages")
+
+    def add_message(self, msg, priority, on_crash=False):
+        """Adds msg to the list of messages to be printed.
+
+        :param str msg: Message to be displayed to the user.
+
+        :param int priority: One of HIGH_PRIORITY, MEDIUM_PRIORITY, or
+            LOW_PRIORITY.
+
+        :param bool on_crash: Whether or not the message should be printed if
+            the program exits abnormally.
+
+        """
+
+    def print_messages(self):
+        """Prints messages to the user and clears the message queue."""
diff --git a/letsencrypt/notifier.py b/letsencrypt/notifier.py
new file mode 100644
index 000000000..fa795673c
--- /dev/null
+++ b/letsencrypt/notifier.py
@@ -0,0 +1,57 @@
+"""Collects and displays information to the user."""
+import collections
+import Queue
+import sys
+import textwrap
+
+import zope.interface
+
+from letsencrypt import interfaces
+
+
+class Notifier(object):
+    """Collects and displays information to the user.
+
+    :ivar `Queue.PriorityQueue` messages: Messages to be displayed to the user.
+
+    """
+
+    zope.interface.implements(interfaces.INotify)
+
+    HIGH_PRIORITY, MEDIUM_PRIORITY, LOW_PRIORITY = xrange(3)
+    _msg_type = collections.namedtuple('Msg', 'priority, text, on_crash')
+
+    def __init__(self):
+        self.messages = Queue.PriorityQueue()
+
+    def add_message(self, msg, priority, on_crash=False):
+        """Adds msg to the list of messages to be printed.
+
+        :param str msg: Message to be displayed to the user.
+
+        :param int priority: One of HIGH_PRIORITY, MEDIUM_PRIORITY, or
+            LOW_PRIORITY.
+
+        :param bool on_crash: Whether or not the message should be printed if
+            the program exits abnormally.
+
+        """
+        assert priority >= self.HIGH_PRIORITY and priority <= self.LOW_PRIORITY
+        self.messages.put(self._msg_type(priority, msg, on_crash))
+
+    def print_messages(self):
+        """Prints messages to the user and clears the message queue.
+
+        If there is an unhandled exception, only messages for which on_crash is
+        True are printed.
+
+        """
+        if not self.messages.empty():
+            no_exception = sys.exc_info()[0] is None
+            print 'IMPORTANT NOTES:'
+            wrapper = textwrap.TextWrapper(initial_indent=' - ',
+                                           subsequent_indent=' '*3)
+        while not self.messages.empty():
+            msg = self.messages.get()
+            if no_exception or msg.on_crash:
+                print wrapper.fill(msg.text)