Add Deferreds

deferred.py

@@ -0,0 +1,97 @@
+class Deferred(object):
+	"""
+	Represents a delayed computation. This is a more elegant way to deal with
+	callbacks.
+
+	A Deferred object can be thought of as a computation whose value is yet to
+	be determined. We can manipulate the Deferred as if it where a regular
+	value by using the then method. Computations dependent on the Deferred will
+	only proceed when the run method is called.
+
+	Attributes of a Deferred can be accessed directly as methods.
+
+	Example:
+		image = Deferred()
+		getImageWithCallback(image.run)
+		image.then(displayFunc)
+
+		colors = Deferred()
+		colors.append('blue')
+		colors.then(print)
+		colors.run(['red', 'green']) #=> ['red', 'green', 'blue']
+	"""
+
+	def __init__(self):
+		self.subscribers = []
+		self.computed = False
+		self.args = None
+		self.kwargs = None
+
+	def run(self, *args, **kwargs):
+		"""
+		Give a value to the deferred. Calling this method more than once will
+		result in a DeferredHasValue exception to be raised.
+		"""
+		if self.computed:
+			raise DeferredHasValue("Deferred object already has a value.")
+		else:
+			self.args = args
+			self.kwargs = kwargs
+			for func, deferred in self.subscribers:
+				deferred.run(func(*args, **kwargs))
+			self.computed = True
+
+	def then(self, func):
+		"""
+		Apply func to Deferred value. Returns a Deferred whose value will be
+		the result of applying func.
+		"""
+		result = Deferred()
+		if self.computed:
+			result.run(func(*self.args, **self.kwargs))
+		else:
+			self.subscribers.append((func, result))
+		return result
+
+	def arg(self, n):
+		"""
+		Returns the nth positional argument of a deferred as a deferred
+
+		Args:
+			n - the index of the positional argument
+		"""
+		def helper(*args, **kwargs):
+			return args[n]
+		return self.then(helper)
+
+	def __getattr__(self, method_name):
+		return getattr(Then(self), method_name)
+
+
+class Then(object):
+	"""
+	Allows you to call methods on a Deferred.
+
+	Example:
+	colors = Deferred()
+	Then(colors).append('blue')
+	colors.run(['red', 'green'])
+	colors.then(print) #=> ['red', 'green', 'blue']
+	"""
+	def __init__(self, deferred):
+		self.deferred = deferred
+
+	def __getattr__(self, name):
+		def tryCall(obj, *args, **kwargs):
+			if callable(obj):
+				return obj(*args, **kwargs)
+			else:
+				return obj
+		def helper(*args, **kwargs):
+			func = (lambda x: tryCall(getattr(x, name), *args, **kwargs))
+			return self.deferred.then(func)
+		return helper
+
+class DeferredHasValue(Exception):
+	def __init__(self, string):
+		super(DeferredHasValue, self).__init__(string)

session.py

@@ -39,7 +39,9 @@ from buddy import BuddyList
 from threading import Timer
 from group import Group
 from bot import Bot
+import deferred
 from yowsupwrapper import YowsupApp
+from functools import partial
 
 
 class MsgIDs:
@@ -723,23 +725,34 @@ class Session(YowsupApp):
 			self.buddies.remove(buddy)
 
 	def requestVCard(self, buddy, ID=None):
-		def onSuccess(response, request):
-			self.logger.debug('Sending VCard (%s) with image id %s',
-					ID, response.pictureId)
-			image_hash = utils.sha1hash(response.pictureData)
-			self.logger.debug('Image hash is %s', image_hash)
-			if ID != None:
-				self.backend.handleVCard(self.user, ID, buddy, "", "", response.pictureData)
-			if not (buddy == self.user or buddy == self.user.split('@')[0]):
-				obuddy = self.buddies[buddy]
-				self.updateBuddy(buddy, obuddy.nick, obuddy.groups, image_hash)
-
 		if buddy == self.user or buddy == self.user.split('@')[0]:
-			newbuddy = self.legacyName
-		else:
-			newbuddy = buddy
-		self.logger.debug('Requesting profile picture of %s', newbuddy)
-		self.requestProfilePicture(newbuddy, onSuccess = onSuccess)
+			buddy = self.legacyName
+
+		# Get profile picture
+		self.logger.debug('Requesting profile picture of %s', buddy)
+		response = deferred.Deferred()
+		self.requestProfilePicture(buddy, onSuccess = response.run)
+		response = response.arg(0)
+
+		# Send VCard
+		if ID != None:
+			response.pictureId().then(partial(
+				self.logger.debug, 'Sending VCard (%s) with image id %s', ID
+			))
+			pictureData = response.pictureData()
+			response.pictureData().then(partial(
+				self.backend.handleVCard, self.user, ID, buddy, "", ""
+			))
+
+		# Send image hash
+		if not buddy == self.legacyName:
+			obuddy = self.buddies[buddy]
+			image_hash = pictureData.then(utils.sha1hash)
+			image_hash.then(partial(self.logger.debug, 'Image hash is %s'))
+			image_hash.then(partial(
+				self.updateBuddy, buddy, obuddy.nick, obuddy.groups
+			))
+
 
 	def onDlsuccess(self, path):
                 self.logger.info("Success: Image downloaded to %s", path)