Add support for `async for` in Client.logs_from.

This is a breaking change. Code will still work in Python 3.4 as-is but
if you use Python 3.5 you will have to change your code to the new
`async for` syntax as the older version is not supported in 3.5.

On the other hand, this comes with performance improvements if you use
Python 3.5 as it will lazily load 100 message chunks on an as needed
basis rather than loading all messages in one go.

2 files changed, 118 insertions, 33 deletions

diff --git a/discord/client.py b/discord/client.py
index 7e49aa89..98f62a44 100644
--- a/discord/client.py
+++ b/discord/client.py
@@ -41,6 +41,7 @@ from .permissions import Permissions
 from . import utils
 from .enums import ChannelType, ServerRegion
 from .voice_client import VoiceClient
+from .iterators import LogsFromIterator
 
 import asyncio
 import aiohttp
@@ -53,6 +54,7 @@ import itertools
 import zlib
 from random import randint as random_integer
 
+PY35 = sys.version_info >= (3, 5)
 log = logging.getLogger(__name__)
 request_logging_format = '{method} {response.url} has returned {response.status}'
 request_success_log = '{response.url} with {json} received {data}'
@@ -1115,24 +1117,6 @@ class Client:
 
     @asyncio.coroutine
     def _logs_from(self, channel, limit=100, before=None, after=None):
-        url = '{}/{}/messages'.format(endpoints.CHANNELS, channel.id)
-        params = {
-            'limit': limit
-        }
-
-        if before:
-            params['before'] = before.id
-        if after:
-            params['after'] = after.id
-
-        response = yield from aiohttp.get(url, params=params, headers=self.headers, loop=self.loop)
-        log.debug(request_logging_format.format(method='GET', response=response))
-        yield from utils._verify_successful_response(response)
-        messages = yield from response.json()
-        return messages
-
-    @asyncio.coroutine
-    def logs_from(self, channel, limit=100, *, before=None, after=None):
         """|coro|
 
         This coroutine returns a generator that obtains logs from a specified channel.
@@ -1172,24 +1156,54 @@ class Client:
                 if message.content.startswith('!hello'):
                     if message.author == client.user:
                         yield from client.edit_message(message, 'goodbye')
+
+        Python 3.5 Usage ::
+
+            counter = 0
+            async for message in client.logs_from(channel, limit=500):
+                if message.author == client.user:
+                    counter += 1
         """
+        url = '{}/{}/messages'.format(endpoints.CHANNELS, channel.id)
+        params = {
+            'limit': limit
+        }
 
-        def generator(data):
-            for message in data:
-                yield Message(channel=channel, **message)
-
-        result = []
-        while limit > 0:
-            retrieve = limit if limit <= 100 else 100
-            data = yield from self._logs_from(channel, retrieve, before, after)
-            if len(data):
-                limit -= retrieve
-                result.extend(data)
-                before = Object(id=data[-1]['id'])
-            else:
-                break
+        if before:
+            params['before'] = before.id
+        if after:
+            params['after'] = after.id
+
+        response = yield from aiohttp.get(url, params=params, headers=self.headers, loop=self.loop)
+        log.debug(request_logging_format.format(method='GET', response=response))
+        yield from utils._verify_successful_response(response)
+        messages = yield from response.json()
+        return messages
+
+    if PY35:
+        def logs_from(self, channel, limit=100, *, before=None, after=None):
+            return LogsFromIterator(self, channel, limit, before, after)
+    else:
+        @asyncio.coroutine
+        def logs_from(self, channel, limit=100, *, before=None, after=None):
+            def generator(data):
+                for message in data:
+                    yield Message(channel=channel, **message)
+
+            result = []
+            while limit > 0:
+                retrieve = limit if limit <= 100 else 100
+                data = yield from self._logs_from(channel, retrieve, before, after)
+                if len(data):
+                    limit -= retrieve
+                    result.extend(data)
+                    before = Object(id=data[-1]['id'])
+                else:
+                    break
+
+            return generator(result)
 
-        return generator(result)
+    logs_from.__doc__ = _logs_from.__doc__
 
     # Member management
 
diff --git a/discord/iterators.py b/discord/iterators.py
new file mode 100644
index 00000000..b0cb0c77
--- /dev/null
+++ b/discord/iterators.py
@@ -0,0 +1,71 @@
+# -*- coding: utf-8 -*-
+
+"""
+The MIT License (MIT)
+
+Copyright (c) 2015-2016 Rapptz
+
+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 sys
+import asyncio
+import aiohttp
+from .message import Message
+from .object import Object
+
+PY35 = sys.version_info >= (3, 5)
+
+class LogsFromIterator:
+    def __init__(self, client, channel, limit, before, after):
+        self.client = client
+        self.channel = channel
+        self.limit = limit
+        self.before = before
+        self.after = after
+        self.messages = asyncio.LifoQueue()
+
+    @asyncio.coroutine
+    def fill_messages(self):
+        if self.limit > 0:
+            retrieve = self.limit if self.limit <= 100 else 100
+            data = yield from self.client._logs_from(self.channel, retrieve, self.before, self.after)
+            if len(data):
+                self.limit -= retrieve
+                self.before = Object(id=data[-1]['id'])
+                for element in data:
+                    yield from self.messages.put(Message(channel=self.channel, **element))
+
+    if PY35:
+        @asyncio.coroutine
+        def __aiter__(self):
+            return self
+
+        @asyncio.coroutine
+        def __anext__(self):
+            if self.messages.empty():
+                yield from self.fill_messages()
+
+            try:
+                msg = self.messages.get_nowait()
+                return msg
+            except asyncio.QueueEmpty:
+                # if we're still empty at this point...
+                # we didn't get any new messages so stop looping
+                raise StopAsyncIteration()