Add support for paginating over message reactors

Ideally I should go back now and implement Paginator for other classes,
but for now this is fine.

disco/api/client.py

@@ -155,8 +155,11 @@ class APIClient(LoggingClass):
     def channels_messages_delete_bulk(self, channel, messages):
         self.http(Routes.CHANNELS_MESSAGES_DELETE_BULK, dict(channel=channel), json={'messages': messages})
 
-    def channels_messages_reactions_get(self, channel, message, emoji):
-        r = self.http(Routes.CHANNELS_MESSAGES_REACTIONS_GET, dict(channel=channel, message=message, emoji=emoji))
+    def channels_messages_reactions_get(self, channel, message, emoji, after=None, limit=100):
+        r = self.http(
+            Routes.CHANNELS_MESSAGES_REACTIONS_GET,
+            dict(channel=channel, message=message, emoji=emoji),
+            params={'after': after, 'limit': limit})
         return User.create_map(self.client, r.json())
 
     def channels_messages_reactions_create(self, channel, message, emoji):

disco/api/http.py

@@ -22,6 +22,7 @@ HTTPMethod = Enum(
 
 
 def to_bytes(obj):
+    if six.PY2:
         if isinstance(obj, six.text_type):
             return obj.encode('utf-8')
     return obj

disco/types/message.py

@@ -10,6 +10,7 @@ from disco.types.base import (
     SlottedModel, Field, ListField, AutoDictField, snowflake, text,
     datetime, enum
 )
+from disco.util.paginator import Paginator
 from disco.util.snowflake import to_snowflake
 from disco.util.functional import cached_property
 from disco.types.user import User
@@ -300,7 +301,22 @@ class Message(SlottedModel):
         """
         return self.client.api.channels_messages_delete(self.channel_id, self.id)
 
-    def get_reactors(self, emoji):
+    def get_reactors_iter(self, emoji, *args, **kwargs):
+        """
+        Returns an iterator which paginates the reactors for the given emoji.
+        """
+        if isinstance(emoji, Emoji):
+            emoji = emoji.to_string()
+
+        return Paginator(
+            self.client.api.channels_messages_reactions_get,
+            self.channel_id,
+            self.id,
+            emoji,
+            *args,
+            **kwargs)
+
+    def get_reactors(self, emoji, *args, **kwargs):
         """
         Returns an list of users who reacted to this message with the given emoji.
 
@@ -309,11 +325,15 @@ class Message(SlottedModel):
         list(:class:`User`)
             The users who reacted.
         """
+        if isinstance(emoji, Emoji):
+            emoji = emoji.to_string()
+
         return self.client.api.channels_messages_reactions_get(
             self.channel_id,
             self.id,
-            emoji
-        )
+            emoji,
+            *args,
+            **kwargs)
 
     def create_reaction(self, emoji):
         warnings.warn(
@@ -322,8 +342,17 @@ class Message(SlottedModel):
         return self.add_reaction(emoji)
 
     def add_reaction(self, emoji):
+        """
+        Adds a reaction to the message.
+
+        Parameters
+        ----------
+        emoji : Emoji|str
+            An emoji or string representing an emoji
+        """
         if isinstance(emoji, Emoji):
             emoji = emoji.to_string()
+
         self.client.api.channels_messages_reactions_create(
             self.channel_id,
             self.id,

disco/util/paginator.py

@@ -0,0 +1,43 @@
+import operator
+
+
+class Paginator(object):
+    """
+    Implements a class which provides paginated iteration over an endpoint.
+    """
+    def __init__(self, func, *args, **kwargs):
+        self.func = func
+        self.args = args
+        self.kwargs = kwargs
+
+        self._key = kwargs.pop('key', operator.attrgetter('id'))
+        self._bulk = kwargs.pop('bulk', False)
+        self._after = kwargs.pop('after', None)
+        self._buffer = []
+
+    def fill(self):
+        self.kwargs['after'] = self._after
+        result = self.func(*self.args, **self.kwargs)
+
+        if not len(result):
+            raise StopIteration
+
+        self._buffer.extend(result)
+        self._after = self._key(result[-1])
+
+    def next(self):
+        return self.__next__()
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        if not len(self._buffer):
+            self.fill()
+
+        if self._bulk:
+            res = self._buffer
+            self._buffer = []
+            return res
+        else:
+            return self._buffer.pop()

examples/basic_plugin.py

@@ -12,7 +12,7 @@ class BasicPlugin(Plugin):
         self.log.info('Message created: {}: {}'.format(msg.author, msg.content))
 
     @Plugin.command('echo', '<content:str...>')
-    def on_test_command(self, event, content):
+    def on_echo_command(self, event, content):
         event.msg.reply(content)
 
     @Plugin.command('spam', '<count:int> <content:str...>')