Re-add support for reactions.

We now store emojis in a global cache and make things like adding
and removing reactions part of the stateful Message class.

6 files changed, 238 insertions, 88 deletions

diff --git a/discord/__init__.py b/discord/__init__.py
index 4806ffbd..345c0d6c 100644
--- a/discord/__init__.py
+++ b/discord/__init__.py
@@ -20,7 +20,7 @@ __version__ = '0.16.0'
 from .client import Client, AppInfo, ChannelPermissions
 from .user import User
 from .game import Game
-from .emoji import Emoji
+from .emoji import Emoji, PartialEmoji
 from .channel import *
 from .guild import Guild
 from .member import Member, VoiceState
diff --git a/discord/emoji.py b/discord/emoji.py
index 1f06c7e4..55d0ab73 100644
--- a/discord/emoji.py
+++ b/discord/emoji.py
@@ -25,10 +25,13 @@ DEALINGS IN THE SOFTWARE.
 """
 
 import asyncio
+from collections import namedtuple
 
 from . import utils
 from .mixins import Hashable
 
+PartialEmoji = namedtuple('PartialEmoji', 'id name')
+
 class Emoji(Hashable):
     """Represents a custom emoji.
 
diff --git a/discord/guild.py b/discord/guild.py
index 3ed07b20..5bb7ca66 100644
--- a/discord/guild.py
+++ b/discord/guild.py
@@ -237,7 +237,7 @@ class Guild(Hashable):
         self.id = int(guild['id'])
         self.roles = [Role(guild=self, data=r, state=self._state) for r in guild.get('roles', [])]
         self.mfa_level = guild.get('mfa_level')
-        self.emojis = [Emoji(server=self, data=r, state=self._state) for r in guild.get('emojis', [])]
+        self.emojis = tuple(map(lambda d: self._state.store_emoji(self, d), guild.get('emojis', [])))
         self.features = guild.get('features', [])
         self.splash = guild.get('splash')
 
@@ -653,7 +653,7 @@ class Guild(Hashable):
 
         img = utils._bytes_to_base64_data(image)
         data = yield from self._state.http.create_custom_emoji(self.id, name, img)
-        return Emoji(guild=self, data=data, state=self._state)
+        return self._state.store_emoji(self, data)
 
     @asyncio.coroutine
     def create_role(self, **fields):
diff --git a/discord/message.py b/discord/message.py
index 403178a7..9a149e1d 100644
--- a/discord/message.py
+++ b/discord/message.py
@@ -29,10 +29,12 @@ import re
 
 from .user import User
 from .reaction import Reaction
+from .emoji import Emoji
 from . import utils, abc
 from .object import Object
 from .calls import CallMessage
 from .enums import MessageType, try_enum
+from .errors import InvalidArgument
 
 class Message:
     """Represents a message from Discord.
@@ -66,8 +68,6 @@ class Message:
         In :issue:`very rare cases <21>` this could be a :class:`Object` instead.
 
         For the sake of convenience, this :class:`Object` instance has an attribute ``is_private`` set to ``True``.
-    guild: Optional[:class:`Guild`]
-        The guild that the message belongs to. If not applicable (i.e. a PM) then it's None instead.
     call: Optional[:class:`CallMessage`]
         The call that the message refers to. This is only applicable to messages of type
         :attr:`MessageType.call`.
@@ -112,16 +112,15 @@ class Message:
 
     __slots__ = ( 'edited_timestamp', 'tts', 'content', 'channel', 'webhook_id',
                   'mention_everyone', 'embeds', 'id', 'mentions', 'author',
-                  '_cs_channel_mentions', 'guild', '_cs_raw_mentions', 'attachments',
+                  '_cs_channel_mentions', '_cs_raw_mentions', 'attachments',
                   '_cs_clean_content', '_cs_raw_channel_mentions', 'nonce', 'pinned',
                   'role_mentions', '_cs_raw_role_mentions', 'type', 'call',
                   '_cs_system_content', '_state', 'reactions' )
 
     def __init__(self, *, state, channel, data):
         self._state = state
-        self.reactions = kwargs.pop('reactions')
-        for reaction in self.reactions:
-            reaction.message = self
+        self.id = int(data['id'])
+        self.reactions = [Reaction(message=self, data=d) for d in data.get('reactions', [])]
         self._update(channel, data)
 
     def _try_patch(self, data, key, transform):
@@ -132,6 +131,41 @@ class Message:
         else:
             setattr(self, key, transform(value))
 
+    def _add_reaction(self, data):
+        emoji = self._state.reaction_emoji(data['emoji'])
+        reaction = utils.find(lambda r: r.emoji == emoji, self.reactions)
+        is_me = data['me'] = int(data['user_id']) == self._state.self_id
+
+        if reaction is None:
+            reaction = Reaction(message=self, data=data, emoji=emoji)
+            self.reactions.append(reaction)
+        else:
+            reaction.count += 1
+            if is_me:
+                reaction.me = is_me
+
+        return reaction
+
+    def _remove_reaction(self, data):
+        emoji = self._state.reaction_emoji(data['emoji'])
+        reaction = utils.find(lambda r: r.emoji == emoji, self.reactions)
+
+        if reaction is None:
+            # already removed?
+            raise ValueError('Emoji already removed?')
+
+        # if reaction isn't in the list, we crash. This means discord
+        # sent bad data, or we stored improperly
+        reaction.count -= 1
+
+        if int(data['user_id']) == self._state.self_id:
+            reaction.me = False
+        if reaction.count == 0:
+            # this raises ValueError if something went wrong as well.
+            self.reactions.remove(reaction)
+
+        return reaction
+
     def _update(self, channel, data):
         self.channel = channel
         for handler in ('mentions', 'mention_roles', 'call'):
@@ -198,6 +232,11 @@ class Message:
         call['participants'] = participants
         self.call = CallMessage(message=self, **call)
 
+    @property
+    def guild(self):
+        """Optional[:class:`Guild`]: The guild that the message belongs to, if applicable."""
+        return getattr(self.channel, 'guild', None)
+
     @utils.cached_slot_property('_cs_raw_mentions')
     def raw_mentions(self):
         """A property that returns an array of user IDs matched with
@@ -428,3 +467,82 @@ class Message:
 
         yield from self._state.http.unpin_message(self.channel.id, self.id)
         self.pinned = False
+
+    @asyncio.coroutine
+    def add_reaction(self, emoji):
+        """|coro|
+
+        Add a reaction to the message.
+
+        The emoji may be a unicode emoji or a custom server :class:`Emoji`.
+
+        You must have the :attr:`Permissions.add_reactions` permission to
+        add new reactions to a message.
+
+        Parameters
+        ------------
+        emoji: :class:`Emoji` or str
+            The emoji to react with.
+
+        Raises
+        --------
+        HTTPException
+            Adding the reaction failed.
+        Forbidden
+            You do not have the proper permissions to react to the message.
+        NotFound
+            The emoji you specified was not found.
+        InvalidArgument
+            The emoji parameter is invalid.
+        """
+
+        if isinstance(emoji, Emoji):
+            emoji = '%s:%s' % (emoji.name, emoji.id)
+        elif isinstance(emoji, str):
+            pass # this is okay
+        else:
+            raise InvalidArgument('emoji argument must be a string or discord.Emoji')
+
+        yield from self._state.http.add_reaction(self.id, self.channel.id, emoji)
+
+    @asyncio.coroutine
+    def remove_reaction(self, emoji, member):
+        """|coro|
+
+        Remove a reaction by the member from the message.
+
+        The emoji may be a unicode emoji or a custom server :class:`Emoji`.
+
+        If the reaction is not your own (i.e. ``member`` parameter is not you) then
+        the :attr:`Permissions.manage_messages` permission is needed.
+
+        The ``member`` parameter must represent a member and meet
+        the :class:`abc.Snowflake` abc.
+
+        Parameters
+        ------------
+        emoji: :class:`Emoji` or str
+            The emoji to remove.
+        member: :class:`abc.Snowflake`
+            The member for which to remove the reaction.
+
+        Raises
+        --------
+        HTTPException
+            Removing the reaction failed.
+        Forbidden
+            You do not have the proper permissions to remove the reaction.
+        NotFound
+            The member or emoji you specified was not found.
+        InvalidArgument
+            The emoji parameter is invalid.
+        """
+
+        if isinstance(emoji, Emoji):
+            emoji = '%s:%s' % (emoji.name, emoji.id)
+        elif isinstance(emoji, str):
+            pass # this is okay
+        else:
+            raise InvalidArgument('emoji argument must be a string or discord.Emoji')
+
+        yield from self._state.http.remove_reaction(self.id, self.channel.id, emoji, member.id)
diff --git a/discord/reaction.py b/discord/reaction.py
index 2e4f3ce4..2e47e397 100644
--- a/discord/reaction.py
+++ b/discord/reaction.py
@@ -24,7 +24,9 @@ FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.
 """
 
-from .emoji import Emoji
+import asyncio
+
+from .user import User
 
 class Reaction:
     """Represents a reaction to a message.
@@ -48,25 +50,27 @@ class Reaction:
 
     Attributes
     -----------
-    emoji : :class:`Emoji` or str
+    emoji: :class:`Emoji` or str
         The reaction emoji. May be a custom emoji, or a unicode emoji.
-    custom_emoji : bool
-        If this is a custom emoji.
-    count : int
+    count: int
         Number of times this reaction was made
-    me : bool
+    me: bool
         If the user sent this reaction.
     message: :class:`Message`
         Message this reaction is for.
     """
-    __slots__ = ['message', 'count', 'emoji', 'me', 'custom_emoji']
+    __slots__ = ('message', 'count', 'emoji', 'me')
+
+    def __init__(self, *, message, data, emoji=None):
+        self.message = message
+        self.emoji = message._state.reaction_emoji(data['emoji']) if emoji is None else emoji
+        self.count = data.get('count', 1)
+        self.me = data.get('me')
 
-    def __init__(self, **kwargs):
-        self.message = kwargs.get('message')
-        self.emoji = kwargs['emoji']
-        self.count = kwargs.get('count', 1)
-        self.me = kwargs.get('me')
-        self.custom_emoji = isinstance(self.emoji, Emoji)
+    @property
+    def custom_emoji(self):
+        """bool: If this is a custom emoji."""
+        return not isinstance(self.emoji, str)
 
     def __eq__(self, other):
         return isinstance(other, self.__class__) and other.emoji == self.emoji
@@ -78,3 +82,45 @@ class Reaction:
 
     def __hash__(self):
         return hash(self.emoji)
+
+    @asyncio.coroutine
+    def users(self, limit=100, after=None):
+        """|coro|
+
+        Get the users that added this reaction.
+
+        The ``after`` parameter must represent a member
+        and meet the :class:`abc.Snowflake` abc.
+
+        Parameters
+        ------------
+        limit: int
+            The maximum number of results to return.
+        after: :class:`abc.Snowflake`
+            For pagination, reactions are sorted by member.
+
+        Raises
+        --------
+        HTTPException
+            Getting the users for the reaction failed.
+
+        Returns
+        --------
+        List[:class:`User`]
+            A list of users who reacted to the message.
+        """
+
+        # TODO: Return an iterator a la `MessageChannel.history`?
+
+        if self.custom_emoji:
+            emoji = '{0.name}:{0.id}'.format(self.emoji)
+        else:
+            emoji = self.emoji
+
+        if after:
+            after = after.id
+
+        msg = self.message
+        state = msg._state
+        data = yield from state.http.get_reaction_users(msg.id, msg.channel.id, emoji, limit, after=after)
+        return [User(state=state, data=user) for user in data]
diff --git a/discord/state.py b/discord/state.py
index c9a330b3..9df9f365 100644
--- a/discord/state.py
+++ b/discord/state.py
@@ -27,7 +27,7 @@ DEALINGS IN THE SOFTWARE.
 from .guild import Guild
 from .user import User
 from .game import Game
-from .emoji import Emoji
+from .emoji import Emoji, PartialEmoji
 from .reaction import Reaction
 from .message import Message
 from .channel import *
@@ -47,10 +47,16 @@ class ListenerType(enum.Enum):
     chunk = 0
 
 Listener = namedtuple('Listener', ('type', 'future', 'predicate'))
-StateContext = namedtuple('StateContext', 'store_user http self_id')
 log = logging.getLogger(__name__)
 ReadyState = namedtuple('ReadyState', ('launch', 'guilds'))
 
+class StateContext:
+    __slots__ = ('store_user', 'http', 'self_id', 'store_emoji', 'reaction_emoji')
+
+    def __init__(self, **kwargs):
+        for attr, value in kwargs.items():
+            setattr(self, attr, value)
+
 class ConnectionState:
     def __init__(self, *, dispatch, chunker, syncer, http, loop, **options):
         self.loop = loop
@@ -60,7 +66,10 @@ class ConnectionState:
         self.syncer = syncer
         self.is_bot = None
         self._listeners = []
-        self.ctx = StateContext(store_user=self.store_user, http=http, self_id=None)
+        self.ctx = StateContext(store_user=self.store_user,
+                                store_emoji=self.store_emoji,
+                                reaction_emoji=self._get_reaction_emoji,
+                                http=http, self_id=None)
         self.clear()
 
     def clear(self):
@@ -69,6 +78,7 @@ class ConnectionState:
         self.session_id = None
         self._calls = {}
         self._users = {}
+        self._emojis = {}
         self._guilds = {}
         self._voice_clients = {}
         self._private_channels = {}
@@ -128,6 +138,14 @@ class ConnectionState:
             self._users[user_id] = user = User(state=self.ctx, data=data)
             return user
 
+    def store_emoji(self, guild, data):
+        emoji_id = int(data['id'])
+        try:
+            return self._emojis[emoji_id]
+        except KeyError:
+            self._emojis[emoji_id] = emoji = Emoji(guild=guild, state=self.ctx, data=data)
+            return emoji
+
     @property
     def guilds(self):
         return self._guilds.values()
@@ -274,26 +292,11 @@ class ConnectionState:
             self.dispatch('message_edit', older_message, message)
 
     def parse_message_reaction_add(self, data):
-        message = self._get_message(data['message_id'])
+        message = self._get_message(int(data['message_id']))
         if message is not None:
-            emoji = self._get_reaction_emoji(**data.pop('emoji'))
-            reaction = utils.get(message.reactions, emoji=emoji)
-
-            is_me = data['user_id'] == self.user.id
-
-            if not reaction:
-                reaction = Reaction(
-                    message=message, emoji=emoji, me=is_me, **data)
-                message.reactions.append(reaction)
-            else:
-                reaction.count += 1
-                if is_me:
-                    reaction.me = True
-
-            channel = self.get_channel(data['channel_id'])
-            member = self._get_member(channel, data['user_id'])
-
-            self.dispatch('reaction_add', reaction, member)
+            reaction = message._add_reaction(data)
+            user = self._get_reaction_user(message.channel, int(data['user_id']))
+            self.dispatch('reaction_add', reaction, user)
 
     def parse_message_reaction_remove_all(self, data):
         message =  self._get_message(data['message_id'])
@@ -303,26 +306,15 @@ class ConnectionState:
             self.dispatch('reaction_clear', message, old_reactions)
 
     def parse_message_reaction_remove(self, data):
-        message = self._get_message(data['message_id'])
+        message = self._get_message(int(data['message_id']))
         if message is not None:
-            emoji = self._get_reaction_emoji(**data['emoji'])
-            reaction = utils.get(message.reactions, emoji=emoji)
-
-            # Eventual consistency means we can get out of order or duplicate removes.
-            if not reaction:
-                log.warning("Unexpected reaction remove {}".format(data))
-                return
-
-            reaction.count -= 1
-            if data['user_id'] == self.user.id:
-                reaction.me = False
-            if reaction.count == 0:
-                message.reactions.remove(reaction)
-
-            channel = self.get_channel(data['channel_id'])
-            member = self._get_member(channel, data['user_id'])
-
-            self.dispatch('reaction_remove', reaction, member)
+            try:
+                reaction = message._remove_reaction(data)
+            except (AttributeError, ValueError) as e: # eventual consistency lol
+                pass
+            else:
+                user = self._get_reaction_user(message.channel, int(data['user_id']))
+                self.dispatch('reaction_remove', reaction, user)
 
     def parse_presence_update(self, data):
         guild = self._get_guild(utils._get_as_snowflake(data, 'guild_id'))
@@ -462,7 +454,7 @@ class ConnectionState:
     def parse_guild_emojis_update(self, data):
         guild = self._get_guild(int(data['guild_id']))
         before_emojis = guild.emojis
-        guild.emojis = [Emoji(guild=guild, data=e, state=self.ctx) for e in data.get('emojis', [])]
+        guild.emojis = tuple(map(lambda d: self.store_emoji(guild, d), data['emojis']))
         self.dispatch('guild_emojis_update', before_emojis, guild.emojis)
 
     def _get_create_guild(self, data):
@@ -675,35 +667,26 @@ class ConnectionState:
         if call is not None:
             self.dispatch('call_remove', call)
 
-    def _get_member(self, channel, id):
-        if channel.is_private:
-            return utils.get(channel.recipients, id=id)
+    def _get_reaction_user(self, channel, user_id):
+        if isinstance(channel, DMChannel) and user_id == channel.recipient.id:
+            return channel.recipient
+        elif isinstance(channel, TextChannel):
+            return channel.guild.get_member(user_id)
+        elif isinstance(channel, GroupChannel):
+            return utils.find(lambda m: m.id == user_id, channel.recipients)
         else:
-            return channel.server.get_member(id)
-
-    def _create_message(self, **message):
-        """Helper mostly for injecting reactions."""
-        reactions = [
-            self._create_reaction(**r) for r in message.pop('reactions', [])
-        ]
-        return Message(channel=message.pop('channel'),
-                       reactions=reactions, **message)
-
-    def _create_reaction(self, **reaction):
-        emoji = self._get_reaction_emoji(**reaction.pop('emoji'))
-        return Reaction(emoji=emoji, **reaction)
+            return None
 
-    def _get_reaction_emoji(self, **data):
-        id = data['id']
+    def _get_reaction_emoji(self, data):
+        emoji_id = utils._get_as_snowflake(data, 'id')
 
-        if not id:
+        if not emoji_id:
             return data['name']
 
-        for server in self.servers:
-            for emoji in server.emojis:
-                if emoji.id == id:
-                    return emoji
-        return Emoji(server=None, **data)
+        try:
+            return self._emojis[emoji_id]
+        except KeyError:
+            return PartialEmoji(id=emoji_id, name=data['name'])
 
     def get_channel(self, id):
         if id is None: