Optimize caching

Improve the cache by keeping track of new maps, making other maps have
`Arc<RwLock>` values, optimizing already-existing methods, and take advantage
of new, more efficient retrievals (e.g. simply keying a value from a map rather
than iterating over vecs or maps and then itering over another vec).

Keep track of two new maps in the cache:

- **channels**: a map of all guild channels that exist, so that they can be
  efficiently found, and so a message's guild can be efficiently found
- **users**: a map of all users that exist, so that it can be shared across
  all members and presences

Other cache fields now have `Arc<RwLock>` values:

- `groups`
- `guilds`
- `private_channels`

`Cache::unavailable_guilds` is now a `HashSet<GuildId>` instead of a
`Vec<GuildId>`. This should slightly optimize removals/insertions for large
bots.

`ext::cache::ChannelRef` has been removed as it became equivilant in
functionality to `model::Channel`. Also, `model::Channel` now has all variant
data encased in `Arc<RwLock>`s. E.g., `Channel::Group(Group)` is now
`Channel::Group(Arc<RwLock<Group>>)`.

Some model struct fields are now wrapped in an `Arc<RwLock>`. These are:

- `Group::recipients`: `HashMap<UserId, User>` -> `HashMap<UserId, Arc<RwLock<User>>>`
- `Guild::channels`: `HashMap<ChannelId, GuildChannel>` -> `HashMap<ChannelId, Arc<RwLock<GuildChannel>>>`
- `Member::user`: `User` -> `Arc<RwLock<User>>`
- `PrivateChannel::recipient`: `User` -> `Arc<RwLock<User>>`

Some (cache-enabled) event handler signatures have changed to use
`Arc<RwLock>`s:

- `Client::on_call_delete`
- `Client::on_call_update`
- `Client::on_guild_delete`
- `Client::on_guild_update`

Many function signatures have changed:

- `Cache::get_call` now returns a `Option<Arc<RwLock<Call>>>` instead of a
  `Option<&Call>`
- `Cache::get_channel` now returns a `Option<Channel>` instead of a
  `Option<ChannelRef>`. This now also retrieves directly from the
  `Guild::channels` instead of iterating over guilds' for a guild channel
- `Cache::get_guild` now returns a `Option<Arc<RwLock<Guild>>>` instead of a
  `Option<&Guild>`
- `Cache::get_guild_channel` now returns a `Option<Arc<RwLock<GuildChannel>>>`
  instead of a `Option<&GuildChannel>`
- `Cache::get_group` now returns a `Option<Arc<RwLock<Group>>>` instead of a
  `Option<&Group>`
- `Cache::get_member` now returns a `Option<Member>` instead of a
  `Option<&Member>`, due to guilds being behind a lock themselves
- `Cache::get_role` now returns a `Option<Role>` instead of a `Option<&Role>`
  for the above reason
- `Cache::get_user` now returns a `Option<Arc<RwLock<User>>>` instead of a
  `Option<&User>`
- `GuildId::find` now returns a `Option<Arc<RwLock<Guild>>>` instead of a
  `Option<Guild>`
- `UserId::find` now returns a `Option<Arc<RwLock<User>>>` instead of a
  `Option<User>`
- `Member::display_name` now returns a `Cow<String>` instead of a `&str`

A new cache method has been added, `Cache::get_private_channel`, to retrieve a
`PrivateChannel`.

The `Display` formatter for `Channel` has been optimized to not clone.

1 files changed, 5 insertions, 5 deletions

diff --git a/src/model/misc.rs b/src/model/misc.rs
index eaae890..3784a59 100644
--- a/src/model/misc.rs
+++ b/src/model/misc.rs
@@ -30,13 +30,13 @@ impl Mentionable for Channel {
     fn mention(&self) -> String {
         match *self {
             Channel::Guild(ref x) => {
-                format!("<#{}>", x.id.0)
+                format!("<#{}>", x.read().unwrap().id.0)
             },
             Channel::Private(ref x) => {
-                format!("<#{}>", x.id.0)
+                format!("<#{}>", x.read().unwrap().id.0)
             },
             Channel::Group(ref x) => {
-                format!("<#{}>", x.channel_id.0)
+                format!("<#{}>", x.read().unwrap().channel_id.0)
             }
         }
     }
@@ -50,7 +50,7 @@ impl Mentionable for Emoji {
 
 impl Mentionable for Member {
     fn mention(&self) -> String {
-        format!("<@{}>", self.user.id.0)
+        format!("<@{}>", self.user.read().unwrap().id.0)
     }
 }
 
@@ -86,7 +86,7 @@ impl FromStr for User {
         match utils::parse_username(s) {
             Some(x) => {
                 match UserId(x as u64).find() {
-                    Some(user) => Ok(user),
+                    Some(user) => Ok(user.read().unwrap().clone()),
                     _ => Err(())
                 }
             },