Allow current user to nickname themselves

Add support for the `PATCH /guilds/:guild_id/members/@me/nick` endpoint,
which allows the current user to edit their own nickname.

A user can only nickname themselves if they have the `Change Nickname`
permission.

This adds 4 methods:

- `serenity::client::http::edit_nickname`;
- `serenity::client::Context::edit_nickname`;
- `serenity::model::Guild::edit_nickname`;
- `serenity::model::LiveGuild::edit_nickname`.

`LiveGuild`'s implementation checks for whether the current user has
permission to change their own nickname.

4 files changed, 69 insertions, 0 deletions

diff --git a/src/client/context.rs b/src/client/context.rs
index 1bee390..f4ddd5e 100644
--- a/src/client/context.rs
+++ b/src/client/context.rs
@@ -514,6 +514,20 @@ impl Context {
         http::edit_member(guild_id.into().0, user_id.into().0, map)
     }
 
+    /// Edits the current user's nickname for the provided [`Guild`] via its Id.
+    ///
+    /// Pass `None` to reset the nickname.
+    ///
+    /// **Note**: Requires the [Change Nickname] permission.
+    ///
+    /// [`Guild`]: ../../model/struct.Guild.html
+    /// [Change Nickname]: permissions/constant.CHANGE_NICKNAME.html
+    #[inline]
+    pub fn edit_nickname<G>(&self, guild_id: G, new_nickname: Option<&str>)
+        -> Result<()> where G: Into<GuildId> {
+        http::edit_nickname(guild_id.into().0, new_nickname)
+    }
+
     pub fn edit_profile<F: FnOnce(EditProfile) -> EditProfile>(&mut self, f: F)
         -> Result<CurrentUser> {
         let user = try!(http::get_current_user());
diff --git a/src/client/http/mod.rs b/src/client/http/mod.rs
index 9fba750..ca21c44 100644
--- a/src/client/http/mod.rs
+++ b/src/client/http/mod.rs
@@ -31,6 +31,7 @@ use hyper::status::StatusCode;
 use hyper::{Error as HyperError, Result as HyperResult, Url, header};
 use multipart::client::Multipart;
 use self::ratelimiting::Route;
+use serde_json::builder::ObjectBuilder;
 use serde_json;
 use std::default::Default;
 use std::io::{ErrorKind as IoErrorKind, Read};
@@ -451,6 +452,23 @@ pub fn edit_message(channel_id: u64,
     Message::decode(try!(serde_json::from_reader(response)))
 }
 
+/// Edits the current user's nickname for the provided [`Guild`] via its Id.
+///
+/// Pass `None` to reset the nickname.
+///
+/// [`Guild`]: ../../model/struct.Guild.html
+pub fn edit_nickname(guild_id: u64, new_nickname: Option<&str>)
+    -> Result<()> {
+    let map = ObjectBuilder::new().insert("nick", new_nickname).build();
+    let body = try!(serde_json::to_string(&map));
+    let response = request!(Route::GuildsIdMembersMeNick(guild_id),
+                            patch(body),
+                            "/guilds/{}/members/@me/nick",
+                            guild_id);
+
+    verify(200, response)
+}
+
 pub fn edit_note(user_id: u64, map: Value) -> Result<()> {
     let body = try!(serde_json::to_string(&map));
 
@@ -1130,6 +1148,7 @@ fn verify(expected_status_code: u16,
           mut response: HyperResponse)
           -> Result<()> {
     let expected_status = match expected_status_code {
+        200 => StatusCode::Ok,
         204 => StatusCode::NoContent,
         401 => StatusCode::Unauthorized,
         _ => {
diff --git a/src/client/http/ratelimiting.rs b/src/client/http/ratelimiting.rs
index 6a5ef17..f1a1713 100644
--- a/src/client/http/ratelimiting.rs
+++ b/src/client/http/ratelimiting.rs
@@ -84,6 +84,7 @@ pub enum Route {
     GuildsIdIntegrationsIdSync(u64),
     GuildsIdInvites(u64),
     GuildsIdMembersId(u64),
+    GuildsIdMembersMeNick(u64),
     GuildsIdPrune(u64),
     GuildsIdRegions(u64),
     GuildsIdRoles(u64),
diff --git a/src/model/guild.rs b/src/model/guild.rs
index 0506115..866cd19 100644
--- a/src/model/guild.rs
+++ b/src/model/guild.rs
@@ -120,6 +120,18 @@ impl Guild {
         self.roles.get(&role_id.into())
     }
 
+    /// Edits the current user's nickname for the guild.
+    ///
+    /// Pass `None` to reset the nickname.
+    ///
+    /// **Note**: Requires the [Change Nickname] permission.
+    ///
+    /// [Change Nickname]: permissions/constant.CHANGE_NICKNAME.html
+    #[inline]
+    pub fn edit_nickname(&self, new_nickname: Option<&str>) -> Result<()> {
+        http::edit_nickname(self.id.0, new_nickname)
+    }
+
     /// Returns a formatted URL of the guild's icon, if the guild has an icon.
     pub fn icon_url(&self) -> Option<String> {
         self.icon.as_ref().map(|icon|
@@ -396,6 +408,29 @@ impl LiveGuild {
         }
     }
 
+    /// Edits the current user's nickname for the guild.
+    ///
+    /// Pass `None` to reset the nickname.
+    ///
+    /// **Note**: Requires the [Change Nickname] permission.
+    ///
+    /// # Errors
+    ///
+    /// Returns a [`ClientError::InvalidPermissions`] if the current user does
+    /// not have permission to change their own nickname.
+    ///
+    /// [`ClientError::InvalidPermissions`]: ../client/enum.ClientError.html#variant.InvalidPermissions
+    /// [Change Nickname]: permissions/constant.CHANGE_NICKNAME.html
+    pub fn edit_nickname(&self, new_nickname: Option<&str>) -> Result<()> {
+        let req = permissions::CHANGE_NICKNAME;
+
+        if !try!(self.has_perms(req)) {
+            return Err(Error::Client(ClientError::InvalidPermissions(req)));
+        }
+
+        http::edit_nickname(self.id.0, new_nickname)
+    }
+
     /// Attempts to retrieve a [`PublicChannel`] with the given Id.
     ///
     /// [`PublicChannel`]: struct.PublicChannel.html