Make parse_emoji accept animated emojis (#952)

Previously, `parse_emoji` only returned true when the emoji was static
and animated emojis passed to the function returned `None` since they
include an extra character (<a:) to denote whether the emoji is animated.

Since we can tell whether an emoji is animated through the mention,
support to the parse_emoji function has been added to detect if an emoji is 
animated or not.

The `EmojiIdentifier` struct is altered to include the animated bool to reflect 
the change.

src/model/misc.rs

@@ -181,9 +181,11 @@ impl_from_str! { struct:
     Role, RoleId, RoleParseError, InvalidRole, parse_role, "invalid role";
 }
 
-/// A version of an emoji used only when solely the Id and name are known.
+/// A version of an emoji used only when solely the animated state, Id, and name are known.
 #[derive(Clone, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
 pub struct EmojiIdentifier {
+    /// Whether the emoji is animated
+    pub animated: bool,
     /// The Id of the emoji.
     pub id: EmojiId,
     /// The name of the emoji. It must be at least 2 characters long and can

src/utils/mod.rs

@@ -247,7 +247,7 @@ pub fn parse_mention(mention: impl AsRef<str>) -> Option<u64> {
     }
 }
 
-/// Retrieves the name and Id from an emoji mention, in the form of an
+/// Retrieves the animated state, name and Id from an emoji mention, in the form of an
 /// `EmojiIdentifier`.
 ///
 /// If the emoji usage is invalid, then `None` is returned.
@@ -262,6 +262,7 @@ pub fn parse_mention(mention: impl AsRef<str>) -> Option<u64> {
 /// use serenity::utils::parse_emoji;
 ///
 /// let expected = EmojiIdentifier {
+///     animated: false,
 ///     id: EmojiId(302516740095606785),
 ///     name: "smugAnimeFace".to_string(),
 /// };
@@ -287,13 +288,16 @@ pub fn parse_emoji(mention: impl AsRef<str>) -> Option<EmojiIdentifier> {
         return None;
     }
 
-    if mention.starts_with("<:") && mention.ends_with('>') {
+    if (mention.starts_with("<:") || mention.starts_with("<a:")) && mention.ends_with('>') {
         let mut name = String::default();
         let mut id = String::default();
+        let animated = &mention[1..3] == "a:";
 
-        for (i, x) in mention[2..].chars().enumerate() {
+        let start = if animated { 3 } else { 2 };
+
+        for (i, x) in mention[start..].chars().enumerate() {
             if x == ':' {
-                let from = i + 3;
+                let from = i + start + 1;
 
                 for y in mention[from..].chars() {
                     if y == '>' {
@@ -311,6 +315,7 @@ pub fn parse_emoji(mention: impl AsRef<str>) -> Option<EmojiIdentifier> {
 
         match id.parse::<u64>() {
             Ok(x) => Some(EmojiIdentifier {
+                animated,
                 name,
                 id: EmojiId(x),
             }),