Don't panic if index is empty

src/commands.rs

@@ -178,7 +178,12 @@ pub enum Command {
 }
 
 impl Command {
-    /// Performs the conversion
+    /// Creates a Command from a `&str`. Currently only `[PING]` and `[PRIVMSG]` are supported.
+    ///
+    /// # Panics
+    ///
+    /// This function will panic if the IRCd sends malformed messages. Please contact the
+    /// maintainer of your IRCd if this happens.
     pub fn from_str(s: &str) -> Self {
         let new = s.trim();
 
@@ -187,12 +192,14 @@ impl Command {
 
         let parts: Vec<&str> = new.split_whitespace().collect();
 
-        if parts[0] == "PING" {
+        if parts.get(0) == Some(&"PING") {
+            // We can assume that [1] exists because if it doesn't then something's gone very wrong
+            // with the IRCD
             let command = parts[1].to_string();
             return Self::PONG(command);
-        } else if parts[1] == "PRIVMSG" {
+        } else if parts.get(1) == Some(&"PRIVMSG") {
             let nick = parts[0];
-            let index = nick.chars().position(|c| c == '!').unwrap();
+            let index = nick.chars().position(|c| c == '!').unwrap(); // This panics for the same reason as above
             let nick = String::from(&nick[1..index]);
             let target = parts[2];
             let mut builder = String::new();