[commands] Split Cooldown state processing to two different functions.

This allows us to check if we are rate limited without
creating a new cool-down window for the command.

discord/ext/commands/cooldowns.py

@@ -48,20 +48,27 @@ class Cooldown:
         if not isinstance(self.type, BucketType):
             raise TypeError('Cooldown type must be a BucketType')
 
-    def is_rate_limited(self):
+    def get_tokens(self, current=None):
+        if not current:
+            current = time.time()
+
+        tokens = self._tokens
+
+        if current > self._window + self.per:
+            tokens = self.rate
+        return tokens
+
+    def update_rate_limit(self):
         current = time.time()
         self._last = current
 
+        self._tokens = self.get_tokens(current)
+
         # first token used means that we start a new rate limit window
         if self._tokens == self.rate:
             self._window = current
 
-        # check if our window has passed and we can refresh our tokens
+        # check if we are rate limited
-        if current > self._window + self.per:
-            self._tokens = self.rate
-            self._window = current
-
-        # check if we're rate limited
         if self._tokens == 0:
             return self.per - (current - self._window)
 

discord/ext/commands/core.py

@@ -439,13 +439,32 @@ class Command:
 
         if self._buckets.valid:
             bucket = self._buckets.get_bucket(ctx)
-            retry_after = bucket.is_rate_limited()
+            retry_after = bucket.update_rate_limit()
             if retry_after:
                 raise CommandOnCooldown(bucket, retry_after)
 
         yield from self._parse_arguments(ctx)
         yield from self.call_before_hooks(ctx)
 
+    def is_on_cooldown(self, ctx):
+        """Checks whether the command is currently on cooldown.
+
+        Parameters
+        -----------
+        ctx: :class:`.Context.`
+            The invocation context to use when checking the commands cooldown status.
+
+        Returns
+        --------
+        bool
+            A boolean indicating if the command is on cooldown.
+        """
+        if not self._buckets.valid:
+            return False
+
+        bucket = self._buckets.get_bucket(ctx)
+        return bucket.get_tokens() == 0
+
     def reset_cooldown(self, ctx):
         """Resets the cooldown on this command.