config, bot: Configurable message rate

Original change description by @larsks (from #908, slightly edited):

This adds several knobs that control how fast the bot sends multiple
messages to the same recipient:

- bucket_burst_tokens -- this controls how many messages may be sent in
  "burst mode", i.e., without any inter-message delay.
- bucket_refill_rate -- once exhausted, burst tokens are refilled at a
  rate of bucket_refill_rate tokens/second.
- bucket_empty_wait -- how long to wait between sending messages when
  not in burst mode.

This permits the bot to return a few lines of information quickly and
not trigger flood protection.

How it works:

When sending to a new recipient, we initialize a token counter to
bucket_burst_tokens. Every time we send a message, we decrement this by
1. If the token counter reaches 0, we engage the rate limiting behavior
(which is identical to the existing code, except that the minimum wait
of 0.7 seconds is now configurable).

When sending a new message to an existing recipient, we check if the
token counter is exhausted. If it is, we refill it based on the elapsed
time since the last message and the value of bucket_refill_rate, and
then proceed as described above.

----

Adapted to current Sopel code and rebased by these users, respectively:

Co-authored-by: kwaaak <kwaaak@users.noreply.github.com>
Co-authored-by: dgw <dgw@technobabbl.es>

sopel/bot.py

@@ -305,18 +305,28 @@ def say(self, text, recipient, max_messages=1):
 
             recipient_id = Identifier(recipient)
 
-            if recipient_id not in self.stack:
-                self.stack[recipient_id] = []
-            elif self.stack[recipient_id]:
-                elapsed = time.time() - self.stack[recipient_id][-1][0]
-                if elapsed < 3:
-                    penalty = float(max(0, len(text) - 40)) / 70
-                    wait = 0.8 + penalty
-                    if elapsed < wait:
-                        time.sleep(wait - elapsed)
+            reciprec = self.stack.get(recipient_id)
+            if not reciprec:
+                reciprec = self.stack[recipient_id] = {
+                    'messages': [],
+                    'burst': self.config.core.bucket_burst_tokens,
+                }
+
+            if not reciprec['burst']:
+                elapsed = time.time() - reciprec['messages'][-1][0]
+                reciprec['burst'] = min(
+                    self.config.core.bucket_burst_tokens,
+                    int(elapsed) * self.config.core.bucket_refill_rate)
+
+            if not reciprec['burst']:
+                elapsed = time.time() - reciprec['messages'][-1][0]
+                penalty = float(max(0, len(text) - 50)) / 70
+                wait = self.config.core.bucket_empty_wait + penalty
+                if elapsed < wait:
+                    time.sleep(wait - elapsed)
 
                 # Loop detection
-                messages = [m[1] for m in self.stack[recipient_id][-8:]]
+                messages = [m[1] for m in reciprec['messages'][-8:]]
 
                 # If what we about to send repeated at least 5 times in the
                 # last 2 minutes, replace with '...'
@@ -327,8 +337,9 @@ def say(self, text, recipient, max_messages=1):
                         return
 
             self.write(('PRIVMSG', recipient), text)
-            self.stack[recipient_id].append((time.time(), self.safe(text)))
-            self.stack[recipient_id] = self.stack[recipient_id][-10:]
+            reciprec['burst'] = max(0, reciprec['burst'] - 1)
+            reciprec['messages'].append((time.time(), self.safe(text)))
+            reciprec['messages'] = reciprec['messages'][-10:]
         finally:
             self.sending.release()
         # Now that we've sent the first part, we need to send the rest. Doing

sopel/config/core_section.py

@@ -216,3 +216,16 @@ def homedir(self):
 
     verify_ssl = ValidatedAttribute('verify_ssl', bool, default=True)
     """Whether to require a trusted SSL certificate for SSL connections."""
+
+    bucket_burst_tokens = ValidatedAttribute('bucket_burst_tokens', int,
+                                             default=4)
+    """How many messages can be sent in burst mode."""
+
+    bucket_refill_rate = ValidatedAttribute('bucket_refill_rate', int,
+                                            default=1)
+    """How many tokens/second to add to the token bucket."""
+
+    bucket_empty_wait = ValidatedAttribute('bucket_empty_wait', float,
+                                           default=0.7)
+    """How long to wait before sending a messaging when not in burst
+    mode."""