processors(filters): add FunctionFilter

CHANGELOG.md

@@ -5,11 +5,13 @@ All notable changes to **pipecat** will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-
+## [Unreleased]
-## Unreleased
 
 ### Added
 
+- Added a new `FunctionFilter`. This filter will let you filter frames based on
+  a given function, except system messages which should never be filtered.
+
 - Added `enable_metrics` to `PipelineParams`.
 
 - Added `MetricsFrame`. The `MetricsFrame` will report different metrics in the

src/pipecat/processors/filters/function_filter.py

@@ -0,0 +1,30 @@
+#
+# Copyright (c) 2024, Daily
+#
+# SPDX-License-Identifier: BSD 2-Clause License
+#
+
+from typing import Awaitable, Callable
+
+from pipecat.frames.frames import Frame, SystemFrame
+from pipecat.processors.frame_processor import FrameDirection, FrameProcessor
+
+
+class FunctionFilter(FrameProcessor):
+
+    def __init__(self, filter: Callable[[Frame], Awaitable[bool]]):
+        super().__init__()
+        self._filter = filter
+
+    #
+    # Frame processor
+    #
+
+    def _should_passthrough_frame(self, frame):
+        return isinstance(frame, SystemFrame)
+
+    async def process_frame(self, frame: Frame, direction: FrameDirection):
+        passthrough = self._should_passthrough_frame(frame)
+        allowed = await self._filter(frame)
+        if passthrough or allowed:
+            await self.push_frame(frame, direction)