refactor(analyzer): improve analyzer pipeline module (#1542)

* rename steps to pipeline module

* move pipeline entrypoint to pipeline module

* rename steps test module to pipeline

* fix paths after renames

* move step protocol to pipeline

* create pipeline status enum

* use Protocol from typing extensions

* Fix linting

analyzer/libretime_analyzer/pipeline/analyze_replaygain.py

@@ -0,0 +1,27 @@
+from subprocess import CalledProcessError
+from typing import Any, Dict
+
+from ..ffmpeg import compute_replaygain, probe_replaygain
+
+
+def analyze_replaygain(filepath: str, metadata: Dict[str, Any]):
+    """
+    Extracts the Replaygain loudness normalization factor of a track using ffmpeg.
+    """
+    try:
+        # First probe for existing replaygain metadata.
+        track_gain = probe_replaygain(filepath)
+        if track_gain is not None:
+            metadata["replay_gain"] = track_gain
+            return metadata
+    except (CalledProcessError, OSError):
+        pass
+
+    try:
+        track_gain = compute_replaygain(filepath)
+        if track_gain is not None:
+            metadata["replay_gain"] = track_gain
+    except (CalledProcessError, OSError):
+        pass
+
+    return metadata