feat(liquidsoap): filename-based fallback when title/album tags are empty

config/liquidsoap.liq

@@ -56,6 +56,27 @@ def make_deck(dir) =
   { source = request.dynamic(next_request), peek = peek }
 end
 
+# filename-based fallbacks for tracks with empty embedded tags.
+# strips leading "08. " / "12 - " etc. from the file stem.
+def filename_title(filename) =
+  base = path.basename(filename)
+  ext = file.extension(leading_dot=true, base)
+  stem =
+    if ext != "" then
+      string.sub(base, start=0, length=string.length(base) - string.length(ext))
+    else base end
+  re = regexp("^[0-9]+[. \\-]+ *")
+  re.replace(fun(_) -> "", stem)
+end
+
+def filename_album(filename) =
+  path.basename(path.dirname(filename))
+end
+
+def or_else(s, fallback) =
+  if s == "" then fallback else s end
+end
+
 # walk up from the audio file to find cover.{jpg,png,webp}.
 # falls back to <station>/cover.* (one level above tracks/).
 def cover_for(filename) =
@@ -85,9 +106,9 @@ def track_meta_json(filename) =
   request.destroy(r)
   d = null.get(default=-1., request.duration(filename))
   obj = json()
-  obj.add("title", m["title"])
+  obj.add("title", or_else(m["title"], filename_title(filename)))
   obj.add("artist", m["artist"])
-  obj.add("album", m["album"])
+  obj.add("album", or_else(m["album"], filename_album(filename)))
   obj.add("duration", if d > 0. then string(int_of_float(d)) else "" end)
   obj.add("cover_path", cover_for(filename))
   obj
@@ -108,8 +129,8 @@ def emit_now_playing(station, m, upcoming) =
     payload = json()
     payload.add("station", station)
     payload.add("artist", m["artist"])
-    payload.add("title", m["title"])
-    payload.add("album", m["album"])
+    payload.add("title", or_else(m["title"], filename_title(filename)))
+    payload.add("album", or_else(m["album"], filename_album(filename)))
     payload.add("filename", filename)
     payload.add("duration", dur_str)
     payload.add("started_at", string(int_of_float(time())))