refactor: klarere typ-extraktion, fullmatch, root-prefix-test

app/ingest/metadata.py

@@ -18,6 +18,10 @@ def parse_path(file_path: str, ingest_root: str) -> PathMetadata | None:
 
     Returns None when the path is outside the ingest root or does not match
     the expected `<root>/<N>.Semester/<Fach>/[<typ>/...]/<file>` pattern.
+
+    Caller must pass a file path. Directory paths (with or without trailing
+    slash) produce undefined results — `PurePosixPath` strips trailing slashes,
+    so a directory ending in `/foo/` is indistinguishable from a file `/foo`.
     """
     norm_path = file_path.lstrip("/")
     norm_root = ingest_root.strip("/")
@@ -28,17 +32,16 @@ def parse_path(file_path: str, ingest_root: str) -> PathMetadata | None:
     relative = norm_path[len(norm_root) + 1:]
     parts = PurePosixPath(relative).parts
 
-    # Need at least: semester / fach / file.ext  → 3 parts
+    # Layout: [semester, fach, *inner, filename] — minimum 3 parts
     if len(parts) < 3:
         return None
 
     semester, fach = parts[0], parts[1]
 
-    if not SEMESTER_RE.match(semester):
+    if not SEMESTER_RE.fullmatch(semester):
         return None
 
-    # parts[-1] is the filename. Anything between fach and filename is "deeper".
-    # The first deeper segment becomes `typ`. None if file lives directly in fach.
-    typ = parts[2] if len(parts) > 3 else None
+    inner = parts[2:-1]  # everything between fach and filename
+    typ = inner[0] if inner else None
 
     return PathMetadata(semester=semester, fach=fach, typ=typ)