refactor(server): extract the chart routes into routers/chart.py (R3) (#846)

Unblocked by the DLC-path substrate (#843): chart's only server-module deps are
now app + meta_db (both seam); _get_dlc_dir/_resolve_dlc_path come from dlc_paths,
sloppak/loose detection from the shared lib modules. 4 routes (split/unsplit/
work/fileinfo), meta_db-only otherwise. 0 setattr targets, 0 helpers to relocate.

Bodies verbatim; @app -> @router, meta_db -> appstate.meta_db. include_router at
the original site; 143-route table identical to origin/main. No test retargeting.

server.py: 8,003 -> 7,909.

Verified: pyflakes clean on the router; no new undefined/dead in server.py; route
table identical; pytest 2401 passed (74 across work_charts/context_menu/
group_filter/packaging); eslint 0. Boot smoke: chart/work 200, chart/fileinfo
resolves the real pack path through _resolve_dlc_path.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -26,7 +26,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   next root-level module can't ship broken.
 
 ### Added
-- **`routers/` — extracting `server.py`'s route layer, cheapest-first (R3).** Each PR moves a cohesive route group into a `fastapi.APIRouter` under `lib/routers/`, mounted with `app.include_router(...)` at its original site (FastAPI matches in registration order; the full route table stays byte-identical). Bodies are verbatim — only the decorator receiver (`@app` → `@router`) and singleton reads (`meta_db` → `appstate.meta_db`, resolved at call time) change. So far: `audio_effects` (5), `artist_aliases` (5), `loops` (3), `playlists` (12 + covers), `ws_highway` (the 902-line highway chart WebSocket — the single largest handler). The DLC library-path resolution (`_get_dlc_dir`, pure `_resolve_dlc_path`) moved to `lib/dlc_paths.py`, reading paths through the seam; `config_dir`/`dlc_dir`/`dlc_dir_env` now ride the `appstate` seam (env-derived, so the pop-and-reimport fixtures reconfigure it for free), and the shared request-field sanitizer `_clean_str` moved to `lib/reqfields.py`. The next cut is picked by a dependency-closure scan that ranks groups by how many `monkeypatch.setattr(server, …)` targets they'd drag along.
+- **`routers/` — extracting `server.py`'s route layer, cheapest-first (R3).** Each PR moves a cohesive route group into a `fastapi.APIRouter` under `lib/routers/`, mounted with `app.include_router(...)` at its original site (FastAPI matches in registration order; the full route table stays byte-identical). Bodies are verbatim — only the decorator receiver (`@app` → `@router`) and singleton reads (`meta_db` → `appstate.meta_db`, resolved at call time) change. So far: `audio_effects` (5), `artist_aliases` (5), `loops` (3), `playlists` (12 + covers), `ws_highway` (the 902-line highway chart WebSocket), `chart` (split/unsplit/work/fileinfo — unblocked by the DLC-path substrate). The DLC library-path resolution (`_get_dlc_dir`, pure `_resolve_dlc_path`) moved to `lib/dlc_paths.py`, reading paths through the seam; `config_dir`/`dlc_dir`/`dlc_dir_env` now ride the `appstate` seam (env-derived, so the pop-and-reimport fixtures reconfigure it for free), and the shared request-field sanitizer `_clean_str` moved to `lib/reqfields.py`. The next cut is picked by a dependency-closure scan that ranks groups by how many `monkeypatch.setattr(server, …)` targets they'd drag along.
 - **`routers/` — the first extracted route module (R3).** The five audio-effects mapping
   endpoints move out of `server.py` into `lib/routers/audio_effects.py` as a
   `fastapi.APIRouter`, mounted with `app.include_router(...)` **at the point in the file

docs/size-exemptions.md

@@ -55,8 +55,8 @@ without a *signed* exemption" is unenforceable.
 ## Planned, NOT exempt (owned by split plans — listed so nothing falls between states)
 
 core `static/app.js` (11,852) · `static/highway.js` (4,168, whole file) · `server.py`
-(8,003 — was 14,037; ratcheted by the R3 `MetadataDB` + `AudioEffectsMappingDB`
+(7,909 — was 14,037; ratcheted by the R3 `MetadataDB` + `AudioEffectsMappingDB`
-extractions and five `routers/` modules) ·
+extractions and six `routers/` modules) ·
 `lib/metadata_db.py` (4,373 — new in R3; the `MetadataDB` class alone is 4,018 lines
 and is a monolith in its own right, to be split per-table once the router train
 lands) · `static/v3/songs.js` (4,134) · `static/capabilities/audio-session.js`

lib/routers/chart.py

@@ -0,0 +1,115 @@
+"""Chart-level endpoints — split/unsplit a chart from its work, resolve work
+membership, and the context-menu "Get info" file inspector.
+
+Extracted verbatim from ``server.py`` (R3); edits: ``@app`` -> ``@router``,
+``meta_db`` -> ``appstate.meta_db``. DLC path resolution comes from
+``dlc_paths``; sloppak/loose detection from the shared lib modules.
+"""
+
+from fastapi import APIRouter, HTTPException
+
+import appstate
+from dlc_paths import _get_dlc_dir, _resolve_dlc_path
+import sloppak as sloppak_mod
+import loosefolder as loosefolder_mod
+
+router = APIRouter()
+
+
+@router.post("/api/chart/{filename:path}/split")
+def api_split_chart(filename: str):
+    """'These aren't the same song' — split this chart out as its own singleton
+    work. Under /api/chart (NOT /api/song) so the DELETE /api/song/{path}
+    catch-all can't shadow it."""
+    key = appstate.meta_db._canonical_song_filename(filename)
+    appstate.meta_db.split_chart(key)
+    return {"ok": True, "filename": key}
+
+
+@router.post("/api/chart/{filename:path}/unsplit")
+def api_unsplit_chart(filename: str):
+    """Undo a split — rejoin the chart to its work."""
+    key = appstate.meta_db._canonical_song_filename(filename)
+    appstate.meta_db.unsplit_chart(key)
+    return {"ok": True, "filename": key}
+
+
+@router.get("/api/chart/{filename:path}/work")
+def api_get_chart_work(filename: str):
+    """Resolve a chart's work membership: {work_key, chart_count}. For openers
+    on rows that came from an ungrouped query (the tree view) — grouped grid
+    rows already carry both fields inline."""
+    return appstate.meta_db.chart_work(filename)
+
+
+@router.get("/api/chart/{filename:path}/fileinfo")
+def api_chart_fileinfo(filename: str):
+    """The context menu's "Get info": where the file lives + what the pack
+    contains. Under /api/chart — the GET /api/song/{path} catch-all would
+    swallow a /api/song/…/fileinfo suffix. Read-only; demo-mode blocks it
+    because it exposes filesystem paths."""
+    dlc = _get_dlc_dir()
+    if not dlc:
+        raise HTTPException(status_code=404, detail="not configured")
+    p = _resolve_dlc_path(dlc, filename)
+    if p is None:
+        raise HTTPException(status_code=403, detail="forbidden")
+    if not p.exists():
+        raise HTTPException(status_code=404, detail="not found")
+    # Restrict to actual charts — sloppak or loose song. Without this the route
+    # would stat ANY file the user happens to keep under DLC_DIR (e.g. notes),
+    # leaking its path/size; the app only recognises these two song formats.
+    is_pak = sloppak_mod.is_sloppak(p)
+    is_loose = loosefolder_mod.is_loose_song(p)
+    if not (is_pak or is_loose):
+        raise HTTPException(status_code=404, detail="not a chart")
+    st = p.stat()
+    info = {
+        "filename": filename,
+        "path": str(p),
+        "folder": str(p.parent),
+        "format": "sloppak" if is_pak else "loose",
+        # Directory-form songs report the tree's total (covers loose folders
+        # and dir-form paks); zip-form paks report the archive size. Symlinked
+        # entries are skipped so a link inside the folder can't pull in — or
+        # leak the size of — a file outside it.
+        "size": (st.st_size if p.is_file()
+                 else sum(f.stat().st_size for f in p.rglob("*")
+                          if f.is_file() and not f.is_symlink())),
+        "mtime": st.st_mtime,
+    }
+    if is_pak:
+        try:
+            m = sloppak_mod.load_manifest(p) or {}
+        except Exception:
+            m = {}
+        arrs = [str(a.get("name", a.get("id", ""))) for a in (m.get("arrangements") or [])
+                if isinstance(a, dict)]
+        stems = [str(s.get("id", "")) for s in (m.get("stems") or []) if isinstance(s, dict)]
+        try:
+            has_cover = sloppak_mod.read_cover_bytes(p, m) is not None
+        except Exception:
+            has_cover = False
+        # The optional identity/catalog keys, listed only when present — the
+        # Get-info panel's "what this pack carries vs what's missing" readout.
+        identity = {k: m.get(k) for k in
+                    ("mbid", "isrc", "genres", "track", "disc", "album_artist",
+                     "feedpak_version", "language")
+                    if m.get(k) not in (None, "", [])}
+        info["manifest"] = {
+            "title": str(m.get("title", "")), "artist": str(m.get("artist", "")),
+            "album": str(m.get("album", "")), "year": str(m.get("year", "") or ""),
+            "arrangements": arrs, "stems": stems,
+            "has_cover": has_cover, "has_lyrics": bool(m.get("lyrics")),
+            "authors": [a.get("name", "") if isinstance(a, dict) else str(a)
+                        for a in (m.get("authors") or [])],
+            "identity": identity,
+        }
+    # The enrichment verdict, so Get info can say "Matched (auto, 96%)" /
+    # "Pinned by you" / "Not matched" alongside the file facts.
+    row = appstate.meta_db.get_enrichment(filename)
+    if row:
+        info["match"] = {k: row.get(k) for k in
+                         ("match_state", "match_source", "match_score",
+                          "canon_artist", "canon_title", "canon_album", "canon_year")}
+    return info

server.py

@@ -55,7 +55,7 @@ from dlc_paths import _get_dlc_dir, _resolve_dlc_path
 # Lives in lib/ because that is the one core dir every packaging path copies.
 import appstate
 # Extracted route modules. They import `appstate`, never `server` — one-way graph.
-from routers import audio_effects, artist_aliases, loops, playlists, ws_highway
+from routers import audio_effects, artist_aliases, loops, playlists, ws_highway, chart
 import sloppak as sloppak_mod
 import loosefolder as loosefolder_mod
 # Pure text-matching engine for MusicBrainz enrichment (P8): denoise/score/
@@ -4256,103 +4256,9 @@ def api_reset_work_preferred(work_key: str):
     return meta_db.work_charts(work_key)
 
 
-@app.post("/api/chart/{filename:path}/split")
+# ── Chart-level endpoints (split/work/fileinfo) ──────────────────────────────
-def api_split_chart(filename: str):
+# Mounted here (registration order). Implementation in lib/routers/chart.py.
-    """'These aren't the same song' — split this chart out as its own singleton
+app.include_router(chart.router)
-    work. Under /api/chart (NOT /api/song) so the DELETE /api/song/{path}
-    catch-all can't shadow it."""
-    key = meta_db._canonical_song_filename(filename)
-    meta_db.split_chart(key)
-    return {"ok": True, "filename": key}
-
-
-@app.post("/api/chart/{filename:path}/unsplit")
-def api_unsplit_chart(filename: str):
-    """Undo a split — rejoin the chart to its work."""
-    key = meta_db._canonical_song_filename(filename)
-    meta_db.unsplit_chart(key)
-    return {"ok": True, "filename": key}
-
-
-@app.get("/api/chart/{filename:path}/work")
-def api_get_chart_work(filename: str):
-    """Resolve a chart's work membership: {work_key, chart_count}. For openers
-    on rows that came from an ungrouped query (the tree view) — grouped grid
-    rows already carry both fields inline."""
-    return meta_db.chart_work(filename)
-
-
-@app.get("/api/chart/{filename:path}/fileinfo")
-def api_chart_fileinfo(filename: str):
-    """The context menu's "Get info": where the file lives + what the pack
-    contains. Under /api/chart — the GET /api/song/{path} catch-all would
-    swallow a /api/song/…/fileinfo suffix. Read-only; demo-mode blocks it
-    because it exposes filesystem paths."""
-    dlc = _get_dlc_dir()
-    if not dlc:
-        raise HTTPException(status_code=404, detail="not configured")
-    p = _resolve_dlc_path(dlc, filename)
-    if p is None:
-        raise HTTPException(status_code=403, detail="forbidden")
-    if not p.exists():
-        raise HTTPException(status_code=404, detail="not found")
-    # Restrict to actual charts — sloppak or loose song. Without this the route
-    # would stat ANY file the user happens to keep under DLC_DIR (e.g. notes),
-    # leaking its path/size; the app only recognises these two song formats.
-    is_pak = sloppak_mod.is_sloppak(p)
-    is_loose = loosefolder_mod.is_loose_song(p)
-    if not (is_pak or is_loose):
-        raise HTTPException(status_code=404, detail="not a chart")
-    st = p.stat()
-    info = {
-        "filename": filename,
-        "path": str(p),
-        "folder": str(p.parent),
-        "format": "sloppak" if is_pak else "loose",
-        # Directory-form songs report the tree's total (covers loose folders
-        # and dir-form paks); zip-form paks report the archive size. Symlinked
-        # entries are skipped so a link inside the folder can't pull in — or
-        # leak the size of — a file outside it.
-        "size": (st.st_size if p.is_file()
-                 else sum(f.stat().st_size for f in p.rglob("*")
-                          if f.is_file() and not f.is_symlink())),
-        "mtime": st.st_mtime,
-    }
-    if is_pak:
-        try:
-            m = sloppak_mod.load_manifest(p) or {}
-        except Exception:
-            m = {}
-        arrs = [str(a.get("name", a.get("id", ""))) for a in (m.get("arrangements") or [])
-                if isinstance(a, dict)]
-        stems = [str(s.get("id", "")) for s in (m.get("stems") or []) if isinstance(s, dict)]
-        try:
-            has_cover = sloppak_mod.read_cover_bytes(p, m) is not None
-        except Exception:
-            has_cover = False
-        # The optional identity/catalog keys, listed only when present — the
-        # Get-info panel's "what this pack carries vs what's missing" readout.
-        identity = {k: m.get(k) for k in
-                    ("mbid", "isrc", "genres", "track", "disc", "album_artist",
-                     "feedpak_version", "language")
-                    if m.get(k) not in (None, "", [])}
-        info["manifest"] = {
-            "title": str(m.get("title", "")), "artist": str(m.get("artist", "")),
-            "album": str(m.get("album", "")), "year": str(m.get("year", "") or ""),
-            "arrangements": arrs, "stems": stems,
-            "has_cover": has_cover, "has_lyrics": bool(m.get("lyrics")),
-            "authors": [a.get("name", "") if isinstance(a, dict) else str(a)
-                        for a in (m.get("authors") or [])],
-            "identity": identity,
-        }
-    # The enrichment verdict, so Get info can say "Matched (auto, 96%)" /
-    # "Pinned by you" / "Not matched" alongside the file facts.
-    row = meta_db.get_enrichment(filename)
-    if row:
-        info["match"] = {k: row.get(k) for k in
-                         ("match_state", "match_source", "match_score",
-                          "canon_artist", "canon_title", "canon_album", "canon_year")}
-    return info
 
 
 @app.get("/api/library/albums")