Import existing LinTunes project

Snapshot of the existing codebase before working through the TASKS.md
backlog. Real library data (data/) and the iTunes import fixture
(itunes-test-library/) are gitignored.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lintunes/preferences.py

@@ -0,0 +1,73 @@
+import copy
+import json
+from pathlib import Path
+
+from PyQt6.QtCore import QObject, pyqtSignal
+
+
+DEFAULTS = {
+    "ui_scale": "medium",          # small | medium | large
+    "highlight": "blue",           # see theme.HIGHLIGHT_COLORS
+    "now_playing_font": None,      # None=prefer Century Gothic, ""=use app
+                                   # default, "Family"=user-chosen substitute
+    "lastfm": {
+        "api_key": "",
+        "api_secret": "",
+        "username": "",
+        "session_key": "",
+        "scrobble_enabled": False,
+    },
+}
+
+
+class Preferences(QObject):
+    """App preferences persisted to <data_dir>/preferences.json (so they ride
+    the same syncthing share as the library)."""
+
+    changed = pyqtSignal()
+
+    def __init__(self, data_dir: Path, parent=None):
+        super().__init__(parent)
+        self._path = Path(data_dir) / "preferences.json"
+        self._data = copy.deepcopy(DEFAULTS)
+        if self._path.exists():
+            try:
+                with open(self._path, "r", encoding="utf-8") as f:
+                    stored = json.load(f)
+                _deep_merge(self._data, stored)
+            except (ValueError, OSError):
+                pass
+
+    def get(self, key: str, default=None):
+        return self._data.get(key, default)
+
+    def set(self, key: str, value):
+        if self._data.get(key) == value:
+            return
+        self._data[key] = value
+        self.save()
+        self.changed.emit()
+
+    def update_lastfm(self, **fields):
+        self._data["lastfm"].update(fields)
+        self.save()
+        self.changed.emit()
+
+    @property
+    def lastfm(self) -> dict:
+        return self._data["lastfm"]
+
+    def save(self):
+        self._path.parent.mkdir(parents=True, exist_ok=True)
+        tmp = self._path.with_suffix(".json.tmp")
+        with open(tmp, "w", encoding="utf-8") as f:
+            json.dump(self._data, f, indent=2)
+        tmp.replace(self._path)
+
+
+def _deep_merge(base: dict, override: dict):
+    for key, value in override.items():
+        if isinstance(value, dict) and isinstance(base.get(key), dict):
+            _deep_merge(base[key], value)
+        else:
+            base[key] = value