Initial commit: Paperwall, a standalone e-ink dashboard

Navidrome now-playing, clock, and weather for a Waveshare epd4in0e panel,
with a local web UI and install/uninstall scripts for the Pi.

config.py

@@ -0,0 +1,87 @@
+"""Single JSON config file, loaded once and kept in memory.
+
+Unlike InkyPi's Config (which we spent a long time debugging), writes happen
+immediately on every change from the web UI, and the scheduler re-reads the
+in-memory structure fresh on every tick -- there's no "did the setting
+actually take effect" gap, because there's no long sleep to get stuck in.
+"""
+
+import json
+import logging
+import threading
+from pathlib import Path
+
+logger = logging.getLogger(__name__)
+
+DEFAULT_CONFIG_PATH = Path(__file__).resolve().parent / "config.json"
+
+DEFAULT_ROTATION = {
+    "screens": ["clock", "weather"],
+    "interval_seconds": 300,
+}
+
+
+class Config:
+    def __init__(self, screens: dict, path: Path = DEFAULT_CONFIG_PATH):
+        self.path = path
+        self._lock = threading.Lock()
+        self._data = self._load(screens)
+
+    def _load(self, screens: dict) -> dict:
+        if self.path.exists():
+            with open(self.path) as f:
+                data = json.load(f)
+        else:
+            data = {}
+
+        data.setdefault("rotation", dict(DEFAULT_ROTATION))
+        data.setdefault("navidrome_priority", True)
+        data.setdefault("settings", {})
+        for screen_id, screen in screens.items():
+            data["settings"].setdefault(screen_id, {})
+            for key, value in screen.default_settings().items():
+                data["settings"][screen_id].setdefault(key, value)
+
+        return data
+
+    def save(self) -> None:
+        with self._lock:
+            tmp_path = self.path.with_suffix(".json.tmp")
+            with open(tmp_path, "w") as f:
+                json.dump(self._data, f, indent=2)
+            tmp_path.replace(self.path)
+            logger.debug("Config written to %s", self.path)
+
+    # ------------------------------------------------------------ screens
+
+    def get_screen_settings(self, screen_id: str) -> dict:
+        """Returns the live, mutable settings dict for a screen -- screens are
+        allowed to write ephemeral state into it (e.g. Navidrome's last-known
+        track for the idle fallback)."""
+        with self._lock:
+            return self._data["settings"].setdefault(screen_id, {})
+
+    def update_screen_settings(self, screen_id: str, updates: dict) -> None:
+        with self._lock:
+            self._data["settings"].setdefault(screen_id, {}).update(updates)
+        self.save()
+
+    # ----------------------------------------------------------- rotation
+
+    def get_rotation(self) -> dict:
+        with self._lock:
+            return dict(self._data["rotation"])
+
+    def set_rotation(self, screens: list[str], interval_seconds: int) -> None:
+        with self._lock:
+            self._data["rotation"] = {"screens": screens, "interval_seconds": interval_seconds}
+        self.save()
+
+    def get_navidrome_priority(self) -> bool:
+        with self._lock:
+            return bool(self._data["navidrome_priority"])
+
+    def set_navidrome_priority(self, enabled: bool) -> None:
+        with self._lock:
+            self._data["navidrome_priority"] = enabled
+        self.save()