Improve controller behavior and update project requirements

核桃派软件源代码/app/mobile/preview_cache.py

@@ -0,0 +1,48 @@
+"""Regenerable BLE library previews, isolated from user-owned media."""
+from __future__ import annotations
+
+import hashlib
+import re
+from io import BytesIO
+from pathlib import Path
+
+from PIL import Image
+
+from app.persistence import atomic_write_bytes
+
+
+_PREVIEW_FILE = re.compile(r"[0-9a-f]{64}\.png\Z")
+
+
+class PreviewCache:
+    def __init__(self, data_dir: Path):
+        self.root = Path(data_dir) / "mobile" / "previews"
+        self.root.mkdir(parents=True, exist_ok=True)
+
+    @staticmethod
+    def name(item: dict) -> str:
+        identity = "\0".join(str(item[key]) for key in ("type", "id", "revision"))
+        return hashlib.sha256(identity.encode("utf-8")).hexdigest() + ".png"
+
+    def reconcile(self, items: list[dict]) -> None:
+        expected = {self.name(item) for item in items}
+        for path in self.root.iterdir():
+            if path.is_file() and _PREVIEW_FILE.fullmatch(path.name) and path.name not in expected:
+                path.unlink(missing_ok=True)
+
+    def get(self, item: dict, image: Image.Image) -> bytes:
+        path = self.root / self.name(item)
+        if path.exists():
+            try:
+                data = path.read_bytes()
+                with Image.open(BytesIO(data)) as cached:
+                    cached.verify()
+                    if cached.format == "PNG" and cached.size == (16, 16):
+                        return data
+            except (OSError, ValueError):
+                pass
+        output = BytesIO()
+        image.convert("RGB").resize((16, 16), Image.Resampling.LANCZOS).save(output, format="PNG", optimize=True)
+        data = output.getvalue()
+        atomic_write_bytes(path, data)
+        return data