275 lines
10 KiB
Python
275 lines
10 KiB
Python
"""ThumbnailService — safe, cached, correctly oriented previews by asset ID.
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Thumbnails are requested by asset ID (never a browser-supplied path), resolved to
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the current path through the database, and validated against the configured library
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boundary. Generation applies EXIF orientation before resizing, preserves
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transparency, and encodes WebP. The cache key is ``pixel_hash + size + version``, so
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an EXIF-only edit reuses the file while a real pixel change invalidates it; writes
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are atomic and the cache is bounded by an LRU quota. Failures are persisted as typed
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errors so a broken original is not retried on every request.
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Reuses photo_analyzer.prepare_image decode/resize/HEIC handling, adding the missing
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EXIF-orientation step, WebP output, and a managed cache (donor_ledger.yaml:
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pa-imaging).
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"""
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from __future__ import annotations
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import uuid
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from pathlib import Path
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from PIL import Image, ImageOps, UnidentifiedImageError
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from sqlalchemy import select
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from sqlalchemy.exc import IntegrityError
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from sqlalchemy.orm import sessionmaker
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from photo_pipeline import path_policy
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from photo_pipeline.config import Config
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from photo_pipeline.models import Asset, Thumbnail
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# Best-effort HEIC support: registered only if the optional decoder is installed.
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try: # pragma: no cover - depends on an optional native dependency
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import pillow_heif
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pillow_heif.register_heif_opener()
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except Exception: # pragma: no cover
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pass
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SIZES = (256, 512, 1280)
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THUMB_VERSION = 1
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THUMB_FORMAT = "webp"
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class ThumbnailError(RuntimeError):
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code = "thumbnail_error"
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http_status = 500
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class InvalidSize(ThumbnailError):
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code = "invalid_size"
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http_status = 422
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class ThumbnailNotFound(ThumbnailError):
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code = "not_found"
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http_status = 404
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class ThumbnailUnavailable(ThumbnailError):
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code = "unavailable"
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http_status = 409
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class UnsupportedImage(ThumbnailError):
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code = "unsupported_image"
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http_status = 415
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class ImageTooLarge(ThumbnailError):
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code = "image_too_large"
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http_status = 413
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class PathNotAllowed(ThumbnailError):
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code = "path_not_allowed"
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http_status = 403
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# Errors that describe a broken source and are persisted to avoid retry loops.
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_PERSISTED_ERRORS = {UnsupportedImage, ImageTooLarge}
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_ERROR_BY_CODE = {cls.code: cls for cls in _PERSISTED_ERRORS}
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class ThumbnailService:
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def __init__(self, session_factory: sessionmaker, config: Config) -> None:
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self._session_factory = session_factory
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self._config = config
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self._cache_dir = config.thumbnail_cache_dir
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def generate(self, asset_id: str, size: int) -> Path:
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if size not in SIZES:
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raise InvalidSize(f"size must be one of {SIZES}")
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with self._session_factory() as session:
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asset = session.get(Asset, asset_id)
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if asset is None:
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raise ThumbnailNotFound(f"unknown asset {asset_id}")
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if asset.availability_state != "active" or not asset.current_path:
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raise ThumbnailUnavailable(f"asset {asset_id} has no active file")
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self._validate_path(asset.current_path)
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cache_key = self._cache_key(asset, size)
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row = session.get(Thumbnail, cache_key)
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if row is not None:
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if row.state == "error":
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raise _ERROR_BY_CODE[row.error_code](
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f"cached failure for {asset_id}: {row.error_code}"
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)
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if row.path and Path(row.path).exists():
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_touch(row.path)
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return Path(row.path)
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source = asset.current_path
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# Rendering happens outside the DB session (no transaction held during I/O).
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try:
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rendered = self._render(source, size, cache_key)
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except ThumbnailError as error:
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if type(error) in _PERSISTED_ERRORS:
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self._record_error(cache_key, asset_id, size, error.code)
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raise
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self._record_ready(cache_key, asset_id, size, rendered)
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self._enforce_quota(keep=rendered["path"])
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return Path(rendered["path"])
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# ── path safety ──────────────────────────────────────────────────────────
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def _validate_path(self, current_path: str) -> None:
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path = Path(current_path)
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if path_policy.is_excluded(path):
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raise PathNotAllowed(f"excluded path: {current_path}")
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roots = self._config.library_roots
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if not roots:
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return
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for root in roots:
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try:
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path_policy.resolve_within(Path(root), path)
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return
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except path_policy.PathPolicyError:
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continue
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raise PathNotAllowed(f"path outside configured roots: {current_path}")
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# ── cache key + rendering ──────────────────────────────────────────────────
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@staticmethod
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def _cache_key(asset: Asset, size: int) -> str:
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if asset.pixel_sha256:
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return f"{asset.pixel_sha256}-{size}-v{THUMB_VERSION}"
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# Undecodable at inventory time: key by source bytes so a fixed file retries.
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return f"src:{asset.current_sha256 or asset.id}-{size}-v{THUMB_VERSION}"
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def _cache_path(self, cache_key: str) -> Path:
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safe = cache_key.replace(":", "_")
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return self._cache_dir / safe[:2] / f"{safe}.{THUMB_FORMAT}"
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def _render(self, source: str, size: int, cache_key: str) -> dict:
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try:
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with Image.open(source) as image:
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width, height = image.size
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if width * height > self._config.thumbnail_max_pixels:
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raise ImageTooLarge(
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f"{width}x{height} exceeds {self._config.thumbnail_max_pixels} px"
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)
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oriented = ImageOps.exif_transpose(image)
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mode = "RGBA" if _has_alpha(oriented) else "RGB"
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converted = oriented.convert(mode)
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converted.thumbnail((size, size), Image.LANCZOS)
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out_width, out_height = converted.size
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destination = self._cache_path(cache_key)
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destination.parent.mkdir(parents=True, exist_ok=True)
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tmp = destination.with_name(f".{destination.name}.{uuid.uuid4().hex}.tmp")
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converted.save(tmp, format="WEBP", quality=82, method=4)
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except ImageTooLarge:
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raise
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except (UnidentifiedImageError, OSError, ValueError) as error:
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raise UnsupportedImage(f"cannot decode {source}: {error}") from error
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import os
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os.replace(tmp, destination)
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return {
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"path": str(destination),
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"width": out_width,
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"height": out_height,
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"format": THUMB_FORMAT,
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}
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# ── persistence ────────────────────────────────────────────────────────────
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def _record_ready(self, cache_key: str, asset_id: str, size: int, rendered: dict) -> None:
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with self._session_factory() as session:
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session.merge(
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Thumbnail(
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cache_key=cache_key,
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asset_id=asset_id,
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size=size,
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state="ready",
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error_code=None,
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path=rendered["path"],
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width=rendered["width"],
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height=rendered["height"],
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format=rendered["format"],
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)
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)
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try:
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session.commit()
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except IntegrityError:
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session.rollback() # another worker recorded it first; the file stands
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def _record_error(self, cache_key: str, asset_id: str, size: int, code: str) -> None:
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with self._session_factory() as session:
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session.merge(
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Thumbnail(
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cache_key=cache_key,
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asset_id=asset_id,
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size=size,
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state="error",
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error_code=code,
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)
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)
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try:
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session.commit()
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except IntegrityError:
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session.rollback()
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# ── quota / eviction ───────────────────────────────────────────────────────
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def _enforce_quota(self, keep: str | None = None) -> None:
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quota = self._config.thumbnail_cache_quota_bytes
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if not self._cache_dir.exists():
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return
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files = [f for f in self._cache_dir.rglob(f"*.{THUMB_FORMAT}") if f.is_file()]
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total = sum(f.stat().st_size for f in files)
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if total <= quota:
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return
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files.sort(key=lambda f: f.stat().st_mtime) # least-recently-used first
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keep_path = str(Path(keep)) if keep else None
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evicted: list[str] = []
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for f in files:
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if total <= quota:
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break
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if str(f) == keep_path:
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continue
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size = f.stat().st_size
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try:
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f.unlink()
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total -= size
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evicted.append(str(f))
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except OSError:
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pass
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if evicted:
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self._forget(evicted)
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def _forget(self, paths: list[str]) -> None:
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with self._session_factory() as session:
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rows = session.execute(
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select(Thumbnail).where(Thumbnail.path.in_(paths))
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).scalars()
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for row in rows:
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session.delete(row)
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session.commit()
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def _has_alpha(image: Image.Image) -> bool:
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return image.mode in ("RGBA", "LA") or (
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image.mode == "P" and "transparency" in image.info
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)
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def _touch(path: str) -> None:
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import os
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import time
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try:
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now = time.time()
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os.utime(path, (now, now))
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except OSError:
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pass
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