Arsitektur: upload tetap menyimpan original apa adanya; optimasi terjadi
saat serving — gambar raster di-resize (maks 1600px) + encode WebP
(quality 80), di-generate on-the-fly lalu di-cache di disk.
- config.CACHE_DIR = sibling ASSETS_DIR ('assets-cache'), WAJIB di luar
ASSETS_DIR supaya export_bundle (os.walk tanpa filter) tetap lossless
- services/image_cache.py: varian WebP, cache key path+mtime+size+width,
invalidasi otomatis via mtime, atomic write, fallback original bila gagal
- routes/lessons.py::send_assets: handler (bukan static serve) —
.png/.jpg/.jpeg/.webp/.gif -> varian WebP; .svg & GIF animasi pass-through;
?orig=1 untuk original; ?w= untuk lebar alternatif; ETag + Cache-Control
- Dockerfile: buat /app/assets-cache writable
Test (services/tests/test_asset_cache.py, 20 test): lokasi cache di luar
ASSETS_DIR, cache reuse, invalidasi mtime, passthrough SVG/GIF animasi,
fallback file korup, ETag/304, dan acceptance test — upload -> request ->
export bundle berisi HANYA original tanpa .webp turunan.
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