feat(media): resolve thumbnail_url using product thumbnail priority (latest still → cad thumbnail)

backend/app/domains/media/router.py

@@ -5,16 +5,60 @@ import zipfile
 
 from fastapi import APIRouter, Depends, HTTPException, Query
 from fastapi.responses import StreamingResponse
+from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.database import get_db
-from app.domains.media.models import MediaAssetType
+from app.domains.media.models import MediaAsset, MediaAssetType
 from app.domains.media.schemas import MediaAssetOut
 from app.domains.media import service
 
 router = APIRouter(prefix="/api/media", tags=["media"], redirect_slashes=False)
 
 
+async def _resolve_thumbnails_bulk(db: AsyncSession, assets: list) -> None:
+    """Resolve thumbnail_url for assets using the same priority as product pages.
+
+    Priority per asset (applied only when thumbnail_url is not yet set):
+      1. Latest 'still' MediaAsset for the same product (rendered preview)
+      2. Product's linked CadFile thumbnail (/api/cad/{id}/thumbnail)
+    """
+    needs = [a for a in assets if not a.thumbnail_url and a.product_id]
+    if not needs:
+        return
+
+    product_ids = list({a.product_id for a in needs})
+
+    # 1. Latest 'still' asset per product (DISTINCT ON product_id ORDER BY created_at DESC)
+    still_rows = await db.execute(
+        select(MediaAsset.product_id, MediaAsset.id)
+        .where(
+            MediaAsset.product_id.in_(product_ids),
+            MediaAsset.asset_type == MediaAssetType.still,
+            MediaAsset.is_archived == False,  # noqa: E712
+        )
+        .order_by(MediaAsset.product_id, MediaAsset.created_at.desc())
+        .distinct(MediaAsset.product_id)
+    )
+    best_still: dict[str, str] = {str(pid): str(sid) for pid, sid in still_rows.all()}
+
+    # 2. Fallback: product's cad_file_id → CAD thumbnail endpoint
+    from app.domains.products.models import Product
+    prod_rows = await db.execute(
+        select(Product.id, Product.cad_file_id).where(Product.id.in_(product_ids))
+    )
+    product_cad: dict[str, str] = {
+        str(pid): str(cid) for pid, cid in prod_rows.all() if cid
+    }
+
+    for a in needs:
+        pid = str(a.product_id)
+        if pid in best_still:
+            a.thumbnail_url = f"/api/media/{best_still[pid]}/download"
+        elif pid in product_cad:
+            a.thumbnail_url = f"/api/cad/{product_cad[pid]}/thumbnail"
+
+
 @router.get("", response_model=list[MediaAssetOut])
 @router.get("/", response_model=list[MediaAssetOut], include_in_schema=False)
 async def list_assets(
@@ -40,6 +84,7 @@ async def list_assets(
     for a in assets:
         a.download_url = service.get_download_url(a)
         a.thumbnail_url = service.get_thumbnail_url(a)
+    await _resolve_thumbnails_bulk(db, assets)
     return assets
 
 
@@ -50,6 +95,7 @@ async def get_asset(asset_id: uuid.UUID, db: AsyncSession = Depends(get_db)):
         raise HTTPException(404, "Asset not found")
     asset.download_url = service.get_download_url(asset)
     asset.thumbnail_url = service.get_thumbnail_url(asset)
+    await _resolve_thumbnails_bulk(db, [asset])
     return asset