From 63da3ad2e2098551143194f8fcc2f58259adb9a1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastjan=20Arti=C4=8D?= <sebastjan@folx.tv>
Date: Thu, 30 Apr 2026 12:05:11 +0000
Subject: [PATCH] Preview-clip: validate cache, support HEAD, cleanup on fail
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Bugs from puppeteer inspection:
1. Old buggy renders left 0-byte cache files behind. New code never
   re-rendered because cache_path.exists() was True.
   Fix: validate cache file is >1KB, otherwise re-render.

2. FastAPI @app.get only handles GET, not HEAD. Frontend's HEAD check
   returned 405, then GET re-rendered (correct), but second click also
   returned 405 then 200 again — confusing.
   Fix: use @app.api_route with methods=['GET', 'HEAD']

3. If ffmpeg fails partway, broken file remains in cache.
   Fix: unlink on any failure path.

Also deleted existing empty cache files in container.
---
 app/main.py | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/app/main.py b/app/main.py
index 88ac19b..ee25d8f 100644
--- a/app/main.py
+++ b/app/main.py
@@ -1249,7 +1249,7 @@ async def source_video(job_id: str, user: str = Depends(check_auth)):
     )
 
 
-@app.get("/api/preview-clip/{job_id}")
+@app.api_route("/api/preview-clip/{job_id}", methods=["GET", "HEAD"])
 async def preview_clip(
     job_id: str,
     start: float,
@@ -1262,6 +1262,7 @@ async def preview_clip(
     Cilj: ~2-3s render za takojšen feedback med Edit dragom.
     
     Cache po start+end timestampih da ponovljeni request ne renderira ponovno.
+    Podpira HEAD (frontend cache check).
     """
     job = load_job(job_id)
     if not job:
@@ -1282,19 +1283,24 @@ async def preview_clip(
     cache_key = f"{job_id}_preview_{start:.1f}_{end:.1f}.mp4"
     cache_path = OUTPUT_DIR / cache_key
     
-    if not cache_path.exists():
-        # ffmpeg low-q clip — copy stream če gre, sicer hitro re-encode
-        # -ss pred -i: hiter seek (keyframe), idealno za preview
+    # Validate cache: datoteka mora obstajati IN biti vsaj 1KB
+    cache_valid = cache_path.exists() and cache_path.stat().st_size > 1024
+    
+    if not cache_valid:
+        # Briši staro prazno če obstaja
+        if cache_path.exists():
+            cache_path.unlink()
+        # ffmpeg low-q clip — fast seek + force even dimensions for libx264
         cmd = [
             "ffmpeg", "-y",
             "-ss", f"{max(0, start - 0.5):.2f}",  # 0.5s buffer za keyframe
             "-i", str(src),
             "-ss", f"{min(0.5, start):.2f}",  # fine seek
             "-t", f"{duration:.2f}",
-            "-vf", "scale=854:480:force_original_aspect_ratio=decrease,scale=trunc(iw/2)*2:trunc(ih/2)*2",  # 480p, even dimensions for libx264
+            "-vf", "scale=854:480:force_original_aspect_ratio=decrease,scale=trunc(iw/2)*2:trunc(ih/2)*2",  # 480p, even dimensions
             "-c:v", "libx264",
-            "-preset", "ultrafast",  # NAJHITREJŠI preset
-            "-crf", "30",  # nižja kvaliteta = hitrejše
+            "-preset", "ultrafast",
+            "-crf", "30",
             "-c:a", "aac",
             "-b:a", "96k",
             "-movflags", "+faststart",
@@ -1303,9 +1309,14 @@ async def preview_clip(
         ]
         try:
             proc = subprocess.run(cmd, capture_output=True, text=True, timeout=20)
-            if proc.returncode != 0 or not cache_path.exists():
-                raise HTTPException(500, f"FFmpeg failed: {proc.stderr[-300:]}")
+            if proc.returncode != 0 or not cache_path.exists() or cache_path.stat().st_size < 1024:
+                # Briši nepopolno datoteko
+                if cache_path.exists():
+                    cache_path.unlink()
+                raise HTTPException(500, f"FFmpeg failed: {(proc.stderr or 'unknown')[-300:]}")
         except subprocess.TimeoutExpired:
+            if cache_path.exists():
+                cache_path.unlink()
             raise HTTPException(500, "Preview render timeout (>20s)")
     
     return FileResponse(