AI Video Generation Implementation

backend/api/story_writer/utils/media_utils.py

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+from __future__ import annotations
+
+from pathlib import Path
+from typing import Optional
+from urllib.parse import urlparse
+
+from fastapi import HTTPException, status
+from loguru import logger
+
+
+BASE_DIR = Path(__file__).resolve().parents[3]  # backend/
+STORY_IMAGES_DIR = (BASE_DIR / "story_images").resolve()
+STORY_IMAGES_DIR.mkdir(parents=True, exist_ok=True)
+
+
+def load_story_image_bytes(image_url: str) -> Optional[bytes]:
+    """
+    Resolve an authenticated story image URL (e.g., /api/story/images/<file>) to raw bytes.
+    Returns None if the file cannot be located.
+    """
+    if not image_url:
+        return None
+
+    try:
+        parsed = urlparse(image_url)
+        path = parsed.path if parsed.scheme else image_url
+        prefix = "/api/story/images/"
+        if prefix not in path:
+            logger.warning(f"[StoryWriter] Unsupported image URL for video reference: {image_url}")
+            return None
+
+        filename = path.split(prefix, 1)[1].split("?", 1)[0].strip()
+        if not filename:
+            return None
+
+        file_path = (STORY_IMAGES_DIR / filename).resolve()
+        if not str(file_path).startswith(str(STORY_IMAGES_DIR)):
+            logger.error(f"[StoryWriter] Attempted path traversal when resolving image: {image_url}")
+            return None
+
+        if not file_path.exists():
+            logger.warning(f"[StoryWriter] Referenced scene image not found on disk: {file_path}")
+            return None
+
+        return file_path.read_bytes()
+    except Exception as exc:
+        logger.error(f"[StoryWriter] Failed to load reference image for video gen: {exc}")
+        return None
+
+
+def resolve_media_file(base_dir: Path, filename: str) -> Path:
+    """
+    Returns a safe resolved path for a media file stored under base_dir.
+    Guards against directory traversal and ensures the file exists.
+    """
+    filename = filename.split("?")[0].strip()
+    resolved = (base_dir / filename).resolve()
+
+    try:
+        resolved.relative_to(base_dir.resolve())
+    except ValueError:
+        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="Access denied")
+
+    if not resolved.exists():
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail=f"File not found: {filename}")
+
+    return resolved
+
+