Refactor podcast media storage to lazy tenant resolver

backend/api/podcast/constants.py

@@ -5,6 +5,7 @@ Centralized constants and directory configuration for podcast module.
 """
 
 from pathlib import Path
+from typing import Literal
 from services.story_writer.audio_generation_service import StoryAudioGenerationService
 
 # Directory paths
@@ -17,15 +18,54 @@ ROOT_DIR = Path(__file__).resolve().parents[3]  # root/
 DATA_MEDIA_DIR = ROOT_DIR / "data" / "media"
 
 PODCAST_AUDIO_DIR = (DATA_MEDIA_DIR / "podcast_audio").resolve()
-PODCAST_AUDIO_DIR.mkdir(parents=True, exist_ok=True)
 PODCAST_IMAGES_DIR = (DATA_MEDIA_DIR / "podcast_images").resolve()
-PODCAST_IMAGES_DIR.mkdir(parents=True, exist_ok=True)
 PODCAST_VIDEOS_DIR = (DATA_MEDIA_DIR / "podcast_videos").resolve()
-PODCAST_VIDEOS_DIR.mkdir(parents=True, exist_ok=True)
 
 # Video subdirectory
 AI_VIDEO_SUBDIR = Path("AI_Videos")
 
-# Initialize audio service
-audio_service = StoryAudioGenerationService(output_dir=str(PODCAST_AUDIO_DIR))
+MediaType = Literal["audio", "image", "video"]
 
+
+def _sanitize_user_id(user_id: str) -> str:
+    return "".join(c for c in user_id if c.isalnum() or c in ("-", "_"))
+
+
+def get_podcast_media_dir(
+    media_type: MediaType,
+    user_id: str | None = None,
+    *,
+    ensure_exists: bool = False,
+) -> Path:
+    """Resolve podcast media directory (tenant workspace first, legacy global fallback)."""
+    media_subdir = {
+        "audio": "podcast_audio",
+        "image": "podcast_images",
+        "video": "podcast_videos",
+    }[media_type]
+
+    if user_id:
+        tenant_media_dir = ROOT_DIR / "workspace" / f"workspace_{_sanitize_user_id(user_id)}" / "media" / media_subdir
+        resolved_dir = tenant_media_dir.resolve()
+    else:
+        resolved_dir = (DATA_MEDIA_DIR / media_subdir).resolve()
+
+    if ensure_exists:
+        resolved_dir.mkdir(parents=True, exist_ok=True)
+
+    return resolved_dir
+
+
+def get_podcast_media_read_dirs(media_type: MediaType, user_id: str | None = None) -> list[Path]:
+    """Return ordered directories to search (tenant path first, then legacy global path)."""
+    dirs: list[Path] = []
+    if user_id:
+        dirs.append(get_podcast_media_dir(media_type, user_id))
+    dirs.append(get_podcast_media_dir(media_type, None))
+    return dirs
+
+
+def get_podcast_audio_service(user_id: str | None = None) -> StoryAudioGenerationService:
+    """Build audio service lazily so directory creation happens only when needed."""
+    output_dir = get_podcast_media_dir("audio", user_id, ensure_exists=True)
+    return StoryAudioGenerationService(output_dir=str(output_dir))