feat: artifact storage module with per-session CRUD

backend/artifacts.py

@@ -0,0 +1,48 @@
+"""Artifact storage module — per-session CRUD operations on the filesystem."""
+
+from pathlib import Path
+
+ARTIFACTS_DIR = Path("/app/artifacts")
+
+
+def list_artifacts(session_id: str) -> list[dict]:
+    """Return sorted list of artifact dicts for a session.
+
+    Each dict contains: name, session_id, size.
+    Returns [] if the session directory does not exist.
+    """
+    session_dir = ARTIFACTS_DIR / session_id
+    if not session_dir.exists():
+        return []
+    return sorted(
+        [
+            {
+                "name": f.name,
+                "session_id": session_id,
+                "size": f.stat().st_size,
+            }
+            for f in session_dir.iterdir()
+            if f.is_file()
+        ],
+        key=lambda d: d["name"],
+    )
+
+
+def get_artifact(session_id: str, name: str) -> str | None:
+    """Return file content (utf-8) or None if the artifact does not exist."""
+    artifact_path = ARTIFACTS_DIR / session_id / name
+    if not artifact_path.exists():
+        return None
+    return artifact_path.read_text(encoding="utf-8")
+
+
+def save_artifact(session_id: str, name: str, content: str) -> Path:
+    """Write content to the artifact file, creating parent dirs as needed.
+
+    Returns the Path of the written file.
+    """
+    session_dir = ARTIFACTS_DIR / session_id
+    session_dir.mkdir(parents=True, exist_ok=True)
+    artifact_path = session_dir / name
+    artifact_path.write_text(content, encoding="utf-8")
+    return artifact_path