Add SFTP storage helper for trainer outputs

backend/worker/sftp_store.py

@@ -0,0 +1,73 @@
+from __future__ import annotations
+
+import base64
+import os
+from pathlib import Path
+from typing import Optional, Tuple
+
+import paramiko
+
+
+def _sftp_client() -> Tuple[paramiko.SFTPClient, paramiko.Transport]:
+    host = (os.environ.get("SFTP_HOST") or "").strip()
+    user = (os.environ.get("SFTP_USER") or "").strip()
+    if not host or not user:
+        raise RuntimeError("Missing SFTP_HOST or SFTP_USER")
+
+    port = int((os.environ.get("SFTP_PORT") or "22").strip())
+    password = os.environ.get("SFTP_PASS")
+    key_b64 = os.environ.get("SFTP_KEY_B64")
+    key_pass = os.environ.get("SFTP_KEY_PASSPHRASE")
+
+    t = paramiko.Transport((host, port))
+    if key_b64:
+        key_bytes = base64.b64decode(key_b64)
+        pkey = paramiko.RSAKey.from_private_key_file(_write_tmp_key(key_bytes), password=key_pass)
+        t.connect(username=user, pkey=pkey)
+    else:
+        if not password:
+            raise RuntimeError("Missing SFTP_PASS (or provide SFTP_KEY_B64)")
+        t.connect(username=user, password=password)
+
+    return paramiko.SFTPClient.from_transport(t), t
+
+
+def _write_tmp_key(key_bytes: bytes) -> str:
+    # HF container FS is writable for tmp; keep it simple.
+    p = Path("/tmp/sftp_key.pem")
+    p.write_bytes(key_bytes)
+    os.chmod(p, 0o600)
+    return str(p)
+
+
+def _mkdir_p(sftp: paramiko.SFTPClient, remote_dir: str) -> None:
+    parts = remote_dir.strip("/").split("/")
+    cur = ""
+    for part in parts:
+        cur += "/" + part
+        try:
+            sftp.stat(cur)
+        except FileNotFoundError:
+            sftp.mkdir(cur)
+
+
+def store_to_sftp(pdf_id: str, template_id: str, cfg_json_bytes: bytes, pdf_bytes: bytes, pdf_name: str) -> str:
+    base = (os.environ.get("SFTP_BASE_DIR") or "/").rstrip("/")
+    remote_dir = f"{base}/{template_id}/{pdf_id}"
+    remote_cfg = f"{remote_dir}/trainer_config_{pdf_id}__{template_id}.json"
+    remote_pdf = f"{remote_dir}/{pdf_name or (pdf_id + '.pdf')}"
+
+    sftp, transport = _sftp_client()
+    try:
+        _mkdir_p(sftp, remote_dir)
+        with sftp.open(remote_cfg, "wb") as f:
+            f.write(cfg_json_bytes)
+        with sftp.open(remote_pdf, "wb") as f:
+            f.write(pdf_bytes)
+    finally:
+        try:
+            sftp.close()
+        finally:
+            transport.close()
+
+    return remote_dir