feat(release): publish minimal self-contained Magent source

backend/app/services/email_queue.py

@@ -0,0 +1,33 @@
+"""Shared claim and completion rules for the two durable email queues."""
+
+import uuid
+
+
+def queue_table(table: str) -> str:
+    if table not in {"email_recap_deliveries", "newsletter_deliveries"}:
+        raise ValueError("Unknown email queue")
+    return table
+
+
+def claim(conn, table: str, now: float) -> dict | None:
+    table = queue_table(table)
+    conn.execute(f"""UPDATE {table} SET state='unknown', detail='Delivery interrupted after sending began; check the mail server.', updated_at=?
+        WHERE state='sending' AND lease_until<?""", (now, now))
+    conn.execute(f"""UPDATE {table} SET state=CASE WHEN attempts>=3 THEN 'failed' ELSE 'retry' END,
+        next_attempt_at=?, updated_at=?, detail='Email preparation interrupted.'
+        WHERE state='preparing' AND lease_until<?""", (now, now, now))
+    row = conn.execute(f"""SELECT * FROM {table} WHERE state IN ('queued', 'retry') AND next_attempt_at<=?
+        ORDER BY created_at, id LIMIT 1""", (now,)).fetchone()
+    if not row:
+        return None
+    claim_id = uuid.uuid4().hex
+    conn.execute(f"""UPDATE {table} SET state='preparing', claim=?, lease_until=?,
+        attempts=attempts+1, updated_at=? WHERE id=?""", (claim_id, now + 1800, now, row["id"]))
+    return dict(conn.execute(f"SELECT * FROM {table} WHERE id=?", (row["id"],)).fetchone())
+
+
+def finish(conn, table: str, delivery: dict, state: str, detail: str, now: float, delay: int = 0):
+    table = queue_table(table)
+    conn.execute(f"""UPDATE {table} SET state=?, detail=?, updated_at=?, next_attempt_at=?, lease_until=NULL
+        WHERE id=? AND claim=? AND state IN ('preparing', 'sending')""",
+        (state, detail, now, now + delay, delivery["id"], delivery["claim"]))