chore: 基础设施 — 阿里云源、北京时间、HEX计数器、打印机配置

backend/app/services/counter_service.py

@@ -0,0 +1,26 @@
+"""16进制自增计数器 — 基于 PostgreSQL Sequence，生成 16 位 HEX 唯一 ID"""
+from sqlalchemy import text
+from sqlalchemy.ext.asyncio import AsyncSession
+
+SEQUENCE_NAME = "product_hex_counter"
+
+
+async def ensure_sequence(db: AsyncSession) -> None:
+    """确保 counter sequence 存在（幂等）"""
+    await db.execute(
+        text(f"CREATE SEQUENCE IF NOT EXISTS {SEQUENCE_NAME} START 1;")
+    )
+
+
+async def next_hex_id(db: AsyncSession, length: int = 16) -> str:
+    """
+    生成下一个 hex ID。
+
+    示例: 1 → "0000000000000001"
+          15 → "000000000000000F"
+          16 → "0000000000000010"
+          255 → "00000000000000FF"
+    """
+    result = await db.execute(text(f"SELECT nextval('{SEQUENCE_NAME}');"))
+    counter: int = result.scalar_one()
+    return format(counter, f"0{length}X")