mtsd/backend/app/services/china_region_tree.py

"""中国行政区划（bas_china_region）树形结构，供运营端与小程序共用。"""
from __future__ import annotations

import copy
import threading
import time
from collections import defaultdict
from typing import Dict, List

from sqlalchemy.orm import Session

from app.models.models import BasChinaRegion

_CHINA_REGION_TREE_CACHE_TTL_SEC = 600
_china_region_tree_cache = {"expires_at": 0.0, "tree": None}
_china_region_tree_cache_lock = threading.Lock()


def query_china_regions_active(db: Session) -> List[BasChinaRegion]:
    return (
        db.query(
            BasChinaRegion.id,
            BasChinaRegion.parent_id,
            BasChinaRegion.region_code,
            BasChinaRegion.region_name,
            BasChinaRegion.sort_order,
        )
        .filter(BasChinaRegion.is_del == 0)
        .order_by(BasChinaRegion.sort_order.asc(), BasChinaRegion.region_code.asc())
        .all()
    )


def build_china_region_tree(rows: List[BasChinaRegion]) -> List[dict]:
    """{ value: region_code, label: region_name, children?: [...] }，与历史 china-region-cascader.json 结构一致。"""
    children_map: Dict[str, List[BasChinaRegion]] = defaultdict(list)
    for r in rows:
        key = getattr(r, "parent_id", None) or ""
        children_map[key].append(r)
    for key in children_map:
        children_map[key].sort(key=lambda x: (getattr(x, "sort_order", 0), getattr(x, "region_code", "")))

    def to_node(r: BasChinaRegion) -> dict:
        rid = getattr(r, "id", None)
        subs = children_map.get(rid, [])
        node: dict = {"value": getattr(r, "region_code", None), "label": getattr(r, "region_name", None)}
        if subs:
            node["children"] = [to_node(c) for c in subs]
        return node

    roots = children_map.get("", [])
    return [to_node(r) for r in roots]


def get_china_region_tree_cached(db: Session) -> List[dict]:
    """获取中国行政区划树，带进程内短 TTL 缓存。"""
    now = time.time()
    with _china_region_tree_cache_lock:
        cache_tree = _china_region_tree_cache.get("tree")
        expires_at = float(_china_region_tree_cache.get("expires_at") or 0.0)
        if cache_tree is not None and now < expires_at:
            return copy.deepcopy(cache_tree)

    rows = query_china_regions_active(db)
    tree = build_china_region_tree(rows)

    with _china_region_tree_cache_lock:
        _china_region_tree_cache["tree"] = tree
        _china_region_tree_cache["expires_at"] = now + _CHINA_REGION_TREE_CACHE_TTL_SEC
    return copy.deepcopy(tree)