import json
import time
from urllib import error, request

from sqlalchemy.orm import Session

from backend.app.core.config import get_settings
from backend.app.core.error_codes import ErrorCode
from backend.app.core.exceptions import AppException


class WeChatNotificationService:
    """微信小程序订阅消息通知服务。

    通过微信 subscribeMessage.send 接口向用户推送服务提醒。
    需要在小程序后台配置消息模板，并将模板 ID 填入系统配置。
    """

    TOKEN_CACHE: dict[str, str] = {"token": "", "expires_at": 0}

    REMINDER_TYPE_TEMPLATE_MAP: dict[str, str] = {
        "order_status_change": "wechat_template_order_status",
        "order_approval_needed": "wechat_template_approval",
        "task_assigned": "wechat_template_task_assigned",
        "logistics_timeout": "wechat_template_logistics_timeout",
        "arrears": "wechat_template_arrears",
        "inactive_customer": "wechat_template_inactive_customer",
    }

    def send_subscribe_message(self, open_id: str, reminder_type: str, title: str, content: str, biz_url: str = "") -> bool:
        settings = get_settings()
        if not settings.wechat_app_id or not settings.wechat_app_secret:
            return False

        template_id = self._get_template_id(settings, reminder_type)
        if not template_id:
            return False

        access_token = self._get_access_token(settings)
        if not access_token:
            return False

        payload = {
            "touser": open_id,
            "template_id": template_id,
            "page": biz_url,
            "data": {
                "thing1": {"value": title[:20]},
                "thing2": {"value": content[:100]},
                "time3": {"value": time.strftime("%Y-%m-%d %H:%M")},
            },
        }

        url = f"https://api.weixin.qq.com/cgi-bin/message/subscribe/send?access_token={access_token}"
        req = request.Request(
            url=url,
            data=json.dumps(payload, ensure_ascii=False).encode("utf-8"),
            headers={"Content-Type": "application/json; charset=UTF-8"},
            method="POST",
        )
        try:
            with request.urlopen(req, timeout=10) as response:
                result = json.loads(response.read().decode("utf-8") or "{}")
                return result.get("errcode", -1) == 0
        except (error.HTTPError, error.URLError, json.JSONDecodeError):
            return False

    def bind_open_id(self, session: Session, user_id: int, open_id: str) -> None:
        from backend.app.models.system import User
        from sqlalchemy import select
        user = session.execute(select(User).where(User.id == user_id)).scalar_one_or_none()
        if user is not None:
            user.open_id = open_id
            session.add(user)
            session.commit()

    def _get_template_id(self, settings, reminder_type: str) -> str:
        config_key = self.REMINDER_TYPE_TEMPLATE_MAP.get(reminder_type, "")
        if not config_key:
            return ""
        return getattr(settings, config_key, "")

    def _get_access_token(self, settings) -> str:
        now = time.time()
        if self.TOKEN_CACHE["token"] and self.TOKEN_CACHE["expires_at"] > now + 60:
            return self.TOKEN_CACHE["token"]

        url = (
            f"https://api.weixin.qq.com/cgi-bin/token"
            f"?grant_type=client_credential"
            f"&appid={settings.wechat_app_id}"
            f"&secret={settings.wechat_app_secret}"
        )
        req = request.Request(url=url, method="GET")
        try:
            with request.urlopen(req, timeout=10) as response:
                result = json.loads(response.read().decode("utf-8") or "{}")
                token = result.get("access_token", "")
                expires_in = int(result.get("expires_in", 0))
                if token and expires_in > 0:
                    self.TOKEN_CACHE["token"] = token
                    self.TOKEN_CACHE["expires_at"] = now + expires_in
                    return token
        except (error.HTTPError, error.URLError, json.JSONDecodeError):
            pass
        return ""


wechat_notification_service = WeChatNotificationService()