"""通知渠道封装。

对 email / webhook / dingtalk / wechat 等渠道做统一封装；真实发送通过
urllib 完成（或按需扩展 SDK），默认 InMemorySender 记录发送历史，便于测试。
"""

from __future__ import annotations

import json
import threading
import urllib.request
from typing import Any, Dict, List, Optional

from .models import Alert


class ChannelSender:
    """通知渠道发送器接口。"""

    def send(self, alert: Alert, target: Optional[str] = None) -> bool:
        raise NotImplementedError


class InMemorySender(ChannelSender):
    """记录发送历史，不真正外呼。"""

    def __init__(self, channel: str) -> None:
        self.channel = channel
        self.sent: List[Dict[str, Any]] = []
        self._lock = threading.Lock()

    def send(self, alert: Alert, target: Optional[str] = None) -> bool:
        with self._lock:
            self.sent.append({"channel": self.channel, "target": target, "alert_id": alert.alert_id})
        return True


class WebhookSender(ChannelSender):
    """通用 Webhook（POST JSON）。"""

    def __init__(self, url: str) -> None:
        self.url = url

    def send(self, alert: Alert, target: Optional[str] = None) -> bool:
        payload = json.dumps(alert.to_dict()).encode("utf-8")
        req = urllib.request.Request(
            target or self.url,
            data=payload,
            headers={"Content-Type": "application/json"},
            method="POST",
        )
        with urllib.request.urlopen(req, timeout=5) as resp:  # noqa: S310
            return 200 <= resp.status < 300


class Notifier:
    """通知分发器：按告警渠道列表投递。"""

    def __init__(self, senders: Optional[Dict[str, ChannelSender]] = None) -> None:
        self.senders = senders or {}
        self.sent: List[Dict[str, Any]] = []
        self._lock = threading.Lock()

    def register(self, channel: str, sender: ChannelSender) -> None:
        self.senders[channel] = sender

    def notify(self, alert: Alert, channels: Optional[List[str]] = None) -> List[str]:
        """发送告警，返回成功渠道列表。"""
        channels = channels or list(self.senders.keys())
        delivered: List[str] = []
        for channel in channels:
            sender = self.senders.get(channel)
            if sender is None:
                continue
            ok = sender.send(alert)
            with self._lock:
                self.sent.append({"channel": channel, "alert_id": alert.alert_id, "ok": ok})
            if ok:
                delivered.append(channel)
        return delivered

    @classmethod
    def memory(cls, channels: Optional[List[str]] = None) -> "Notifier":
        """构造内存版 Notifier，便于本地运行/测试。"""
        channels = channels or ["email", "webhook", "dingtalk", "wechat"]
        return cls({c: InMemorySender(c) for c in channels})