"""
微信公众号 FastAPI 应用

GET  /wechat  - 微信服务器验证（签名校验 + 返回 echostr）
POST /wechat  - 接收微信推送的消息和事件
"""

import hashlib
import time
import xml.etree.ElementTree as ET

from fastapi import FastAPI, Request, Query, HTTPException
from fastapi.responses import PlainTextResponse

from config import WECHAT_TOKEN

app = FastAPI(title="WeChat API", version="0.1.0")


def verify_signature(signature: str, timestamp: str, nonce: str) -> bool:
    """
    微信签名验证:
    1. 将 token、timestamp、nonce 三个参数字典序排序
    2. 拼成一个字符串
    3. sha1 加密
    4. 和 signature 对比
    """
    if not WECHAT_TOKEN:
        return False
    items = sorted([WECHAT_TOKEN, timestamp, nonce])
    sha1 = hashlib.sha1("".join(items).encode()).hexdigest()
    return sha1 == signature


@app.get("/wechat")
async def wechat_verify(
    signature: str = Query(...),
    timestamp: str = Query(...),
    nonce: str = Query(...),
    echostr: str = Query(...),
):
    """GET: 微信服务器验证回调地址有效性"""
    if not verify_signature(signature, timestamp, nonce):
        raise HTTPException(status_code=403, detail="Invalid signature")
    # 验证通过，原样返回 echostr
    return PlainTextResponse(content=echostr)


@app.post("/wechat")
async def wechat_message(
    request: Request,
    signature: str = Query(...),
    timestamp: str = Query(...),
    nonce: str = Query(...),
    openid: str = Query(...),
):
    """POST: 接收微信推送的消息和事件"""
    # 验证签名
    if not verify_signature(signature, timestamp, nonce):
        raise HTTPException(status_code=403, detail="Invalid signature")

    # 解析 XML 消息体
    body = await request.body()
    root = ET.fromstring(body)

    msg_type = root.findtext("MsgType", "")
    from_user = root.findtext("FromUserName", "")   # 发送方（用户 openid）
    to_user = root.findtext("ToUserName", "")       # 接收方（公众号）
    content = root.findtext("Content", "")
    event = root.findtext("Event", "")
    event_key = root.findtext("EventKey", "")

    print(f"[WeChat] type={msg_type} from={from_user} event={event} content={content} key={event_key}")

    # 处理事件推送
    if msg_type == "event":
        if event == "subscribe":
            # 用户关注
            return _reply_text(from_user, to_user, "欢迎关注！")
        elif event == "unsubscribe":
            # 用户取关
            print(f"[WeChat] 用户取关: {from_user}")
            return PlainTextResponse(content="success")
        elif event == "SCAN":
            # 已关注用户扫码
            return _reply_text(from_user, to_user, f"扫码成功，场景值: {event_key}")
        elif event == "CLICK":
            # 菜单点击
            return _reply_text(from_user, to_user, f"点击了: {event_key}")

    # 处理文本消息
    if msg_type == "text":
        # 原样返回（echo 模式，方便测试）
        return _reply_text(from_user, to_user, f"你说: {content}")

    # 其他类型暂不处理
    return _reply_text(from_user, to_user, "收到")


def _reply_text(from_user: str, to_user: str, content: str) -> PlainTextResponse:
    """构造文本回复 XML"""
    xml = (
        "<xml>"
        f"<ToUserName><![CDATA[{from_user}]]></ToUserName>"
        f"<FromUserName><![CDATA[{to_user}]]></FromUserName>"
        f"<CreateTime>{int(time.time())}</CreateTime>"
        "<MsgType><![CDATA[text]]></MsgType>"
        f"<Content><![CDATA[{content}]]></Content>"
        "</xml>"
    )
    return PlainTextResponse(content=xml, media_type="application/xml")