#!/usr/bin/env python3
"""105 固定 IP 出站：仅转发 api.weixin.qq.com/cgi-bin/* 到微信官方 API。"""
from http.server import BaseHTTPRequestHandler, HTTPServer
import os
import urllib.error
import urllib.parse
import urllib.request

ALLOWED_PREFIX = "/cgi-bin/"
TIMEOUT_SEC = 120


class Handler(BaseHTTPRequestHandler):
    def do_GET(self):
        if self.path == "/healthz" or self.path.startswith("/healthz?"):
            self.send_response(200)
            self.send_header("Content-Type", "text/plain; charset=utf-8")
            self.end_headers()
            self.wfile.write(b"ok")
            return
        self._proxy("GET")

    def do_POST(self):
        self._proxy("POST")

    def _proxy(self, method):
        parsed = urllib.parse.urlsplit(self.path)
        if not parsed.path.startswith(ALLOWED_PREFIX):
            self.send_error(403)
            return

        length = int(self.headers.get("Content-Length", "0")) if method == "POST" else 0
        body = self.rfile.read(length) if length else None
        url = "https://api.weixin.qq.com" + self.path
        headers = {}
        content_type = self.headers.get("Content-Type")
        if content_type:
            headers["Content-Type"] = content_type
        req = urllib.request.Request(url, data=body, headers=headers, method=method)
        try:
            with urllib.request.urlopen(req, timeout=TIMEOUT_SEC) as resp:
                payload = resp.read()
                self.send_response(resp.status)
                out_type = resp.headers.get("Content-Type", "application/json")
                self.send_header("Content-Type", out_type)
                self.send_header("Content-Length", str(len(payload)))
                self.end_headers()
                self.wfile.write(payload)
        except urllib.error.HTTPError as err:
            payload = err.read()
            self.send_response(err.code)
            out_type = err.headers.get("Content-Type", "application/json")
            self.send_header("Content-Type", out_type)
            self.send_header("Content-Length", str(len(payload)))
            self.end_headers()
            self.wfile.write(payload)

    def log_message(self, fmt, *args):
        return


if __name__ == "__main__":
    host = os.environ.get("WECHAT_EGRESS_HOST", "10.10.0.1")
    port = int(os.environ.get("WECHAT_EGRESS_PORT", "19090"))
    HTTPServer((host, port), Handler).serve_forever()