#!/usr/bin/env python3
"""
local_pos_proxy.py — 本機 POS Proxy
在「接收端電腦」執行，監聽 127.0.0.1:18080
讓瀏覽器透過此 Proxy 發動 HTTP request 到 POS 設備，繞過瀏覽器 CORS 限制。

使用方式：
  python local_pos_proxy.py
  python local_pos_proxy.py --port 18080   # 自訂 port
  python local_pos_proxy.py --host 0.0.0.0 # 對外監聽（同網段其他裝置也可使用）

需求：
  pip install requests
"""
import json
import argparse
from http.server import HTTPServer, BaseHTTPRequestHandler

try:
    import requests
except ImportError:
    print("[ERROR] 請先安裝：pip install requests")
    exit(1)


class PosProxyHandler(BaseHTTPRequestHandler):

    def _cors(self):
        self.send_header("Access-Control-Allow-Origin", "*")
        self.send_header("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
        self.send_header("Access-Control-Allow-Headers", "Content-Type")
        # Chrome Private Network Access policy（公開頁面存取 localhost 需要此 header）
        self.send_header("Access-Control-Allow-Private-Network", "true")

    def do_OPTIONS(self):
        """回應 CORS preflight 請求"""
        self.send_response(200)
        self._cors()
        self.end_headers()

    def do_GET(self):
        if self.path == "/health":
            self._respond(200, {"status": "ok", "proxy": "local_pos_proxy"})
        else:
            self._respond(404, {"error": "not found"})

    def do_POST(self):
        try:
            length = int(self.headers.get("Content-Length", 0))
            body = json.loads(self.rfile.read(length))
        except Exception:
            self._respond(400, {"error": "invalid request body"})
            return

        method  = (body.get("method") or "GET").upper()
        url     = (body.get("url") or "").strip()
        payload = body.get("payload")
        timeout = int(body.get("timeout") or 60)

        if not url:
            self._respond(400, {"error": "missing url"})
            return

        print(f"  → {method} {url}")
        try:
            if method == "POST":
                r = requests.post(url, json=payload, timeout=timeout)
            else:
                r = requests.get(url, timeout=timeout)

            try:
                resp_body = r.json()
            except Exception:
                resp_body = r.text

            print(f"  ← HTTP {r.status_code}")
            self._respond(200, {"status": r.status_code, "body": resp_body})

        except requests.exceptions.Timeout:
            print("  ← timeout")
            self._respond(504, {"error": "request timeout", "status": 504})
        except Exception as exc:
            print(f"  ← error: {exc}")
            self._respond(500, {"error": str(exc), "status": 0})

    def _respond(self, code, data):
        out = json.dumps(data, ensure_ascii=False).encode("utf-8")
        self.send_response(code)
        self.send_header("Content-Type", "application/json; charset=utf-8")
        self.send_header("Content-Length", str(len(out)))
        self._cors()
        self.end_headers()
        self.wfile.write(out)

    def log_message(self, fmt, *args):
        pass  # 由 do_POST / do_GET 自行輸出


def main():
    parser = argparse.ArgumentParser(description="本機 POS Proxy")
    parser.add_argument("--port", type=int, default=18080, help="監聽 port（預設 18080）")
    parser.add_argument("--host", default="127.0.0.1", help="監聽位址（預設 127.0.0.1）")
    args = parser.parse_args()

    server = HTTPServer((args.host, args.port), PosProxyHandler)
    addr = f"http://{args.host}:{args.port}"
    print(f"[POS Proxy] 啟動於 {addr}")
    print(f"[POS Proxy] 健康檢查：{addr}/health")
    print(f"[POS Proxy] 按 Ctrl+C 停止\n")
    try:
        server.serve_forever()
    except KeyboardInterrupt:
        print("\n[POS Proxy] 已停止")


if __name__ == "__main__":
    main()