#!/usr/bin/env python3
"""Serve the browser UI independently of the FunASR backend."""

from __future__ import annotations

import json
import os
from http.server import SimpleHTTPRequestHandler, ThreadingHTTPServer
from pathlib import Path
from urllib.parse import urlsplit

from dotenv import load_dotenv

PROJECT_ROOT = Path(__file__).resolve().parents[1]
STATIC_ROOT = PROJECT_ROOT / "realtime_websocket" / "static"
load_dotenv(PROJECT_ROOT / ".env")


class FrontendHandler(SimpleHTTPRequestHandler):
    """Serve static assets and a browser-visible backend URL at runtime."""

    def __init__(self, *args, **kwargs):
        super().__init__(*args, directory=str(STATIC_ROOT), **kwargs)

    def do_GET(self) -> None:
        if self.path.split("?", 1)[0] != "/runtime-config.js":
            return super().do_GET()
        backend_url = os.getenv("BACKEND_PUBLIC_URL", "http://127.0.0.1:8082").rstrip("/")
        parsed = urlsplit(backend_url)
        if parsed.scheme not in {"http", "https"} or not parsed.netloc or parsed.path:
            self.send_error(500, "BACKEND_PUBLIC_URL must be an HTTP origin")
            return
        # JSON escaping also yields a valid JavaScript string literal.
        body = ("window.ASR_BACKEND_URL = " + json.dumps(backend_url) + ";\n").encode("utf-8")
        self.send_response(200)
        self.send_header("Content-Type", "application/javascript; charset=utf-8")
        self.send_header("Cache-Control", "no-store")
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)


def main() -> None:
    host = os.getenv("FRONTEND_HOST", "127.0.0.1")
    port = int(os.getenv("FRONTEND_PORT", "8080"))
    server = ThreadingHTTPServer((host, port), FrontendHandler)
    print(f"Frontend: http://{host}:{port}/", flush=True)
    try:
        server.serve_forever()
    except KeyboardInterrupt:
        pass
    finally:
        server.server_close()


if __name__ == "__main__":
    main()