"""The only way out of a generation container: an HTTPS CONNECT proxy that opens tunnels to the agent CLI's own hosts.

Agent containers sit on an internal Docker network with no route out; this proxy sits on that network and the default
bridge. It tunnels CONNECT host:443 when host is in the allow-list (exact name or a subdomain of one), refuses everything
else with 403, and logs one line per request. Plain HTTP is refused. Standard library only.

    python egress_proxy.py --port 3128 --allow api.anthropic.com,chatgpt.com [--log-all]
"""
import argparse
import asyncio
import sys


def allowed(host, hosts):
    host = host.lower().rstrip(".")
    return any(host == h or host.endswith("." + h) for h in hosts)


async def pipe(reader, writer):
    try:
        while data := await reader.read(65536):
            writer.write(data)
            await writer.drain()
    except (ConnectionError, asyncio.CancelledError):
        pass
    finally:
        writer.close()


async def handle(reader, writer, hosts, log_all):
    try:
        head = await asyncio.wait_for(reader.readuntil(b"\r\n\r\n"), 30)
    except (asyncio.IncompleteReadError, asyncio.LimitOverrunError, asyncio.TimeoutError, ConnectionError):
        writer.close()
        return
    method, target = (head.split(b"\r\n", 1)[0].decode("latin-1").split(" ") + ["", ""])[:2]
    host, _, port = target.rpartition(":")
    ok = method == "CONNECT" and port == "443" and allowed(host, hosts)
    print(f"{'ALLOW' if ok else 'DENY'} {method} {target}", flush=True)
    if not ok and not log_all:
        writer.write(b"HTTP/1.1 403 Forbidden\r\nContent-Length: 0\r\n\r\n")
        await writer.drain()
        writer.close()
        return
    try:
        upstream_reader, upstream_writer = await asyncio.wait_for(asyncio.open_connection(host, int(port or 443)), 30)
    except (OSError, asyncio.TimeoutError, ValueError):
        writer.write(b"HTTP/1.1 502 Bad Gateway\r\nContent-Length: 0\r\n\r\n")
        await writer.drain()
        writer.close()
        return
    writer.write(b"HTTP/1.1 200 Connection established\r\n\r\n")
    await writer.drain()
    await asyncio.gather(pipe(reader, upstream_writer), pipe(upstream_reader, writer))


async def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--port", type=int, default=3128)
    parser.add_argument("--allow", required=True, help="Comma-separated host names; subdomains are included")
    parser.add_argument("--log-all", action="store_true", help="Discovery only: tunnel every CONNECT and log it")
    args = parser.parse_args()
    hosts = [h.strip().lower() for h in args.allow.split(",") if h.strip()]
    server = await asyncio.start_server(lambda r, w: handle(r, w, hosts, args.log_all), "0.0.0.0", args.port)
    print(f"egress proxy on :{args.port}, allowing {hosts}", flush=True)
    async with server:
        await server.serve_forever()


if __name__ == "__main__":
    asyncio.run(main())
    sys.exit(0)