#!/usr/bin/env python3
import os
import selectors
import signal
import socket
import sys


LISTEN_HOST = os.getenv("LISTEN_HOST", "127.0.0.1")
LISTEN_PORT = int(os.getenv("LISTEN_PORT", "6380"))
REDIS_HOST = os.getenv("REDIS_HOST", "100.90.90.91")
REDIS_PORT = int(os.getenv("REDIS_PORT", "6379"))
REDIS_USER = os.getenv("REDIS_USER", "lisglosips")
CONNECT_TIMEOUT = float(os.getenv("CONNECT_TIMEOUT", "2.0"))


def credential(name: str) -> str:
    cred_dir = os.getenv("CREDENTIALS_DIRECTORY")
    if not cred_dir:
        raise RuntimeError("CREDENTIALS_DIRECTORY is not set")
    path = os.path.join(cred_dir, name)
    with open(path, "r", encoding="utf-8") as handle:
        return handle.read().strip()


def resp_array(parts: list[str]) -> bytes:
    output = f"*{len(parts)}\r\n".encode("utf-8")
    for part in parts:
        data = part.encode("utf-8")
        output += f"${len(data)}\r\n".encode("utf-8") + data + b"\r\n"
    return output


def read_line(sock: socket.socket) -> bytes:
    data = b""
    while not data.endswith(b"\r\n"):
        chunk = sock.recv(1)
        if not chunk:
            break
        data += chunk
        if len(data) > 4096:
            break
    return data


def connect_upstream() -> socket.socket:
    password = credential("redis_password")
    upstream = socket.create_connection((REDIS_HOST, REDIS_PORT), timeout=CONNECT_TIMEOUT)
    upstream.sendall(resp_array(["AUTH", REDIS_USER, password]))
    reply = read_line(upstream)
    if not reply.startswith(b"+OK"):
        upstream.close()
        raise RuntimeError("Redis AUTH failed")
    upstream.setblocking(False)
    return upstream


def bridge(client: socket.socket) -> None:
    upstream = connect_upstream()
    client.setblocking(False)
    selector = selectors.DefaultSelector()
    selector.register(client, selectors.EVENT_READ, upstream)
    selector.register(upstream, selectors.EVENT_READ, client)
    try:
        while True:
            for key, _ in selector.select(timeout=30):
                src = key.fileobj
                dst = key.data
                data = src.recv(65536)
                if not data:
                    return
                dst.sendall(data)
    finally:
        selector.close()
        client.close()
        upstream.close()


def main() -> int:
    signal.signal(signal.SIGCHLD, signal.SIG_IGN)
    server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    server.bind((LISTEN_HOST, LISTEN_PORT))
    server.listen(128)
    print(f"lisglosips redis auth proxy listening on {LISTEN_HOST}:{LISTEN_PORT}", flush=True)
    while True:
        client, _ = server.accept()
        pid = os.fork()
        if pid == 0:
            server.close()
            try:
                bridge(client)
            except Exception as exc:
                print(f"redis proxy client failed: {exc}", file=sys.stderr, flush=True)
            return 0
        client.close()


if __name__ == "__main__":
    raise SystemExit(main())