import json
from datetime import datetime, timezone
from typing import Any

import redis.asyncio as redis

from ..config import settings

_redis_client: redis.Redis | None = None


def _session_key(session_token: str) -> str:
    return f"voice:session:{session_token}"


async def get_redis() -> redis.Redis:
    global _redis_client
    if _redis_client is None:
        _redis_client = redis.from_url(settings.redis_url, decode_responses=True)
    return _redis_client


async def save_session(session_token: str, data: dict[str, Any]) -> None:
    client = await get_redis()
    payload = dict(data)
    payload["session_token"] = session_token
    payload.setdefault("created_at", datetime.now(timezone.utc).isoformat())
    await client.set(_session_key(session_token), json.dumps(payload), ex=settings.voice_session_ttl_seconds)


async def get_session(session_token: str) -> dict[str, Any] | None:
    client = await get_redis()
    raw = await client.get(_session_key(session_token))
    if not raw:
        return None
    return json.loads(raw)


async def update_session(session_token: str, **fields: Any) -> dict[str, Any] | None:
    session = await get_session(session_token)
    if not session:
        return None
    session.update(fields)
    await save_session(session_token, session)
    return session


async def delete_session(session_token: str) -> None:
    client = await get_redis()
    await client.delete(_session_key(session_token))