"""
Redis-based event bus for pipeline job progress.

Celery workers push events, SSE endpoints poll them.
Only depends on redis — safe to import from any context.
"""

import json
import os

import redis

REDIS_URL = os.environ.get("REDIS_URL", "redis://localhost:6379/0")


def _get_redis():
    return redis.from_url(REDIS_URL, decode_responses=True)


def push_event(job_id: str, event_type: str, data: dict) -> None:
    """Push an event to the Redis list for a job."""
    r = _get_redis()
    key = f"chunk_events:{job_id}"
    event = json.dumps({"event": event_type, **data})
    r.rpush(key, event)
    r.expire(key, 3600)


def poll_events(job_id: str, cursor: int = 0) -> tuple[list[dict], int]:
    """Poll new events from Redis. Returns (events, new_cursor)."""
    r = _get_redis()
    key = f"chunk_events:{job_id}"
    raw_events = r.lrange(key, cursor, -1)
    parsed = []
    for raw in raw_events:
        try:
            parsed.append(json.loads(raw))
        except (json.JSONDecodeError, TypeError):
            pass
    return parsed, cursor + len(raw_events)