import os
from celery import Celery

# Reuse existing RabbitMQ configuration env vars with vhost and optional TLS support
# If RABBITMQ_URL is provided, it takes precedence. Otherwise compose from parts.
if os.getenv("RABBITMQ_URL"):
    RABBITMQ_URL = os.getenv("RABBITMQ_URL")  # type: ignore
else:
    from urllib.parse import quote

    username = os.getenv("RABBITMQ_USERNAME", "user")
    password = os.getenv("RABBITMQ_PASSWORD", "bitnami123")
    host = os.getenv("RABBITMQ_HOST", "localhost")
    port = os.getenv("RABBITMQ_PORT", "5672")
    vhost = os.getenv("RABBITMQ_VHOST", "/")
    use_ssl = os.getenv("RABBITMQ_USE_SSL", "0").lower() in {"1", "true", "yes"}
    scheme = "amqps" if use_ssl else "amqp"

    # Kombu uses '//' to denote the default '/' vhost. For custom vhosts, URL-encode them.
    if vhost in ("/", ""):
        vhost_path = "/"  # will become '//' after concatenation below
    else:
        vhost_path = f"/{quote(vhost, safe='')}"

    # Ensure we end up with e.g. amqp://user:pass@host:5672// (for '/')
    RABBITMQ_URL = f"{scheme}://{username}:{password}@{host}:{port}{vhost_path}"
    if vhost in ("/", "") and not RABBITMQ_URL.endswith("//"):
        RABBITMQ_URL += "/"

# Default queue name to keep parity with the previous worker
DEFAULT_QUEUE = os.getenv("MAIL_QUEUE", "mail_queue")

# Use RPC backend by default to avoid coupling to Redis
CELERY_BACKEND = os.getenv("CELERY_BACKEND", "rpc://")

celery_app = Celery(
    "app",
    broker=RABBITMQ_URL,
    backend=CELERY_BACKEND,
    include=[
        "app.workers.celery_tasks",
    ],
)

# Ensure this Celery app becomes the default for producers (e.g., FastAPI process)
# so that @shared_task.delay(...) uses the same broker/credentials as the worker.
celery_app.set_default()

# Basic, safe defaults – single prefetch helps fairness similarly to the old worker
celery_app.conf.update(
    task_default_queue=DEFAULT_QUEUE,
    task_acks_late=True,
    worker_prefetch_multiplier=int(os.getenv("CELERY_PREFETCH", "1")),
    task_serializer="json",
    result_serializer="json",
    accept_content=["json"],
    broker_heartbeat=0,  # let kombu handle heartbeats robustly in some envs
)

# Expose a shortcut for Celery CLI discovery: `celery -A app.celery_app worker ...`
__all__ = ["celery_app"]