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

from app.api.producer import MessageProducer
from app.common.config import config
from app.common.logging import setup_logger
from app.worker.metrics import worker_metrics

logger = setup_logger("processing-worker")

ALLOWED_FAILURE_REASONS = {
    "missing_required_field",
    "invalid_rat_value",
    "invalid_epoch",
    "malformed_json",
    "normalization_error",
    "ch_insert_failed",
}


def build_dlq_envelope(
    original_payload: Any,
    failure_reason: str,
    failed_field: Optional[str] = None,
    worker_instance: Optional[str] = None,
) -> Dict[str, Any]:
    """
    Constructs a standardized DLQ envelope according to specification.
    """
    if failure_reason not in ALLOWED_FAILURE_REASONS:
        raise ValueError(f"Unsupported DLQ reason: {failure_reason}")
    return {
        "original_payload": original_payload,
        "failure_reason": failure_reason,
        "failed_field": failed_field,
        "failed_at": datetime.now(timezone.utc).strftime("%Y-%m-%dT%H:%M:%SZ"),
        "worker_instance": worker_instance or config.worker.instance_id,
    }


def route_to_dlq(
    producer: MessageProducer,
    topic: str,
    original_payload: Any,
    failure_reason: str,
    failed_field: Optional[str] = None,
    raw_id: Optional[str] = None,
) -> bool:
    """
    Wraps unprocessable record in a DLQ envelope, updates DLQ metric,
    and publishes to the DLQ topic.
    """
    envelope = build_dlq_envelope(
        original_payload=original_payload,
        failure_reason=failure_reason,
        failed_field=failed_field,
    )
    envelope_bytes = json.dumps(envelope, default=str).encode("utf-8")

    producer.produce(topic=topic, key=raw_id, value=envelope_bytes).result(
        timeout=config.kafka.delivery_timeout_seconds + 1
    )
    worker_metrics.record_dlq(failure_reason, 1)

    logger.warning(
        f"Record routed to DLQ: reason={failure_reason}, field={failed_field}",
        extra={"raw_id": raw_id, "event": "routed_to_dlq"},
    )
    return True