import threading


class APIMetrics:
    """
    In-memory metrics tracker for the Ingestion API.
    Thread-safe and async-safe counter for Prometheus scraping.
    """

    def __init__(self):
        self._lock = threading.Lock()
        self._received_total: int = 0
        self._acknowledged_total: int = 0

    def increment_received(self, count: int = 1) -> None:
        with self._lock:
            self._received_total += count

    def increment_acknowledged(self, count: int = 1) -> None:
        with self._lock:
            self._acknowledged_total += count

    @property
    def total_received(self) -> int:
        with self._lock:
            return self._received_total

    @property
    def total_acknowledged(self) -> int:
        with self._lock:
            return self._acknowledged_total

    def get_prometheus_metrics(self) -> str:
        """
        Formats metrics into standard Prometheus text format.
        """
        with self._lock:
            val_received = self._received_total
            val_ack = self._acknowledged_total

        return (
            "# HELP cdr_api_received_total Total CDRs received by the API\n"
            "# TYPE cdr_api_received_total counter\n"
            f"cdr_api_received_total {val_received}\n"
            "# HELP cdr_api_acknowledged_total Total CDRs successfully acknowledged by Kafka\n"
            "# TYPE cdr_api_acknowledged_total counter\n"
            f"cdr_api_acknowledged_total {val_ack}\n"
        )


api_metrics = APIMetrics()