# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
from dataclasses import dataclass, field
from typing import Any

from vllm.config.kv_transfer import KVTransferConfig
from vllm.distributed.kv_transfer.kv_connector.factory import KVConnectorFactory
from vllm.distributed.kv_transfer.kv_transfer_state import has_kv_transfer_group
from vllm.logger import init_logger

logger = init_logger(__name__)


@dataclass
class KVConnectorStats:
    """
    Base class for KV Connector Stats, a container for transfer performance
    metrics or otherwise important telemetry from the connector.
    All sub-classes need to be serializable as stats are sent from worker to
    logger process.
    """

    data: dict[str, Any] = field(default_factory=dict)

    def reset(self):
        """Reset the stats, clear the state."""
        raise NotImplementedError

    def aggregate(self, other: "KVConnectorStats") -> "KVConnectorStats":
        """
        Aggregate stats with another `KVConnectorStats` object.
        """
        raise NotImplementedError

    def reduce(self) -> dict[str, int | float]:
        """
        Reduce the observations collected during a time interval to one or
        more representative values (eg avg/median/sum of the series).
        This is meant to be called by the logger to produce a summary of the
        stats for the last time interval.
        """
        raise NotImplementedError

    def is_empty(self) -> bool:
        """Return True if the stats are empty."""
        raise NotImplementedError


class KVConnectorLogging:
    def __init__(self, kv_tranfer_config: KVTransferConfig):
        # This should be called on frontend process.
        assert not has_kv_transfer_group()
        # Instantiate the connector's stats class.
        if kv_tranfer_config and kv_tranfer_config.kv_connector:
            self.connector_cls = KVConnectorFactory.get_connector_class(
                kv_tranfer_config
            )
        self.reset()

    def reset(self):
        self.transfer_stats_accumulator: KVConnectorStats | None = None

    def observe(self, transfer_stats_data: dict[str, Any]):
        # Should not be called when a KVConnector is not configured.
        assert self.connector_cls is not None
        # Called periodically when connector syncs with the scheduler.
        # Note that this is not the same as the logging interval.
        # We expect transfer_stats_data to be aggregated across all workers and
        # consist of observations from a single connector or a MultiConnector.
        transfer_stats = self.connector_cls.build_kv_connector_stats(
            transfer_stats_data
        )
        if transfer_stats is None:
            logger.warning_once(
                "The connector %s is collecting stats but "
                "does not implement the "
                "`build_kv_connector_stats` method. "
                "Stats will not be logged.",
                self.connector_cls,
            )
            return

        if self.transfer_stats_accumulator is None:
            self.transfer_stats_accumulator = transfer_stats
        else:
            # Accumulate last interval stats.
            self.transfer_stats_accumulator = self.transfer_stats_accumulator.aggregate(
                transfer_stats
            )

    def log(self, log_fn=logger.info):
        """Log transfer metrics periodically, similar to throughput logging"""
        if (
            self.transfer_stats_accumulator
            and not self.transfer_stats_accumulator.is_empty()
        ):
            # Produce a single cumulative stats object for the last time
            # interval from the recorded observations.
            xfer_metrics = self.transfer_stats_accumulator.reduce()
            xfer_metrics_str = ", ".join(f"{k}={v}" for k, v in xfer_metrics.items())
            log_fn("KV Transfer metrics: %s", xfer_metrics_str)

            # Reset metrics for next interval
            self.reset()
