# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0

import asyncio
import concurrent.futures
import logging
import threading
import traceback
import weakref
from contextlib import asynccontextmanager
from queue import Queue
from typing import Callable, Optional, Union

from dynamo.llm import KvEventPublisher, WorkerMetricsPublisher

logging.basicConfig(level=logging.DEBUG)


def _to_signed_i64(value: int | None) -> int | None:
    """Convert a Python int to signed 64-bit range by two's complement."""
    if value is None:
        return None

    if value >= 2**63:
        return value - 2**64
    if value < -(2**63):
        return ((value + 2**63) % 2**64) - 2**63
    return value


class ManagedThread(threading.Thread):
    """
    A thread that runs a task and handles errors.
    """

    def __init__(
        self,
        task: Optional[Union[Callable[..., bool], weakref.WeakMethod]],
        error_queue: Optional[Queue] = None,
        name: Optional[str] = None,
        loop: Optional[asyncio.AbstractEventLoop] = None,
        **kwargs,
    ):
        super().__init__(name=name)
        self.task = task
        self.error_queue = error_queue
        self.kwargs = kwargs
        self.loop = loop
        self.daemon = True
        self._current_future: Optional[concurrent.futures.Future] = None

        self._stop_event = threading.Event()

    def set_loop(self, loop: asyncio.AbstractEventLoop):
        self.loop = loop

    def run(self):
        while not self._stop_event.is_set():
            task: Optional[Union[Callable[..., bool], weakref.WeakMethod]] = self.task
            if isinstance(task, weakref.WeakMethod):
                task = task()
                if task is None:
                    # Normally, this should not happen.
                    logging.warning("WeakMethod is expired.")
                    break

            if task is None:
                break

            try:
                if self.loop is None:
                    logging.error("[ManagedThread] Loop not initialized!")
                    break
                self._current_future = asyncio.run_coroutine_threadsafe(
                    task(**self.kwargs), self.loop
                )
                _ = self._current_future.result()
            except (asyncio.CancelledError, concurrent.futures.CancelledError):
                logging.debug(f"Thread {self.name} was cancelled")
                break
            except Exception as e:
                logging.error(
                    f"Error in thread {self.name}: {e}\n{traceback.format_exc()}"
                )
                if self.error_queue is not None:
                    self.error_queue.put(e)

        logging.info(f"Thread {self.name} stopped.")

    def stop(self):
        self._stop_event.set()
        if self._current_future and not self._current_future.done():
            self._current_future.cancel()


class Publisher:
    """
    A class to retrieve stats and kv cache events from TRTLLM engine and publish them to the metrics and events publishers.
    """

    def __init__(self, component, engine, kv_listener, worker_id, kv_block_size):
        self.component = component
        self.engine = engine
        self.kv_listener = kv_listener
        self.worker_id = worker_id
        self.kv_block_size = kv_block_size

        # Needed by the events and metrics publishers
        self.metrics_publisher = None
        self.kv_event_publisher = None
        self.publish_kv_cache_events_thread = None
        self.publish_stats_thread = None
        # A set to store the block hash of partial block (i.e. block containing less than kv_block_size tokens) hashes.
        # It is used to prevent sending remove event to kv router since partial blocks are not stored.
        self.partial_block_hashes = set()
        self.error_queue: Queue = Queue()
        self._stop_event = threading.Event()

    async def _create_metrics_publisher_endpoint(self):
        logging.debug("Creating metrics publisher endpoint")
        if self.metrics_publisher is None:
            logging.error("KV metrics publisher not initialized!")
            return
        await self.metrics_publisher.create_endpoint(self.component)

    def initialize(self):
        # Setup the metrics publisher
        self.metrics_publisher = WorkerMetricsPublisher()
        self._init_publish_metrics_thread()
        task = asyncio.create_task(self._create_metrics_publisher_endpoint())
        task.add_done_callback(
            lambda _: logging.debug("metrics publisher endpoint created")
        )

        # Setup the kv cache events publisher
        self.kv_event_publisher = KvEventPublisher(
            self.kv_listener, self.worker_id, self.kv_block_size
        )
        self._init_publish_kv_cache_events_thread()

    def _init_publish_metrics_thread(self):
        # Need to publish stats once so that worker can be selected.
        # Publishing some dummy values...
        request_active_slots = 0
        request_total_slots = 4
        kv_active_block = 0
        kv_total_blocks = 4
        num_requests_waiting = 0
        gpu_cache_usage_perc = 0.0
        gpu_prefix_cache_hit_rate = 0.0

        num_requests_waiting = 0
        gpu_cache_usage_perc = 0.0
        gpu_prefix_cache_hit_rate = 0.0

        if self.metrics_publisher is None:
            logging.error("KV metrics publisher not initialized!")
            return

        self.metrics_publisher.publish(
            request_active_slots,
            request_total_slots,
            kv_active_block,
            kv_total_blocks,
            num_requests_waiting,
            gpu_cache_usage_perc,
            gpu_prefix_cache_hit_rate,
        )

        # Prepare threads for publishing stats but don't start them yet.
        # TRTLLM needs to start generating tokens first before stats
        # can be retrieved.
        self.publish_stats_thread = ManagedThread(
            self._publish_stats_task,
            error_queue=self.error_queue,
            name="publish_stats_thread",
        )

    def _init_publish_kv_cache_events_thread(self):
        if self.kv_event_publisher is None:
            logging.error("KV event publisher not initialized!")
            return

        # Prepare threads for publishing kv cache events but don't start them yet.
        # TRTLLM needs to start generating tokens first before kv cache events
        # can be retrieved.
        self.publish_kv_cache_events_thread = ManagedThread(
            self._publish_kv_cache_events_task,
            error_queue=self.error_queue,
            name="publish_kv_cache_events_thread",
        )

    async def _publish_stats_task(self):
        """
        Publish stats to the metrics publisher.
        """
        if self.engine is None:
            logging.error("LLM engine not initialized!")
            return

        if self.metrics_publisher is None:
            logging.error("KV metrics publisher not initialized!")
            return False

        stats = self.engine.llm.get_stats_async(timeout=5)
        async for stat in stats:
            request_active_slots = stat["numActiveRequests"]
            request_total_slots = stat["maxNumActiveRequests"]
            kv_active_block = stat["kvCacheStats"]["usedNumBlocks"]
            kv_total_blocks = stat["kvCacheStats"]["maxNumBlocks"]
            reused_blocks = stat["kvCacheStats"]["reusedBlocks"]
            freeNumBlocks = stat["kvCacheStats"]["freeNumBlocks"]
            allocTotalBlocks = stat["kvCacheStats"]["allocTotalBlocks"]
            allocNewBlocks = stat["kvCacheStats"]["allocNewBlocks"]
            # NOTE: num paused requests is always 0 when using guarantee no evict scheduler (default).
            num_requests_waiting = (
                stat["numQueuedRequests"]
                + stat["inflightBatchingStats"]["numPausedRequests"]
            )
            gpu_cache_usage_perc = allocTotalBlocks / kv_total_blocks
            gpu_prefix_cache_hit_rate = stat["kvCacheStats"]["cacheHitRate"]

            logging.debug(
                f"Publishing stats: request_active_slots: {request_active_slots}, request_total_slots: {request_total_slots}, kv_active_block: {kv_active_block}, kv_total_blocks: {kv_total_blocks}, num_requests_waiting: {num_requests_waiting}, reused_blocks: {reused_blocks}, freeNumBlocks: {freeNumBlocks}, allocTotalBlocks: {allocTotalBlocks}, allocNewBlocks: {allocNewBlocks}, gpu_cache_usage_perc: {gpu_cache_usage_perc}, gpu_prefix_cache_hit_rate: {gpu_prefix_cache_hit_rate}"
            )

            self.metrics_publisher.publish(
                request_active_slots,
                request_total_slots,
                kv_active_block,
                kv_total_blocks,
                num_requests_waiting,
                gpu_cache_usage_perc,
                gpu_prefix_cache_hit_rate,
            )

        return True

    async def _publish_kv_cache_events_task(self):
        """
        Publish kv cache events to the events publisher.
        """
        if self.engine is None:
            logging.error("LLM engine not initialized!")
            return

        if self.kv_event_publisher is None:
            logging.error("KV event publisher not initialized!")
            return

        events = self.engine.llm.get_kv_cache_events_async(timeout=5)
        async for event in events:
            logging.debug(f"KV cache event received: {event}")
            event_id = event["event_id"]
            data = event["data"]
            if data["type"] == "stored":
                parent_hash = _to_signed_i64(data["parent_hash"])
                token_ids = []
                num_block_tokens = []
                block_hashes = []
                for block in data["blocks"]:
                    token_num_in_block = len(block["tokens"])
                    block_hash = _to_signed_i64(block["block_hash"])
                    if token_num_in_block > self.kv_block_size:
                        logging.error(
                            f"Block {block_hash} contains {token_num_in_block} tokens, which is greater than kv_block_size {self.kv_block_size}"
                        )
                        return
                    if token_num_in_block < self.kv_block_size:
                        logging.debug(
                            f"Early stop when block {block_hash} containing {token_num_in_block} tokens not equal to kv_block_size {self.kv_block_size}"
                        )
                        self.partial_block_hashes.add(block_hash)
                        break
                    num_block_tokens.append(token_num_in_block)
                    block_hashes.append(block_hash)
                    for token in block["tokens"]:
                        token_ids.append(int(token["token_id"]))

                # Note: Currently data does not have lora_id.
                # Using 0 as default value. If later data has
                # lora_id, we need to verify if this is correct.
                lora_id = data.get("lora_id", 0)

                logging.debug(
                    f"publish stored event: event_id: {event_id}, token_ids: {token_ids}, num_block_tokens: {num_block_tokens}, block_hashes: {block_hashes}, lora_id: {lora_id}, parent_hash: {parent_hash}"
                )
                self.kv_event_publisher.publish_stored(
                    event_id,
                    token_ids,
                    num_block_tokens,
                    block_hashes,
                    lora_id,
                    parent_hash,
                )
            elif data["type"] == "removed":
                block_hashes = []
                for block_hash in data["block_hashes"]:
                    block_hash = _to_signed_i64(block_hash)
                    if block_hash in self.partial_block_hashes:
                        logging.debug(
                            f"Skipping removing block hash {block_hash} since it is a partial block"
                        )
                        self.partial_block_hashes.remove(block_hash)
                        continue
                    block_hashes.append(block_hash)

                logging.debug(
                    f"publish removed event: event_id: {event_id}, block_hashes: {block_hashes}"
                )
                self.kv_event_publisher.publish_removed(event_id, block_hashes)
        return True

    def start(self):
        if (
            self.publish_kv_cache_events_thread
            and not self.publish_kv_cache_events_thread.is_alive()
        ):
            # REVISIT
            # [NOTE:] TRTLLM needs the stats to be collected on the same loop as the request handler.
            self._stats_loop = asyncio.get_running_loop()
            self.publish_kv_cache_events_thread.set_loop(self._stats_loop)
            self.publish_kv_cache_events_thread.start()
            logging.debug("Started kv cache events thread")

        if self.publish_stats_thread and not self.publish_stats_thread.is_alive():
            self._stats_loop = asyncio.get_running_loop()
            self.publish_stats_thread.set_loop(self._stats_loop)
            self.publish_stats_thread.start()
            logging.debug("Started stats thread")

    def check_error_queue(self):
        if not self.error_queue.empty():
            logging.error("Error in publishers error queue")
            return self.error_queue.get()
        return None

    async def cleanup(self):
        """Cleanup threads and resources"""
        self._stop_event.set()
        # Add timeout to prevent hanging
        cleanup_timeout = 5.0  # seconds

        if self.publish_stats_thread and self.publish_stats_thread.is_alive():
            self.publish_stats_thread.stop()
            self.publish_stats_thread.join(timeout=cleanup_timeout)
            if self.publish_stats_thread.is_alive():
                logging.warning("Stats thread did not stop within timeout")

        if (
            self.publish_kv_cache_events_thread
            and self.publish_kv_cache_events_thread.is_alive()
        ):
            self.publish_kv_cache_events_thread.stop()
            self.publish_kv_cache_events_thread.join(timeout=cleanup_timeout)
            if self.publish_kv_cache_events_thread.is_alive():
                logging.warning("KV cache events thread did not stop within timeout")


@asynccontextmanager
async def get_publisher(component, engine, kv_listener, worker_id, kv_block_size):
    publisher = Publisher(component, engine, kv_listener, worker_id, kv_block_size)
    try:
        publisher.initialize()
        yield publisher
    except Exception as e:
        logging.error(f"Error in engine context: {e}")
        raise
    finally:
        await publisher.cleanup()
