from __future__ import annotations

"""
Copyright 2023-2025 SGLang Team
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
    http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
"""

import logging
import math
import threading
from queue import Empty, Full, PriorityQueue, Queue
from typing import TYPE_CHECKING, List, Optional

import torch

if TYPE_CHECKING:
    from sglang.srt.mem_cache.allocator import BaseTokenToKVPoolAllocator
    from sglang.srt.mem_cache.memory_pool_host import HostKVCache

logger = logging.getLogger(__name__)


class LayerDoneCounter:
    def __init__(self, num_layers):
        self.num_layers = num_layers
        # extra producer and consumer counters for overlap mode
        self.num_counters = 3
        self.counters = [num_layers] * self.num_counters
        self.conditions = [threading.Condition() for _ in range(self.num_counters)]
        self.producer_index = 0
        self.consumer_index = 0

    def next_producer(self):
        return (self.producer_index + 1) % self.num_counters

    def update_producer(self):
        self.producer_index = self.next_producer()
        return self.producer_index

    def set_consumer(self, index):
        self.consumer_index = index

    def increment(self):
        with self.conditions[self.producer_index]:
            self.counters[self.producer_index] += 1
            self.conditions[self.producer_index].notify_all()

    def wait_until(self, threshold):
        with self.conditions[self.consumer_index]:
            while self.counters[self.consumer_index] <= threshold:
                self.conditions[self.consumer_index].wait()

    def reset(self):
        with self.conditions[self.producer_index]:
            self.counters[self.producer_index] = 0


class CacheOperation:

    counter = 0

    def __init__(
        self,
        host_indices: torch.Tensor,
        device_indices: torch.Tensor,
        node_id: int,
        priority: Optional[int] = None,
    ):
        self.host_indices = host_indices
        self.device_indices = device_indices
        self.node_ids = [node_id]
        self.data = None

        self.id = CacheOperation.counter
        CacheOperation.counter += 1
        # default priority is the order of creation
        self.priority = priority if priority is not None else self.id

    def merge(self, other: "CacheOperation") -> None:
        # multiple operations can be merged into a single operation for batch processing
        self.host_indices = torch.cat([self.host_indices, other.host_indices])
        self.device_indices = torch.cat([self.device_indices, other.device_indices])
        self.priority = min(self.priority, other.priority)
        self.node_ids.extend(other.node_ids)

    def split(self, factor) -> List["CacheOperation"]:
        # split an operation into smaller operations to reduce the size of intermediate buffers
        if factor <= 1:
            return [self]

        chunk_size = math.ceil(len(self.host_indices) / factor)
        split_ops = []
        for i in range(0, len(self.host_indices), chunk_size):
            split_ops.append(
                CacheOperation(
                    host_indices=self.host_indices[i : i + chunk_size],
                    device_indices=self.device_indices[i : i + chunk_size],
                    node_id=0,
                )
            )
        # Inherit the node_ids on the final chunk
        if split_ops:
            split_ops[-1].node_ids = self.node_ids

        return split_ops

    def __lt__(self, other: "CacheOperation"):
        return self.priority < other.priority


class TransferBuffer:
    """
    Overlapping buffer preparation and transfer operations to improve throughput.
    """

    def __init__(
        self, stop_event, buffer_count: int = 3, max_buffer_size: int = 1000
    ) -> None:
        self.stop_event = stop_event
        self.buffers = Queue(maxsize=buffer_count)
        # todo: adjust the buffer size based on throughput profile of the system
        self.max_buffer_size = max_buffer_size

    def full(self) -> bool:
        return self.buffers.full()

    def empty(self) -> bool:
        return self.buffers.empty()

    def put(self, item, block=True, timeout=1) -> None:
        while not self.stop_event.is_set():
            try:
                self.buffers.put(item, block=block, timeout=timeout)
                break
            except Full:
                if not block:
                    break
                continue
            except Exception as e:
                logger.error(e)

    def get(self, block=True, timeout=1) -> Optional[CacheOperation]:
        try:
            return self.buffers.get(block=block, timeout=timeout)
        except Empty:
            return None
        except Exception as e:
            logger.error(e)

    def clear(self):
        self.buffers.queue.clear()


class HiCacheController:

    def __init__(
        self,
        token_to_kv_pool_allocator: BaseTokenToKVPoolAllocator,
        mem_pool_host: HostKVCache,
        page_size: int,
        load_cache_event: threading.Event = None,
        write_policy: str = "write_through_selective",
        io_backend: str = "",
    ):
        self.mem_pool_device_allocator = token_to_kv_pool_allocator
        self.mem_pool_device = token_to_kv_pool_allocator.get_kvcache()
        self.mem_pool_host = mem_pool_host
        self.write_policy = write_policy
        self.page_size = page_size
        # using kernel for small page KV cache transfer and DMA for large pages
        if not io_backend:
            IO_BACKEND_PAGE_SIZE_THRESHOLD = 64
            self.io_backend = (
                "direct"
                if self.page_size >= IO_BACKEND_PAGE_SIZE_THRESHOLD
                else "kernel"
            )
        else:
            self.io_backend = io_backend

        self.load_cache_event = load_cache_event
        self.layer_done_counter = LayerDoneCounter(self.mem_pool_device.layer_num)
        self.mem_pool_device.register_layer_transfer_counter(self.layer_done_counter)

        if write_policy not in [
            "write_through",
            "write_through_selective",
            "write_back",
        ]:
            raise ValueError(f"Invalid write policy: {write_policy}")

        self.write_queue = PriorityQueue()
        self.load_queue = PriorityQueue()

        self.ack_write_queue = Queue()
        self.ack_load_queue = Queue()

        self.stop_event = threading.Event()
        self.write_buffer = TransferBuffer(self.stop_event)
        self.load_buffer = TransferBuffer(
            self.stop_event, buffer_count=10, max_buffer_size=100
        )

        self.write_stream = torch.cuda.Stream()
        self.load_stream = torch.cuda.Stream()

        self.write_thread = threading.Thread(
            target=self.write_thread_func_direct, daemon=True
        )
        self.load_thread = threading.Thread(
            target=self.load_thread_func_layer_by_layer, daemon=True
        )
        self.write_thread.start()
        self.load_thread.start()

    def reset(self):
        self.stop_event.set()
        self.write_thread.join()
        self.load_thread.join()

        self.write_queue.queue.clear()
        self.load_queue.queue.clear()
        self.write_buffer.clear()
        self.load_buffer.clear()
        self.ack_write_queue.queue.clear()
        self.ack_load_queue.queue.clear()

        self.write_thread = threading.Thread(
            target=self.write_thread_func_direct, daemon=True
        )
        self.load_thread = threading.Thread(
            target=self.load_thread_func_layer_by_layer, daemon=True
        )
        self.stop_event.clear()
        self.write_thread.start()
        self.load_thread.start()

    def write(
        self,
        device_indices: torch.Tensor,
        priority: Optional[int] = None,
        node_id: int = 0,
    ) -> Optional[torch.Tensor]:
        """
        Back up KV caches from device memory to host memory.
        """
        host_indices = self.mem_pool_host.alloc(len(device_indices))
        if host_indices is None:
            return None
        self.mem_pool_host.protect_write(host_indices)
        self.write_queue.put(
            CacheOperation(host_indices, device_indices, node_id, priority)
        )
        return host_indices

    def load(
        self,
        host_indices: torch.Tensor,
        priority: Optional[int] = None,
        node_id: int = 0,
    ) -> Optional[torch.Tensor]:
        """
        Load KV caches from host memory to device memory.
        """
        device_indices = self.mem_pool_device_allocator.alloc(len(host_indices))
        if device_indices is None:
            return None
        self.mem_pool_host.protect_load(host_indices)
        # to ensure the device indices are ready before accessed by another CUDA stream
        torch.cuda.current_stream().synchronize()
        self.load_queue.put(
            CacheOperation(host_indices, device_indices, node_id, priority)
        )
        return device_indices

    def move_indices(self, host_indices, device_indices):
        # move indices to GPU if using kernels, to host if using direct indexing
        if self.io_backend == "kernel":
            return host_indices.to(self.mem_pool_device.device), device_indices
        elif self.io_backend == "direct":
            return host_indices, device_indices.cpu()
        else:
            raise ValueError(f"Unsupported io backend")

    def write_thread_func_direct(self):
        """
        Directly write through KV caches to host memory without buffering.
        """
        torch.cuda.set_stream(self.write_stream)
        while not self.stop_event.is_set():
            try:
                operation = self.write_queue.get(block=True, timeout=1)
                host_indices, device_indices = self.move_indices(
                    operation.host_indices, operation.device_indices
                )
                self.mem_pool_device.backup_to_host_all_layer(
                    self.mem_pool_host,
                    host_indices,
                    device_indices,
                    self.io_backend,
                )
                self.write_stream.synchronize()
                self.mem_pool_host.complete_io(operation.host_indices)
                for node_id in operation.node_ids:
                    if node_id != 0:
                        self.ack_write_queue.put(node_id)
            except Empty:
                continue
            except Exception as e:
                logger.error(e)

    def load_thread_func_layer_by_layer(self):
        """
        Load KV caches from host memory to device memory layer by layer.
        """
        torch.cuda.set_stream(self.load_stream)
        while not self.stop_event.is_set():
            self.load_cache_event.wait(timeout=1)
            if not self.load_cache_event.is_set():
                continue
            self.load_cache_event.clear()
            self.layer_done_counter.update_producer()

            batch_operation = None
            while self.load_queue.qsize() > 0:
                op = self.load_queue.get(block=True)
                if batch_operation is None:
                    batch_operation = op
                else:
                    batch_operation.merge(op)
            if batch_operation is None:
                continue

            # start layer-wise KV cache transfer from CPU to GPU
            self.layer_done_counter.reset()
            host_indices, device_indices = self.move_indices(
                batch_operation.host_indices, batch_operation.device_indices
            )
            for i in range(self.mem_pool_host.layer_num):
                self.mem_pool_device.load_from_host_per_layer(
                    self.mem_pool_host,
                    host_indices,
                    device_indices,
                    i,
                    self.io_backend,
                )
                self.load_stream.synchronize()
                self.layer_done_counter.increment()

            self.mem_pool_host.complete_io(batch_operation.host_indices)
            for node_id in batch_operation.node_ids:
                if node_id != 0:
                    self.ack_load_queue.put(node_id)

    def evict_device(
        self, device_indices: torch.Tensor, host_indices: torch.Tensor
    ) -> int:
        if self.mem_pool_host.is_synced(host_indices):
            self.mem_pool_device_allocator.free(device_indices)
            self.mem_pool_host.update_backup(host_indices)
            return len(device_indices)
        else:
            raise ValueError(
                f"Inconsistent states: {self.mem_pool_host.get_state(host_indices)}"
            )

    def evict_host(self, host_indices: torch.Tensor, backup_only: bool = True) -> int:
        if not backup_only:
            raise ValueError("Other eviction policies are not supported yet.")

        if self.mem_pool_host.is_backup(host_indices):
            self.mem_pool_host.free(host_indices)
            return len(host_indices)
        else:
            raise ValueError(
                f"Inconsistent states: {self.mem_pool_host.get_state(host_indices)}"
            )