from collections.abc import Iterator
from typing import Optional

import torch
from vllm.attention.backends.abstract import AttentionBackend
from vllm.config import VllmConfig
from vllm.v1.kv_offload.abstract import LoadStoreSpec, OffloadingManager
from vllm.v1.kv_offload.backends.cpu import CPUBackend
from vllm.v1.kv_offload.lru_manager import LRUOffloadingManager
from vllm.v1.kv_offload.mediums import CPULoadStoreSpec, GPULoadStoreSpec
from vllm.v1.kv_offload.spec import OffloadingSpec
from vllm.v1.kv_offload.worker.worker import OffloadingHandler

from vllm_ascend.kv_offload.cpu_npu import CpuNpuOffloadingHandler


class NPUOffloadingSpec(OffloadingSpec):

    def __init__(self, vllm_config: VllmConfig):
        super().__init__(vllm_config)

        num_cpu_blocks = self.extra_config.get("num_cpu_blocks")
        if not num_cpu_blocks:
            raise Exception(
                "num_cpu_blocks must be specified in kv_connector_extra_config"
            )
        self.num_cpu_blocks: int = num_cpu_blocks

        # scheduler-side
        self._manager: Optional[OffloadingManager] = None

        # worker-side
        self._handler: Optional[OffloadingHandler] = None

    def get_manager(self) -> OffloadingManager:
        if not self._manager:
            kv_events_config = self.vllm_config.kv_events_config
            enable_events = (kv_events_config is not None
                             and kv_events_config.enable_kv_cache_events)
            self._manager = LRUOffloadingManager(
                CPUBackend(block_size=self.offloaded_block_size,
                           num_blocks=self.num_cpu_blocks),
                enable_events=enable_events,
            )
        return self._manager

    def get_handlers(
        self,
        kv_caches: dict[str, torch.Tensor],
        attn_backends: dict[str, type[AttentionBackend]],
    ) -> Iterator[tuple[type[LoadStoreSpec], type[LoadStoreSpec],
                        OffloadingHandler]]:
        if not self._handler:
            self._handler = CpuNpuOffloadingHandler(
                attn_backends=attn_backends,
                gpu_block_size=self.gpu_block_size,
                cpu_block_size=self.offloaded_block_size,
                num_cpu_blocks=self.num_cpu_blocks,
                gpu_caches=kv_caches,
            )

        assert self._handler is not None
        yield GPULoadStoreSpec, CPULoadStoreSpec, self._handler
        yield CPULoadStoreSpec, GPULoadStoreSpec, self._handler
