import abc
import logging
import threading
from enum import IntEnum
from functools import wraps

import psutil
import torch

from sglang.srt.mem_cache.memory_pool import KVCache, MHATokenToKVPool, MLATokenToKVPool

logger = logging.getLogger(__name__)


class MemoryStateInt(IntEnum):
    IDLE = 0
    RESERVED = 1
    PROTECTED = 2
    SYNCED = 3
    BACKUP = 4


def synchronized(debug_only=False):
    def _decorator(func):
        @wraps(func)
        def wrapper(self, *args, **kwargs):
            if (not debug_only) or self.debug:
                return func(self, *args, **kwargs)
                with self.lock:
                    return func(self, *args, **kwargs)
            else:
                return True

        return wrapper

    return _decorator


class HostKVCache(abc.ABC):

    def __init__(
        self,
        device_pool: KVCache,
        host_to_device_ratio: float,
        host_size: int,
        pin_memory: bool,
        device: str,
        page_size: int,
    ):
        self.device_pool = device_pool
        self.dtype = device_pool.store_dtype
        self.pin_memory = pin_memory
        self.device = device
        self.page_size = page_size
        self.size_per_token = self.get_size_per_token()
        if host_size > 0:
            self.size = int(host_size * 1e9 // self.size_per_token)
        else:
            self.size = int(device_pool.size * host_to_device_ratio)
        # Align the host memory pool size to the page size
        self.size = self.size - (self.size % self.page_size)
        self.start_layer = device_pool.start_layer
        self.end_layer = device_pool.end_layer

        assert (
            self.size > device_pool.size
        ), "The host memory should be larger than the device memory with the current protocol"

        # Verify there is enough available host memory.
        host_mem = psutil.virtual_memory()
        requested_bytes = self.size * self.size_per_token
        # preserve at least 10GB for other usage
        ten_gb = 10 * (1024**3)
        if requested_bytes > host_mem.available - ten_gb:
            raise ValueError(
                f"Not enough host memory available. Requesting "
                f"{requested_bytes / 1e9:.2f} GB but only have "
                f"{host_mem.available / 1e9:.2f} GB free. Please reduce the "
                f"size of the hierarchical cache."
            )
        else:
            logger.info(
                f"Allocating {requested_bytes / 1e9:.2f} GB host memory for hierarchical KV cache."
            )

        self.kv_buffer = self.init_kv_buffer()

        # A lock for synchronized operations on memory allocation and state transitions.
        self.lock = threading.RLock()
        self.debug = logger.isEnabledFor(logging.DEBUG)
        self.clear()

    @abc.abstractmethod
    def get_size_per_token(self):
        raise NotImplementedError()

    @abc.abstractmethod
    def init_kv_buffer(self):
        raise NotImplementedError()

    @synchronized()
    def clear(self):
        # Initialize memory states and tracking structures.
        self.mem_state = torch.zeros(
            (self.size,), dtype=torch.uint8, device=self.device
        )
        self.free_slots = torch.arange(self.size, dtype=torch.int64)

    def available_size(self):
        return len(self.free_slots)

    @synchronized()
    def alloc(self, need_size: int) -> torch.Tensor:
        if need_size > self.available_size():
            return None

        select_index = self.free_slots[:need_size]
        self.free_slots = self.free_slots[need_size:]

        if self.debug:
            self.mem_state[select_index] = MemoryStateInt.RESERVED

        return select_index

    @synchronized()
    def free(self, indices: torch.Tensor) -> int:
        self.free_slots = torch.cat([self.free_slots, indices])
        if self.debug:
            self.mem_state[indices] = MemoryStateInt.IDLE
        return len(indices)

    @synchronized(debug_only=True)
    def get_state(self, indices: torch.Tensor) -> MemoryStateInt:
        assert len(indices) > 0, "The indices should not be empty"
        states = self.mem_state[indices]
        assert (
            states == states[0]
        ).all(), "The memory slots should have the same state {}".format(states)
        return MemoryStateInt(states[0].item())

    @synchronized(debug_only=True)
    def is_reserved(self, indices: torch.Tensor) -> bool:
        return self.get_state(indices) == MemoryStateInt.RESERVED

    @synchronized(debug_only=True)
    def is_protected(self, indices: torch.Tensor) -> bool:
        return self.get_state(indices) == MemoryStateInt.PROTECTED

    @synchronized(debug_only=True)
    def is_synced(self, indices: torch.Tensor) -> bool:
        return self.get_state(indices) == MemoryStateInt.SYNCED

    @synchronized(debug_only=True)
    def is_backup(self, indices: torch.Tensor) -> bool:
        return self.get_state(indices) == MemoryStateInt.BACKUP

    @synchronized(debug_only=True)
    def update_backup(self, indices: torch.Tensor):
        if not self.is_synced(indices):
            raise ValueError(
                f"The host memory slots should be in SYNCED state before turning into BACKUP. "
                f"Current state: {self.get_state(indices)}"
            )
        self.mem_state[indices] = MemoryStateInt.BACKUP

    @synchronized(debug_only=True)
    def update_synced(self, indices: torch.Tensor):
        self.mem_state[indices] = MemoryStateInt.SYNCED

    @synchronized(debug_only=True)
    def protect_write(self, indices: torch.Tensor):
        if not self.is_reserved(indices):
            raise ValueError(
                f"The host memory slots should be RESERVED before write operations. "
                f"Current state: {self.get_state(indices)}"
            )
        self.mem_state[indices] = MemoryStateInt.PROTECTED

    @synchronized(debug_only=True)
    def protect_load(self, indices: torch.Tensor):
        if not self.is_backup(indices):
            raise ValueError(
                f"The host memory slots should be in BACKUP state before load operations. "
                f"Current state: {self.get_state(indices)}"
            )
        self.mem_state[indices] = MemoryStateInt.PROTECTED

    @synchronized(debug_only=True)
    def complete_io(self, indices: torch.Tensor):
        if not self.is_protected(indices):
            raise ValueError(
                f"The host memory slots should be PROTECTED during I/O operations. "
                f"Current state: {self.get_state(indices)}"
            )
        self.mem_state[indices] = MemoryStateInt.SYNCED


class MHATokenToKVPoolHost(HostKVCache):
    device_pool: MHATokenToKVPool

    def __init__(
        self,
        device_pool: MHATokenToKVPool,
        host_to_device_ratio: float,
        host_size: int,
        page_size: int,
        pin_memory: bool = True,
        device: str = "cpu",
    ):
        super().__init__(
            device_pool, host_to_device_ratio, host_size, pin_memory, device, page_size
        )

    def get_size_per_token(self):
        self.head_num = self.device_pool.head_num
        self.head_dim = self.device_pool.head_dim
        self.layer_num = self.device_pool.layer_num

        return self.head_dim * self.head_num * self.layer_num * self.dtype.itemsize * 2

    def init_kv_buffer(self):
        return torch.empty(
            (2, self.layer_num, self.size, self.head_num, self.head_dim),
            dtype=self.dtype,
            device=self.device,
            pin_memory=self.pin_memory,
        )

    @property
    def k_buffer(self):
        return self.kv_buffer[0]

    @property
    def v_buffer(self):
        return self.kv_buffer[1]


class MLATokenToKVPoolHost(HostKVCache):
    device_pool: MLATokenToKVPool

    def __init__(
        self,
        device_pool: MLATokenToKVPool,
        host_to_device_ratio: float,
        host_size: int,
        page_size: int,
        pin_memory: bool = True,
        device: str = "cpu",
    ):
        super().__init__(
            device_pool, host_to_device_ratio, host_size, pin_memory, device, page_size
        )

    def get_size_per_token(self):
        self.kv_lora_rank = self.device_pool.kv_lora_rank
        self.qk_rope_head_dim = self.device_pool.qk_rope_head_dim
        self.layer_num = self.device_pool.layer_num

        return (
            (self.kv_lora_rank + self.qk_rope_head_dim)
            * 1
            * self.dtype.itemsize
            * self.layer_num
        )

    def init_kv_buffer(self):
        return torch.empty(
            (
                self.layer_num,
                self.size,
                1,
                self.kv_lora_rank + self.qk_rope_head_dim,
            ),
            dtype=self.dtype,
            device=self.device,
            pin_memory=self.pin_memory,
        )
