import ctypes
import numpy as np
from collections import defaultdict, deque
from typing import TypeVar, Type, Any, Dict, Deque, Tuple
from tinygrad.helpers import DType, dtypes, prod, GlobalCounters, ImageDType

_T = TypeVar("_T")
class RawBuffer:  # pylint: disable=abstract-method
  def __init__(self, size:int, dtype:DType, buf:Any=None, allocator:Any=None, **kwargs):
    self.size: int = size
    self.dtype: DType = dtype
    self._buf = buf if buf is not None else (allocator.alloc(size, dtype, **kwargs) if allocator else None) # If buf is provided, use it. Otherwise try to allocate from the allocator.
    self._memsz: int = size*dtype.itemsize
    self._allocator = allocator
    self._device = kwargs.get('device', None)
    GlobalCounters.mem_used += self._memsz
  def __del__(self):  # NOTE: if it fails on init (bad dtype), it won't have a _memsz
    if hasattr(self, '_memsz'): GlobalCounters.mem_used -= self._memsz
    if hasattr(self, '_allocator') and self._allocator: self._allocator.free(self._buf)
  def __repr__(self): return f"buffer<{self.size}, {self.dtype}, {id(self)}>"
  @property
  def key(self): return (self.size, self.dtype)

  # NOTE: this interface allows for 0 copy
  @classmethod
  def fromCPU(cls:Type[_T], x:np.ndarray) -> _T: raise NotImplementedError("must be implemented")
  def toCPU(self) -> np.ndarray: raise NotImplementedError("must be implemented")

class RawBufferCopyIn(RawBuffer):
  def _copyin(self, x:np.ndarray) -> None: raise NotImplementedError("must be implemented")

  @classmethod
  def fromCPU(cls, x:np.ndarray, **kwargs):
    ret = cls(prod(x.shape), dtypes.from_np(x.dtype), **kwargs)
    if x.size > 0: ret._copyin(x)
    return ret

class RawBufferMapped(RawBufferCopyIn):
  def _buffer(self) -> memoryview: raise NotImplementedError("must be implemented")
  # NOTE: this metadata prevents the backing buffer from being freed. hack can be removed with PEP688
  def buffer_view(self) -> np.ndarray: return np.frombuffer(self._buffer(), dtype=np.dtype(self.dtype.np, metadata={"backing": self}), count=self.size)  # type: ignore
  def toCPU(self) -> np.ndarray: return self.buffer_view().copy() # Need a copy, since jit will write to the same buffer.
  def _copyin(self, x:np.ndarray) -> None: np.copyto(self.buffer_view(), x.reshape(-1))

# this one is simple enough that i moved it out of the runtimes
class RawMallocBuffer(RawBufferMapped):
  def __init__(self, size, dtype: DType): super().__init__(size, dtype, ({dtypes.float64:ctypes.c_double, dtypes.float32: ctypes.c_float, dtypes.float16: ctypes.c_int16, dtypes.bfloat16: ctypes.c_int16, dtypes.int8: ctypes.c_int8, dtypes.uint8: ctypes.c_uint8, dtypes.bool: ctypes.c_uint8, dtypes.int32: ctypes.c_int32, dtypes.uint32: ctypes.c_uint32, dtypes.int64: ctypes.c_int64, dtypes.uint64: ctypes.c_uint64, dtypes.int16: ctypes.c_int16, dtypes.uint16: ctypes.c_uint16}[dtype] * size)())
  def _buffer(self): return memoryview(self._buf)

class RawBufferCopyInOut(RawBufferCopyIn):
  def _copyout(self, x:np.ndarray) -> None: raise NotImplementedError("must be implemented")

  def toCPU(self) -> np.ndarray:
    x: np.ndarray = np.empty(self.size, dtype=self.dtype.np)
    if x.size > 0: self._copyout(x)
    return x

class RawBufferTransfer(RawBuffer):
  def _transfer(self, x) -> None: raise NotImplementedError("must be implemented")

  @classmethod
  def transfer(cls, x, shape, dtype, **kwargs):
    ret = cls(prod(shape), dtype, **kwargs)
    ret._transfer(x)
    return ret

class LRUAllocator:
  def __init__(self, dev_memsz=(4<<30)):
    self.epoch = 0
    self.free_space: Dict[Any, int] = defaultdict(lambda: dev_memsz)
    self.buffer_info: Dict[Any, Tuple[int, DType, str]] = dict()
    self.cached_buffers: Dict[Tuple[int, ...], Deque[Tuple[Any, int]]] = defaultdict(deque) # Cached buffer storage, splitted by type and size, newest first.
    self.aging_order: Dict[Any, Deque[Tuple[Tuple[int, ...], int]]] = defaultdict(deque) # Keys of cached_buffers, ordered from oldest to newest updates.

  def _cache_reuse_buffer(self, rawbufs: Deque[Tuple[Any, int]]): # The newest cached buffer is reused.
    GlobalCounters.mem_cached -= self._underlying_buf_memsz(rawbufs[0][0])
    return rawbufs.popleft()[0]

  def ensure_has_free_space(self, size, dtype, device):
    while len(self.aging_order[device]) and (self.free_space[device]-size*dtype.itemsize) < 0: # When OOM removing lru buffers.
      bucket, epoch = self.aging_order[device].popleft()
      if self.cached_buffers[bucket] and self.cached_buffers[bucket][-1][1] == epoch: self._free_buffer(self.cached_buffers[bucket].pop()[0]) # Free cached buffer if it is still in cache.

  def _alloc_buffer(self, size, dtype, device, **kwargs):
    self.ensure_has_free_space(size, dtype, device)
    self.free_space[device] -= size*dtype.itemsize
    newbuf = self._do_alloc(max(1, size), dtype, device, **kwargs)
    self.buffer_info[newbuf] = (size, dtype, device)
    return newbuf

  def _free_buffer(self, buf_to_free):
    self.free_space[self.buffer_info[buf_to_free][2]] += self._underlying_buf_memsz(buf_to_free)
    GlobalCounters.mem_cached -= self._underlying_buf_memsz(buf_to_free)
    self.buffer_info.pop(buf_to_free)
    self._do_free(buf_to_free)

  def alloc(self, size, dtype, device='0', **kwargs):
    rawbufs = self.cached_buffers.get(self._cached_bufkey(size, dtype, device), None)
    return self._cache_reuse_buffer(rawbufs) if rawbufs else self._alloc_buffer(size, dtype, device, **kwargs)

  def free(self, buf): # free() just caches buffer. It might be freed later when OOM during allocation.
    self.epoch += 1
    size, dtype, device = self.buffer_info[buf]
    self.cached_buffers[self._cached_bufkey(size, dtype, device)].appendleft((buf, self.epoch))
    self.aging_order[device].append((self._cached_bufkey(size, dtype, device), self.epoch))
    GlobalCounters.mem_cached += self._underlying_buf_memsz(buf)

  def _underlying_buf_memsz(self, buf): return self.buffer_info[buf][0] * self.buffer_info[buf][1].itemsize
  def _cached_bufkey(self, size, dtype, device) -> Tuple[int, ...]: return (device, size, dtype, dtype.shape) if isinstance(dtype, ImageDType) else (device, size, dtype) # Provides a key for reusing device buffers with identical keys.
  def _do_alloc(self, size, dtype, device, **kwargs): raise NotImplementedError("must be implemented")
  def _do_free(self, buf): pass