import math
from logging import getLogger

import numpy as np
import torch
import torch.nn as nn

logger = getLogger(__name__)

try:
    import quant_cuda

    _quant_cuda_available = True
except ImportError:
    logger.warning('CUDA extension not installed.')
    _quant_cuda_available = False


class QuantLinear(nn.Module):
    def __init__(
        self,
        bits,
        groupsize,
        infeatures,
        outfeatures,
        bias,
        kernel_switch_threshold=128,
    ):
        super().__init__()
        if bits not in [2, 3, 4, 8]:
            raise NotImplementedError("Only 2,3,4,8 bits are supported.")

        self.infeatures = infeatures
        self.outfeatures = outfeatures
        self.bits = bits
        self.groupsize = groupsize if groupsize != -1 else infeatures
        self.maxq = 2 ** self.bits - 1

        self.register_buffer(
            'qweight',
            torch.zeros((infeatures // 32 * self.bits, outfeatures), dtype=torch.int32)
        )
        self.register_buffer(
            'qzeros',
            torch.zeros((math.ceil(infeatures / self.groupsize), outfeatures // 32 * self.bits), dtype=torch.int32)
        )
        self.register_buffer(
            'scales',
            torch.zeros((math.ceil(infeatures / self.groupsize), outfeatures), dtype=torch.float16)
        )
        self.register_buffer(
            'g_idx',
            torch.tensor([i // self.groupsize for i in range(infeatures)], dtype=torch.int32)
        )
        if bias:
            self.register_buffer('bias', torch.zeros((outfeatures), dtype=torch.float16))
        else:
            self.bias = None

        # is performed by unpacking the weights and using torch.matmul
        if self.bits in [2, 4, 8]:
            self.register_buffer(
                'wf',
                torch.tensor(list(range(0, 32, self.bits)), dtype=torch.int32).unsqueeze(0),
                persistent=False
            )
        elif self.bits == 3:
            self.register_buffer(
                'wf',
                torch.tensor(
                    [
                        [0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 0],
                        [0, 1, 4, 7, 10, 13, 16, 19, 22, 25, 28, 31],
                        [0, 2, 5, 8, 11, 14, 17, 20, 23, 26, 29, 0],
                    ],
                    dtype=torch.int32).reshape(1, 3, 12),
                persistent=False
            )

        self.kernel_switch_threshold = kernel_switch_threshold
        self.quant_cuda_available = _quant_cuda_available

    def pack(self, linear, scales, zeros, g_idx=None):
        self.g_idx = g_idx.clone() if g_idx is not None else self.g_idx

        scales = scales.t().contiguous()
        zeros = zeros.t().contiguous()
        scale_zeros = zeros * scales
        self.scales = scales.clone().half()
        if linear.bias is not None:
            self.bias = linear.bias.clone().half()

        intweight = []
        for idx in range(self.infeatures):
            intweight.append(
                torch.round(
                    (
                        linear.weight.data[:, idx] + scale_zeros[self.g_idx[idx]]) / self.scales[self.g_idx[idx]]
                ).to(torch.int)[:, None]
            )
        intweight = torch.cat(intweight, dim=1)
        intweight = intweight.t().contiguous()
        intweight = intweight.numpy().astype(np.uint32)

        i = 0
        row = 0
        qweight = np.zeros(
            (intweight.shape[0] // 32 * self.bits, intweight.shape[1]), dtype=np.uint32
        )
        while row < qweight.shape[0]:
            if self.bits in [2, 4, 8]:
                for j in range(i, i + (32 // self.bits)):
                    qweight[row] |= intweight[j] << (self.bits * (j - i))
                i += 32 // self.bits
                row += 1
            elif self.bits == 3:
                for j in range(i, i + 10):
                    qweight[row] |= intweight[j] << (3 * (j - i))
                i += 10
                qweight[row] |= intweight[i] << 30
                row += 1
                qweight[row] |= (intweight[i] >> 2) & 1
                i += 1
                for j in range(i, i + 10):
                    qweight[row] |= intweight[j] << (3 * (j - i) + 1)
                i += 10
                qweight[row] |= intweight[i] << 31
                row += 1
                qweight[row] |= (intweight[i] >> 1) & 0x3
                i += 1
                for j in range(i, i + 10):
                    qweight[row] |= intweight[j] << (3 * (j - i) + 2)
                i += 10
                row += 1
            else:
                raise NotImplementedError("Only 2,3,4,8 bits are supported.")

        qweight = qweight.astype(np.int32)
        self.qweight = torch.from_numpy(qweight)

        zeros -= 1
        zeros = zeros.numpy().astype(np.uint32)
        qzeros = np.zeros((zeros.shape[0], zeros.shape[1] // 32 * self.bits), dtype=np.uint32)
        i = 0
        col = 0
        while col < qzeros.shape[1]:
            if self.bits in [2, 4, 8]:
                for j in range(i, i + (32 // self.bits)):
                    qzeros[:, col] |= zeros[:, j] << (self.bits * (j - i))
                i += 32 // self.bits
                col += 1
            elif self.bits == 3:
                for j in range(i, i + 10):
                    qzeros[:, col] |= zeros[:, j] << (3 * (j - i))
                i += 10
                qzeros[:, col] |= zeros[:, i] << 30
                col += 1
                qzeros[:, col] |= (zeros[:, i] >> 2) & 1
                i += 1
                for j in range(i, i + 10):
                    qzeros[:, col] |= zeros[:, j] << (3 * (j - i) + 1)
                i += 10
                qzeros[:, col] |= zeros[:, i] << 31
                col += 1
                qzeros[:, col] |= (zeros[:, i] >> 1) & 0x3
                i += 1
                for j in range(i, i + 10):
                    qzeros[:, col] |= zeros[:, j] << (3 * (j - i) + 2)
                i += 10
                col += 1
            else:
                raise NotImplementedError("Only 2,3,4,8 bits are supported.")

        qzeros = qzeros.astype(np.int32)
        self.qzeros = torch.from_numpy(qzeros)

    def forward(self, x: torch.Tensor):
        out_shape = x.shape[:-1] + (self.outfeatures,)
        x = x.reshape(-1, x.shape[-1])
        if self.quant_cuda_available and (
            self.kernel_switch_threshold == 0 or x.shape[0] < self.kernel_switch_threshold
        ):
            out = torch.zeros((x.shape[0], self.outfeatures), device='cuda', dtype=torch.float32)
            if self.bits == 2:
                quant_cuda.vecquant2matmul(x.float(), self.qweight, out, self.scales.float(), self.qzeros, self.g_idx)
            elif self.bits == 3:
                quant_cuda.vecquant3matmul(x.float(), self.qweight, out, self.scales.float(), self.qzeros, self.g_idx)
            elif self.bits == 4:
                quant_cuda.vecquant4matmul(x.float(), self.qweight, out, self.scales.float(), self.qzeros, self.g_idx)
            elif self.bits == 8:
                quant_cuda.vecquant8matmul(x.float(), self.qweight, out, self.scales.float(), self.qzeros, self.g_idx)
            else:
                raise NotImplementedError("Only 2,3,4,8 bits are supported.")
            out = out.half()
        else:
            if self.bits in [2, 4, 8]:
                zeros = torch.bitwise_right_shift(
                    torch.unsqueeze(self.qzeros, 2).expand(-1, -1, 32 // self.bits),
                    self.wf.unsqueeze(0)
                ).to(torch.int16 if self.bits == 8 else torch.int8)
                torch.bitwise_and(zeros, (2 ** self.bits) - 1, out=zeros)

                zeros = zeros + 1
                zeros = zeros.reshape(self.scales.shape)

                weight = torch.bitwise_right_shift(
                    torch.unsqueeze(self.qweight, 1).expand(-1, 32 // self.bits, -1),
                    self.wf.unsqueeze(-1)
                ).to(torch.int16 if self.bits == 8 else torch.int8)
                torch.bitwise_and(weight, (2 ** self.bits) - 1, out=weight)
            elif self.bits == 3:
                zeros = self.qzeros.reshape(
                    self.qzeros.shape[0], self.qzeros.shape[1] // 3, 3, 1
                ).expand(-1, -1, -1, 12)
                zeros = (zeros >> self.wf.unsqueeze(0))
                zeros[:, :, 0, 10] = (zeros[:, :, 0, 10] & 0x3) | ((zeros[:, :, 1, 0] << 2) & 0x4)
                zeros[:, :, 1, 11] = (zeros[:, :, 1, 11] & 0x1) | ((zeros[:, :, 2, 0] << 1) & 0x6)
                zeros = zeros & 0x7
                zeros = torch.cat([zeros[:, :, 0, :11], zeros[:, :, 1, 1:12], zeros[:, :, 2, 1:11]], dim=2)

                zeros = zeros + 1
                zeros = zeros.reshape(self.scales.shape)

                weight = self.qweight.reshape(
                    self.qweight.shape[0] // 3, 3, 1, self.qweight.shape[1]
                ).expand(-1, -1, 12, -1)
                weight = (weight >> self.wf.unsqueeze(-1)) & 0x7
                weight[:, 0, 10] = (weight[:, 0, 10] & 0x3) | ((weight[:, 1, 0] << 2) & 0x4)
                weight[:, 1, 11] = (weight[:, 1, 11] & 0x1) | ((weight[:, 2, 0] << 1) & 0x6)
                weight = weight & 0x7
                weight = torch.cat([weight[:, 0, :11], weight[:, 1, 1:12], weight[:, 2, 1:11]], dim=1)
            else:
                raise NotImplementedError("Only 2,3,4,8 bits are supported.")

            weight = weight.reshape(weight.shape[0] * weight.shape[1], weight.shape[2])

            weights = (self.scales[self.g_idx.long()] * (weight - zeros[self.g_idx.long()]))
            out = torch.matmul(x.half(), weights)
        out = out.reshape(out_shape)
        out = out + self.bias if self.bias is not None else out
        return out


__all__ = ["QuantLinear"]