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# Copyright 2024-2025 qubitium@modelcloud.ai
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# Licensed under the Apache License, Version 2.0 (the "License");
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#
#     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.

# adapted from @qwopqwop200 's [GPTQ-for-LLaMa](https://github.com/qwopqwop200/GPTQ-for-LLaMa/tree/cuda), which itself is based on [gptq](https://github.com/IST-DASLab/gptq)

import torch
import torch.nn as nn

from ..quantization import QuantizeConfig
from ..utils.logger import setup_logger

log = setup_logger()

HF_OPTIMUM = "hf_optimum"

def quantize(x, scale, zero, maxq, requires_groupwise_processing: bool):
    if maxq < 0:
        return (x > scale / 2).float() * scale + (x < zero / 2).float() * zero
    if requires_groupwise_processing:
        q = torch.clamp(torch.round(x / scale), -maxq, maxq)
        return scale * q
    else:
        q = torch.clamp(torch.round(x / scale) + zero, 0, maxq)
        return scale * (q - zero)


class Quantizer(nn.Module):
    def __init__(self, qcfg: QuantizeConfig, shape=1, name: str=None):
        super(Quantizer, self).__init__()

        self.qcfg = qcfg
        self.register_buffer("maxq", torch.tensor(0))
        self.register_buffer("scale", torch.zeros(shape))
        self.register_buffer("zero", torch.zeros(shape))

        self.name=name

    def requires_groupwise_processing(self) -> bool:
        return False

    # FIXME, optimum shouldn't call this directly, it should call hf_configure
    def configure(
        self,
        perchannel=False,
        grid=100,
        maxshrink=0.8,
        trits=False,
        bits:int=4, # for hf compat
        sym:bool=False, # for hf compat
    ):
        if self.name == HF_OPTIMUM:
            self.qcfg.bits = bits
            self.qcfg.sym = sym

        if self.requires_groupwise_processing():
            self.maxq = torch.tensor(2 ** (self.qcfg.bits - 1) - 1)
        else:
            self.maxq = torch.tensor(2 ** self.qcfg.bits - 1)

        self.perchannel = perchannel
        self.grid = grid
        self.maxshrink = maxshrink
        if trits:
            self.maxq = torch.tensor(-1)

    def find_params(self, x, weight=False):
        dev = x.device
        self.maxq = self.maxq.to(dev)

        shape = x.shape
        if self.perchannel:
            if weight:
                x = x.flatten(1)
            else:
                if len(shape) == 4:
                    x = x.permute([1, 0, 2, 3])
                    x = x.flatten(1)
                if len(shape) == 3:
                    x = x.reshape((-1, shape[-1])).t()
                if len(shape) == 2:
                    x = x.t()
        else:
            x = x.flatten().unsqueeze(0)

        tmp = torch.zeros(x.shape[0], device=dev)
        xmin = torch.minimum(x.min(1)[0], tmp)
        xmax = torch.maximum(x.max(1)[0], tmp)

        if self.qcfg.sym:
            xmax = torch.maximum(torch.abs(xmin), xmax)
            tmp = xmin < 0
            if torch.any(tmp):
                xmin[tmp] = -xmax[tmp]
        tmp = (xmin == 0) & (xmax == 0)
        xmin[tmp] = -1
        xmax[tmp] = +1

        if self.maxq < 0:
            self.scale = xmax
            self.zero = xmin
        else:
            if self.requires_groupwise_processing():
                self.scale = xmax / self.maxq
                self.zero = torch.zeros_like(self.scale)
            else:
                self.scale = (xmax - xmin) / self.maxq
                if self.qcfg.sym:
                    self.zero = torch.full_like(self.scale, (self.maxq + 1) / 2)
                else:
                    self.zero = torch.round(-xmin / self.scale)

        if self.qcfg.mse > 0.0:
            best = torch.full([x.shape[0]], float("inf"), device=dev)
            for i in range(int(self.maxshrink * self.grid)):
                p = 1 - i / self.grid
                xmin1 = p * xmin
                xmax1 = p * xmax
                scale1 = (
                    xmax1 / self.maxq
                    if self.requires_groupwise_processing()
                    else (xmax1 - xmin1) / self.maxq
                )
                zero1 = torch.round(-xmin1 / scale1) if not self.qcfg.sym else self.zero
                q = quantize(x, scale1.unsqueeze(1), zero1.unsqueeze(1), self.maxq, self.requires_groupwise_processing())
                q -= x
                q.abs_()
                q.pow_(self.qcfg.mse)
                err = torch.sum(q, 1)
                tmp = err < best
                if torch.any(tmp):
                    best[tmp] = err[tmp]
                    self.scale[tmp] = scale1[tmp]
                    self.zero[tmp] = zero1[tmp]
        if not self.perchannel:
            if weight:
                tmp = shape[0]
            else:
                tmp = shape[1] if len(shape) != 3 else shape[2]
            self.scale = self.scale.repeat(tmp)
            self.zero = self.zero.repeat(tmp)

        if weight:
            shape = [-1] + [1] * (len(shape) - 1)
            self.scale = self.scale.reshape(shape)
            self.zero = self.zero.reshape(shape)
            return
        if len(shape) == 4:
            self.scale = self.scale.reshape((1, -1, 1, 1))
            self.zero = self.zero.reshape((1, -1, 1, 1))
        if len(shape) == 3:
            self.scale = self.scale.reshape((1, 1, -1))
            self.zero = self.zero.reshape((1, 1, -1))
        if len(shape) == 2:
            self.scale = self.scale.unsqueeze(0)
            self.zero = self.zero.unsqueeze(0)

    def quantize(self, x):
        return quantize(x, self.scale, self.zero, self.maxq, self.requires_groupwise_processing())

    # def enabled(self):
    #     return self.maxq > 0

    # def ready(self):
    # return torch.all(self.scale != 0)

class QQQQuantizer(Quantizer):
    def requires_groupwise_processing(self) -> bool:
        return self.qcfg.group_size == -1 and self.qcfg.sym

__all__ = ["Quantizer"]