# Copyright (c) 2023 PaddlePaddle Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     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.
from __future__ import annotations

import copy
from typing import TYPE_CHECKING

from paddle.distributed import fleet

from .quantize import Quantization

if TYPE_CHECKING:
    from paddle.nn import Layer

    from .config import QuantConfig


class PTQ(Quantization):
    """
    Applying post training quantization to the model.
    """

    def __init__(self, config: QuantConfig) -> None:
        super().__init__(config)

    def _is_parallel_training(self):
        try:
            if fleet.worker_num() > 2:
                return True
            else:
                return False
        except Exception:  # fleet is not initialized
            return False

    def quantize(self, model: Layer, inplace: bool = False) -> Layer:
        r"""
        Create a model for post-training quantization.

        The quantization configuration will be propagated in the model.
        And it will insert observers into the model to collect and compute
        quantization parameters.

        Args:
            model(Layer): The model to be quantized.
            inplace(bool): Whether to modify the model in-place.

        Return: The prepared model for post-training quantization.

        Examples:
            .. code-block:: python

                >>> from paddle.quantization import PTQ, QuantConfig
                >>> from paddle.quantization.observers import AbsmaxObserver
                >>> from paddle.vision.models import LeNet

                >>> observer = AbsmaxObserver()
                >>> q_config = QuantConfig(activation=observer, weight=observer)
                >>> ptq = PTQ(q_config)
                >>> model = LeNet()
                >>> model.eval()
                >>> quant_model = ptq.quantize(model)
                >>> print(quant_model)
                LeNet(
                  (features): Sequential(
                    (0): QuantedConv2D(
                      (weight_quanter): AbsmaxObserverLayer()
                      (activation_quanter): AbsmaxObserverLayer()
                    )
                    (1): ObserveWrapper(
                      (_observer): AbsmaxObserverLayer()
                      (_observed): ReLU()
                    )
                    (2): ObserveWrapper(
                      (_observer): AbsmaxObserverLayer()
                      (_observed): MaxPool2D(kernel_size=2, stride=2, padding=0)
                    )
                    (3): QuantedConv2D(
                      (weight_quanter): AbsmaxObserverLayer()
                      (activation_quanter): AbsmaxObserverLayer()
                    )
                    (4): ObserveWrapper(
                      (_observer): AbsmaxObserverLayer()
                      (_observed): ReLU()
                    )
                    (5): ObserveWrapper(
                      (_observer): AbsmaxObserverLayer()
                      (_observed): MaxPool2D(kernel_size=2, stride=2, padding=0)
                    )
                  )
                  (fc): Sequential(
                    (0): QuantedLinear(
                      (weight_quanter): AbsmaxObserverLayer()
                      (activation_quanter): AbsmaxObserverLayer()
                    )
                    (1): QuantedLinear(
                      (weight_quanter): AbsmaxObserverLayer()
                      (activation_quanter): AbsmaxObserverLayer()
                    )
                    (2): QuantedLinear(
                      (weight_quanter): AbsmaxObserverLayer()
                      (activation_quanter): AbsmaxObserverLayer()
                    )
                  )
                )
        """
        _model = model
        if not inplace:
            assert not self._is_parallel_training(), (
                "'inplace' is not compatible with parallel training."
            )
            _model = copy.deepcopy(model)
            _model.eval()
        assert not model.training, (
            "Post-Training Quantization should not work on training models. Please set evaluation mode by model.eval()."
        )
        self._config._specify(_model)
        self._convert_to_quant_layers(_model, self._config)
        self._insert_activation_observers(_model, self._config)
        return _model