#   Copyright (c) 2019 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

from paddle.fluid.optimizer import RecomputeOptimizer as RO

from .meta_optimizer_base import MetaOptimizerBase

__all__ = []


class RecomputeOptimizer(MetaOptimizerBase):
    def __init__(self, optimizer):
        super().__init__(optimizer)
        self.inner_opt = optimizer
        self.wrapped_opt = None
        # we do not allow meta optimizer to be inner optimizer currently
        self.meta_optimizers_white_list = [
            "LarsOptimizer",
            "LambOptimizer",
            "DGCOptimizer",
        ]
        self.meta_optimizers_black_list = []

    def _set_basic_info(
        self, loss, role_maker, user_defined_optimizer, user_defined_strategy
    ):
        super()._set_basic_info(
            loss, role_maker, user_defined_optimizer, user_defined_strategy
        )

    def _init_wrapped_opt(self):
        if self.wrapped_opt is not None:
            return

        configs = self.user_defined_strategy.recompute_configs
        self.wrapped_opt = RO(self.inner_opt)
        self.wrapped_opt._set_checkpoints(list(configs["checkpoints"]))
        if configs["enable_offload"]:
            self.wrapped_opt._enable_offload()
            # TODO(JZ-LIANG) might found a way to infer the checkpoint shape automatically
            checkpoint_shapes = list(configs["checkpoint_shape"])
            self.wrapped_opt.checkpoint_shape = checkpoint_shapes

    def _can_apply(self):
        if not self.role_maker._is_collective:
            return False

        if self.user_defined_strategy.recompute:
            if (
                len(self.user_defined_strategy.recompute_configs["checkpoints"])
                == 0
            ):
                return False
            else:
                return True

    def _disable_strategy(self, dist_strategy):
        dist_strategy.recompute = False
        dist_strategy.recompute_configs = {}

    def _enable_strategy(self, dist_strategy, context):
        # we do not support automatically recompute checkpoints currently
        return

    def backward(
        self,
        loss,
        startup_program=None,
        parameter_list=None,
        no_grad_set=None,
        callbacks=None,
    ):
        # maybe inner_opt of other meta optimizer
        self._init_wrapped_opt()
        return self.wrapped_opt.backward(
            loss, startup_program, parameter_list, no_grad_set, callbacks
        )

    def apply_gradients(self, params_grads):
        return self.wrapped_opt.apply_gradients(params_grads=params_grads)

    def apply_optimize(self, loss, startup_program, params_grads):
        return self.wrapped_opt.apply_optimize(
            loss, startup_program=startup_program, params_grads=params_grads
        )

    def minimize_impl(
        self, loss, startup_program=None, parameter_list=None, no_grad_set=None
    ):
        self._init_wrapped_opt()
        optimize_ops, params_grads = self.wrapped_opt.minimize(
            loss, startup_program, parameter_list, no_grad_set
        )
        return optimize_ops, params_grads
