#   Copyright (c) 2020 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

import logging
from functools import reduce

from .meta_optimizer_base import MetaOptimizerBase

__all__ = []

import paddle
from paddle.common_ops_import import LayerHelper
from paddle.fluid import framework
from paddle.fluid.dygraph import base as imperative_base
from paddle.framework import core, in_dynamic_mode
from paddle.nn.clip import ClipGradByNorm, append_gradient_clip_ops
from paddle.optimizer import Momentum, Optimizer
from paddle.regularizer import L1Decay, L2Decay
from paddle.static import create_global_var


class DGCMomentumOptimizer(Optimizer):
    _u_velocity_acc_str = "_dgc_u_"
    _v_velocity_acc_str = "_dgc_v_"

    def __init__(
        self,
        learning_rate,
        momentum,
        rampup_begin_step,
        rampup_step=1,
        sparsity=[0.999],
        parameter_list=None,
        use_nesterov=False,
        num_trainers=None,
        regularization=None,
        grad_clip=None,
        name=None,
    ):
        if in_dynamic_mode():
            raise Exception("In dygraph, don't support DGCMomentumOptimizer.")

        assert (
            core.is_compiled_with_cuda()
        ), "Paddle is not compiled with CUDA. DGC is only support GPU for now."

        assert learning_rate is not None
        assert momentum is not None
        super().__init__(
            learning_rate=learning_rate,
            parameters=parameter_list,
            weight_decay=regularization,
            grad_clip=grad_clip,
            name=name,
        )
        self.type = "dgc_momentum"
        self._momentum = momentum
        self._use_nesterov = bool(use_nesterov)

        assert rampup_begin_step >= 0, "rampup_begin_step must >= 0"
        self._rampup_begin_step = rampup_begin_step
        self._rampup_step = rampup_step
        self._sparsity = sparsity

        self._rampup_begin_step_var = None
        self._global_step_var = None

        self._dgc_clip_norm = None
        self._num_trainers = num_trainers
        if grad_clip is not None:
            if not isinstance(grad_clip, ClipGradByNorm):
                raise TypeError(
                    "The type of grad_clip should be 'ClipGradByNorm', because DGCMomentumOptimizer only support ClipGradByNorm"
                )
            assert isinstance(num_trainers, int), (
                "The type of num_trainers should be 'int', but received %s"
                % type(num_trainers)
            )
            assert (
                num_trainers > 0
            ), "The value of num_trainers should be greater than 0!"

            self._dgc_clip_norm = grad_clip.clip_norm * (num_trainers**-0.5)

        self.regular_type, self.regular_coeff = self._get_regularization_param(
            self.regularization
        )

    def _get_regularization_param(self, regularization):
        regular_type = 0
        regular_coeff = 0.0

        if regularization is not None:
            regular_coeff = regularization._coeff

            if isinstance(regularization, L1Decay):
                regular_type = 1
            elif isinstance(regularization, L2Decay):
                regular_type = 2
            else:
                raise AssertionError(
                    "regularization must be None|L1Decay|L2Deacy"
                )
        return regular_type, regular_coeff

    def _is_use_dgc(self, param_var, grad_var):
        var_numel = abs(reduce(lambda x, y: x * y, param_var.shape, 1))
        if (
            var_numel < 16384
            or param_var.type == core.VarDesc.VarType.SELECTED_ROWS
            or grad_var.type == core.VarDesc.VarType.SELECTED_ROWS
            or param_var.dtype != core.VarDesc.VarType.FP32
        ):
            return False
        return True

    def _append_optimize_op(self, block, param_and_grad):
        assert isinstance(block, paddle.framework.Block)
        velocity_acc = self._get_accumulator(
            self._u_velocity_acc_str, param_and_grad[0]
        )
        assert velocity_acc is not None

        inputs = {
            "Param": param_and_grad[0],
            "Grad": param_and_grad[1],
            "Velocity": velocity_acc,
            "LearningRate": self._create_param_lr(param_and_grad),
        }
        outputs = {
            "ParamOut": param_and_grad[0],
            "VelocityOut": velocity_acc,
        }
        attrs = {"mu": self._momentum, "use_nesterov": self._use_nesterov}

        if not self._is_use_dgc(param_and_grad[0], param_and_grad[1]):
            type = "momentum"
        else:
            type = "dgc_momentum"
            inputs.update(
                {
                    "current_step": self._global_step_var,
                    "nranks": self._nranks_var,
                }
            )
            outputs.update({'Grad_out': param_and_grad[1]})
            attrs.update({"rampup_begin_step": float(self._rampup_begin_step)})

        # create the dgc momentum optimize op
        dgc_momentum_op = block.append_op(
            type=type,
            inputs=inputs,
            outputs=outputs,
            attrs=attrs,
            stop_gradient=True,
        )
        return dgc_momentum_op

    def _add_auto_increment_var(self, counter_name, begin, step=1):
        helper = LayerHelper('global_step_counter')
        counter, is_new_var = helper.create_or_get_global_variable(
            name=counter_name, dtype='float32', shape=[1], persistable=True
        )
        if is_new_var:
            helper.set_variable_initializer(
                counter,
                initializer=paddle.nn.initializer.ConstantInitializer(
                    value=float(begin - 1), force_cpu=True
                ),
            )
            helper.main_program.global_block()._prepend_op(
                type='increment',
                inputs={'X': [counter]},
                outputs={'Out': [counter]},
                attrs={'step': float(step)},
                stop_gradient=True,
            )
            counter.stop_gradient = True

        return counter

    def _add_nranks_var(self, name, value=-1):
        helper = LayerHelper('global_step_counter')
        counter, is_new_var = helper.create_or_get_global_variable(
            name=name, dtype='float32', shape=[1], persistable=True
        )
        if is_new_var:
            helper.set_variable_initializer(
                counter,
                initializer=paddle.nn.initializer.ConstantInitializer(
                    value=float(value), force_cpu=True
                ),
            )
            counter.stop_gradient = True

        return counter

    def _append_dgc_ops(self, param_and_grads):
        main_program = paddle.static.default_main_program()
        main_program._enable_dgc = True

        # step counter
        self._global_step_var = self._add_auto_increment_var(
            counter_name=core.dgc.kDGCCounterName(), begin=0
        )

        self._nranks_var = self._add_nranks_var(
            name=core.dgc.kDGCNRanksName(), value=self._num_trainers
        )

        # rampup begin step var for all_reduce_op_handle
        self._rampup_begin_step_var = create_global_var(
            shape=[1],
            dtype=core.VarDesc.VarType.FP32,
            persistable=True,
            name=core.dgc.kDGCRampUpBeginStepName(),
            value=self._rampup_begin_step * 1.0,
            force_cpu=True,
        )

        self.helper = LayerHelper(self.__class__.__name__)

        for param_var, grad_var in param_and_grads:
            # reuse velocity in dgc_op and dgc_momentum_op
            u_var = self._add_accumulator(self._u_velocity_acc_str, param_var)

            if not self._is_use_dgc(param_var, grad_var):
                continue

            v_var = self._add_accumulator(self._v_velocity_acc_str, param_var)

            k_var = create_global_var(
                shape=[1],
                dtype=param_var.dtype,
                persistable=True,
                name=param_var.name + core.dgc.kDGCKName(),
                value=0.0,
                force_cpu=True,
            )

            encoded_var = create_global_var(
                shape=[1],
                dtype=param_var.dtype,
                persistable=True,
                name=param_var.name + core.dgc.kDGCEncodedName(),
                value=0.0,
                force_cpu=False,
            )

            gather_var = create_global_var(
                shape=[1],
                dtype=param_var.dtype,
                persistable=True,
                name=param_var.name + core.dgc.kDGCGatherName(),
                value=0.0,
                force_cpu=False,
            )

            # del back oprolevarname
            op_maker = core.op_proto_and_checker_maker
            backward = core.op_proto_and_checker_maker.OpRole.Backward
            for op in main_program.global_block().ops:
                if not self._is_the_backward_op(op):
                    continue

                var_attr = op.all_attrs()[op_maker.kOpRoleVarAttrName()]
                if param_var.name not in var_attr:
                    continue

                var_attr.remove(param_var.name)
                var_attr.remove(grad_var.name)
                if len(var_attr) > 1:
                    op._set_attr(op_maker.kOpRoleVarAttrName(), var_attr)
                else:
                    op._remove_attr(op_maker.kOpRoleVarAttrName())

            clip_var = grad_var
            if self._dgc_clip_norm is not None:
                clip_var = self._append_clip_norm(grad_var, self._dgc_clip_norm)
            self._dgc_op(
                param_var,
                clip_var,
                grad_var,
                u_var,
                v_var,
                k_var,
                encoded_var,
                gather_var,
            )

    def _is_the_backward_op(self, op):
        op_maker = core.op_proto_and_checker_maker
        backward = core.op_proto_and_checker_maker.OpRole.Backward
        if op_maker.kOpRoleVarAttrName() in op.attr_names and int(
            op.all_attrs()[op_maker.kOpRoleAttrName()]
        ) == int(backward):
            return True
        return False

    def _clip_by_norm(self, x, max_norm, name=None):
        args = {'x': x, 'max_norm': max_norm, 'name': name}

        helper = LayerHelper("dgc_clip_by_norm_op", **args)

        if name is None:
            name = paddle.fluid.unique_name.generate_with_ignorable_key(
                ".".join([helper.name, 'tmp'])
            )

        out = helper.create_variable(
            type=x.type, name=name, dtype=x.dtype, persistable=False
        )

        helper.append_op(
            type="dgc_clip_by_norm",
            inputs={"X": x, "current_step": self._global_step_var},
            attrs={
                "max_norm": max_norm,
                "rampup_begin_step": float(self._rampup_begin_step),
            },
            outputs={"Out": out},
        )
        return out

    def _append_clip_norm(self, grad_var, clip_norm):
        with grad_var.block.program._backward_role_guard():
            return self._clip_by_norm(
                x=grad_var, max_norm=clip_norm, name=grad_var.name
            )

    def _dgc_op(
        self,
        param_var,
        clip_var,
        grad_var,
        u_var,
        v_var,
        k_var,
        encoded_var,
        gather_var,
    ):
        block = paddle.static.default_main_program().global_block()
        op_maker = core.op_proto_and_checker_maker

        regular_type = self.regular_type
        regular_coeff = self.regular_coeff
        # The regularizer of the Parameters have higher priority
        if param_var.regularizer is not None:
            regular_type, regular_coeff = self._get_regularization_param(
                param_var.regularizer
            )

        dgc_op = block.append_op(
            type="dgc",
            inputs={
                "U": u_var,
                "V": v_var,
                "Grad": clip_var,
                "Param": param_var,
                "current_step": self._global_step_var,
                "nranks": self._nranks_var,
            },
            outputs={
                "U_out": u_var,
                "V_out": v_var,
                "EncodeGrad": encoded_var,
                "k": k_var,
                "Grad_out": grad_var,
                "GatherBuff": gather_var,
            },
            attrs={
                "m": self._momentum,
                "sparsity": self._sparsity,
                "use_nesterov": self._use_nesterov,
                "rampup_begin_step": float(self._rampup_begin_step),
                "rampup_step": float(self._rampup_step),
                "regular_coeff": float(regular_coeff),
                "regular_type": int(regular_type),
            },
            stop_gradient=True,
        )

        backward = op_maker.OpRole.Backward
        dgc_op._set_attr(op_maker.kOpRoleAttrName(), backward)
        dgc_op._set_attr(
            op_maker.kOpRoleVarAttrName(), [param_var.name, grad_var.name]
        )

    def _process_distribute_lookuptable(self, param_grads):
        """
        Because distribute lookup table only support SGD optimizer for now, not support
        other optimizer and regularization, so we should find the table parameter out,
        and avoid to add regularization and other op for it, and add sgd optimize op
        for it independently.
        :param param_grads(list((Var, Var))): list of (param, grad) pair.
        :param loss: the loss variable.
        :param startup_program: the startup program
        """
        from paddle.distributed.distribute_lookup_table import (
            find_distributed_lookup_table,
        )

        program = framework.default_main_program()
        global_block = framework.default_main_program().global_block()
        table_name = find_distributed_lookup_table(program)
        table_param = None
        table_grad = None
        new_param_grads = []
        for p, g in param_grads:
            if p.name == table_name:
                if table_param is not None:
                    raise RuntimeError(
                        "multi dist table var found, only support one now!"
                    )
                table_param = p
                table_grad = g
            else:
                new_param_grads.append((p, g))
        sgd_op = None
        if table_param is not None:
            param_and_grad = [table_param, table_grad]
            with table_param.block.program._optimized_guard(
                param_and_grad
            ), framework.name_scope("optimizer"):
                self._create_global_learning_rate()
                # create the optimize op
                sgd_op = global_block.append_op(
                    type='sgd',
                    inputs={
                        "Param": table_param,
                        "Grad": table_grad,
                        "LearningRate": self._create_param_lr(param_and_grad),
                    },
                    outputs={"ParamOut": param_and_grad[0]},
                )
        return new_param_grads, (table_param, table_grad), sgd_op

    @imperative_base.no_grad()
    def apply_gradients(self, params_grads):
        # Note: since we can't use all_reduce_op now,
        # dgc_op should be the last op of one grad.
        # Maybe need a grad allreduce pass.
        self._append_dgc_ops(params_grads)

        params_grads = sorted(params_grads, key=lambda x: x[0].name)
        (
            params_grads,
            table_param_and_grad,
            table_optimize_op,
        ) = self._process_distribute_lookuptable(params_grads)

        not_dgc_params_grads = []
        dgc_params_grads = []
        # DGC clip and regularization in optimizer.backward
        for param, grad in params_grads:
            if not self._is_use_dgc(param, grad):
                not_dgc_params_grads.append((param, grad))
            else:
                dgc_params_grads.append((param, grad))

        # 'optimizer(grad_clip)' or 'set_gradient_clip'
        if self._grad_clip is not None:
            not_dgc_params_grads = self._grad_clip(not_dgc_params_grads)
        else:
            not_dgc_params_grads = append_gradient_clip_ops(
                not_dgc_params_grads
            )

        not_dgc_params_grads = self.append_regularization_ops(
            not_dgc_params_grads, self.regularization
        )

        params_grads = not_dgc_params_grads + dgc_params_grads
        params_grads = sorted(params_grads, key=lambda x: x[0].name)

        optimize_ops = self._create_optimization_pass(params_grads)
        if table_optimize_op is not None:
            optimize_ops.append(table_optimize_op)
            params_grads.append(table_param_and_grad)

        return optimize_ops


class DGCOptimizer(MetaOptimizerBase):
    def __init__(self, optimizer):
        super().__init__(optimizer)
        self.inner_opt = optimizer
        self.dgc_opt = None
        # we do not allow meta optimizer to be inner optimizer currently
        self.meta_optimizers_white_list = []
        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_dgc_opt(self):
        if self.dgc_opt is not None:
            return

        opt = self.inner_opt

        if not self.role_maker._is_collective:
            return

        if not isinstance(opt, Momentum):
            return

        configs = self.user_defined_strategy.dgc_configs
        if len(configs['sparsity']) == 0:
            # default is [0.999]
            configs['sparsity'] = [0.999]

        self.dgc_opt = DGCMomentumOptimizer(
            learning_rate=opt._learning_rate,
            momentum=opt._momentum,
            rampup_begin_step=configs['rampup_begin_step'],
            rampup_step=configs['rampup_step'],
            sparsity=configs['sparsity'],
            parameter_list=opt._parameter_list,
            use_nesterov=opt._use_nesterov,
            num_trainers=self.role_maker._worker_num(),
            regularization=opt.regularization,
            grad_clip=opt._grad_clip,
            name=opt._name,
        )

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

        if self.user_defined_strategy.dgc:
            if not isinstance(self.inner_opt, Momentum):
                logging.warn("dgc only works on Momentum optimizer")
                return False
            if self.role_maker._worker_num() <= 1:
                logging.warn("dgc only works on multi cards")
                return False

            return True

        return False

    def _disable_strategy(self, dist_strategy):
        dist_strategy.dgc = False
        dist_strategy.dgc_configs = {}

    def _enable_strategy(self, dist_strategy, context):
        dist_strategy.dgc = True
        dist_strategy.dgc_configs = {"rampup_begin_step": 0, "rampup_step": 1}

    def backward(
        self,
        loss,
        startup_program=None,
        parameter_list=None,
        no_grad_set=None,
        callbacks=None,
    ):
        self._init_dgc_opt()
        return self.dgc_opt.backward(
            loss, startup_program, parameter_list, no_grad_set, callbacks
        )

    def apply_gradients(self, params_grads):
        self._init_dgc_opt()
        return self.dgc_opt.apply_gradients(params_grads=params_grads)

    def apply_optimize(self, loss, startup_program, params_grads):
        self._init_dgc_opt()
        return self.dgc_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_dgc_opt()
        optimize_ops, params_grads = self.dgc_opt.minimize(
            loss, startup_program, parameter_list, no_grad_set
        )
        return optimize_ops, params_grads
