#   Copyright (c) 2021 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.

import paddle
import contextlib

__all__ = []

MODEL_PARALLEL_RNG = 'model_parallel_rng'


class RNGStatesTracker:
    """
    Tracker the RNG states.
    """

    def __init__(self):
        # Map from name to the rng state.
        self.states_ = {}
        self.seeds_ = set()

    def reset(self):
        self.states_ = {}
        self.seeds_ = set()

    def add(self, name, seed):
        if seed in self.seeds_:
            raise ValueError('seed {} already exists'.format(seed))
        self.seeds_.add(seed)
        if name in self.states_:
            raise ValueError('state {} already exists'.format(name))
        orig_rng_state = paddle.get_cuda_rng_state()
        paddle.seed(seed)
        self.states_[name] = paddle.get_cuda_rng_state()
        paddle.set_cuda_rng_state(orig_rng_state)

    @contextlib.contextmanager
    def rng_state(self, name=MODEL_PARALLEL_RNG):
        if name not in self.states_:
            raise ValueError('state {} does not exist'.format(name))
        orig_cuda_rng_state = paddle.get_cuda_rng_state()
        paddle.set_cuda_rng_state(self.states_[name])
        try:
            yield
        finally:
            self.states_[name] = paddle.get_cuda_rng_state()
            paddle.set_cuda_rng_state(orig_cuda_rng_state)


RNG_STATE_TRACKER = RNGStatesTracker()


def get_rng_state_tracker():
    return RNG_STATE_TRACKER


def model_parallel_random_seed(seed=2048):
    import paddle.distributed.fleet as fleet
    hcg = fleet.get_hybrid_communicate_group()
    rank = hcg.get_model_parallel_rank()

    local_seed = seed + 1024 + rank
    global_seed = seed

    RNG_STATE_TRACKER.reset()
    paddle.seed(global_seed)
    RNG_STATE_TRACKER.add(MODEL_PARALLEL_RNG, local_seed)
