# 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 contextlib
import paddle

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 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