# Copyright 2018 Amazon.com, Inc. or its affiliates. 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.
# A copy of the License is located at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# or in the "license" file accompanying this file. This file 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 typing import List, Optional

import numpy as np
import torch

from gluonts.dataset.common import DataBatch


def stack(data, device: Optional[torch.device] = None):
    if isinstance(data[0], np.ndarray):
        data = torch.tensor(np.array(data), device=device)
    elif isinstance(data[0], (list, tuple)):
        return list(stack(t, device=device) for t in zip(*data))
    return data


def batchify(
    data: List[dict], device: Optional[torch.device] = None
) -> DataBatch:
    return {
        key: stack(data=[item[key] for item in data], device=device)
        for key in data[0].keys()
    }
