# 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
# limitations under the License.

import argparse
import os
from functools import partial

import paddle
from model import SimNet
from utils import convert_example

from paddlenlp.data import JiebaTokenizer, Pad, Stack, Tuple, Vocab
from paddlenlp.datasets import load_dataset

# yapf: disable
parser = argparse.ArgumentParser(__doc__)
parser.add_argument("--epochs", type=int, default=10, help="Number of epoches for training.")
parser.add_argument('--device', choices=['cpu', 'gpu', 'npu'], default="gpu", help="Select which device to train model, defaults to gpu.")
parser.add_argument("--lr", type=float, default=5e-4, help="Learning rate used to train.")
parser.add_argument("--save_dir", type=str, default='checkpoints/', help="Directory to save model checkpoint")
parser.add_argument("--batch_size", type=int, default=64, help="Total examples' number of a batch for training.")
parser.add_argument("--vocab_path", type=str, default="./simnet_vocab.txt", help="The directory to dataset.")
parser.add_argument('--network', type=str, default="lstm", help="Which network you would like to choose bow, cnn, lstm or gru ?")
parser.add_argument("--init_from_ckpt", type=str, default=None, help="The path of checkpoint to be loaded.")
args = parser.parse_args()
# yapf: enable


def create_dataloader(dataset, trans_fn=None, mode="train", batch_size=1, batchify_fn=None):
    """
    Creates dataloader.

    Args:
        dataset(obj:`paddle.io.Dataset`): Dataset instance.
        trans_fn(obj:`callable`, optional, defaults to `None`): function to convert a data sample to input ids, etc.
        mode(obj:`str`, optional, defaults to obj:`train`): If mode is 'train', it will shuffle the dataset randomly.
        batch_size(obj:`int`, optional, defaults to 1): The sample number of a mini-batch.
        batchify_fn(obj:`callable`, optional, defaults to `None`): function to generate mini-batch data by merging
            the sample list, None for only stack each fields of sample in axis
            0(same as :attr::`np.stack(..., axis=0)`).

    Returns:
        dataloader(obj:`paddle.io.DataLoader`): The dataloader which generates batches.
    """
    if trans_fn:
        dataset = dataset.map(trans_fn)

    shuffle = True if mode == "train" else False
    if mode == "train":
        sampler = paddle.io.DistributedBatchSampler(dataset=dataset, batch_size=batch_size, shuffle=True)
    else:
        sampler = paddle.io.BatchSampler(dataset=dataset, batch_size=batch_size, shuffle=shuffle)
    dataloader = paddle.io.DataLoader(dataset, batch_sampler=sampler, return_list=True, collate_fn=batchify_fn)
    return dataloader


if __name__ == "__main__":
    paddle.set_device(args.device)

    # Loads vocab.
    if not os.path.exists(args.vocab_path):
        raise RuntimeError("The vocab_path  can not be found in the path %s" % args.vocab_path)
    vocab = Vocab.load_vocabulary(args.vocab_path, unk_token="[UNK]", pad_token="[PAD]")

    # Loads dataset.
    train_ds, dev_ds, test_ds = load_dataset("lcqmc", splits=["train", "dev", "test"])

    # Constructs the network.
    model = SimNet(network=args.network, vocab_size=len(vocab), num_classes=len(train_ds.label_list))
    model = paddle.Model(model)

    # Reads data and generates mini-batches.
    batchify_fn = lambda samples, fn=Tuple(
        Pad(axis=0, pad_val=vocab.token_to_idx.get("[PAD]", 0)),  # query_ids
        Pad(axis=0, pad_val=vocab.token_to_idx.get("[PAD]", 0)),  # title_ids
        Stack(dtype="int64"),  # query_seq_lens
        Stack(dtype="int64"),  # title_seq_lens
        Stack(dtype="int64"),  # label
    ): [data for data in fn(samples)]
    tokenizer = JiebaTokenizer(vocab)
    trans_fn = partial(convert_example, tokenizer=tokenizer, is_test=False)
    train_loader = create_dataloader(
        train_ds, trans_fn=trans_fn, batch_size=args.batch_size, mode="train", batchify_fn=batchify_fn
    )
    dev_loader = create_dataloader(
        dev_ds, trans_fn=trans_fn, batch_size=args.batch_size, mode="validation", batchify_fn=batchify_fn
    )
    test_loader = create_dataloader(
        test_ds, trans_fn=trans_fn, batch_size=args.batch_size, mode="test", batchify_fn=batchify_fn
    )

    optimizer = paddle.optimizer.Adam(parameters=model.parameters(), learning_rate=args.lr)

    # Defines loss and metric.
    criterion = paddle.nn.CrossEntropyLoss()
    metric = paddle.metric.Accuracy()

    model.prepare(optimizer, criterion, metric)

    # Loads pre-trained parameters.
    if args.init_from_ckpt:
        model.load(args.init_from_ckpt)
        print("Loaded checkpoint from %s" % args.init_from_ckpt)

    # Starts training and evaluating.
    model.fit(
        train_loader,
        dev_loader,
        epochs=args.epochs,
        save_dir=args.save_dir,
    )