# 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 argparse
import os
import random
import time
from functools import partial

import numpy as np
import paddle
from data import convert_pointwise_example as convert_example
from data import create_dataloader
from model import PointwiseMatching

from paddlenlp.data import Pad, Stack, Tuple
from paddlenlp.datasets import load_dataset
from paddlenlp.transformers import AutoModel, AutoTokenizer, LinearDecayWithWarmup


def set_seed(seed):
    """sets random seed"""
    random.seed(seed)
    np.random.seed(seed)
    paddle.seed(seed)


@paddle.no_grad()
def evaluate(model, criterion, metric, data_loader, phase="dev"):
    """
    Given a dataset, it evals model and computes the metric.

    Args:
        model(obj:`paddle.nn.Layer`): A model to classify texts.
        data_loader(obj:`paddle.io.DataLoader`): The dataset loader which generates batches.
        criterion(obj:`paddle.nn.Layer`): It can compute the loss.
        metric(obj:`paddle.metric.Metric`): The evaluation metric.
    """
    model.eval()
    metric.reset()
    losses = []
    for batch in data_loader:
        input_ids, token_type_ids, labels = batch
        probs = model(input_ids=input_ids, token_type_ids=token_type_ids)
        loss = criterion(probs, labels)
        losses.append(loss.numpy())
        correct = metric.compute(probs, labels)
        metric.update(correct)
        accu = metric.accumulate()
    print("eval {} loss: {:.5}, accu: {:.5}".format(phase, np.mean(losses), accu))
    model.train()
    metric.reset()


def do_train(args):
    paddle.set_device(args.device)
    rank = paddle.distributed.get_rank()
    if paddle.distributed.get_world_size() > 1:
        paddle.distributed.init_parallel_env()

    set_seed(args.seed)

    train_ds, dev_ds = load_dataset("lcqmc", splits=["train", "dev"])

    pretrained_model = AutoModel.from_pretrained("ernie-3.0-medium-zh")
    tokenizer = AutoTokenizer.from_pretrained("ernie-3.0-medium-zh")

    trans_func = partial(convert_example, tokenizer=tokenizer, max_seq_length=args.max_seq_length)

    batchify_fn = lambda samples, fn=Tuple(
        Pad(axis=0, pad_val=tokenizer.pad_token_id),  # text_pair_input
        Pad(axis=0, pad_val=tokenizer.pad_token_type_id),  # text_pair_segment
        Stack(dtype="int64"),  # label
    ): [data for data in fn(samples)]

    train_data_loader = create_dataloader(
        train_ds, mode="train", batch_size=args.batch_size, batchify_fn=batchify_fn, trans_fn=trans_func
    )

    dev_data_loader = create_dataloader(
        dev_ds, mode="dev", batch_size=args.batch_size, batchify_fn=batchify_fn, trans_fn=trans_func
    )

    model = PointwiseMatching(pretrained_model)

    if args.init_from_ckpt and os.path.isfile(args.init_from_ckpt):
        state_dict = paddle.load(args.init_from_ckpt)
        model.set_dict(state_dict)

    model = paddle.DataParallel(model)

    num_training_steps = len(train_data_loader) * args.epochs

    lr_scheduler = LinearDecayWithWarmup(args.learning_rate, num_training_steps, args.warmup_proportion)

    # Generate parameter names needed to perform weight decay.
    # All bias and LayerNorm parameters are excluded.
    decay_params = [p.name for n, p in model.named_parameters() if not any(nd in n for nd in ["bias", "norm"])]
    optimizer = paddle.optimizer.AdamW(
        learning_rate=lr_scheduler,
        parameters=model.parameters(),
        weight_decay=args.weight_decay,
        apply_decay_param_fun=lambda x: x in decay_params,
    )

    criterion = paddle.nn.loss.CrossEntropyLoss()
    metric = paddle.metric.Accuracy()

    global_step = 0
    tic_train = time.time()
    for epoch in range(1, args.epochs + 1):
        for step, batch in enumerate(train_data_loader, start=1):
            input_ids, token_type_ids, labels = batch
            probs = model(input_ids=input_ids, token_type_ids=token_type_ids)
            loss = criterion(probs, labels)
            correct = metric.compute(probs, labels)
            metric.update(correct)
            acc = metric.accumulate()

            global_step += 1
            if global_step % 10 == 0 and rank == 0:
                print(
                    "global step %d, epoch: %d, batch: %d, loss: %.5f, accu: %.5f, speed: %.2f step/s"
                    % (global_step, epoch, step, loss, acc, 10 / (time.time() - tic_train))
                )
                tic_train = time.time()
            loss.backward()
            optimizer.step()
            lr_scheduler.step()
            optimizer.clear_grad()

            if global_step % args.eval_step == 0 and rank == 0:
                evaluate(model, criterion, metric, dev_data_loader)
                save_dir = os.path.join(args.save_dir, "model")
                tokenizer.save_pretrained(save_dir)
                model_to_save = model._layers if isinstance(model, paddle.DataParallel) else model
                paddle.save(model_to_save.state_dict(), os.path.join(save_dir, "model_state.pdparams"))

            if global_step > args.max_steps:
                return


if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--save_dir",
        default="./checkpoint",
        type=str,
        help="The output directory where the model checkpoints will be written.",
    )
    parser.add_argument(
        "--max_seq_length",
        default=128,
        type=int,
        help="The maximum total input sequence length after tokenization. "
        "Sequences longer than this will be truncated, sequences shorter will be padded.",
    )
    parser.add_argument("--batch_size", default=32, type=int, help="Batch size per GPU/CPU for training.")
    parser.add_argument("--learning_rate", default=5e-5, type=float, help="The initial learning rate for Adam.")
    parser.add_argument("--weight_decay", default=0.0, type=float, help="Weight decay if we apply some.")
    parser.add_argument("--epochs", default=3, type=int, help="Total number of training epochs to perform.")
    parser.add_argument("--eval_step", default=100, type=int, help="Step interval for evaluation.")
    parser.add_argument("--save_step", default=10000, type=int, help="Step interval for saving checkpoint.")
    parser.add_argument(
        "--warmup_proportion", default=0.0, type=float, help="Linear warmup proportion over the training process."
    )
    parser.add_argument("--init_from_ckpt", type=str, default=None, help="The path of checkpoint to be loaded.")
    parser.add_argument("--seed", type=int, default=1000, help="Random seed for initialization.")
    parser.add_argument(
        "--max_steps", default=-1, type=int, help="If > 0: set total number of training steps to perform."
    )
    parser.add_argument(
        "--device",
        choices=["cpu", "gpu", "npu", "xpu"],
        default="gpu",
        help="Select which device to train model, defaults to gpu.",
    )
    args = parser.parse_args()
    do_train(args)
