# 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 numpy as np

from paddlenlp.datasets import MapDataset


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

    shuffle = True if mode == "train" else False
    if mode == "train":
        batch_sampler = paddle.io.DistributedBatchSampler(dataset, batch_size=batch_size, shuffle=shuffle)
    else:
        batch_sampler = paddle.io.BatchSampler(dataset, batch_size=batch_size, shuffle=shuffle)

    return paddle.io.DataLoader(dataset=dataset, batch_sampler=batch_sampler, collate_fn=batchify_fn, return_list=True)


def read_text_pair(data_path):
    """Reads data."""
    with open(data_path, "r", encoding="utf-8") as f:
        for line in f:
            data = line.rstrip().split("\t")
            if len(data) != 2:
                continue
            yield {"query": data[0], "title": data[1]}


def convert_pointwise_example(example, tokenizer, max_seq_length=512, is_test=False):

    query, title = example["query"], example["title"]

    encoded_inputs = tokenizer(text=query, text_pair=title, max_seq_len=max_seq_length)

    input_ids = encoded_inputs["input_ids"]
    token_type_ids = encoded_inputs["token_type_ids"]

    if not is_test:
        label = np.array([example["label"]], dtype="int64")
        return input_ids, token_type_ids, label
    else:
        return input_ids, token_type_ids


def convert_pairwise_example(example, tokenizer, max_seq_length=512, phase="train"):

    if phase == "train":
        query, pos_title, neg_title = example["query"], example["title"], example["neg_title"]

        pos_inputs = tokenizer(text=query, text_pair=pos_title, max_seq_len=max_seq_length)
        neg_inputs = tokenizer(text=query, text_pair=neg_title, max_seq_len=max_seq_length)

        pos_input_ids = pos_inputs["input_ids"]
        pos_token_type_ids = pos_inputs["token_type_ids"]
        neg_input_ids = neg_inputs["input_ids"]
        neg_token_type_ids = neg_inputs["token_type_ids"]

        return (pos_input_ids, pos_token_type_ids, neg_input_ids, neg_token_type_ids)

    else:
        query, title = example["query"], example["title"]

        inputs = tokenizer(text=query, text_pair=title, max_seq_len=max_seq_length)

        input_ids = inputs["input_ids"]
        token_type_ids = inputs["token_type_ids"]
        if phase == "eval":
            return input_ids, token_type_ids, example["label"]
        elif phase == "predict":
            return input_ids, token_type_ids
        else:
            raise ValueError("not supported phase:{}".format(phase))


def gen_pair(dataset, pool_size=100):
    """
    Generate triplet randomly based on dataset

    Args:
        dataset: A `MapDataset` or `IterDataset` or a tuple of those.
            Each example is composed of 2 texts: example["query"], example["title"]
        pool_size: the number of example to sample negative example randomly

    Return:
        dataset: A `MapDataset` or `IterDataset` or a tuple of those.
        Each example is composed of 2 texts: example["query"], example["pos_title"]、example["neg_title"]
    """

    if len(dataset) < pool_size:
        pool_size = len(dataset)

    new_examples = []
    pool = []
    tmp_examples = []

    for example in dataset:
        label = example["label"]

        # Filter negative example
        if label == 0:
            continue

        tmp_examples.append(example)
        pool.append(example["title"])

        if len(pool) >= pool_size:
            np.random.shuffle(pool)
            for idx, example in enumerate(tmp_examples):
                example["neg_title"] = pool[idx]
                new_examples.append(example)
            tmp_examples = []
            pool = []
        else:
            continue
    return MapDataset(new_examples)
