# copyright (c) 2020 PaddlePaddle Authors. All Rights Reserve.
#
# 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 random
import numpy as np
import imghdr
import os
import signal

from paddle.io import Dataset, DataLoader, DistributedBatchSampler

from . import imaug
from .imaug import transform
from ppcls.utils import logger

trainers_num = int(os.environ.get('PADDLE_TRAINERS_NUM', 1))
trainer_id = int(os.environ.get("PADDLE_TRAINER_ID", 0))


class ModeException(Exception):
    """
    ModeException
    """

    def __init__(self, message='', mode=''):
        message += "\nOnly the following 3 modes are supported: " \
            "train, valid, test. Given mode is {}".format(mode)
        super(ModeException, self).__init__(message)


class SampleNumException(Exception):
    """
    SampleNumException
    """

    def __init__(self, message='', sample_num=0, batch_size=1):
        message += "\nError: The number of the whole data ({}) " \
            "is smaller than the batch_size ({}), and drop_last " \
            "is turnning on, so nothing  will feed in program, " \
            "Terminated now. Please reset batch_size to a smaller " \
            "number or feed more data!".format(sample_num, batch_size)
        super(SampleNumException, self).__init__(message)


class ShuffleSeedException(Exception):
    """
    ShuffleSeedException
    """

    def __init__(self, message=''):
        message += "\nIf trainers_num > 1, the shuffle_seed must be set, " \
            "because the order of batch data generated by reader " \
            "must be the same in the respective processes."
        super(ShuffleSeedException, self).__init__(message)


def check_params(params):
    """
    check params to avoid unexpect errors

    Args:
        params(dict):
    """
    if 'shuffle_seed' not in params:
        params['shuffle_seed'] = None

    if trainers_num > 1 and params['shuffle_seed'] is None:
        raise ShuffleSeedException()

    data_dir = params.get('data_dir', '')
    assert os.path.isdir(data_dir), \
        "{} doesn't exist, please check datadir path".format(data_dir)

    if params['mode'] != 'test':
        file_list = params.get('file_list', '')
        assert os.path.isfile(file_list), \
            "{} doesn't exist, please check file list path".format(file_list)


def create_file_list(params):
    """
    if mode is test, create the file list

    Args:
        params(dict):
    """
    data_dir = params.get('data_dir', '')
    params['file_list'] = ".tmp.txt"
    imgtype_list = {'jpg', 'bmp', 'png', 'jpeg', 'rgb', 'tif', 'tiff'}
    with open(params['file_list'], "w") as fout:
        tmp_file_list = os.listdir(data_dir)
        for file_name in tmp_file_list:
            file_path = os.path.join(data_dir, file_name)
            if imghdr.what(file_path) not in imgtype_list:
                continue
            fout.write(file_name + " 0" + "\n")


def shuffle_lines(full_lines, seed=None):
    """
    random shuffle lines
    Args:
        full_lines(list):
        seed(int): random seed
    """
    if seed is not None:
        np.random.RandomState(seed).shuffle(full_lines)
    else:
        np.random.shuffle(full_lines)

    return full_lines


def get_file_list(params):
    """
    read label list from file and shuffle the list

    Args:
        params(dict):
    """
    if params['mode'] == 'test':
        create_file_list(params)

    with open(params['file_list']) as flist:
        full_lines = [line.strip() for line in flist]

    if params["mode"] == "train":
        full_lines = shuffle_lines(full_lines, seed=params['shuffle_seed'])

    return full_lines


def create_operators(params):
    """
    create operators based on the config

    Args:
        params(list): a dict list, used to create some operators
    """
    assert isinstance(params, list), ('operator config should be a list')
    ops = []
    for operator in params:
        assert isinstance(operator,
                          dict) and len(operator) == 1, "yaml format error"
        op_name = list(operator)[0]
        param = {} if operator[op_name] is None else operator[op_name]
        op = getattr(imaug, op_name)(**param)
        ops.append(op)

    return ops


def term_mp(sig_num, frame):
    """ kill all child processes
    """
    pid = os.getpid()
    pgid = os.getpgid(os.getpid())
    logger.info("main proc {} exit, kill process group "
                "{}".format(pid, pgid))
    os.killpg(pgid, signal.SIGKILL)
    return


class CommonDataset(Dataset):
    def __init__(self, params):
        self.params = params
        self.mode = params.get("mode", "train")
        self.full_lines = get_file_list(params)
        self.delimiter = params.get('delimiter', ' ')
        self.ops = create_operators(params['transforms'])
        self.num_samples = len(self.full_lines)
        return

    def __getitem__(self, idx):
        try:
            line = self.full_lines[idx]
            img_path, label = line.split(self.delimiter)
            img_path = os.path.join(self.params['data_dir'], img_path)
            with open(img_path, 'rb') as f:
                img = f.read()
        except Exception as e:
            logger.error('data read faild: "{}"'.format(line))
            return self.__getitem__(random.randint(0, len(self)))
        return (transform(img, self.ops), int(label))

    def __len__(self):
        return self.num_samples


class Reader:
    """
    Create a reader for trainning/validate/test

    Args:
        config(dict): arguments
        mode(str): train or val or test
        seed(int): random seed used to generate same sequence in each trainer

    Returns:
        the specific reader
    """

    def __init__(self, config, mode='train', places=None):
        try:
            self.params = config[mode.upper()]
        except KeyError:
            raise ModeException(mode=mode)

        use_mix = config.get('use_mix')
        self.params['mode'] = mode
        self.shuffle = mode == "train"

        self.collate_fn = None
        self.batch_ops = []
        if use_mix and mode == "train":
            self.batch_ops = create_operators(self.params['mix'])
            self.collate_fn = self.mix_collate_fn

        self.places = places

    def mix_collate_fn(self, batch):
        batch = transform(batch, self.batch_ops)
        # batch each field
        slots = []
        for items in batch:
            for i, item in enumerate(items):
                if len(slots) < len(items):
                    slots.append([item])
                else:
                    slots[i].append(item)

        return [np.stack(slot, axis=0) for slot in slots]

    def __call__(self):
        batch_size = int(self.params['batch_size']) // trainers_num

        dataset = CommonDataset(self.params)

        is_train = self.params['mode'] == "train"
        batch_sampler = DistributedBatchSampler(
            dataset,
            batch_size=batch_size,
            shuffle=self.shuffle and is_train,
            drop_last=is_train)
        loader = DataLoader(
            dataset,
            batch_sampler=batch_sampler,
            collate_fn=self.collate_fn if is_train else None,
            places=self.places,
            return_list=True,
            num_workers=self.params["num_workers"])
        return loader


signal.signal(signal.SIGINT, term_mp)
signal.signal(signal.SIGTERM, term_mp)
