# Copyright (c) 2022 Microsoft
# Licensed under The MIT License [see LICENSE for details]

import os
import gzip
import numpy as np
from random import Random
from typing import Any, Callable, Dict, Generator, Iterable, Iterator, List, Optional, Tuple, Union
import collections
from infinibatch import iterators

def apply_to_sample(f, sample):
    if hasattr(sample, "__len__") and len(sample) == 0:
        return {}

    def _apply(x):
        if isinstance(x, np.ndarray):
            return f(x)
        elif isinstance(x, collections.OrderedDict):
            # OrderedDict has attributes that needs to be preserved
            od = collections.OrderedDict((key, _apply(value)) for key, value in x.items())
            od.__dict__ = x.__dict__
            return od
        elif isinstance(x, dict):
            return {key: _apply(value) for key, value in x.items()}
        elif isinstance(x, list):
            return [_apply(x) for x in x]
        elif isinstance(x, tuple):
            return tuple(_apply(x) for x in x)
        elif isinstance(x, set):
            return {_apply(x) for x in x}
        else:
            return x

    return _apply(sample)

class NativeCheckpointableIterator(iterators.CheckpointableIterator):
    def __init__(self, iterable: Iterable):
        self._input_iterable = iterable
        self.setstate(None)

    def getstate(self) -> Dict:
        return {'num_items_yielded': self._num_items_yielded}

    def setstate(self, checkpoint: Optional[Dict]):
        self._iterator = iter(self._input_iterable)
        self._num_items_yielded = iterators._advance_iterator(self._iterator, checkpoint['num_items_yielded']) if checkpoint is not None else 0

    def __next__(self):
        item = next(self._iterator)
        self._num_items_yielded += 1
        return item
    
    def close(self):
        pass


class WeightIterator(object):
    def __init__(self, weights, seed):
        self.weights = weights
        self.seed = seed
        self.control_index = list(range(len(weights)))
        self.setstate(None)
        
    def __iter__(self):
        return self
    
    def getstate(self):
        return {"random_state": self._random_state}

    def setstate(self, checkpoint):
        self._random_state = checkpoint["random_state"] if checkpoint else None
        self._random = None  # this will trigger the lazy initialization in self.__next__
        
    def __next__(self):
        if self._random is None:
            self._random = Random(self.seed)
            if self._random_state is not None:
                self._random.setstate(self._random_state)
        idx = self._random.choices(self.control_index, self.weights)[0]
        self._random_state = self._random.getstate()
        return idx
    
    def close(self):
        pass