import numpy as np
from numpy import dot
from numpy.linalg import norm
import os
from scipy import stats
import shutil
from sklearn import metrics
import torch
from torch import Tensor
import torch.distributed as dist
import torch.autograd as autograd
from typing import TypeVar, Optional, Iterator, Sequence
from torch.utils.data import Dataset, Sampler, DistributedSampler
import math

T_co = TypeVar('T_co', covariant=True)

class WeightedRandomSampler(Sampler[int]):
    r"""Samples elements from ``[0,..,len(weights)-1]`` with given probabilities (weights).

    Args:
        weights (sequence)   : a sequence of weights, not necessary summing up to one
        num_samples (int): number of samples to draw
        replacement (bool): if ``True``, samples are drawn with replacement.
            If not, they are drawn without replacement, which means that when a
            sample index is drawn for a row, it cannot be drawn again for that row.
        generator (Generator): Generator used in sampling.

    Example:
        >>> list(WeightedRandomSampler([0.1, 0.9, 0.4, 0.7, 3.0, 0.6], 5, replacement=True))
        [4, 4, 1, 4, 5]
        >>> list(WeightedRandomSampler([0.9, 0.4, 0.05, 0.2, 0.3, 0.1], 5, replacement=False))
        [0, 1, 4, 3, 2]
    """
    weights: Tensor
    num_samples: int
    replacement: bool

    def __init__(self, weights: Sequence[float], num_samples: int,
                 replacement: bool = True, generator=None) -> None:
        if not isinstance(num_samples, int) or isinstance(num_samples, bool) or \
                num_samples <= 0:
            raise ValueError("num_samples should be a positive integer "
                             "value, but got num_samples={}".format(num_samples))
        if not isinstance(replacement, bool):
            raise ValueError("replacement should be a boolean value, but got "
                             "replacement={}".format(replacement))
        self.weights = torch.as_tensor(weights, dtype=torch.double)
        self.num_samples = num_samples
        self.replacement = replacement
        self.generator = generator

    def __iter__(self) -> Iterator[int]:
        rand_tensor = torch.multinomial(self.weights, self.num_samples, self.replacement, generator=self.generator)
        yield from iter(rand_tensor.tolist())

    def __len__(self) -> int:
        return self.num_samples

class DistributedSamplerWrapper(DistributedSampler):
    def __init__(
            self, sampler, dataset,
            num_replicas=None,
            rank=None,
            shuffle: bool = True):
        super(DistributedSamplerWrapper, self).__init__(
            dataset, num_replicas, rank, shuffle)
        # source: @awaelchli https://github.com/PyTorchLightning/pytorch-lightning/issues/3238
        self.sampler = sampler

    def __iter__(self):
        if self.sampler.generator is None:
            self.sampler.generator = torch.Generator()
        self.sampler.generator.manual_seed(self.seed + self.epoch)
        indices = list(self.sampler)
        if self.epoch == 0:
            print(f"\n DistributedSamplerWrapper :  {indices[:10]} \n\n")
        indices = indices[self.rank:self.total_size:self.num_replicas]
        return iter(indices)
    

class DistributedWeightedSampler(Sampler):

    weights: Tensor
    num_samples: int
    replacement: bool

    #dataset_train, samples_weight,  num_replicas=num_tasks, rank=global_rank
    def __init__(self, dataset: Dataset, weights: Sequence[float], num_replicas: Optional[int] = None, 
                 rank: Optional[int] = None, replacement: bool = True, shuffle: bool = True,
                 seed: int = 0, drop_last: bool = False) -> None:
        if num_replicas is None:
            if not dist.is_available():
                raise RuntimeError("Requires distributed package to be available")
            num_replicas = dist.get_world_size()
        if rank is None:
            if not dist.is_available():
                raise RuntimeError("Requires distributed package to be available")
            rank = dist.get_rank()
        if rank >= num_replicas or rank < 0:
            raise ValueError(
                "Invalid rank {}, rank should be in the interval"
                " [0, {}]".format(rank, num_replicas - 1))
        self.dataset = dataset
        self.num_replicas = num_replicas
        self.rank = rank
        self.epoch = 0
        self.drop_last = drop_last
        if self.drop_last and len(self.dataset) % self.num_replicas != 0:  # type: ignore[arg-type]
            # Split to nearest available length that is evenly divisible.
            # This is to ensure each rank receives the same amount of data when
            # using this Sampler.
            self.num_samples = math.ceil(
                (len(self.dataset) - self.num_replicas) / self.num_replicas  # type: ignore[arg-type]
            )
        else:
            self.num_samples = math.ceil(len(self.dataset) / self.num_replicas)  # type: ignore[arg-type]
        self.total_size = self.num_samples * self.num_replicas
        self.replacement = replacement
        self.weights = torch.from_numpy(weights)
        self.shuffle = shuffle
        self.seed = seed

    def __iter__(self) -> Iterator[T_co]:
        # deterministically shuffle based on epoch
        if self.shuffle:
            g = torch.Generator()
            g.manual_seed(self.seed + self.epoch)
            indices = torch.randperm(len(self.dataset), generator=g).tolist()
        else:
            indices = list(range(len(self.dataset)))

        if not self.drop_last:
            # add extra samples to make it evenly divisible
            padding_size = self.total_size - len(indices)
            if padding_size <= len(indices):
                indices += indices[:padding_size]
            else:
                indices += (indices * math.ceil(padding_size / len(indices)))[:padding_size]
        else:
            indices = indices[:self.total_size]
        assert len(indices) == self.total_size

        # subsample
        indices = indices[self.rank:self.total_size:self.num_replicas]
        assert len(indices) == self.num_samples

        # # get targets (you can alternatively pass them in __init__, if this op is expensive)
        # targets = self.dataset.targets
        # # select only the wanted targets for this subsample
        # targets = torch.tensor(targets)[indices]
        # assert len(targets) == self.num_samples
        # # randomly sample this subset, producing balanced classes
        # weights = self.calculate_weights(targets)
        weights = self.weights[indices]

        subsample_rand_tensor = torch.multinomial(weights, self.num_samples, self.replacement)
        # now map these target indicies back to the original dataset index...
        dataset_indices = torch.tensor(indices)[subsample_rand_tensor]
        return iter(dataset_indices.tolist())
        # return iter(indices)

    def __len__(self) -> int:
        return self.num_samples

    def set_epoch(self, epoch) -> None:
        self.epoch = epoch

def off_diagonal(x):
    n, m = x.shape
    assert n == m
    return x.flatten()[:-1].view(n - 1, n + 1)[:, 1:].flatten()

def is_dist_avail_and_initialized():
    if not dist.is_available():
        return False
    if not dist.is_initialized():
        return False
    return True

def get_world_size():
    if not is_dist_avail_and_initialized():
        return 1
    return dist.get_world_size()


def get_rank():
    if not is_dist_avail_and_initialized():
        return 0
    return dist.get_rank()


def is_main_process():
    return get_rank() == 0


def save_on_master(state, is_best, output_dir):
    if is_main_process():
        ckpt_path = f'{output_dir}/checkpoint.pt'
        best_path = f'{output_dir}/checkpoint_best.pt'
        torch.save(state, ckpt_path)
        if is_best:
            shutil.copyfile(ckpt_path, best_path)

def init_distributed_mode(args):
    if 'RANK' in os.environ and 'WORLD_SIZE' in os.environ:
        args.rank = int(os.environ["RANK"])
        args.world_size = int(os.environ['WORLD_SIZE'])
        args.gpu = int(os.environ['LOCAL_RANK'])
    elif 'SLURM_PROCID' in os.environ:
        args.rank = int(os.environ['SLURM_PROCID'])
        args.gpu = args.rank % torch.cuda.device_count()
    else:
        print('Not using distributed mode')
        args.distributed = False
        return

    args.distributed = True

    torch.cuda.set_device(args.gpu)
    args.dist_backend = 'nccl'
    print('| distributed init (rank {}): {}'.format(
        args.rank, args.dist_url), flush=True)
    torch.distributed.init_process_group(backend=args.dist_backend, init_method=args.dist_url,
                                         world_size=args.world_size, rank=args.rank)
    torch.distributed.barrier()
    setup_for_distributed(args.rank == 0)


def scaled_all_reduce(tensors, is_scale=True):
    """Performs the scaled all_reduce operation on the provided tensors.
    The input tensors are modified in-place. Currently supports only the sum
    reduction operator. The reduced values are scaled by the inverse size of the
    world size.
    """
    world_size = get_world_size()
    # There is no need for reduction in the single-proc case
    if world_size == 1:
        return tensors
    # Queue the reductions
    reductions = []
    for tensor in tensors:
        reduction = dist.all_reduce(tensor, async_op=True)
        reductions.append(reduction)
    # Wait for reductions to finish
    for reduction in reductions:
        reduction.wait()
    # Scale the results
    if is_scale:
        for tensor in tensors:
            tensor.mul_(1.0 / world_size)
    return tensors


def all_gather_batch(tensors):
    """
    Performs all_gather operation on the provided tensors.
    """
    # Queue the gathered tensors
    world_size = get_world_size()
    # There is no need for reduction in the single-proc case
    if world_size == 1:
        return tensors
    tensor_list = []
    output_tensor = []
    for tensor in tensors:
        tensor_all = [torch.ones_like(tensor) for _ in range(world_size)]
        dist.all_gather(
            tensor_all,
            tensor,
            async_op=False  # performance opt
        )

        tensor_list.append(tensor_all)

    for tensor_all in tensor_list:
        output_tensor.append(torch.cat(tensor_all, dim=0))
    return output_tensor


class GatherLayer(autograd.Function):
    """
    Gather tensors from all workers with support for backward propagation:
    This implementation does not cut the gradients as torch.distributed.all_gather does.
    """

    @staticmethod
    def forward(ctx, x):
        output = [torch.zeros_like(x) for _ in range(dist.get_world_size())]
        dist.all_gather(output, x)
        return tuple(output)

    @staticmethod
    def backward(ctx, *grads):
        all_gradients = torch.stack(grads)
        dist.all_reduce(all_gradients)
        return all_gradients[dist.get_rank()]


def all_gather_batch_with_grad(tensors):
    """
    Performs all_gather operation on the provided tensors.
    Graph remains connected for backward grad computation.
    """
    # Queue the gathered tensors
    world_size = get_world_size()
    # There is no need for reduction in the single-proc case
    if world_size == 1:
        return tensors
    tensor_list = []
    output_tensor = []

    for tensor in tensors:
        tensor_all = GatherLayer.apply(tensor)
        tensor_list.append(tensor_all)

    for tensor_all in tensor_list:
        output_tensor.append(torch.cat(tensor_all, dim=0))
    return output_tensor


class AverageMeter(object):
    """Computes and stores the average and current value"""
    def __init__(self, name, fmt=':f'):
        self.name = name
        self.fmt = fmt
        self.reset()

    def reset(self):
        self.val = 0
        self.avg = 0
        self.sum = 0
        self.count = 0

    def update(self, val, n=1):
        self.val = val
        self.sum += val * n
        self.count += n
        self.avg = self.sum / self.count

    def cat(self, val, n=1):
        self.val = val
        self.sum += val * n
        self.count += n
        self.avg = self.sum / self.count

    def synchronize(self):
        if not is_dist_avail_and_initialized():
            return
        t = torch.tensor([self.sum, self.count], dtype=torch.float64, device='cuda')
        dist.barrier()
        dist.all_reduce(t)
        t = t.tolist()
        if math.isnan(t[0]):
            # import pdb; pdb.set_trace()
            self.sum = 1e9
        else: 
            self.sum = int(t[0])
        self.count = t[1]
        self.avg = self.sum / self.count

    def __str__(self):
        # import pdb; pdb.set_trace()
        fmtstr = '{name} {val' + self.fmt + '} ({avg' + self.fmt + '})'
        return fmtstr.format(**self.__dict__)

        
class ProgressMeter(object):
    def __init__(self, num_batches, meters, prefix=""):
        self.batch_fmtstr = self._get_batch_fmtstr(num_batches)
        self.meters = meters
        self.prefix = prefix

    def display(self, batch):
        entries = [self.prefix + self.batch_fmtstr.format(batch)]
        entries += [str(meter) for meter in self.meters]
        print('\t'.join(entries))

        return entries

    def synchronize(self):
        for meter in self.meters:
            meter.synchronize()

    def _get_batch_fmtstr(self, num_batches):
        num_digits = len(str(num_batches // 1))
        fmt = '{:' + str(num_digits) + 'd}'
        return '[' + fmt + '/' + fmt.format(num_batches) + ']'

def accuracy(output, target, topk=(1,)):
    """Computes the accuracy over the k top predictions for the specified values of k"""
    with torch.no_grad():
        maxk = max(topk)
        batch_size = target.size(0)

        _, pred = output.topk(maxk, 1, True, True)
        pred = pred.t()
        correct = pred.eq(target.reshape(1, -1).expand_as(pred))

        res = []
        for k in topk:
            correct_k = correct[:k].reshape(-1).float().sum(0, keepdim=True)
            res.append(correct_k.mul_(100.0 / batch_size))
        return res

# Calculate the Metrics for event classification

def d_prime(auc):
    standard_normal = stats.norm()
    d_prime = standard_normal.ppf(auc) * np.sqrt(2.0)
    return d_prime

def calculate_stats(output, target):
    """Calculate statistics including mAP, AUC, etc.

    Args:
      output: 2d array, (samples_num, classes_num)
      target: 2d array, (samples_num, classes_num)

    Returns:
      stats: list of statistic of each class.
    """

    classes_num = target.shape[-1]
    stats = []

    output = output.cpu()
    target = target.cpu()

    # Accuracy, only used for single-label classification such as esc-50, not for multiple label one such as AudioSet
    acc = metrics.accuracy_score(np.argmax(target, 1), np.argmax(output, 1))

    # Class-wise statistics
    for k in range(classes_num):

        # Average precision
        avg_precision = metrics.average_precision_score(
            target[:, k], output[:, k], average=None)

        # AUC
        try:
            auc = metrics.roc_auc_score(target[:, k], output[:, k], average=None)

            # Precisions, recalls
            (precisions, recalls, thresholds) = metrics.precision_recall_curve(
                target[:, k], output[:, k])

            # FPR, TPR
            (fpr, tpr, thresholds) = metrics.roc_curve(target[:, k], output[:, k])

            save_every_steps = 1000     # Sample statistics to reduce size
            dict = {'precisions': precisions[0::save_every_steps],
                    'recalls': recalls[0::save_every_steps],
                    'AP': avg_precision,
                    'fpr': fpr[0::save_every_steps],
                    'fnr': 1. - tpr[0::save_every_steps],
                    'auc': auc,
                    # note acc is not class-wise, this is just to keep consistent with other metrics
                    'acc': acc
                    }
        except:
            dict = {'precisions': -1,
                    'recalls': -1,
                    'AP': avg_precision,
                    'fpr': -1,
                    'fnr': -1,
                    'auc': -1,
                    # note acc is not class-wise, this is just to keep consistent with other metrics
                    'acc': acc
                    }
            print('class {:s} no true sample'.format(str(k)))
        stats.append(dict)

    return stats


### for retrieval task
def get_similarity(a, b):
    cos_sim = dot(a, b) / (norm(a) * norm(b))
    return cos_sim

# get mean
def get_sim_mat(a, b):
    B = a.shape[0]
    sim_mat = np.empty([B, B])
    for i in range(B):
        for j in range(B):
            sim_mat[i, j] = get_similarity(a[i, :], b[j, :])
    return sim_mat

def compute_metrics(x):
    sx = np.sort(-x, axis=1)
    d = np.diag(-x)
    d = d[:, np.newaxis]
    ind = sx - d
    ind = np.where(ind == 0)
    ind = ind[1]
    metrics = {}
    metrics['R1'] = float(np.sum(ind == 0)) / len(ind)
    metrics['R5'] = float(np.sum(ind < 5)) / len(ind)
    metrics['R10'] = float(np.sum(ind < 10)) / len(ind)
    metrics['MR'] = np.median(ind) + 1
    return metrics