import math
import torch

from typing import List, Optional

def init_weights(m, mean=0.0, std=0.01):
    classname = m.__class__.__name__
    if classname.find("Conv") != -1: m.weight.data.normal_(mean, std)

def get_padding(kernel_size, dilation=1):
    return int((kernel_size * dilation - dilation) / 2)

def convert_pad_shape(pad_shape):
    l = pad_shape[::-1]
    pad_shape = [item for sublist in l for item in sublist]
    return pad_shape

def kl_divergence(m_p, logs_p, m_q, logs_q):
    kl = (logs_q - logs_p) - 0.5
    kl += (0.5 * (torch.exp(2.0 * logs_p) + ((m_p - m_q) ** 2)) * torch.exp(-2.0 * logs_q))
    return kl

def slice_segments(x: torch.Tensor, ids_str: torch.Tensor, segment_size: int = 4, dim: int = 2):
    if dim == 2: ret = torch.zeros_like(x[:, :segment_size])
    elif dim == 3: ret = torch.zeros_like(x[:, :, :segment_size])

    for i in range(x.size(0)):
        idx_str = ids_str[i].item()
        idx_end = idx_str + segment_size

        if dim == 2: ret[i] = x[i, idx_str:idx_end]
        else: ret[i] = x[i, :, idx_str:idx_end]

    return ret

def rand_slice_segments(x, x_lengths=None, segment_size=4):
    b, d, t = x.size()

    if x_lengths is None: x_lengths = t

    ids_str_max = x_lengths - segment_size + 1
    ids_str = (torch.rand([b]).to(device=x.device) * ids_str_max).to(dtype=torch.long)
    ret = slice_segments(x, ids_str, segment_size, dim=3)
    return ret, ids_str

def get_timing_signal_1d(length, channels, min_timescale=1.0, max_timescale=1.0e4):
    position = torch.arange(length, dtype=torch.float)
    num_timescales = channels // 2
    log_timescale_increment = math.log(float(max_timescale) / float(min_timescale)) / (num_timescales - 1)
    inv_timescales = min_timescale * torch.exp(torch.arange(num_timescales, dtype=torch.float) * -log_timescale_increment)
    scaled_time = position.unsqueeze(0) * inv_timescales.unsqueeze(1)
    signal = torch.cat([torch.sin(scaled_time), torch.cos(scaled_time)], 0)
    signal = torch.nn.functional.pad(signal, [0, 0, 0, channels % 2])
    signal = signal.view(1, channels, length)
    return signal


def subsequent_mask(length):
    mask = torch.tril(torch.ones(length, length)).unsqueeze(0).unsqueeze(0)
    return mask


@torch.jit.script
def fused_add_tanh_sigmoid_multiply(input_a, input_b, n_channels):
    n_channels_int = n_channels[0]
    in_act = input_a + input_b
    t_act = torch.tanh(in_act[:, :n_channels_int, :])
    s_act = torch.sigmoid(in_act[:, n_channels_int:, :])
    acts = t_act * s_act
    return acts


def convert_pad_shape(pad_shape: List[List[int]]) -> List[int]:
    return torch.tensor(pad_shape).flip(0).reshape(-1).int().tolist()


def sequence_mask(length: torch.Tensor, max_length: Optional[int] = None):
    if max_length is None: max_length = length.max()
    
    x = torch.arange(max_length, dtype=length.dtype, device=length.device)
    return x.unsqueeze(0) < length.unsqueeze(1)


def clip_grad_value(parameters, clip_value, norm_type=2):
    if isinstance(parameters, torch.Tensor): parameters = [parameters]

    parameters = list(filter(lambda p: p.grad is not None, parameters))
    norm_type = float(norm_type)

    if clip_value is not None: clip_value = float(clip_value)

    total_norm = 0

    for p in parameters:
        param_norm = p.grad.data.norm(norm_type)
        total_norm += param_norm.item() ** norm_type
        if clip_value is not None: p.grad.data.clamp_(min=-clip_value, max=clip_value)

    total_norm = total_norm ** (1.0 / norm_type)
    return total_norm