"""Some helper functions for PyTorch, including:
- get_mean_and_std: calculate the mean and std value of dataset.
- msr_init: net parameter initialization.
- progress_bar: progress bar mimic xlua.progress.
"""
import errno
import os
import random
import shutil
import sys
import time

import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F
import torch.nn.init as init

__all__ = [
    "get_mean_and_std",
    "init_params",
    "mkdir_p",
    "AverageMeter",
    "progress_bar",
    "save_model",
    "save_args",
    "set_seed",
    "IOStream",
    "cal_loss",
]


def get_mean_and_std(dataset):
    """Compute the mean and std value of dataset."""
    dataloader = torch.utils.data.DataLoader(dataset, batch_size=1, shuffle=True, num_workers=2)

    mean = torch.zeros(3)
    std = torch.zeros(3)
    print("==> Computing mean and std..")
    for inputs, _targets in dataloader:
        for i in range(3):
            mean[i] += inputs[:, i, :, :].mean()
            std[i] += inputs[:, i, :, :].std()
    mean.div_(len(dataset))
    std.div_(len(dataset))
    return mean, std


def init_params(net):
    """Init layer parameters."""
    for m in net.modules():
        if isinstance(m, nn.Conv2d):
            init.kaiming_normal(m.weight, mode="fan_out")
            if m.bias:
                init.constant(m.bias, 0)
        elif isinstance(m, nn.BatchNorm2d):
            init.constant(m.weight, 1)
            init.constant(m.bias, 0)
        elif isinstance(m, nn.Linear):
            init.normal(m.weight, std=1e-3)
            if m.bias:
                init.constant(m.bias, 0)


def mkdir_p(path):
    """Make dir if not exist."""
    try:
        os.makedirs(path)
    except OSError as exc:  # Python >2.5
        if exc.errno == errno.EEXIST and os.path.isdir(path):
            pass
        else:
            raise


class AverageMeter:
    """Computes and stores the average and current value
    Imported from https://github.com/pytorch/examples/blob/master/imagenet/main.py#L247-L262.
    """

    def __init__(self):
        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


TOTAL_BAR_LENGTH = 65.0
last_time = time.time()
begin_time = last_time


def progress_bar(current, total, msg=None):
    global last_time, begin_time
    if current == 0:
        begin_time = time.time()  # Reset for new bar.

    cur_len = int(TOTAL_BAR_LENGTH * current / total)
    rest_len = int(TOTAL_BAR_LENGTH - cur_len) - 1

    sys.stdout.write(" [")
    for _i in range(cur_len):
        sys.stdout.write("=")
    sys.stdout.write(">")
    for _i in range(rest_len):
        sys.stdout.write(".")
    sys.stdout.write("]")

    cur_time = time.time()
    step_time = cur_time - last_time
    last_time = cur_time
    tot_time = cur_time - begin_time

    L = []
    L.append("  Step: %s" % format_time(step_time))
    L.append(" | Tot: %s" % format_time(tot_time))
    if msg:
        L.append(" | " + msg)

    msg = "".join(L)
    sys.stdout.write(msg)
    # for i in range(term_width-int(TOTAL_BAR_LENGTH)-len(msg)-3):
    #     sys.stdout.write(' ')

    # Go back to the center of the bar.
    # for i in range(term_width-int(TOTAL_BAR_LENGTH/2)+2):
    #     sys.stdout.write('\b')
    sys.stdout.write(" %d/%d " % (current + 1, total))

    if current < total - 1:
        sys.stdout.write("\r")
    else:
        sys.stdout.write("\n")
    sys.stdout.flush()


def format_time(seconds):
    days = int(seconds / 3600 / 24)
    seconds = seconds - days * 3600 * 24
    hours = int(seconds / 3600)
    seconds = seconds - hours * 3600
    minutes = int(seconds / 60)
    seconds = seconds - minutes * 60
    secondsf = int(seconds)
    seconds = seconds - secondsf
    millis = int(seconds * 1000)

    f = ""
    i = 1
    if days > 0:
        f += str(days) + "D"
        i += 1
    if hours > 0 and i <= 2:
        f += str(hours) + "h"
        i += 1
    if minutes > 0 and i <= 2:
        f += str(minutes) + "m"
        i += 1
    if secondsf > 0 and i <= 2:
        f += str(secondsf) + "s"
        i += 1
    if millis > 0 and i <= 2:
        f += str(millis) + "ms"
        i += 1
    if f == "":
        f = "0ms"
    return f


def save_model(net, epoch, path, acc, is_best, **kwargs):
    state = {
        "net": net.state_dict(),
        "epoch": epoch,
        "acc": acc,
    }
    for key, value in kwargs.items():
        state[key] = value
    filepath = os.path.join(path, "last_checkpoint.pth")
    torch.save(state, filepath)
    if is_best:
        shutil.copyfile(filepath, os.path.join(path, "best_checkpoint.pth"))


def save_args(args):
    file = open(os.path.join(args.checkpoint, "args.txt"), "w")
    for k, v in vars(args).items():
        file.write(f"{k}:\t {v}\n")
    file.close()


def set_seed(seed=None):
    if seed is None:
        return
    random.seed(seed)
    os.environ["PYTHONHASHSEED"] = "%s" % seed
    np.random.seed(seed)
    torch.manual_seed(seed)
    torch.cuda.manual_seed(seed)
    torch.cuda.manual_seed_all(seed)
    torch.backends.cudnn.benchmark = False
    torch.backends.cudnn.deterministic = True


# create a file and write the text into it
class IOStream:
    def __init__(self, path):
        self.f = open(path, "a")

    def cprint(self, text):
        print(text)
        self.f.write(text + "\n")
        self.f.flush()

    def close(self):
        self.f.close()


def cal_loss(pred, gold, smoothing=True):
    """Calculate cross entropy loss, apply label smoothing if needed."""
    gold = gold.contiguous().view(-1)

    if smoothing:
        eps = 0.2
        n_class = pred.size(1)

        one_hot = torch.zeros_like(pred).scatter(1, gold.view(-1, 1), 1)
        one_hot = one_hot * (1 - eps) + (1 - one_hot) * eps / (n_class - 1)
        log_prb = F.log_softmax(pred, dim=1)

        loss = -(one_hot * log_prb).sum(dim=1).mean()
    else:
        loss = F.cross_entropy(pred, gold, reduction="mean")

    return loss