import argparse
import logging
import os
import sys
import numpy as np
from tqdm import tqdm
import torch
import torch.nn as nn
from torch import optim
from tensorboardX import SummaryWriter
from torch.utils.data import DataLoader, random_split

from .unet3D import UNet
from .eval import eval_net
from .utils.dataset import CustomDataset

data_dir = ''
dir_checkpoint = './checkpoints/'


def train_net(net, device, epochs=1, batch_size=1, lr=0.001, val_percent=0.1,
              save_cp=True, img_scale=0.5):
    dataset = CustomDataset(data_dir)
    n_val = int(len(dataset) * val_percent)
    n_train = len(dataset) - n_val
    train, val = random_split(dataset, [n_train, n_val])
    train_loader = DataLoader(train, batch_size=batch_size, shuffle=True,
                              num_workers=8, pin_memory=True)
    val_loader = DataLoader(val, batch_size=batch_size, shuffle=False,
                            num_workers=8, pin_memory=True, drop_last=True)

    writer = SummaryWriter(comment=f'LR_{lr}_BS_{batch_size}_SCALE_{img_scale}')
    global_step = 0

    logging.info(f'''Starting training:
        Epochs:          {epochs}
        Batch size:      {batch_size}
        Learning rate:   {lr}
        Training size:   {n_train}
        Validation size: {n_val}
        Checkpoints:     {save_cp}
        Device:          {device.type}
        Images scaling:  {img_scale}
    ''')

    optimizer = optim.RMSprop(net.parameters(), lr=lr, weight_decay=1e-8, momentum=0.9)
    scheduler = optim.lr_scheduler.ReduceLROnPlateau(optimizer,
                                                     'min' if net.n_classes > 1 else 'max', patience=2)
    if net.n_classes > 2:
        criterion = nn.CrossEntropyLoss()
    else:
        criterion = nn.BCEWithLogitsLoss()

    for epoch in range(epochs):
        net.train()

        epoch_loss = 0
        with tqdm(total=n_train, desc=f'Epoch {epoch + 1}/{epochs}', unit='img') as pbar:
            for batch in train_loader:
                imgs = batch['image']
                true_masks = batch['mask']

                imgs = imgs.to(device=device, dtype=torch.float32)
                mask_type = torch.float32 if net.n_classes == 1 else torch.long
                true_masks = true_masks.to(device=device, dtype=mask_type)

                masks_pred = net(imgs)
                # import pdb
                # pdb.set_trace()

                loss = criterion(masks_pred[:, 0].float(), true_masks[:, 0].float())
                epoch_loss += loss.item()
                writer.add_scalar('Loss/train', loss.item(), global_step)

                pbar.set_postfix(**{'loss (batch)': loss.item()})

                optimizer.zero_grad()
                loss.backward()
                nn.utils.clip_grad_value_(net.parameters(), 0.1)
                optimizer.step()

                pbar.update(imgs.shape[0])
                global_step += 1
                if global_step % (n_train // (10 * batch_size)) == 0:
                    for tag, value in net.named_parameters():
                        tag = tag.replace('.', '/')
                        writer.add_histogram('weights/' + tag, value.data.cpu().numpy(), global_step)
                        writer.add_histogram('grads/' + tag, value.grad.data.cpu().numpy(), global_step)
                    val_score = eval_net(net, val_loader, device)
                    scheduler.step(val_score)
                    writer.add_scalar('learning_rate', optimizer.param_groups[0]['lr'], global_step)

                    if net.n_classes > 1:
                        logging.info('Validation cross entropy: {}'.format(val_score))
                        writer.add_scalar('Loss/test', val_score, global_step)
                    else:
                        logging.info('Validation Dice Coeff: {}'.format(val_score))
                        writer.add_scalar('Dice/test', val_score, global_step)

        if save_cp:
            try:
                os.mkdir(dir_checkpoint)
                logging.info('Created checkpoint directory')
            except OSError:
                pass
            torch.save(net.state_dict(),
                       dir_checkpoint + f'CP_epoch{epoch + 1}.pth')
            logging.info(f'Checkpoint {epoch + 1} saved !')

    writer.close()


def get_args():
    parser = argparse.ArgumentParser(description='Train the UNet on images and target masks',
                                     formatter_class=argparse.ArgumentDefaultsHelpFormatter)
    parser.add_argument('-e', '--epochs', metavar='E', type=int, default=1,
                        help='Number of epochs', dest='epochs')
    parser.add_argument('-b', '--batch-size', metavar='B', type=int, nargs='?', default=1,
                        help='Batch size', dest='batchsize')
    parser.add_argument('-l', '--learning-rate', metavar='LR', type=float, nargs='?', default=0.1,
                        help='Learning rate', dest='lr')
    parser.add_argument('-f', '--load', dest='load', type=str, default=False,
                        help='Load model from a .pth file')
    parser.add_argument('-s', '--scale', dest='scale', type=float, default=0.5,
                        help='Downscaling factor of the images')
    parser.add_argument('-v', '--validation', dest='val', type=float, default=10.0,
                        help='Percent of the data that is used as validation (0-100)')

    return parser.parse_args()


if __name__ == '__main__':
    logging.basicConfig(level=logging.INFO, format='%(levelname)s: %(message)s')
    args = get_args()
    device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')
    logging.info(f'Using device {device}')

    # Change here to adapt to your data
    # n_channels=3 for RGB images
    # n_classes is the number of probabilities you want to get per pixel
    #   - For 1 class and background, use n_classes=1
    #   - For 2 classes, use n_classes=1
    #   - For N > 2 classes, use n_classes=N
    net = UNet(n_channels=1, n_classes=2, bilinear=False)
    logging.info(f'Network:\n'
                 f'\t{net.n_channels} input channels\n'
                 f'\t{net.n_classes} output channels (classes)\n'
                 f'\t{"Bilinear" if net.bilinear else "Transposed conv"} upscaling')

    if args.load:
        net.load_state_dict(
            torch.load(args.load, map_location=device)
        )
        logging.info(f'Model loaded from {args.load}')

    net.to(device=device)
    # faster convolutions, but more memory
    # cudnn.benchmark = True

    try:
        train_net(net=net,
                  epochs=args.epochs,
                  batch_size=args.batchsize,
                  lr=args.lr,
                  device=device,
                  img_scale=args.scale,
                  val_percent=args.val / 100)
    except KeyboardInterrupt:
        torch.save(net.state_dict(), 'INTERRUPTED.pth')
        logging.info('Saved interrupt')
        try:
            sys.exit(0)
        except SystemExit:
            os._exit(0)
