import argparse
import os
import copy

import torch
from torch import nn
import torch.optim as optim
import torch.backends.cudnn as cudnn
from torch.utils.data.dataloader import DataLoader
from tqdm import tqdm

from models import ESPCN
from datasets import TrainDataset, EvalDataset
from utils import AverageMeter, calc_psnr


if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('--train-file', type=str, required=True) 
    parser.add_argument('--eval-file', type=str, required=True)
    parser.add_argument('--outputs-dir', type=str, required=True)
    parser.add_argument('--weights-file', type=str)
    parser.add_argument('--scale', type=int, default=3)
    parser.add_argument('--lr', type=float, default=1e-3)
    parser.add_argument('--batch-size', type=int, default=16)
    parser.add_argument('--num-epochs', type=int, default=200)
    parser.add_argument('--num-workers', type=int, default=8)
    parser.add_argument('--seed', type=int, default=123)
    args = parser.parse_args()

    args.outputs_dir = os.path.join(args.outputs_dir, 'x{}'.format(args.scale))

    if not os.path.exists(args.outputs_dir):
        os.makedirs(args.outputs_dir)

    cudnn.benchmark = True
    device = torch.device('cuda:0' if torch.cuda.is_available() else 'cpu')

    torch.manual_seed(args.seed)

    model = ESPCN(scale_factor=args.scale).to(device)
    criterion = nn.MSELoss()
    optimizer = optim.Adam([
        {'params': model.first_part.parameters()},
        {'params': model.last_part.parameters(), 'lr': args.lr * 0.1}
    ], lr=args.lr)

    train_dataset = TrainDataset(args.train_file)
    train_dataloader = DataLoader(dataset=train_dataset,
                                  batch_size=args.batch_size,
                                  shuffle=True,
                                  num_workers=args.num_workers,
                                  pin_memory=True)
    eval_dataset = EvalDataset(args.eval_file)
    eval_dataloader = DataLoader(dataset=eval_dataset, batch_size=1)

    best_weights = copy.deepcopy(model.state_dict())
    best_epoch = 0
    best_psnr = 0.0

    # 开始训练
    for epoch in range(args.num_epochs):
        # 更新lr
        for param_group in optimizer.param_groups:
            param_group['lr'] = args.lr * (0.1 ** (epoch // int(args.num_epochs * 0.8)))

        model.train()
        epoch_losses = AverageMeter()

        with tqdm(total=(len(train_dataset) - len(train_dataset) % args.batch_size), ncols=80) as t:
            t.set_description('epoch: {}/{}'.format(epoch, args.num_epochs - 1))

            for data in train_dataloader:
                inputs, labels = data

                inputs = inputs.to(device)
                labels = labels.to(device)

                preds = model(inputs)

                loss = criterion(preds, labels)

                epoch_losses.update(loss.item(), len(inputs))

                optimizer.zero_grad()
                loss.backward()
                optimizer.step()

                t.set_postfix(loss='{:.6f}'.format(epoch_losses.avg))
                t.update(len(inputs))

        torch.save(model.state_dict(), os.path.join(args.outputs_dir, 'epoch_{}.pth'.format(epoch)))

        model.eval()
        epoch_psnr = AverageMeter()

        # 验证模型
        for data in eval_dataloader:
            inputs, labels = data

            inputs = inputs.to(device)
            labels = labels.to(device)

            with torch.no_grad():
                preds = model(inputs).clamp(0.0, 1.0)  # 把数据限制在0~1

            epoch_psnr.update(calc_psnr(preds, labels), len(inputs)) 
        # 计算平均PSNR值
        print('eval psnr: {:.2f}'.format(epoch_psnr.avg))
        
        # 记录所有epochs中最好的PSNR模型
        if epoch_psnr.avg > best_psnr:
            best_epoch = epoch
            best_psnr = epoch_psnr.avg
            best_weights = copy.deepcopy(model.state_dict())

    # 保存最好的PNSR模型
    print('best epoch: {}, psnr: {:.2f}'.format(best_epoch, best_psnr))
    torch.save(best_weights, os.path.join(args.outputs_dir, 'best.pth'))