import os

import torch
from tqdm import tqdm

from utils.utils import get_lr


def fit_one_epoch(model_train, model, yolo_loss, loss_history, eval_callback, optimizer, epoch, epoch_step,
                  epoch_step_val, gen, gen_val, Epoch, cuda, fp16, scaler, save_period, save_dir, local_rank=0):
    loss = 0
    val_loss = 0

    if local_rank == 0:
        print('Start Train')
        pbar = tqdm(total=epoch_step, desc=f'Epoch {epoch + 1}/{Epoch}', postfix=dict, mininterval=0.3)
    model_train.train()  # 调整所有的模块为train模式
    for iteration, batch in enumerate(gen):
        if iteration >= epoch_step:  # 有什么意义？
            break

        images, targets = batch[0], batch[1]   # targets也是归一化了的
        with torch.no_grad():
            if cuda:
                images = images.cuda(local_rank)
                targets = [ann.cuda(local_rank) for ann in
                           targets]  # targets是一个python的list，里面是tensor，把tensor逐个转到cuda上，然后targets还是python的列表
        # ----------------------#
        #   清零梯度
        # ----------------------#
        optimizer.zero_grad()
        if not fp16:
            # ----------------------#
            #   前向传播
            # ----------------------#
            outputs = model_train(images)

            loss_value_all = 0
            # ----------------------#
            #   计算损失
            # ----------------------#
            for l in range(len(outputs)):  # 三组不同分辨率大小的输出特征分别计算
                loss_item = yolo_loss(l, outputs[l], targets)
                loss_value_all += loss_item
            loss_value = loss_value_all

            # ----------------------#
            #   反向传播
            # ----------------------#
            loss_value.backward()
            optimizer.step()
        else:  # 不进入这条分支
            from torch.cuda.amp import autocast
            with autocast():
                # ----------------------#
                #   前向传播
                # ----------------------#
                outputs = model_train(images)

                loss_value_all = 0
                # ----------------------#
                #   计算损失
                # ----------------------#
                for l in range(len(outputs)):
                    loss_item = yolo_loss(l, outputs[l], targets)
                    loss_value_all += loss_item
                loss_value = loss_value_all

            # ----------------------#
            #   反向传播
            # ----------------------#
            scaler.scale(loss_value).backward()
            scaler.step(optimizer)
            scaler.update()

        loss += loss_value.item()

        # # 调试用 begin
        # if iteration > 2:
        #     break
        # # 调试用 end

        if local_rank == 0:
            pbar.set_postfix(**{'loss': loss / (iteration + 1),
                                'lr': get_lr(optimizer)})
            pbar.update(1)

    if local_rank == 0:
        pbar.close()
        print('Finish Train')
        print('Start Validation')
        pbar = tqdm(total=epoch_step_val, desc=f'Epoch {epoch + 1}/{Epoch}', postfix=dict, mininterval=0.3)

    model_train.eval()
    for iteration, batch in enumerate(gen_val):
        if iteration >= epoch_step_val:
            break
        images, targets = batch[0], batch[1]
        with torch.no_grad():
            if cuda:
                images = images.cuda(local_rank)
                targets = [ann.cuda(local_rank) for ann in targets]
            # ----------------------#
            #   清零梯度
            # ----------------------#
            optimizer.zero_grad()
            # ----------------------#
            #   前向传播
            # ----------------------#
            outputs = model_train(images)

            loss_value_all = 0
            # ----------------------#
            #   计算损失
            # ----------------------#
            for l in range(len(outputs)):
                loss_item = yolo_loss(l, outputs[l], targets)
                loss_value_all += loss_item
            loss_value = loss_value_all

        val_loss += loss_value.item()

        # # 调试用 begin
        # if iteration > 2:
        #     break
        # # 调试用 end

        if local_rank == 0:
            pbar.set_postfix(**{'val_loss': val_loss / (iteration + 1)})
            pbar.update(1)

    if local_rank == 0:
        pbar.close()
        print('Finish Validation')
        loss_history.append_loss(epoch + 1, loss / epoch_step, val_loss / epoch_step_val)
        eval_callback.on_epoch_end(epoch + 1, model_train)
        print('Epoch:' + str(epoch + 1) + '/' + str(Epoch))
        print('Total Loss: %.3f || Val Loss: %.3f ' % (loss / epoch_step, val_loss / epoch_step_val))

        # -----------------------------------------------#
        #   保存权值
        # -----------------------------------------------#
        if (epoch + 1) % save_period == 0 or epoch + 1 == Epoch:
            torch.save(model.state_dict(), os.path.join(save_dir, "ep%03d-loss%.3f-val_loss%.3f.pth" % (
                epoch + 1, loss / epoch_step, val_loss / epoch_step_val)))

        if len(loss_history.val_loss) <= 1 or (val_loss / epoch_step_val) <= min(loss_history.val_loss):
            print('Save best model to best_epoch_weights.pth')
            torch.save(model.state_dict(), os.path.join(save_dir, "best_epoch_weights.pth"))

        torch.save(model.state_dict(), os.path.join(save_dir, "last_epoch_weights.pth"))