'''
This is a simplified training code of GPEN. It achieves comparable performance as in the paper.

@Created by rosinality

@Modified by yangxy (yangtao9009@gmail.com)
'''
import argparse
import math
import random
import os
import cv2
import glob
from tqdm import tqdm

import torch
from torch import nn, autograd, optim
from torch.nn import functional as F
from torch.utils import data
import torch.distributed as dist
from torchvision import transforms, utils

import __init_paths
from training.data_loader.dataset_face import FaceDataset
from face_model.gpen_model import FullGenerator, Discriminator

from training.loss.id_loss import IDLoss
from distributed import (
    get_rank,
    synchronize,
    reduce_loss_dict,
    reduce_sum,
    get_world_size,
)

from training import lpips


def data_sampler(dataset, shuffle, distributed):
    if distributed:
        return data.distributed.DistributedSampler(dataset, shuffle=shuffle)

    if shuffle:
        return data.RandomSampler(dataset)

    else:
        return data.SequentialSampler(dataset)


def requires_grad(model, flag=True):
    for p in model.parameters():
        p.requires_grad = flag


def accumulate(model1, model2, decay=0.999):
    par1 = dict(model1.named_parameters())
    par2 = dict(model2.named_parameters())

    for k in par1.keys():
        par1[k].data.mul_(decay).add_(1 - decay, par2[k].data)


def sample_data(loader):
    while True:
        for batch in loader:
            yield batch


def d_logistic_loss(real_pred, fake_pred):
    real_loss = F.softplus(-real_pred)
    fake_loss = F.softplus(fake_pred)

    return real_loss.mean() + fake_loss.mean()


def d_r1_loss(real_pred, real_img):
    grad_real, = autograd.grad(
        outputs=real_pred.sum(), inputs=real_img, create_graph=True
    )
    grad_penalty = grad_real.pow(2).view(grad_real.shape[0], -1).sum(1).mean()

    return grad_penalty


def g_nonsaturating_loss(fake_pred, loss_funcs=None, fake_img=None, real_img=None, input_img=None):
    smooth_l1_loss, id_loss = loss_funcs
    
    loss = F.softplus(-fake_pred).mean()
    loss_l1 = smooth_l1_loss(fake_img, real_img)
    loss_id, __, __ = id_loss(fake_img, real_img, input_img)
    loss += 1.0*loss_l1 + 1.0*loss_id

    return loss


def g_path_regularize(fake_img, latents, mean_path_length, decay=0.01):
    noise = torch.randn_like(fake_img) / math.sqrt(
        fake_img.shape[2] * fake_img.shape[3]
    )
    grad, = autograd.grad(
        outputs=(fake_img * noise).sum(), inputs=latents, create_graph=True
    )
    path_lengths = torch.sqrt(grad.pow(2).sum(2).mean(1))

    path_mean = mean_path_length + decay * (path_lengths.mean() - mean_path_length)

    path_penalty = (path_lengths - path_mean).pow(2).mean()

    return path_penalty, path_mean.detach(), path_lengths

def validation(model, lpips_func, args, device):
    lq_files = sorted(glob.glob(os.path.join(args.val_dir, 'lq', '*.*')))
    hq_files = sorted(glob.glob(os.path.join(args.val_dir, 'hq', '*.*')))

    assert len(lq_files) == len(hq_files)

    dist_sum = 0
    model.eval()
    for lq_f, hq_f in zip(lq_files, hq_files):
        img_lq = cv2.imread(lq_f, cv2.IMREAD_COLOR)
        img_t = torch.from_numpy(img_lq).to(device).permute(2, 0, 1).unsqueeze(0)
        img_t = (img_t/255.-0.5)/0.5
        img_t = F.interpolate(img_t, (args.size, args.size))
        img_t = torch.flip(img_t, [1])
        
        with torch.no_grad():
            img_out, __ = model(img_t)
        
            img_hq = lpips.im2tensor(lpips.load_image(hq_f)).to(device)
            img_hq = F.interpolate(img_hq, (args.size, args.size))
            dist_sum += lpips_func.forward(img_out, img_hq)
    
    return dist_sum.data/len(lq_files)


def train(args, loader, generator, discriminator, losses, g_optim, d_optim, g_ema, lpips_func, device):
    loader = sample_data(loader)

    pbar = range(0, args.iter)

    if get_rank() == 0:
        pbar = tqdm(pbar, initial=args.start_iter, dynamic_ncols=True, smoothing=0.01)

    mean_path_length = 0

    d_loss_val = 0
    r1_loss = torch.tensor(0.0, device=device)
    g_loss_val = 0
    path_loss = torch.tensor(0.0, device=device)
    path_lengths = torch.tensor(0.0, device=device)
    mean_path_length_avg = 0
    loss_dict = {}

    if args.distributed:
        g_module = generator.module
        d_module = discriminator.module

    else:
        g_module = generator
        d_module = discriminator
 
    accum = 0.5 ** (32 / (10 * 1000))

    for idx in pbar:
        i = idx + args.start_iter

        if i > args.iter:
            print('Done!')

            break

        degraded_img, real_img = next(loader)
        degraded_img = degraded_img.to(device)
        real_img = real_img.to(device)

        requires_grad(generator, False)
        requires_grad(discriminator, True)

        fake_img, _ = generator(degraded_img)
        fake_pred = discriminator(fake_img)

        real_pred = discriminator(real_img)
        d_loss = d_logistic_loss(real_pred, fake_pred)

        loss_dict['d'] = d_loss
        loss_dict['real_score'] = real_pred.mean()
        loss_dict['fake_score'] = fake_pred.mean()

        discriminator.zero_grad()
        d_loss.backward()
        d_optim.step()

        d_regularize = i % args.d_reg_every == 0

        if d_regularize:
            real_img.requires_grad = True
            real_pred = discriminator(real_img)
            r1_loss = d_r1_loss(real_pred, real_img)

            discriminator.zero_grad()
            (args.r1 / 2 * r1_loss * args.d_reg_every + 0 * real_pred[0]).backward()

            d_optim.step()

        loss_dict['r1'] = r1_loss

        requires_grad(generator, True)
        requires_grad(discriminator, False)

        fake_img, _ = generator(degraded_img)
        fake_pred = discriminator(fake_img)
        g_loss = g_nonsaturating_loss(fake_pred, losses, fake_img, real_img, degraded_img)

        loss_dict['g'] = g_loss

        generator.zero_grad()
        g_loss.backward()
        g_optim.step()

        g_regularize = i % args.g_reg_every == 0

        if g_regularize:
            path_batch_size = max(1, args.batch // args.path_batch_shrink)

            fake_img, latents = generator(degraded_img, return_latents=True)

            path_loss, mean_path_length, path_lengths = g_path_regularize(
                fake_img, latents, mean_path_length
            )

            generator.zero_grad()
            weighted_path_loss = args.path_regularize * args.g_reg_every * path_loss

            if args.path_batch_shrink:
                weighted_path_loss += 0 * fake_img[0, 0, 0, 0]

            weighted_path_loss.backward()

            g_optim.step()

            mean_path_length_avg = (
                reduce_sum(mean_path_length).item() / get_world_size()
            )

        loss_dict['path'] = path_loss
        loss_dict['path_length'] = path_lengths.mean()

        accumulate(g_ema, g_module, accum)

        loss_reduced = reduce_loss_dict(loss_dict)

        d_loss_val = loss_reduced['d'].mean().item()
        g_loss_val = loss_reduced['g'].mean().item()
        r1_val = loss_reduced['r1'].mean().item()
        path_loss_val = loss_reduced['path'].mean().item()
        real_score_val = loss_reduced['real_score'].mean().item()
        fake_score_val = loss_reduced['fake_score'].mean().item()
        path_length_val = loss_reduced['path_length'].mean().item()

        if get_rank() == 0:
            pbar.set_description(
                (
                    f'd: {d_loss_val:.4f}; g: {g_loss_val:.4f}; r1: {r1_val:.4f}; '
                )
            )
            
            if i % args.save_freq == 0:
                with torch.no_grad():
                    g_ema.eval()
                    sample, _ = g_ema(degraded_img)
                    sample = torch.cat((degraded_img, sample, real_img), 0) 
                    utils.save_image(
                        sample,
                        f'{args.sample}/{str(i).zfill(6)}.png',
                        nrow=args.batch,
                        normalize=True,
                        range=(-1, 1),
                    )

                lpips_value = validation(g_ema, lpips_func, args, device)
                print(f'{i}/{args.iter}: lpips: {lpips_value.cpu().numpy()[0][0][0][0]}')

            if i and i % args.save_freq == 0:
                torch.save(
                    {
                        'g': g_module.state_dict(),
                        'd': d_module.state_dict(),
                        'g_ema': g_ema.state_dict(),
                        'g_optim': g_optim.state_dict(),
                        'd_optim': d_optim.state_dict(),
                    },
                    f'{args.ckpt}/{str(i).zfill(6)}.pth',
                )


if __name__ == '__main__':

    parser = argparse.ArgumentParser()

    parser.add_argument('--path', type=str, required=True)
    parser.add_argument('--base_dir', type=str, default='./')
    parser.add_argument('--iter', type=int, default=4000000)
    parser.add_argument('--batch', type=int, default=4)
    parser.add_argument('--size', type=int, default=256)
    parser.add_argument('--channel_multiplier', type=int, default=2)
    parser.add_argument('--narrow', type=float, default=1.0)
    parser.add_argument('--r1', type=float, default=10)
    parser.add_argument('--path_regularize', type=float, default=2)
    parser.add_argument('--path_batch_shrink', type=int, default=2)
    parser.add_argument('--d_reg_every', type=int, default=16)
    parser.add_argument('--g_reg_every', type=int, default=4)
    parser.add_argument('--save_freq', type=int, default=10000)
    parser.add_argument('--lr', type=float, default=0.002)
    parser.add_argument('--local_rank', type=int, default=0)
    parser.add_argument('--ckpt', type=str, default='ckpts')
    parser.add_argument('--pretrain', type=str, default=None)
    parser.add_argument('--sample', type=str, default='sample')
    parser.add_argument('--val_dir', type=str, default='val')

    args = parser.parse_args()

    os.makedirs(args.ckpt, exist_ok=True)
    os.makedirs(args.sample, exist_ok=True)

    device = 'cuda'

    n_gpu = int(os.environ['WORLD_SIZE']) if 'WORLD_SIZE' in os.environ else 1
    args.distributed = n_gpu > 1

    if args.distributed:
        torch.cuda.set_device(args.local_rank)
        torch.distributed.init_process_group(backend='nccl', init_method='env://')
        synchronize()

    args.latent = 512
    args.n_mlp = 8

    args.start_iter = 0

    generator = FullGenerator(
        args.size, args.latent, args.n_mlp, channel_multiplier=args.channel_multiplier, narrow=args.narrow, device=device
    ).to(device)
    discriminator = Discriminator(
        args.size, channel_multiplier=args.channel_multiplier, narrow=args.narrow, device=device
    ).to(device)
    g_ema = FullGenerator(
        args.size, args.latent, args.n_mlp, channel_multiplier=args.channel_multiplier, narrow=args.narrow, device=device
    ).to(device)
    g_ema.eval()
    accumulate(g_ema, generator, 0)

    g_reg_ratio = args.g_reg_every / (args.g_reg_every + 1)
    d_reg_ratio = args.d_reg_every / (args.d_reg_every + 1)
    
    g_optim = optim.Adam(
        generator.parameters(),
        lr=args.lr * g_reg_ratio,
        betas=(0 ** g_reg_ratio, 0.99 ** g_reg_ratio),
    )

    d_optim = optim.Adam(
        discriminator.parameters(),
        lr=args.lr * d_reg_ratio,
        betas=(0 ** d_reg_ratio, 0.99 ** d_reg_ratio),
    )

    if args.pretrain is not None:
        print('load model:', args.pretrain)
        
        ckpt = torch.load(args.pretrain)

        generator.load_state_dict(ckpt['g'])
        discriminator.load_state_dict(ckpt['d'])
        g_ema.load_state_dict(ckpt['g_ema'])
            
        g_optim.load_state_dict(ckpt['g_optim'])
        d_optim.load_state_dict(ckpt['d_optim'])
    
    smooth_l1_loss = torch.nn.SmoothL1Loss().to(device)
    id_loss = IDLoss(args.base_dir, device, ckpt_dict=None)
    lpips_func = lpips.LPIPS(net='alex',version='0.1').to(device)
    
    if args.distributed:
        generator = nn.parallel.DistributedDataParallel(
            generator,
            device_ids=[args.local_rank],
            output_device=args.local_rank,
            broadcast_buffers=False,
        )

        discriminator = nn.parallel.DistributedDataParallel(
            discriminator,
            device_ids=[args.local_rank],
            output_device=args.local_rank,
            broadcast_buffers=False,
        )

        id_loss = nn.parallel.DistributedDataParallel(
            id_loss,
            device_ids=[args.local_rank],
            output_device=args.local_rank,
            broadcast_buffers=False,
        )

    dataset = FaceDataset(args.path, args.size)
    loader = data.DataLoader(
        dataset,
        batch_size=args.batch,
        sampler=data_sampler(dataset, shuffle=True, distributed=args.distributed),
        drop_last=True,
    )

    train(args, loader, generator, discriminator, [smooth_l1_loss, id_loss], g_optim, d_optim, g_ema, lpips_func, device)