# File: diffusion-models-class-main/unit2/finetune_model.py
import wandb
import numpy as np
import torch, torchvision
import torch.nn.functional as F
from PIL import Image
from tqdm.auto import tqdm
from fastcore.script import call_parse
from torchvision import transforms
from diffusers import DDPMPipeline
from diffusers import DDIMScheduler
from datasets import load_dataset
from matplotlib import pyplot as plt

@call_parse
def train(image_size=256, batch_size=16, grad_accumulation_steps=2, num_epochs=1, start_model='google/ddpm-bedroom-256', dataset_name='huggan/wikiart', device='cuda', model_save_name='wikiart_1e', wandb_project='dm_finetune', log_samples_every=250, save_model_every=2500):
    wandb.init(project=wandb_project, config=locals())
    image_pipe = DDPMPipeline.from_pretrained(start_model)
    image_pipe.to(device)
    sampling_scheduler = DDIMScheduler.from_config(start_model)
    sampling_scheduler.set_timesteps(num_inference_steps=50)
    dataset = load_dataset(dataset_name, split='train')
    preprocess = transforms.Compose([transforms.Resize((image_size, image_size)), transforms.RandomHorizontalFlip(), transforms.ToTensor(), transforms.Normalize([0.5], [0.5])])

    def transform(examples):
        images = [preprocess(image.convert('RGB')) for image in examples['image']]
        return {'images': images}
    dataset.set_transform(transform)
    train_dataloader = torch.utils.data.DataLoader(dataset, batch_size=batch_size, shuffle=True)
    optimizer = torch.optim.AdamW(image_pipe.unet.parameters(), lr=1e-05)
    scheduler = torch.optim.lr_scheduler.ExponentialLR(optimizer, gamma=0.9)
    for epoch in range(num_epochs):
        for (step, batch) in tqdm(enumerate(train_dataloader), total=len(train_dataloader)):
            clean_images = batch['images'].to(device)
            noise = torch.randn(clean_images.shape).to(clean_images.device)
            bs = clean_images.shape[0]
            timesteps = torch.randint(0, image_pipe.scheduler.num_train_timesteps, (bs,), device=clean_images.device).long()
            noisy_images = image_pipe.scheduler.add_noise(clean_images, noise, timesteps)
            noise_pred = image_pipe.unet(noisy_images, timesteps, return_dict=False)[0]
            loss = F.mse_loss(noise_pred, noise)
            wandb.log({'loss': loss.item()})
            loss.backward()
            if (step + 1) % grad_accumulation_steps == 0:
                optimizer.step()
                optimizer.zero_grad()
            if (step + 1) % log_samples_every == 0:
                x = torch.randn(8, 3, 256, 256).to(device)
                for (i, t) in tqdm(enumerate(sampling_scheduler.timesteps)):
                    model_input = sampling_scheduler.scale_model_input(x, t)
                    with torch.no_grad():
                        noise_pred = image_pipe.unet(model_input, t)['sample']
                    x = sampling_scheduler.step(noise_pred, t, x).prev_sample
                grid = torchvision.utils.make_grid(x, nrow=4)
                im = grid.permute(1, 2, 0).cpu().clip(-1, 1) * 0.5 + 0.5
                im = Image.fromarray(np.array(im * 255).astype(np.uint8))
                wandb.log({'Sample generations': wandb.Image(im)})
            if (step + 1) % save_model_every == 0:
                image_pipe.save_pretrained(model_save_name + f'step_{step + 1}')
        scheduler.step()
    image_pipe.save_pretrained(model_save_name)
    wandb.finish()