import argparse
import logging
import math
import os
from pathlib import Path

import jax
import jax.numpy as jnp
import numpy as np
import optax
import torch
import torch.utils.checkpoint
import transformers
from flax import jax_utils
from flax.training import train_state
from flax.training.common_utils import shard
from huggingface_hub import create_repo, upload_folder
from huggingface_hub.utils import insecure_hashlib
from jax.experimental.compilation_cache import compilation_cache as cc
from PIL import Image
from torch.utils.data import Dataset
from torchvision import transforms
from tqdm.auto import tqdm
from transformers import CLIPImageProcessor, CLIPTokenizer, FlaxCLIPTextModel, set_seed

from diffusers import (
    FlaxAutoencoderKL,
    FlaxDDPMScheduler,
    FlaxPNDMScheduler,
    FlaxStableDiffusionPipeline,
    FlaxUNet2DConditionModel,
)
from diffusers.pipelines.stable_diffusion import FlaxStableDiffusionSafetyChecker
from diffusers.utils import check_min_version


# Will error if the minimal version of diffusers is not installed. Remove at your own risks.
check_min_version("0.26.0.dev0")

# Cache compiled models across invocations of this script.
cc.initialize_cache(os.path.expanduser("~/.cache/jax/compilation_cache"))

logger = logging.getLogger(__name__)


def parse_args():
    parser = argparse.ArgumentParser(description="Simple example of a training script.")
    parser.add_argument(
        "--pretrained_model_name_or_path",
        type=str,
        default=None,
        required=True,
        help="Path to pretrained model or model identifier from huggingface.co/models.",
    )
    parser.add_argument(
        "--pretrained_vae_name_or_path",
        type=str,
        default=None,
        help="Path to pretrained vae or vae identifier from huggingface.co/models.",
    )
    parser.add_argument(
        "--revision",
        type=str,
        default=None,
        required=False,
        help="Revision of pretrained model identifier from huggingface.co/models.",
    )
    parser.add_argument(
        "--tokenizer_name",
        type=str,
        default=None,
        help="Pretrained tokenizer name or path if not the same as model_name",
    )
    parser.add_argument(
        "--instance_data_dir",
        type=str,
        default=None,
        required=True,
        help="A folder containing the training data of instance images.",
    )
    parser.add_argument(
        "--class_data_dir",
        type=str,
        default=None,
        required=False,
        help="A folder containing the training data of class images.",
    )
    parser.add_argument(
        "--instance_prompt",
        type=str,
        default=None,
        help="The prompt with identifier specifying the instance",
    )
    parser.add_argument(
        "--class_prompt",
        type=str,
        default=None,
        help="The prompt to specify images in the same class as provided instance images.",
    )
    parser.add_argument(
        "--with_prior_preservation",
        default=False,
        action="store_true",
        help="Flag to add prior preservation loss.",
    )
    parser.add_argument("--prior_loss_weight", type=float, default=1.0, help="The weight of prior preservation loss.")
    parser.add_argument(
        "--num_class_images",
        type=int,
        default=100,
        help=(
            "Minimal class images for prior preservation loss. If there are not enough images already present in"
            " class_data_dir, additional images will be sampled with class_prompt."
        ),
    )
    parser.add_argument(
        "--output_dir",
        type=str,
        default="text-inversion-model",
        help="The output directory where the model predictions and checkpoints will be written.",
    )
    parser.add_argument("--save_steps", type=int, default=None, help="Save a checkpoint every X steps.")
    parser.add_argument("--seed", type=int, default=0, help="A seed for reproducible training.")
    parser.add_argument(
        "--resolution",
        type=int,
        default=512,
        help=(
            "The resolution for input images, all the images in the train/validation dataset will be resized to this"
            " resolution"
        ),
    )
    parser.add_argument(
        "--center_crop",
        default=False,
        action="store_true",
        help=(
            "Whether to center crop the input images to the resolution. If not set, the images will be randomly"
            " cropped. The images will be resized to the resolution first before cropping."
        ),
    )
    parser.add_argument("--train_text_encoder", action="store_true", help="Whether to train the text encoder")
    parser.add_argument(
        "--train_batch_size", type=int, default=4, help="Batch size (per device) for the training dataloader."
    )
    parser.add_argument(
        "--sample_batch_size", type=int, default=4, help="Batch size (per device) for sampling images."
    )
    parser.add_argument("--num_train_epochs", type=int, default=1)
    parser.add_argument(
        "--max_train_steps",
        type=int,
        default=None,
        help="Total number of training steps to perform.  If provided, overrides num_train_epochs.",
    )
    parser.add_argument(
        "--learning_rate",
        type=float,
        default=5e-6,
        help="Initial learning rate (after the potential warmup period) to use.",
    )
    parser.add_argument(
        "--scale_lr",
        action="store_true",
        default=False,
        help="Scale the learning rate by the number of GPUs, gradient accumulation steps, and batch size.",
    )
    parser.add_argument("--adam_beta1", type=float, default=0.9, help="The beta1 parameter for the Adam optimizer.")
    parser.add_argument("--adam_beta2", type=float, default=0.999, help="The beta2 parameter for the Adam optimizer.")
    parser.add_argument("--adam_weight_decay", type=float, default=1e-2, help="Weight decay to use.")
    parser.add_argument("--adam_epsilon", type=float, default=1e-08, help="Epsilon value for the Adam optimizer")
    parser.add_argument("--max_grad_norm", default=1.0, type=float, help="Max gradient norm.")
    parser.add_argument("--push_to_hub", action="store_true", help="Whether or not to push the model to the Hub.")
    parser.add_argument("--hub_token", type=str, default=None, help="The token to use to push to the Model Hub.")
    parser.add_argument(
        "--hub_model_id",
        type=str,
        default=None,
        help="The name of the repository to keep in sync with the local `output_dir`.",
    )
    parser.add_argument(
        "--logging_dir",
        type=str,
        default="logs",
        help=(
            "[TensorBoard](https://www.tensorflow.org/tensorboard) log directory. Will default to"
            " *output_dir/runs/**CURRENT_DATETIME_HOSTNAME***."
        ),
    )
    parser.add_argument(
        "--mixed_precision",
        type=str,
        default="no",
        choices=["no", "fp16", "bf16"],
        help=(
            "Whether to use mixed precision. Choose"
            "between fp16 and bf16 (bfloat16). Bf16 requires PyTorch >= 1.10."
            "and an Nvidia Ampere GPU."
        ),
    )
    parser.add_argument("--local_rank", type=int, default=-1, help="For distributed training: local_rank")

    args = parser.parse_args()
    env_local_rank = int(os.environ.get("LOCAL_RANK", -1))
    if env_local_rank != -1 and env_local_rank != args.local_rank:
        args.local_rank = env_local_rank

    if args.instance_data_dir is None:
        raise ValueError("You must specify a train data directory.")

    if args.with_prior_preservation:
        if args.class_data_dir is None:
            raise ValueError("You must specify a data directory for class images.")
        if args.class_prompt is None:
            raise ValueError("You must specify prompt for class images.")

    return args


class DreamBoothDataset(Dataset):
    """
    A dataset to prepare the instance and class images with the prompts for fine-tuning the model.
    It pre-processes the images and the tokenizes prompts.
    """

    def __init__(
        self,
        instance_data_root,
        instance_prompt,
        tokenizer,
        class_data_root=None,
        class_prompt=None,
        class_num=None,
        size=512,
        center_crop=False,
    ):
        self.size = size
        self.center_crop = center_crop
        self.tokenizer = tokenizer

        self.instance_data_root = Path(instance_data_root)
        if not self.instance_data_root.exists():
            raise ValueError("Instance images root doesn't exists.")

        self.instance_images_path = list(Path(instance_data_root).iterdir())
        self.num_instance_images = len(self.instance_images_path)
        self.instance_prompt = instance_prompt
        self._length = self.num_instance_images

        if class_data_root is not None:
            self.class_data_root = Path(class_data_root)
            self.class_data_root.mkdir(parents=True, exist_ok=True)
            self.class_images_path = list(self.class_data_root.iterdir())
            if class_num is not None:
                self.num_class_images = min(len(self.class_images_path), class_num)
            else:
                self.num_class_images = len(self.class_images_path)
            self._length = max(self.num_class_images, self.num_instance_images)
            self.class_prompt = class_prompt
        else:
            self.class_data_root = None

        self.image_transforms = transforms.Compose(
            [
                transforms.Resize(size, interpolation=transforms.InterpolationMode.BILINEAR),
                transforms.CenterCrop(size) if center_crop else transforms.RandomCrop(size),
                transforms.ToTensor(),
                transforms.Normalize([0.5], [0.5]),
            ]
        )

    def __len__(self):
        return self._length

    def __getitem__(self, index):
        example = {}
        instance_image = Image.open(self.instance_images_path[index % self.num_instance_images])
        if not instance_image.mode == "RGB":
            instance_image = instance_image.convert("RGB")
        example["instance_images"] = self.image_transforms(instance_image)
        example["instance_prompt_ids"] = self.tokenizer(
            self.instance_prompt,
            padding="do_not_pad",
            truncation=True,
            max_length=self.tokenizer.model_max_length,
        ).input_ids

        if self.class_data_root:
            class_image = Image.open(self.class_images_path[index % self.num_class_images])
            if not class_image.mode == "RGB":
                class_image = class_image.convert("RGB")
            example["class_images"] = self.image_transforms(class_image)
            example["class_prompt_ids"] = self.tokenizer(
                self.class_prompt,
                padding="do_not_pad",
                truncation=True,
                max_length=self.tokenizer.model_max_length,
            ).input_ids

        return example


class PromptDataset(Dataset):
    "A simple dataset to prepare the prompts to generate class images on multiple GPUs."

    def __init__(self, prompt, num_samples):
        self.prompt = prompt
        self.num_samples = num_samples

    def __len__(self):
        return self.num_samples

    def __getitem__(self, index):
        example = {}
        example["prompt"] = self.prompt
        example["index"] = index
        return example


def get_params_to_save(params):
    return jax.device_get(jax.tree_util.tree_map(lambda x: x[0], params))


def main():
    args = parse_args()

    logging.basicConfig(
        format="%(asctime)s - %(levelname)s - %(name)s - %(message)s",
        datefmt="%m/%d/%Y %H:%M:%S",
        level=logging.INFO,
    )
    # Setup logging, we only want one process per machine to log things on the screen.
    logger.setLevel(logging.INFO if jax.process_index() == 0 else logging.ERROR)
    if jax.process_index() == 0:
        transformers.utils.logging.set_verbosity_info()
    else:
        transformers.utils.logging.set_verbosity_error()

    if args.seed is not None:
        set_seed(args.seed)

    rng = jax.random.PRNGKey(args.seed)

    if args.with_prior_preservation:
        class_images_dir = Path(args.class_data_dir)
        if not class_images_dir.exists():
            class_images_dir.mkdir(parents=True)
        cur_class_images = len(list(class_images_dir.iterdir()))

        if cur_class_images < args.num_class_images:
            pipeline, params = FlaxStableDiffusionPipeline.from_pretrained(
                args.pretrained_model_name_or_path, safety_checker=None, revision=args.revision
            )
            pipeline.set_progress_bar_config(disable=True)

            num_new_images = args.num_class_images - cur_class_images
            logger.info(f"Number of class images to sample: {num_new_images}.")

            sample_dataset = PromptDataset(args.class_prompt, num_new_images)
            total_sample_batch_size = args.sample_batch_size * jax.local_device_count()
            sample_dataloader = torch.utils.data.DataLoader(sample_dataset, batch_size=total_sample_batch_size)

            for example in tqdm(
                sample_dataloader, desc="Generating class images", disable=not jax.process_index() == 0
            ):
                prompt_ids = pipeline.prepare_inputs(example["prompt"])
                prompt_ids = shard(prompt_ids)
                p_params = jax_utils.replicate(params)
                rng = jax.random.split(rng)[0]
                sample_rng = jax.random.split(rng, jax.device_count())
                images = pipeline(prompt_ids, p_params, sample_rng, jit=True).images
                images = images.reshape((images.shape[0] * images.shape[1],) + images.shape[-3:])
                images = pipeline.numpy_to_pil(np.array(images))

                for i, image in enumerate(images):
                    hash_image = insecure_hashlib.sha1(image.tobytes()).hexdigest()
                    image_filename = class_images_dir / f"{example['index'][i] + cur_class_images}-{hash_image}.jpg"
                    image.save(image_filename)

            del pipeline

    # Handle the repository creation
    if jax.process_index() == 0:
        if args.output_dir is not None:
            os.makedirs(args.output_dir, exist_ok=True)

        if args.push_to_hub:
            repo_id = create_repo(
                repo_id=args.hub_model_id or Path(args.output_dir).name, exist_ok=True, token=args.hub_token
            ).repo_id

    # Load the tokenizer and add the placeholder token as a additional special token
    if args.tokenizer_name:
        tokenizer = CLIPTokenizer.from_pretrained(args.tokenizer_name)
    elif args.pretrained_model_name_or_path:
        tokenizer = CLIPTokenizer.from_pretrained(
            args.pretrained_model_name_or_path, subfolder="tokenizer", revision=args.revision
        )
    else:
        raise NotImplementedError("No tokenizer specified!")

    train_dataset = DreamBoothDataset(
        instance_data_root=args.instance_data_dir,
        instance_prompt=args.instance_prompt,
        class_data_root=args.class_data_dir if args.with_prior_preservation else None,
        class_prompt=args.class_prompt,
        class_num=args.num_class_images,
        tokenizer=tokenizer,
        size=args.resolution,
        center_crop=args.center_crop,
    )

    def collate_fn(examples):
        input_ids = [example["instance_prompt_ids"] for example in examples]
        pixel_values = [example["instance_images"] for example in examples]

        # Concat class and instance examples for prior preservation.
        # We do this to avoid doing two forward passes.
        if args.with_prior_preservation:
            input_ids += [example["class_prompt_ids"] for example in examples]
            pixel_values += [example["class_images"] for example in examples]

        pixel_values = torch.stack(pixel_values)
        pixel_values = pixel_values.to(memory_format=torch.contiguous_format).float()

        input_ids = tokenizer.pad(
            {"input_ids": input_ids}, padding="max_length", max_length=tokenizer.model_max_length, return_tensors="pt"
        ).input_ids

        batch = {
            "input_ids": input_ids,
            "pixel_values": pixel_values,
        }
        batch = {k: v.numpy() for k, v in batch.items()}
        return batch

    total_train_batch_size = args.train_batch_size * jax.local_device_count()
    if len(train_dataset) < total_train_batch_size:
        raise ValueError(
            f"Training batch size is {total_train_batch_size}, but your dataset only contains"
            f" {len(train_dataset)} images. Please, use a larger dataset or reduce the effective batch size. Note that"
            f" there are {jax.local_device_count()} parallel devices, so your batch size can't be smaller than that."
        )

    train_dataloader = torch.utils.data.DataLoader(
        train_dataset, batch_size=total_train_batch_size, shuffle=True, collate_fn=collate_fn, drop_last=True
    )

    weight_dtype = jnp.float32
    if args.mixed_precision == "fp16":
        weight_dtype = jnp.float16
    elif args.mixed_precision == "bf16":
        weight_dtype = jnp.bfloat16

    if args.pretrained_vae_name_or_path:
        # TODO(patil-suraj): Upload flax weights for the VAE
        vae_arg, vae_kwargs = (args.pretrained_vae_name_or_path, {"from_pt": True})
    else:
        vae_arg, vae_kwargs = (args.pretrained_model_name_or_path, {"subfolder": "vae", "revision": args.revision})

    # Load models and create wrapper for stable diffusion
    text_encoder = FlaxCLIPTextModel.from_pretrained(
        args.pretrained_model_name_or_path,
        subfolder="text_encoder",
        dtype=weight_dtype,
        revision=args.revision,
    )
    vae, vae_params = FlaxAutoencoderKL.from_pretrained(
        vae_arg,
        dtype=weight_dtype,
        **vae_kwargs,
    )
    unet, unet_params = FlaxUNet2DConditionModel.from_pretrained(
        args.pretrained_model_name_or_path,
        subfolder="unet",
        dtype=weight_dtype,
        revision=args.revision,
    )

    # Optimization
    if args.scale_lr:
        args.learning_rate = args.learning_rate * total_train_batch_size

    constant_scheduler = optax.constant_schedule(args.learning_rate)

    adamw = optax.adamw(
        learning_rate=constant_scheduler,
        b1=args.adam_beta1,
        b2=args.adam_beta2,
        eps=args.adam_epsilon,
        weight_decay=args.adam_weight_decay,
    )

    optimizer = optax.chain(
        optax.clip_by_global_norm(args.max_grad_norm),
        adamw,
    )

    unet_state = train_state.TrainState.create(apply_fn=unet.__call__, params=unet_params, tx=optimizer)
    text_encoder_state = train_state.TrainState.create(
        apply_fn=text_encoder.__call__, params=text_encoder.params, tx=optimizer
    )

    noise_scheduler = FlaxDDPMScheduler(
        beta_start=0.00085, beta_end=0.012, beta_schedule="scaled_linear", num_train_timesteps=1000
    )
    noise_scheduler_state = noise_scheduler.create_state()

    # Initialize our training
    train_rngs = jax.random.split(rng, jax.local_device_count())

    def train_step(unet_state, text_encoder_state, vae_params, batch, train_rng):
        dropout_rng, sample_rng, new_train_rng = jax.random.split(train_rng, 3)

        if args.train_text_encoder:
            params = {"text_encoder": text_encoder_state.params, "unet": unet_state.params}
        else:
            params = {"unet": unet_state.params}

        def compute_loss(params):
            # Convert images to latent space
            vae_outputs = vae.apply(
                {"params": vae_params}, batch["pixel_values"], deterministic=True, method=vae.encode
            )
            latents = vae_outputs.latent_dist.sample(sample_rng)
            # (NHWC) -> (NCHW)
            latents = jnp.transpose(latents, (0, 3, 1, 2))
            latents = latents * vae.config.scaling_factor

            # Sample noise that we'll add to the latents
            noise_rng, timestep_rng = jax.random.split(sample_rng)
            noise = jax.random.normal(noise_rng, latents.shape)
            # Sample a random timestep for each image
            bsz = latents.shape[0]
            timesteps = jax.random.randint(
                timestep_rng,
                (bsz,),
                0,
                noise_scheduler.config.num_train_timesteps,
            )

            # Add noise to the latents according to the noise magnitude at each timestep
            # (this is the forward diffusion process)
            noisy_latents = noise_scheduler.add_noise(noise_scheduler_state, latents, noise, timesteps)

            # Get the text embedding for conditioning
            if args.train_text_encoder:
                encoder_hidden_states = text_encoder_state.apply_fn(
                    batch["input_ids"], params=params["text_encoder"], dropout_rng=dropout_rng, train=True
                )[0]
            else:
                encoder_hidden_states = text_encoder(
                    batch["input_ids"], params=text_encoder_state.params, train=False
                )[0]

            # Predict the noise residual
            model_pred = unet.apply(
                {"params": params["unet"]}, noisy_latents, timesteps, encoder_hidden_states, train=True
            ).sample

            # Get the target for loss depending on the prediction type
            if noise_scheduler.config.prediction_type == "epsilon":
                target = noise
            elif noise_scheduler.config.prediction_type == "v_prediction":
                target = noise_scheduler.get_velocity(noise_scheduler_state, latents, noise, timesteps)
            else:
                raise ValueError(f"Unknown prediction type {noise_scheduler.config.prediction_type}")

            if args.with_prior_preservation:
                # Chunk the noise and noise_pred into two parts and compute the loss on each part separately.
                model_pred, model_pred_prior = jnp.split(model_pred, 2, axis=0)
                target, target_prior = jnp.split(target, 2, axis=0)

                # Compute instance loss
                loss = (target - model_pred) ** 2
                loss = loss.mean()

                # Compute prior loss
                prior_loss = (target_prior - model_pred_prior) ** 2
                prior_loss = prior_loss.mean()

                # Add the prior loss to the instance loss.
                loss = loss + args.prior_loss_weight * prior_loss
            else:
                loss = (target - model_pred) ** 2
                loss = loss.mean()

            return loss

        grad_fn = jax.value_and_grad(compute_loss)
        loss, grad = grad_fn(params)
        grad = jax.lax.pmean(grad, "batch")

        new_unet_state = unet_state.apply_gradients(grads=grad["unet"])
        if args.train_text_encoder:
            new_text_encoder_state = text_encoder_state.apply_gradients(grads=grad["text_encoder"])
        else:
            new_text_encoder_state = text_encoder_state

        metrics = {"loss": loss}
        metrics = jax.lax.pmean(metrics, axis_name="batch")

        return new_unet_state, new_text_encoder_state, metrics, new_train_rng

    # Create parallel version of the train step
    p_train_step = jax.pmap(train_step, "batch", donate_argnums=(0, 1))

    # Replicate the train state on each device
    unet_state = jax_utils.replicate(unet_state)
    text_encoder_state = jax_utils.replicate(text_encoder_state)
    vae_params = jax_utils.replicate(vae_params)

    # Train!
    num_update_steps_per_epoch = math.ceil(len(train_dataloader))

    # Scheduler and math around the number of training steps.
    if args.max_train_steps is None:
        args.max_train_steps = args.num_train_epochs * num_update_steps_per_epoch

    args.num_train_epochs = math.ceil(args.max_train_steps / num_update_steps_per_epoch)

    logger.info("***** Running training *****")
    logger.info(f"  Num examples = {len(train_dataset)}")
    logger.info(f"  Num Epochs = {args.num_train_epochs}")
    logger.info(f"  Instantaneous batch size per device = {args.train_batch_size}")
    logger.info(f"  Total train batch size (w. parallel & distributed) = {total_train_batch_size}")
    logger.info(f"  Total optimization steps = {args.max_train_steps}")

    def checkpoint(step=None):
        # Create the pipeline using the trained modules and save it.
        scheduler, _ = FlaxPNDMScheduler.from_pretrained("CompVis/stable-diffusion-v1-4", subfolder="scheduler")
        safety_checker = FlaxStableDiffusionSafetyChecker.from_pretrained(
            "CompVis/stable-diffusion-safety-checker", from_pt=True
        )
        pipeline = FlaxStableDiffusionPipeline(
            text_encoder=text_encoder,
            vae=vae,
            unet=unet,
            tokenizer=tokenizer,
            scheduler=scheduler,
            safety_checker=safety_checker,
            feature_extractor=CLIPImageProcessor.from_pretrained("openai/clip-vit-base-patch32"),
        )

        outdir = os.path.join(args.output_dir, str(step)) if step else args.output_dir
        pipeline.save_pretrained(
            outdir,
            params={
                "text_encoder": get_params_to_save(text_encoder_state.params),
                "vae": get_params_to_save(vae_params),
                "unet": get_params_to_save(unet_state.params),
                "safety_checker": safety_checker.params,
            },
        )

        if args.push_to_hub:
            message = f"checkpoint-{step}" if step is not None else "End of training"
            upload_folder(
                repo_id=repo_id,
                folder_path=args.output_dir,
                commit_message=message,
                ignore_patterns=["step_*", "epoch_*"],
            )

    global_step = 0

    epochs = tqdm(range(args.num_train_epochs), desc="Epoch ... ", position=0)
    for epoch in epochs:
        # ======================== Training ================================

        train_metrics = []

        steps_per_epoch = len(train_dataset) // total_train_batch_size
        train_step_progress_bar = tqdm(total=steps_per_epoch, desc="Training...", position=1, leave=False)
        # train
        for batch in train_dataloader:
            batch = shard(batch)
            unet_state, text_encoder_state, train_metric, train_rngs = p_train_step(
                unet_state, text_encoder_state, vae_params, batch, train_rngs
            )
            train_metrics.append(train_metric)

            train_step_progress_bar.update(jax.local_device_count())

            global_step += 1
            if jax.process_index() == 0 and args.save_steps and global_step % args.save_steps == 0:
                checkpoint(global_step)
            if global_step >= args.max_train_steps:
                break

        train_metric = jax_utils.unreplicate(train_metric)

        train_step_progress_bar.close()
        epochs.write(f"Epoch... ({epoch + 1}/{args.num_train_epochs} | Loss: {train_metric['loss']})")

    if jax.process_index() == 0:
        checkpoint()


if __name__ == "__main__":
    main()
