"""This script demonstrates how to train Diffusion Policy on a real-world dataset."""

from pathlib import Path

import torch

from lerobot.configs.types import FeatureType
from lerobot.datasets.lerobot_dataset import LeRobotDataset, LeRobotDatasetMetadata
from lerobot.datasets.utils import dataset_to_policy_features
from lerobot.policies.diffusion.configuration_diffusion import DiffusionConfig
from lerobot.policies.diffusion.modeling_diffusion import DiffusionPolicy
from lerobot.policies.factory import make_pre_post_processors


def make_delta_timestamps(delta_indices: list[int] | None, fps: int) -> list[float]:
    if delta_indices is None:
        return [0]

    return [i / fps for i in delta_indices]


output_directory = Path("outputs/robot_learning_tutorial/diffusion")
output_directory.mkdir(parents=True, exist_ok=True)

# Select your device
device = torch.device("mps")  # or "cuda" or "cpu"

dataset_id = "lerobot/svla_so101_pickplace"

# This specifies the inputs the model will be expecting and the outputs it will produce
dataset_metadata = LeRobotDatasetMetadata(dataset_id)
features = dataset_to_policy_features(dataset_metadata.features)

output_features = {key: ft for key, ft in features.items() if ft.type is FeatureType.ACTION}
input_features = {key: ft for key, ft in features.items() if key not in output_features}

cfg = DiffusionConfig(input_features=input_features, output_features=output_features)
policy = DiffusionPolicy(cfg)
preprocessor, postprocessor = make_pre_post_processors(cfg, dataset_stats=dataset_metadata.stats)

policy.train()
policy.to(device)

# To perform action chunking, ACT expects a given number of actions as targets
delta_timestamps = {
    "observation.state": make_delta_timestamps(cfg.observation_delta_indices, dataset_metadata.fps),
    "action": make_delta_timestamps(cfg.action_delta_indices, dataset_metadata.fps),
}

# add image features if they are present
delta_timestamps |= {
    k: make_delta_timestamps(cfg.observation_delta_indices, dataset_metadata.fps) for k in cfg.image_features
}

# Instantiate the dataset
dataset = LeRobotDataset(dataset_id, delta_timestamps=delta_timestamps)

# Create the optimizer and dataloader for offline training
optimizer = cfg.get_optimizer_preset().build(policy.parameters())
batch_size = 32
dataloader = torch.utils.data.DataLoader(
    dataset,
    batch_size=batch_size,
    shuffle=True,
    pin_memory=device.type != "cpu",
    drop_last=True,
)

# Number of training steps and logging frequency
training_steps = 1
log_freq = 1

# Run training loop
step = 0
done = False
while not done:
    for batch in dataloader:
        batch = preprocessor(batch)
        loss, _ = policy.forward(batch)
        loss.backward()
        optimizer.step()
        optimizer.zero_grad()

        if step % log_freq == 0:
            print(f"step: {step} loss: {loss.item():.3f}")
        step += 1
        if step >= training_steps:
            done = True
            break

# Save the policy checkpoint, alongside the pre/post processors
policy.save_pretrained(output_directory)
preprocessor.save_pretrained(output_directory)
postprocessor.save_pretrained(output_directory)

# Save all assets to the Hub
policy.push_to_hub("fracapuano/robot_learning_tutorial_diffusion")
preprocessor.push_to_hub("fracapuano/robot_learning_tutorial_diffusion")
postprocessor.push_to_hub("fracapuano/robot_learning_tutorial_diffusion")