"""Utils for training/fine-tuning scripts."""

import torch
import os
from .constants import ACTION_DIM, ACTION_TOKEN_BEGIN_IDX, IGNORE_INDEX


def get_current_action_mask(token_ids):
    # Create a tensor marking positions of IGNORE_INDEX
    newline_positions = token_ids != IGNORE_INDEX

    # Calculate cumulative sum to identify regions between newlines
    cumsum = torch.cumsum(newline_positions, dim=1)

    # Create the mask
    mask = (1 <= cumsum) & (cumsum <= ACTION_DIM)

    # Extract the action part only
    action_tokens_only_mask = token_ids > ACTION_TOKEN_BEGIN_IDX
    mask = action_tokens_only_mask * mask

    return mask


def get_next_actions_mask(token_ids):
    # Create a tensor marking positions of IGNORE_INDEX
    newline_positions = token_ids != IGNORE_INDEX

    # Calculate cumulative sum to identify regions between newlines
    cumsum = torch.cumsum(newline_positions, dim=1)

    # Create the mask
    mask = cumsum > ACTION_DIM

    # Extract the action part only
    action_tokens_only_mask = token_ids > ACTION_TOKEN_BEGIN_IDX
    mask = action_tokens_only_mask * mask

    return mask


def compute_token_accuracy(predicted_token_ids, ground_truth_token_ids, mask):
    correct_preds = (predicted_token_ids == ground_truth_token_ids) & mask
    accuracy = correct_preds.sum().float() / mask.sum().float()
    return accuracy


def compute_actions_l1_loss(action_tokenizer, predicted_token_ids, ground_truth_token_ids, mask):
    pred_continuous_actions = torch.tensor(
        action_tokenizer.decode_token_ids_to_actions(predicted_token_ids[mask].cpu().numpy())
    )
    true_continuous_actions = torch.tensor(
        action_tokenizer.decode_token_ids_to_actions(ground_truth_token_ids[mask].cpu().numpy())
    )
    l1_loss = torch.nn.functional.l1_loss(pred_continuous_actions, true_continuous_actions)
    return l1_loss

def find_checkpoint_file(pretrained_checkpoint, file_pattern) :
    """
    Find a specific checkpoint file matching a pattern.

    Args:
        pretrained_checkpoint: Path to the checkpoint directory
        file_pattern: String pattern to match in filenames

    Returns:
        str: Path to the matching checkpoint file

    Raises:
        AssertionError: If no files or multiple files match the pattern
    """
    assert os.path.isdir(pretrained_checkpoint), f"Checkpoint path must be a directory: {pretrained_checkpoint}"

    checkpoint_files = []
    for filename in os.listdir(pretrained_checkpoint):
        if file_pattern in filename and "checkpoint" in filename:
            full_path = os.path.join(pretrained_checkpoint, filename)
            checkpoint_files.append(full_path)

    assert len(checkpoint_files) == 1, (
        f"Expected exactly 1 {file_pattern} checkpoint but found {len(checkpoint_files)} in directory: {pretrained_checkpoint}"
    )

    return checkpoint_files[0]


def load_component_state_dict(checkpoint_path) :
    """
    Load a component's state dict from checkpoint and handle DDP prefix if present.

    Args:
        checkpoint_path: Path to the checkpoint file

    Returns:
        Dict: The processed state dictionary for loading
    """
    state_dict = torch.load(checkpoint_path, weights_only=True)

    # If the component was trained with DDP, elements in the state dict have prefix "module." which we must remove
    new_state_dict = {}
    for k, v in state_dict.items():
        if k.startswith("module."):
            new_state_dict[k[7:]] = v
        else:
            new_state_dict[k] = v

    return new_state_dict