"""Utility helper functions."""

import random
import torch
import numpy as np


def set_seed(seed: int) -> None:
    """Set random seed for reproducibility."""
    random.seed(seed)
    np.random.seed(seed)
    torch.manual_seed(seed)
    if torch.cuda.is_available():
        torch.cuda.manual_seed_all(seed)


def get_device(device_str: str = "cuda") -> torch.device:
    """
    Get torch device.
    
    Args:
        device_str: Device string ("cuda" or "cpu")
    
    Returns:
        torch.device instance
    """
    if device_str == "cuda" and torch.cuda.is_available():
        return torch.device("cuda")
    return torch.device("cpu")


def format_size(num_bytes: int) -> str:
    """Format bytes to human-readable size."""
    for unit in ["B", "KB", "MB", "GB"]:
        if num_bytes < 1024:
            return f"{num_bytes:.1f}{unit}"
        num_bytes /= 1024
    return f"{num_bytes:.1f}TB"


def count_parameters(model: torch.nn.Module) -> tuple[int, int]:
    """
    Count parameters in model.
    
    Args:
        model: PyTorch model
    
    Returns:
        Tuple of (total_params, trainable_params)
    """
    total_params = sum(p.numel() for p in model.parameters())
    trainable_params = sum(p.numel() for p in model.parameters() if p.requires_grad)
    return total_params, trainable_params


def get_dtype(dtype_str: str) -> torch.dtype:
    """
    Get torch dtype from string.
    
    Args:
        dtype_str: Dtype string (float32, float16, bfloat16)
    
    Returns:
        torch.dtype
    """
    dtype_map = {
        "float32": torch.float32,
        "float16": torch.float16,
        "bfloat16": torch.bfloat16,
    }
    return dtype_map.get(dtype_str, torch.float32)