import importlib.util
import logging
import os
import random
import sys

import numpy as np
import torch


def load_config(config_path):
    """Load configuration from a Python file.

    Args:
        config_path (str): Path to the configuration file.

    Returns:
        dict: The loaded configuration dictionary.
    """
    try:
        config_path = os.path.abspath(config_path)
        if not os.path.exists(config_path):
            print(f"Error: Config file not found at {config_path}")
            sys.exit(1)

        # Derive module path from file path relative to workspace root
        workspace_root = os.path.abspath(os.getcwd())
        relative_path = os.path.relpath(config_path, workspace_root)
        if relative_path.startswith(".."):
            print(f"Error: Config file {config_path} is outside the project directory.")
            sys.exit(1)

        module_path_no_ext, _ = os.path.splitext(relative_path)
        module_path_str = module_path_no_ext.replace(os.sep, ".")

        print(f"Attempting to import config module: {module_path_str}")
        config_module = importlib.import_module(module_path_str)
        config = config_module.config

        print(
            f"Loaded configuration from: {config_path} (via module {module_path_str})"
        )
        return config

    except ImportError as e:
        print(f"Error importing config module '{module_path_str}': {e}")
        print(
            "Ensure the config file path is correct and relative imports within it are valid."
        )
        import traceback

        traceback.print_exc()
        sys.exit(1)
    except AttributeError as e:
        print(
            f"Error: Could not find 'config' dictionary in module {module_path_str}. {e}"
        )
        sys.exit(1)
    except Exception as e:
        print(f"Error loading configuration file {config_path}: {e}")
        import traceback

        traceback.print_exc()
        sys.exit(1)


def setup_environment(config):
    """Set up the environment based on configuration.

    Args:
        config (dict): Configuration dictionary.

    Returns:
        tuple: (output_path, device) - the output directory path and torch device.
    """
    # Setup output directory
    output_dir = config.get("output_dir", "outputs")
    config_name = config.get("config_name", "default_run")
    output_path = os.path.join(output_dir, config_name)
    os.makedirs(output_path, exist_ok=True)

    # Set random seeds
    seed = config.get("seed", 42)
    random.seed(seed)
    np.random.seed(seed)
    torch.manual_seed(seed)
    if torch.cuda.is_available():
        torch.cuda.manual_seed_all(seed)
    logging.info(f"Set random seed to: {seed}")

    # Setup device
    device_name = config.get("device", "cuda")
    if device_name == "cuda" and not torch.cuda.is_available():
        logging.warning("CUDA requested but not available, falling back to CPU.")
        device_name = "cpu"
    device = torch.device(device_name)
    logging.info(f"Using device: {device}")

    return output_path, device


def load_checkpoint(
    checkpoint_path,
    model,
    device,
    load_optimizer=False,
    optimizer=None,
    load_scheduler=False,
    scheduler=None,
):
    """Load a checkpoint into the model and optionally optimizer and scheduler.

    Args:
        checkpoint_path (str): Path to the checkpoint file.
        model (torch.nn.Module): The model to load the weights into.
        device (torch.device): The device to load the checkpoint on.
        load_optimizer (bool): Whether to load optimizer state.
        optimizer (torch.optim.Optimizer, optional): The optimizer to load state into.
        load_scheduler (bool): Whether to load scheduler state.
        scheduler (torch.optim.lr_scheduler._LRScheduler, optional): The scheduler to load state into.

    Returns:
        dict: The loaded checkpoint.
        int: The starting epoch (checkpoint epoch + 1).
    """
    try:
        logging.info(f"Loading checkpoint from: {checkpoint_path}")
        checkpoint = torch.load(checkpoint_path, map_location=device)

        # Handle potential DataParallel prefix
        state_dict = checkpoint.get("model_state_dict", checkpoint)
        if isinstance(state_dict, dict):
            # Handle case where model was trained with DataParallel
            if all(k.startswith("module.") for k in state_dict.keys()):
                logging.info(
                    "Detected DataParallel checkpoint, removing 'module.' prefix"
                )
                state_dict = {
                    k.replace("module.", ""): v for k, v in state_dict.items()
                }

            model.load_state_dict(state_dict)
            logging.info("Model state loaded successfully")

            # Load optimizer state if requested
            if (
                load_optimizer
                and optimizer is not None
                and "optimizer_state_dict" in checkpoint
            ):
                optimizer.load_state_dict(checkpoint["optimizer_state_dict"])
                logging.info("Optimizer state loaded successfully")

            # Load scheduler state if requested
            if (
                load_scheduler
                and scheduler is not None
                and "scheduler_state_dict" in checkpoint
            ):
                scheduler.load_state_dict(checkpoint["scheduler_state_dict"])
                logging.info("Scheduler state loaded successfully")

            # Get the epoch number
            start_epoch = checkpoint.get("epoch", 0) + 1 if load_optimizer else 0
            if "epoch" in checkpoint:
                logging.info(f"Loaded checkpoint from epoch: {checkpoint['epoch']}")

            return checkpoint, start_epoch
        else:
            logging.error("Checkpoint does not contain a valid state dictionary.")
            sys.exit(1)
    except Exception as e:
        logging.error(f"Error loading checkpoint: {e}", exc_info=True)
        sys.exit(1)


def check_data_path(data_root):
    """Check if the data path exists and is valid.

    Args:
        data_root (str): Path to the data directory.
    """
    if not data_root or not os.path.isdir(data_root):
        logging.error(f"Data root directory not found or not specified: {data_root}")
        sys.exit(1)