import os
from typing import Any, Dict, Optional

import torch
import torch.nn as nn


def save_checkpoint(
    path: str,
    model: nn.Module,
    optimizer: Optional[torch.optim.Optimizer] = None,
    epoch: int = 0,
    metrics: Optional[Dict[str, Any]] = None,
    config: Optional[Dict[str, Any]] = None,
) -> None:
    os.makedirs(os.path.dirname(path) or ".", exist_ok=True)
    state = {
        "epoch": epoch,
        "model_state_dict": model.state_dict(),
        "metrics": metrics or {},
    }
    if optimizer is not None:
        state["optimizer_state_dict"] = optimizer.state_dict()
    if config is not None:
        state["config"] = config
    torch.save(state, path)


def load_checkpoint(
    path: str,
    model: nn.Module,
    optimizer: Optional[torch.optim.Optimizer] = None,
    device: Optional[torch.device] = None,
) -> Dict[str, Any]:
    state = torch.load(path, map_location=device or "cpu", weights_only=False)
    model.load_state_dict(state["model_state_dict"])
    if optimizer is not None and "optimizer_state_dict" in state:
        optimizer.load_state_dict(state["optimizer_state_dict"])
    return state