"""Optimizer registry and factory for instantiating optimizers."""

from typing import Dict, Type, Callable, Any
import torch.optim as optim
from taoTrain.core.base import BaseModel
from taoTrain.config import TrainingConfig, OptimizerEnum


# Global registry for optimizers
_OPTIMIZER_REGISTRY: Dict[str, Callable] = {}


def register_optimizer(name: str):
    """
    Decorator to register a custom optimizer factory function.
    
    Args:
        name: Name of the optimizer (e.g., 'adamw', 'adam', 'sgd')
    """
    def decorator(fn: Callable) -> Callable:
        if name in _OPTIMIZER_REGISTRY:
            raise ValueError(f"Optimizer '{name}' is already registered")
        _OPTIMIZER_REGISTRY[name] = fn
        return fn
    return decorator


def get_registered_optimizers() -> Dict[str, Callable]:
    """Get all registered optimizer factory functions."""
    return _OPTIMIZER_REGISTRY.copy()


def get_optimizer(
    model: BaseModel,
    config: TrainingConfig,
) -> optim.Optimizer:
    """
    Create an optimizer instance from config.
    
    Args:
        model: Model to optimize
        config: TrainingConfig with optimizer configuration
    
    Returns:
        Optimizer instance
    
    Raises:
        ValueError: If optimizer type is not registered
    """
    # Handle both enum and string values
    optimizer_type = config.optimizer.optimizer_type
    if isinstance(optimizer_type, str):
        optimizer_name = optimizer_type
    else:
        optimizer_name = optimizer_type.value
    
    if optimizer_name not in _OPTIMIZER_REGISTRY:
        raise ValueError(
            f"Unknown optimizer: {optimizer_name}. "
            f"Available: {list(_OPTIMIZER_REGISTRY.keys())}"
        )
    
    factory_fn = _OPTIMIZER_REGISTRY[optimizer_name]
    return factory_fn(model, config)


def register_builtin_optimizers():
    """Register all built-in optimizers."""
    # Import here to trigger decorator registration (avoid circular imports)
    from . import adamw  # noqa: F401
    from . import adam  # noqa: F401
    from . import sgd  # noqa: F401
    from . import hybrid_muon_adamw  # noqa: F401


# Auto-register built-in optimizers when module is imported
register_builtin_optimizers()