"""Pipeline step handler registry.

Handlers are async functions: async def handler(tenant_id, task_id, step_name, input_data, config) -> output_data
Register via register_handler(step_type, fn).
Lookup via get_handler(step_type).
"""

import asyncio
import logging
from typing import Callable, Dict, Optional

logger = logging.getLogger("pipeline.handlers")

# step_type -> handler function
_HANDLERS: Dict[str, Callable] = {}


def register_handler(step_type: str, handler: Callable):
    """Register a step handler function.
    
    Args:
        step_type: matches pipeline_steps.step_type
        handler: async def handler(tenant_id, task_id, step_name, input_data, config) -> dict
    """
    _HANDLERS[step_type] = handler
    logger.info(f"Registered handler: {step_type}")


def get_handler(step_type: str) -> Optional[Callable]:
    """Get handler for a step type. Returns None if not registered."""
    return _HANDLERS.get(step_type)


def list_handlers() -> Dict[str, str]:
    """List all registered handlers. Returns {step_type: function_name}."""
    return {k: v.__name__ for k, v in _HANDLERS.items()}


async def default_handler(tenant_id: str, task_id: str, step_name: str, input_data: dict, config: dict) -> dict:
    """Default handler - passthrough for testing. Returns input as output."""
    logger.info(f"Default handler: step={step_name}, task={task_id}, tenant={tenant_id}")
    await asyncio.sleep(0.1)
    return {
        "step": step_name,
        "status": "completed",
        "input_summary": str(input_data)[:500],
    }


def register_default_handler():
    """Register the default handler as fallback for '__default__'."""
    _HANDLERS["__default__"] = default_handler