"""Message handler registry and routing."""

from __future__ import annotations

import sys
from collections.abc import Callable

from voice_to_notes.ipc.messages import IPCMessage, error_message

# Handler function type: takes a message, returns a response message
HandlerFunc = Callable[[IPCMessage], IPCMessage | None]


class HandlerRegistry:
    """Registry mapping message types to handler functions."""

    def __init__(self) -> None:
        self._handlers: dict[str, HandlerFunc] = {}

    def register(self, message_type: str, handler: HandlerFunc) -> None:
        """Register a handler for a message type."""
        self._handlers[message_type] = handler

    def handle(self, msg: IPCMessage) -> IPCMessage | None:
        """Route a message to its handler. Returns a response or error."""
        handler = self._handlers.get(msg.type)
        if handler is None:
            print(f"[sidecar] Unknown message type: {msg.type}", file=sys.stderr, flush=True)
            return error_message(msg.id, "unknown_type", f"Unknown message type: {msg.type}")
        try:
            return handler(msg)
        except Exception as e:
            print(f"[sidecar] Handler error for {msg.type}: {e}", file=sys.stderr, flush=True)
            return error_message(msg.id, "handler_error", str(e))


def ping_handler(msg: IPCMessage) -> IPCMessage:
    """Simple ping handler for testing connectivity."""
    return IPCMessage(id=msg.id, type="pong", payload={"echo": msg.payload})