from typing import Dict, Any, Optional

class SchemaRegistry:
    """
    Registry for event schemas (Protobuf).
    In production, this would communicate with a central registry service
    to ensure backward/forward compatibility.
    """
    def __init__(self) -> None:
        self.schemas: Dict[str, Any] = {}

    def register(self, event_type: str, schema_def: Any) -> None:
        self.schemas[event_type] = schema_def

    def get_schema(self, event_type: str) -> Optional[Any]:
        return self.schemas.get(event_type)

    def check_compatibility(self, event_type: str, new_schema: Any) -> bool:
        """
        Ensures the new schema version doesn't break consumers.
        Placeholder for real Protobuf descriptor comparison.
        """
        old_schema = self.get_schema(event_type)
        if not old_schema:
            return True # New type is always compatible
        
        # Simple heuristic: Field counts must not decrease? 
        # (Very naive, but demonstrates the hook)
        try:
            old_fields = len(old_schema.DESCRIPTOR.fields)
            new_fields = len(new_schema.DESCRIPTOR.fields)
            return new_fields >= old_fields
        except:
            return True

# Global stub for internal use
registry = SchemaRegistry()
