from abc import ABC, abstractmethod
from typing import Any, Iterable

class IVoiceActivityEngine(ABC):
    """Contract for a Voice Activity Detector (VAD)."""

    @abstractmethod
    def __call__(self, audio_chunk: bytes) -> bool:
        """
        Analyzes an audio chunk and returns True if speech is detected, 
        False otherwise.
        """
        pass

class IStreamingSpeechEngine(ABC):
    """Contract for a streaming transcription service."""

    @abstractmethod
    def transcribe_chunk(self, audio_chunk: bytes) -> str:
        """Processes an audio chunk and returns a transcription (partial or final)."""
        pass
    
    @abstractmethod
    def finalize_segment(self) -> str:
        """Called at the end of the stream to get the final transcription."""
        pass