from abc import ABC, abstractmethod
from dataclasses import dataclass
from pathlib import Path


@dataclass
class GenerationRequest:
    prompt: str
    mode: str  # "instrumental" | "vocals"
    lyrics: str | None
    duration_seconds: int


@dataclass
class GenerationResult:
    audio_path: Path
    duration_seconds: float
    sample_rate: int


class MusicGenerationProvider(ABC):
    """Pluggable backend for turning a prompt (+ optional lyrics) into a song.

    Swap implementations (mock, local model, remote GPU endpoint) without
    touching the worker or API — the worker only depends on this interface.
    """

    @abstractmethod
    def generate(self, request: GenerationRequest, output_dir: Path) -> GenerationResult:
        ...