"""Small compatibility layer for live denoising previews from local backends."""

from __future__ import annotations

import inspect
from pathlib import Path
from typing import Any, Callable

from adam.executor import ToolContext


def accepts_preview_callback(function: Callable[..., Any]) -> bool:
    """Only opt in to the explicit protocol; ``**kwargs`` is not enough."""
    try:
        return "preview_callback" in inspect.signature(function).parameters
    except (TypeError, ValueError):
        return False


def publish_generation_preview(
    context: ToolContext, output: Path, payload: Any, *, image_index: int,
    image_count: int, step: int = 0, total_steps: int = 0,
) -> None:
    """Persist only the newest preview and publish it to ADAM's live viewer."""
    if isinstance(payload, dict):
        step = int(payload.get("step", payload.get("current_step", step)) or step)
        total_steps = int(payload.get("total_steps", payload.get("steps", total_steps)) or total_steps)
        payload = payload.get("image", payload.get("path"))
    if not payload:
        return
    preview_dir = output / ".live_previews"
    preview_dir.mkdir(parents=True, exist_ok=True)
    destination = preview_dir / f"{context.job_id}_latest.png"
    try:
        if isinstance(payload, (str, Path)):
            source = Path(payload).expanduser().resolve()
            if not source.is_file():
                return
            destination.write_bytes(source.read_bytes())
        elif callable(getattr(payload, "save", None)):
            payload.save(destination, format="PNG")
        else:
            return
    except (OSError, ValueError, TypeError):
        return
    context.preview(destination, kind="generation", current=step, total=total_steps,
                    image_index=image_index + 1, image_count=image_count)