"""Story audio cache storage helpers."""

from __future__ import annotations

from dataclasses import dataclass
from datetime import datetime, timezone
from pathlib import Path

from app.core.config import settings


@dataclass(frozen=True)
class AudioCacheMetadata:
    """Metadata about one cached story audio file."""

    exists: bool
    path: str | None = None
    size_bytes: int | None = None
    updated_at: datetime | None = None


def build_story_audio_path(story_id: int) -> str:
    """Build the cache path for a story audio file."""

    return str(Path(settings.story_audio_cache_dir) / f"story-{story_id}.mp3")


def audio_cache_exists(audio_path: str | None) -> bool:
    """Whether the cached audio file exists on disk."""

    return bool(audio_path) and Path(audio_path).is_file()


def read_audio_cache(audio_path: str) -> bytes:
    """Read cached story audio bytes."""

    return Path(audio_path).read_bytes()


def get_audio_cache_metadata(audio_path: str | None) -> AudioCacheMetadata:
    """Return cache metadata without reading the audio bytes."""

    if not audio_path:
        return AudioCacheMetadata(exists=False)

    path = Path(audio_path)
    if not path.is_file():
        return AudioCacheMetadata(exists=False, path=str(path))

    stat = path.stat()
    return AudioCacheMetadata(
        exists=True,
        path=str(path),
        size_bytes=stat.st_size,
        updated_at=datetime.fromtimestamp(stat.st_mtime, tz=timezone.utc),
    )


def delete_audio_cache(audio_path: str | None) -> bool:
    """Delete cached story audio if it exists."""

    if not audio_path:
        return False

    path = Path(audio_path)
    if not path.is_file():
        return False

    path.unlink()
    return True


def write_story_audio_cache(story_id: int, audio_data: bytes) -> str:
    """Persist story audio and return the saved file path."""

    final_path = Path(build_story_audio_path(story_id))
    final_path.parent.mkdir(parents=True, exist_ok=True)

    temp_path = final_path.with_suffix(".tmp")
    temp_path.write_bytes(audio_data)
    temp_path.replace(final_path)

    return str(final_path)