"""Voice co-creation session storage helpers."""

from __future__ import annotations

from pathlib import Path

from app.core.config import settings


def session_storage_dir(session_id: str) -> Path:
    """Return the storage directory for one voice session."""

    return Path(settings.voice_session_storage_dir) / session_id


def build_turn_user_audio_path(session_id: str, turn_index: int, suffix: str) -> Path:
    """Build the persisted path for one user-uploaded turn audio file."""

    normalized_suffix = suffix.lstrip(".") or "webm"
    return session_storage_dir(session_id) / f"turn-{turn_index:03d}-user.{normalized_suffix}"


def build_turn_assistant_audio_path(session_id: str, turn_index: int) -> Path:
    """Build the persisted path for one generated assistant turn audio file."""

    return session_storage_dir(session_id) / f"turn-{turn_index:03d}-assistant.mp3"


def _normalize_audio_suffix(file_name: str | None, mime_type: str | None) -> str:
    if file_name and "." in file_name:
        return file_name.rsplit(".", 1)[-1].lower()

    if mime_type == "audio/webm":
        return "webm"
    if mime_type == "audio/wav":
        return "wav"
    if mime_type == "audio/mpeg":
        return "mp3"
    if mime_type == "audio/mp4":
        return "m4a"
    return "bin"


def write_uploaded_user_audio(
    *,
    session_id: str,
    turn_index: int,
    file_name: str | None,
    mime_type: str | None,
    audio_data: bytes,
) -> str:
    """Persist one uploaded user-audio turn and return the saved file path."""

    suffix = _normalize_audio_suffix(file_name, mime_type)
    return write_session_audio(
        build_turn_user_audio_path(session_id, turn_index, suffix),
        audio_data,
    )


def write_session_audio(path: Path, audio_data: bytes) -> str:
    """Persist session audio bytes atomically and return the saved path."""

    path.parent.mkdir(parents=True, exist_ok=True)
    temp_path = path.with_suffix(f"{path.suffix}.tmp")
    temp_path.write_bytes(audio_data)
    temp_path.replace(path)
    return str(path)


def read_session_audio(audio_path: str) -> bytes:
    """Read persisted session audio bytes."""

    return Path(audio_path).read_bytes()


def session_audio_exists(audio_path: str | None) -> bool:
    """Whether one stored session audio file currently exists."""

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