//! Filesystem backend abstraction.
//!
//! At compile time the active backend is selected by Cargo feature:
//! - default → [`prod::ProdBackend`] (real FSKit mount via [`fskit_rs::mount`]).
//! - `dev`   → [`dev::DevBackend`] (socket-only, no FSKit / no `mount(8)`).
//!
//! Both expose the same shape via the [`Backend`] trait, so [`crate::main`]
//! and any caller can be feature-agnostic.

use async_trait::async_trait;
use fskit_rs::{Filesystem, MountOptions};

pub type Result<T> = std::result::Result<T, Error>;

#[async_trait]
pub trait Backend: Send + Sync + Sized + 'static {
    /// Start the backend; returns once it's ready to accept requests.
    async fn start<FS>(fs: FS, opts: MountOptions) -> Result<Self>
    where
        FS: Filesystem + Send + Sync + Clone + 'static;

    /// Short, user-facing description (mount point, socket address, ...).
    fn describe(&self) -> String;
}

#[cfg(not(feature = "dev"))]
mod prod;
#[cfg(not(feature = "dev"))]
pub use prod::ProdBackend as ActiveBackend;

#[cfg(feature = "dev")]
mod dev;
#[cfg(feature = "dev")]
pub use dev::DevBackend as ActiveBackend;

#[derive(thiserror::Error, Debug)]
pub enum Error {
    #[error(transparent)]
    Session(#[from] fskit_rs::session::Error),

    #[error(transparent)]
    DevSession(#[from] fskit_rs::dev_session::Error),
}