//! Pluggable blob storage.
//!
//! Handlers depend on the `Storage` trait, never on a concrete backend.
//! Add new backends (S3, GCS, …) as new impls in this module and wire
//! them up in `app::build` based on config.

mod local;

use std::io;
use std::pin::Pin;

use async_trait::async_trait;
use bytes::Bytes;
use futures_core::Stream;

pub use local::LocalStorage;

#[derive(thiserror::Error, Debug)]
pub enum StorageError {
    #[error(transparent)]
    Io(#[from] io::Error),
    #[error("not found")]
    NotFound,
    #[error("invalid storage key")]
    BadKey,
}

/// Boxed byte stream returned by `Storage::get_stream` so the trait stays
/// object-safe regardless of the concrete reader behind it.
pub type ByteStream = Pin<Box<dyn Stream<Item = io::Result<Bytes>> + Send>>;

pub struct StreamingFile {
    pub stream: ByteStream,
    pub size_bytes: u64,
}

#[async_trait]
pub trait Storage: Send + Sync {
    async fn put(&self, key: &str, bytes: &[u8]) -> Result<(), StorageError>;
    /// Reads the entire blob into memory. Convenient for small assets
    /// (covers, thumbnails). For pages and other large blobs, use
    /// `get_stream` so axum can pipe bytes straight to the client.
    async fn get(&self, key: &str) -> Result<Vec<u8>, StorageError>;
    async fn get_stream(&self, key: &str) -> Result<StreamingFile, StorageError>;
    async fn delete(&self, key: &str) -> Result<(), StorageError>;
    async fn exists(&self, key: &str) -> Result<bool, StorageError>;
}