//! Standard generated devices discard writes and retain their read behavior across opens.
use sausage_vfs::{Device, Generated, Layer, Open};

#[tokio::test]
async fn generated_devices() {
    let mut layer = Generated::default();
    for (name, device) in [
        ("null", Device::Null),
        ("zero", Device::Zero),
        ("urandom", Device::Random),
    ] {
        layer.insert_device(&format!("/{name}"), device);
    }
    assert_eq!(layer.list("/").await.unwrap().len(), 3);
    for name in ["null", "zero", "urandom"] {
        let file = layer
            .open(
                &format!("/{name}"),
                Open {
                    write: true,
                    create: true,
                    truncate: true,
                    ..Default::default()
                },
            )
            .await
            .unwrap();
        assert_eq!(file.write(100, b"discard".to_vec()).await.unwrap(), 7);
        assert_eq!(file.append(b"discard".to_vec()).await.unwrap(), 7);
        file.set_size(100).await.unwrap();
        file.sync().await.unwrap();
        assert_eq!(file.stat().await.unwrap().size, 0);
        let reopened = layer
            .open(&format!("/{name}"), Open::default())
            .await
            .unwrap();
        let bytes = reopened.read(100, 64).await.unwrap();
        match name {
            "null" => assert!(bytes.is_empty()),
            "zero" => assert_eq!(bytes, vec![0; 64]),
            _ => {
                assert_eq!(bytes.len(), 64);
                assert_ne!(bytes, reopened.read(0, 64).await.unwrap());
            }
        }
    }
}