use std::path::PathBuf;
use async_trait::async_trait;
use microsandbox_utils::{EXTRACTED_LAYER_SUFFIX, LAYERS_SUBDIR, env};
use oci_spec::image::Digest;
/// Result of downloading an image.
pub enum ImageLayerBlob {
/// The layer was downloaded successfully to the provided path.
Downloaded(Digest, PathBuf),
/// The layer already exists in the global layer directory.
ExistsInGlobalCache(Digest),
}
impl ImageLayerBlob {
/// Returns the path to the downloaded layer. If the layer already exists in the global layer directory,
/// returns None.
pub fn download_path(&self) -> Option<PathBuf> {
match self {
ImageLayerBlob::Downloaded(_, path) => Some(path.clone()),
ImageLayerBlob::ExistsInGlobalCache(_) => None,
}
}
}
/// Trait defining methods for interacting with on-disk image layers.
#[async_trait]
pub trait GlobalLayerOps {
/// Checks if a layer exists on disk.
///
/// # Arguments
///
/// * `digest` - The digest of the layer to check
///
/// # Returns
///
/// Returns `true` if the layer exists, `false` otherwise.
async fn get_layer(&self, digest: &Digest) -> Option<PathBuf>;
}
/// Perform operation against the directory where layers are stored
pub(crate) struct GlobalLayerCache {
layers_dir: PathBuf,
}
impl Default for GlobalLayerCache {
fn default() -> Self {
Self {
layers_dir: env::get_microsandbox_home_path().join(LAYERS_SUBDIR),
}
}
}
#[async_trait]
impl GlobalLayerOps for GlobalLayerCache {
async fn get_layer(&self, digest: &Digest) -> Option<PathBuf> {
let path = self
.layers_dir
.join(format!("{digest}.{EXTRACTED_LAYER_SUFFIX}"));
if !path.exists() {
return None;
}
// if there's at least one file in that specific layer directory, it means the layer already exists
if let Ok(mut read_dir) = tokio::fs::read_dir(&path).await
&& let Ok(Some(_)) = read_dir.next_entry().await
{
return Some(path);
}
None
}
}
