krata/hypha/src/image/cache.rs

use crate::image::{ImageInfo, Result};
use log::debug;
use oci_spec::image::ImageManifest;
use std::fs;
use std::path::{Path, PathBuf};

pub struct ImageCache {
    cache_dir: PathBuf,
}

impl ImageCache {
    pub fn new(cache_dir: &Path) -> Result<ImageCache> {
        Ok(ImageCache {
            cache_dir: cache_dir.to_path_buf(),
        })
    }

    pub fn recall(&self, digest: &str) -> Result<Option<ImageInfo>> {
        let mut squashfs_path = self.cache_dir.clone();
        let mut manifest_path = self.cache_dir.clone();
        squashfs_path.push(format!("{}.squashfs", digest));
        manifest_path.push(format!("{}.json", digest));
        Ok(if squashfs_path.exists() && manifest_path.exists() {
            let squashfs_metadata = fs::metadata(&squashfs_path)?;
            let manifest_metadata = fs::metadata(&manifest_path)?;
            if squashfs_metadata.is_file() && manifest_metadata.is_file() {
                let manifest_text = fs::read_to_string(&manifest_path)?;
                let manifest: ImageManifest = serde_json::from_str(manifest_text.as_str())?;
                debug!("cache hit digest={}", digest);
                Some(ImageInfo::new(squashfs_path.clone(), manifest)?)
            } else {
                None
            }
        } else {
            debug!("cache miss digest={}", digest);
            None
        })
    }

    pub fn store(&self, digest: &str, info: &ImageInfo) -> Result<ImageInfo> {
        debug!("cache store digest={}", digest);
        let mut squashfs_path = self.cache_dir.clone();
        let mut manifest_path = self.cache_dir.clone();
        squashfs_path.push(format!("{}.squashfs", digest));
        manifest_path.push(format!("{}.json", digest));
        fs::copy(&info.squashfs, &squashfs_path)?;
        let manifest_text = serde_json::to_string_pretty(&info.manifest)?;
        fs::write(&manifest_path, manifest_text)?;
        ImageInfo::new(squashfs_path.clone(), info.manifest.clone())
    }
}