hypha: implement custom image fetcher

hypha/src/image/fetch.rs

@@ -0,0 +1,69 @@
+use crate::error::{HyphaError, Result};
+use oci_spec::image::{Arch, Descriptor, ImageIndex, ImageManifest, MediaType, Os, ToDockerV2S2};
+use std::io::Read;
+use ureq::{Agent, Request, Response};
+use url::Url;
+
+pub struct RegistryClient {
+    agent: Agent,
+    url: Url,
+}
+
+impl RegistryClient {
+    pub fn new(url: Url) -> Result<RegistryClient> {
+        Ok(RegistryClient {
+            agent: Agent::new(),
+            url,
+        })
+    }
+
+    fn call(&mut self, req: Request) -> Result<Response> {
+        Ok(req.call()?)
+    }
+
+    pub fn get_blob(&mut self, name: &str, descriptor: &Descriptor) -> Result<Vec<u8>> {
+        let url = self
+            .url
+            .join(&format!("/v2/{}/blobs/{}", name, descriptor.digest()))?;
+        let response = self.call(self.agent.get(url.as_str()))?;
+        let mut buffer: Vec<u8> = Vec::new();
+        response.into_reader().read_to_end(&mut buffer)?;
+        Ok(buffer)
+    }
+
+    pub fn get_manifest(&mut self, name: &str, reference: &str) -> Result<ImageManifest> {
+        let url = self
+            .url
+            .join(&format!("/v2/{}/manifests/{}", name, reference))?;
+        let accept = format!(
+            "{}, {}, {}",
+            MediaType::ImageManifest.to_docker_v2s2()?,
+            MediaType::ImageManifest,
+            MediaType::ImageIndex,
+        );
+        let response = self.call(self.agent.get(url.as_str()).set("Accept", &accept))?;
+        let content_type = response.header("Content-Type").ok_or_else(|| {
+            HyphaError::new("registry response did not have a Content-Type header")
+        })?;
+        if content_type == MediaType::ImageIndex.to_string() {
+            let index = ImageIndex::from_reader(response.into_reader())?;
+            let descriptor = self
+                .pick_manifest(index)
+                .ok_or_else(|| HyphaError::new("unable to pick manifest from index"))?;
+            return self.get_manifest(name, descriptor.digest());
+        }
+        let manifest = ImageManifest::from_reader(response.into_reader())?;
+        Ok(manifest)
+    }
+
+    fn pick_manifest(&mut self, index: ImageIndex) -> Option<Descriptor> {
+        for item in index.manifests() {
+            if let Some(platform) = item.platform() {
+                if *platform.os() == Os::Linux && *platform.architecture() == Arch::Amd64 {
+                    return Some(item.clone());
+                }
+            }
+        }
+        None
+    }
+}