Introduce caching for GitHub access method and add tests for the downloader

pkg/common/accessio/downloader/downloader.go

@@ -0,0 +1,9 @@
+package downloader
+
+import "io"
+
+// Downloader defines a downloader for various objects using a WriterAt to
+// transfer data to.
+type Downloader interface {
+	Download(w io.WriterAt) error
+}

pkg/common/accessio/downloader/http/downloader.go

@@ -0,0 +1,36 @@
+package http
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net/http"
+)
+
+// Downloader simply uses the default HTTP client to download the contents of a URL.
+type Downloader struct {
+	link string
+}
+
+func NewDownloader(link string) *Downloader {
+	return &Downloader{
+		link: link,
+	}
+}
+
+func (h *Downloader) Download(w io.WriterAt) error {
+	resp, err := http.Get(h.link)
+	if err != nil {
+		return fmt.Errorf("failed to get link: %w", err)
+	}
+	defer resp.Body.Close()
+	var blob []byte
+	buf := bytes.NewBuffer(blob)
+	if _, err := io.Copy(buf, resp.Body); err != nil {
+		return fmt.Errorf("failed to copy response body: %w", err)
+	}
+	if _, err := w.WriteAt(buf.Bytes(), 0); err != nil {
+		return fmt.Errorf("failed to WriteAt to the writer: %w", err)
+	}
+	return nil
+}

pkg/contexts/ocm/accessmethods/s3/downloader.go → pkg/common/accessio/downloader/s3/downloader.go

@@ -14,19 +14,14 @@ import (
 
 const defaultRegion = "us-west-1"
 
-// Downloader defines a downloader for AWS S3 objects.
-type Downloader interface {
-	Download(w io.WriterAt) error
-}
-
-// S3Downloader is a downloader capable of downloading S3 Objects.
-type S3Downloader struct {
+// Downloader is a downloader capable of downloading S3 Objects.
+type Downloader struct {
 	region, bucket, key, version string
 	creds                        *AWSCreds
 }
 
-func NewS3Downloader(region, bucket, key, version string, creds *AWSCreds) *S3Downloader {
-	return &S3Downloader{
+func NewDownloader(region, bucket, key, version string, creds *AWSCreds) *Downloader {
+	return &Downloader{
 		region:  region,
 		bucket:  bucket,
 		key:     key,
@@ -42,7 +37,7 @@ type AWSCreds struct {
 	SessionToken string
 }
 
-func (s *S3Downloader) Download(w io.WriterAt) error {
+func (s *Downloader) Download(w io.WriterAt) error {
 	ctx := context.Background()
 	opts := []func(*config.LoadOptions) error{
 		config.WithRegion(s.region),
@@ -79,6 +74,7 @@ func (s *S3Downloader) Download(w io.WriterAt) error {
 	}
 
 	client := s3.NewFromConfig(cfg, func(o *s3.Options) {
+		// Pass in creds because of https://github.com/aws/aws-sdk-go-v2/issues/1797
 		o.Credentials = awsCred
 		o.Region = s.region
 	})