Convert the cache to golang

In the interest of performance, convert the fetcher and uploader to
golang and use the minio library, rather than repeated calls to the
server with the command line

nix/cache/cache.go

@@ -0,0 +1,190 @@
+package main
+
+import (
+	"bufio"
+	"context"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"strings"
+
+	"github.com/minio/minio-go/v7"
+	"github.com/minio/minio-go/v7/pkg/credentials"
+	"github.com/schollz/progressbar/v3"
+)
+
+func listBucketContents(minioClient *minio.Client, bucketName string) ([]string, error) {
+	var contents []string
+
+	// Create a done channel to control the listing
+	ctx := context.Background()
+
+	// List all objects from bucket
+	for object := range minioClient.ListObjects(ctx, bucketName, minio.ListObjectsOptions{
+		Recursive: true,
+	}) {
+		if object.Err != nil {
+			return nil, object.Err
+		}
+		contents = append(contents, object.Key)
+	}
+
+	return contents, nil
+}
+
+type IsoInfo struct {
+	Url    string
+	Hash   string
+	Distro string
+}
+
+func processStdin() []IsoInfo {
+	var isos []IsoInfo
+	scanner := bufio.NewScanner(os.Stdin)
+
+	for scanner.Scan() {
+		parts := strings.Split(scanner.Text(), " ")
+		if len(parts) == 3 {
+			iso := IsoInfo{
+				Url:    parts[0],
+				Hash:   parts[1],
+				Distro: parts[2],
+			}
+			isos = append(isos, iso)
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		log.Println("Error reading from stdin:", err)
+	}
+
+	return isos
+}
+
+// CustomReader wraps an io.Reader with a progress bar
+type CustomReader struct {
+	Reader      io.Reader
+	ProgressBar *progressbar.ProgressBar
+}
+
+func (r *CustomReader) Read(p []byte) (int, error) {
+	n, err := r.Reader.Read(p)
+	if n > 0 {
+		r.ProgressBar.Add(n)
+	}
+	return n, err
+}
+
+func downloadAndUploadIso(minioClient *minio.Client, iso IsoInfo) error {
+	// Create the destination file path
+	destPath := "cache/" + iso.Hash + ".iso"
+
+	// Download the ISO file
+	resp, err := http.Get(iso.Url)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	//
+	// Create download progress bar
+	downloadBar := progressbar.DefaultBytes(
+		resp.ContentLength,
+		"Downloading: "+iso.Url,
+	)
+
+	// Create the destination file
+	destFile, err := os.Create(destPath)
+	if err != nil {
+		return err
+	}
+	defer destFile.Close()
+
+	// Create a wrapped reader with progress bar
+	reader := io.TeeReader(resp.Body, downloadBar)
+
+	// Copy the downloaded content to the file
+	_, err = io.Copy(destFile, reader)
+	if err != nil {
+		return err
+	}
+
+	// Reopen file for uploading
+	uploadFile, err := os.Open(destPath)
+	if err != nil {
+		return err
+	}
+	defer uploadFile.Close()
+
+	// Get file info for content-length
+	fileInfo, err := uploadFile.Stat()
+	if err != nil {
+		return err
+	}
+
+	// Create upload progress bar
+	uploadBar := progressbar.DefaultBytes(
+		fileInfo.Size(),
+		"Uploading: "+destPath,
+	)
+
+	// Create wrapped reader for upload progress
+	uploadReader := &CustomReader{
+		Reader:      uploadFile,
+		ProgressBar: uploadBar,
+	}
+
+	// Upload the file to MinIO
+	_, err = minioClient.PutObject(context.Background(), "isos", "cache/"+iso.Hash+".iso", uploadReader, fileInfo.Size(), minio.PutObjectOptions{
+		ContentType: "application/x-iso9660-image",
+	})
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func main() {
+	endpoint := os.Getenv("STORAGE_URL")
+	accessKeyID := "root"
+	secretAccessKey := os.Getenv("MINIO_SECRET")
+	if secretAccessKey == "" {
+		log.Fatalln("MINIO_SECRET environment variable not set")
+	}
+	useSSL := false
+
+	// Initialize minio client
+	minioClient, err := minio.New(endpoint, &minio.Options{
+		Creds:  credentials.NewStaticV4(accessKeyID, secretAccessKey, ""),
+		Secure: useSSL,
+	})
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	// List contents of the "isos" bucket
+	contents, err := listBucketContents(minioClient, "isos")
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	isos := processStdin()
+
+	for _, iso := range isos {
+		// Check if ISO exists in Minio
+		isoPath := "cache/" + iso.Distro + "/" + iso.Hash + ".iso"
+		exists := false
+
+		for _, item := range contents {
+			if item == isoPath {
+				exists = true
+				break
+			}
+		}
+
+		if !exists {
+			downloadAndUploadIso(minioClient, iso)
+		}
+	}
+}