ORAS and afero in WASM

afero_oci_mod.go

//go:build js && wasm
// +build js,wasm

package main

import (
	"context"
	"io"
	"strings"
	"syscall/js"
	"time"

	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
	"github.com/spf13/afero"
	"oras.land/oras-go/v2"
	"oras.land/oras-go/v2/content"
	"oras.land/oras-go/v2/content/memory"
	"oras.land/oras-go/v2/registry/remote"
	"oras.land/oras-go/v2/registry/remote/auth"
	"oras.land/oras-go/v2/registry/remote/retry"

	"github.com/opencontainers/go-digest"
)

var fs afero.Fs

func main() {
	fs = afero.NewMemMapFs()

	// Expose the writeFile function to JavaScript
	js.Global().Set("writeFile", js.FuncOf(writeToFile))

	// Keep the program running to interact with the JavaScript environment
	select {}
}

func writeToFile(this js.Value, args []js.Value) interface{} {

	go func() {
		if len(args) != 2 {
			logError("Invalid number of arguments")
			return
		}

		uploadedData := args[0].String()

		file, err := fs.Create("/example.txt")
		if err != nil {
			logError("Error creating file: " + err.Error())
			return
		}
		_, err = file.WriteString(uploadedData)
		if err != nil {
			logError("Error writing to file: " + err.Error())
			return
		}
		file.Close()

		registry := args[1].String()

		ufile, err := fs.Open("/example.txt")
		if err != nil {
			logError("Error opening file: " + err.Error())
			return
		}
		data, err := io.ReadAll(ufile)
		if err != nil {
			logError("Error reading file: " + err.Error())
			return
		}

		desc := ocispec.Descriptor{
			MediaType: "application/vnd.example+type",
			Digest:    digest.FromBytes(data),
			Size:      int64(len(data)),
			ArtifactType: "application/vnd.example.art+type",
		}

		store := memory.New()

		opts := oras.PackManifestOptions{
			Layers: []ocispec.Descriptor{
				desc,
			},
			ManifestAnnotations: map[string]string{
				"uor.module": "hello",
			},
		}
		ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
		defer cancel()

		artifactType := "application/vnd.example.wasm+type"
		manifestDesc, err := oras.PackManifest(ctx, store, oras.PackManifestVersion1_1, artifactType, opts)
		if err != nil {
			logError("Error packing manifest: " + err.Error())
			return
		}
		logInfo("Manifest descriptor: " + manifestDesc.Digest.String())

		// Verify the packed manifest
		manifestData, err := content.FetchAll(ctx, store, manifestDesc)
		if err != nil {
			logError("Error fetching manifest content: " + err.Error())
			return
		}
		logInfo("Manifest content: " + string(manifestData))
		logInfo("Registry: " + registry)
		tag := "latest"
		if err = store.Tag(ctx, manifestDesc, tag); err != nil {
			logError("Unable to tag manifest: " + err.Error())
			return
		}
		logInfo("Tagged manifest as: " + tag)

		// Connect to a remote repository
		repo, err := remote.NewRepository(registry + "/myrepo")
		if err != nil {
			logError("Unable to connect to registry: " + err.Error())
			return
		}

		logInfo("Connected to: " + repo.Reference.Repository)
		repo.Client = &auth.Client{
			Client: retry.DefaultClient,
			Cache:  auth.NewCache(),
		}

		const maxRetries = 3
		for retries := 0; retries < maxRetries; retries++ {
			logInfo("Attempting to push artifact, attempt: " + string(retries+1))
			_, err = oras.Copy(ctx, store, tag, repo, tag, oras.DefaultCopyOptions)
			if err != nil {
				if isNotFoundError(err) {
					logInfo("Ignoring 404 error: " + err.Error())
					break
				} else {
					logError("Error pushing artifact, retrying: " + err.Error())
					time.Sleep(2 * time.Second)
					continue
				}
			}
			logInfo("Successfully pushed artifact")
			break // Break out of the loop if successful
		}
		if err != nil {
			logError("Failed to push artifact after retries: " + err.Error())
		}
	}()
	return nil
}

// logError logs an error message to the JavaScript console
func logError(message string) {
	js.Global().Get("console").Call("log", message)
}

// logInfo logs an informational message to the JavaScript console
func logInfo(message string) {
	js.Global().Get("console").Call("log", message)
}

// isNotFoundError checks if the error indicates a 404 Not Found status
func isNotFoundError(err error) bool {
	if err == nil {
		return false
	}
	// This check assumes the error message contains "404", "NAME_UNKNOWN", or "BLOB_UNKNOWN"
	return strings.Contains(err.Error(), "404") || strings.Contains(err.Error(), "NAME_UNKNOWN") || strings.Contains(err.Error(), "BLOB_UNKNOWN")
}

server.go

package main

import (
	"fmt"
	"log"
	"net"
	"net/http"
	"time"

	"github.com/google/go-containerregistry/pkg/registry"
)

var port = 5000

// CORS middleware function
func corsMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Set CORS headers
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization, Accept, X-Requested-With")
		w.Header().Set("Access-Control-Expose-Headers", "Location")

		// Handle preflight requests
		if r.Method == http.MethodOptions {
			w.WriteHeader(http.StatusOK)
			return
		}

		// Call the next handler
		next.ServeHTTP(w, r)
	})
}

func main() {

	listener, err := net.Listen("tcp", fmt.Sprintf("localhost:%d", port))
	if err != nil {
		log.Fatal(err)
	}
	porti := listener.Addr().(*net.TCPAddr).Port
	log.Printf("serving on port %d", porti)
	s := &http.Server{
		ReadHeaderTimeout: 5 * time.Second, // prevent slowloris, quiet linter
		Handler: corsMiddleware(registry.New(
			registry.WithWarning(.01, "Congratulations! You've won a lifetime's supply of free image pulls from this in-memory registry!"),
		)),
	}
	go func() {
		log.Fatal(s.Serve(listener))
	}()

	fs := http.FileServer(http.Dir("."))
	corsHandler := corsMiddleware(fs)

	http.Handle("/", corsHandler)

	go func() {
		err = http.ListenAndServe(":8080", nil)
		if err != nil {
			log.Fatal(err)
		}
	}()

	select {}
}