[release-4.1] feat: Adapt to oci-based helmchart repo (#6203)

* add oci client for registry

* add LoadRepoIndexFormOci

* feat: Adapt to oci-based helmchart repo

* Update the golang base image version in the dockerfile

* update oci_test.go

Signed-off-by: lingbo <lingbo@lingbohome.com>

* fix: Update oci_test.go

Signed-off-by: 凌波 <lingbo@lingbohome.com>

* Update go imports

---------

Signed-off-by: lingbo <lingbo@lingbohome.com>
Signed-off-by: 凌波 <lingbo@lingbohome.com>
Co-authored-by: lingbo <lingbo@lingbohome.com>
Co-authored-by: hongming <coder.scala@gmail.com>

pkg/simple/client/oci/oci_test.go

@@ -0,0 +1,96 @@
+package oci
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+	"time"
+
+	"oras.land/oras-go/pkg/registry"
+)
+
+func TestRegistry_Api(t *testing.T) {
+	testRepos := []string{"helmcharts/nginx", "helmcharts/test-api", "helmcharts/test-ui", "helmcharts/demo-app"}
+	testTags := []string{"1.0.0", "1.2.0", "1.0.3"}
+	testRepo := testRepos[1]
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method == http.MethodGet && (r.URL.Path == "/v2" || r.URL.Path == "/v2/") {
+			w.WriteHeader(http.StatusOK)
+			return
+		}
+		if r.Method == http.MethodGet && r.URL.Path == "/v2/_catalog" {
+			result := struct {
+				Repositories []string `json:"repositories"`
+			}{
+				Repositories: testRepos,
+			}
+			if err := json.NewEncoder(w).Encode(result); err != nil {
+				t.Errorf("failed to write response: %v", err)
+			}
+			return
+		}
+		if r.Method == http.MethodGet && r.URL.Path == fmt.Sprintf("/v2/%s/tags/list", testRepo) {
+			result := struct {
+				Tags []string `json:"tags"`
+			}{
+				Tags: testTags,
+			}
+			if err := json.NewEncoder(w).Encode(result); err != nil {
+				t.Errorf("failed to write response: %v", err)
+			}
+			return
+		}
+
+		t.Errorf("unexpected access: %s %s", r.Method, r.URL)
+		w.WriteHeader(http.StatusNotFound)
+	}))
+	defer ts.Close()
+	uri, err := url.Parse(ts.URL)
+	if err != nil {
+		t.Fatalf("invalid test http server: %v", err)
+	}
+
+	reg, err := NewRegistry(uri.Host,
+		WithTimeout(5*time.Second),
+		WithBasicAuth("", ""),
+		WithInsecureSkipVerifyTLS(true))
+	if err != nil {
+		t.Fatalf("NewRegistry() error = %v", err)
+	}
+
+	ctx := context.Background()
+	err = reg.Ping(ctx)
+	if err != nil {
+		t.Fatalf("Registry.Ping() error = %v", err)
+	}
+
+	var registryTags []string
+
+	repo, err := reg.Repository(ctx, testRepo)
+	if err != nil {
+		t.Fatalf("Registry.Repository() error = %v", err)
+	}
+	registryTags, err = registry.Tags(ctx, repo)
+	if err != nil {
+		t.Fatalf("Registry.Repository().Tags() error = %v", err)
+	}
+	t.Log(len(registryTags))
+
+	err = reg.Repositories(ctx, "", func(repos []string) error {
+		for _, repo := range repos {
+			if subRepo, found := strings.CutPrefix(repo, ""); found {
+				t.Log(subRepo)
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatalf("Registry.Repositories() error = %v", err)
+	}
+
+}