/*
Copyright The Helm Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package registry // import "helm.sh/helm/v4/pkg/registry"

import (
	"context"
	"crypto/tls"
	"crypto/x509"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"sort"
	"strings"
	"sync"

	"github.com/Masterminds/semver/v3"
	"github.com/containerd/containerd/remotes"
	"github.com/opencontainers/image-spec/specs-go"
	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
	"github.com/pkg/errors"
	"oras.land/oras-go/v2"
	"oras.land/oras-go/v2/content"
	"oras.land/oras-go/v2/content/memory"
	"oras.land/oras-go/v2/registry"
	"oras.land/oras-go/v2/registry/remote"
	"oras.land/oras-go/v2/registry/remote/auth"
	"oras.land/oras-go/v2/registry/remote/credentials"
	"oras.land/oras-go/v2/registry/remote/retry"

	"helm.sh/helm/v4/internal/version"
	"helm.sh/helm/v4/pkg/chart"
	"helm.sh/helm/v4/pkg/helmpath"
)

// See https://github.com/helm/helm/issues/10166
const registryUnderscoreMessage = `
OCI artifact references (e.g. tags) do not support the plus sign (+). To support
storing semantic versions, Helm adopts the convention of changing plus (+) to
an underscore (_) in chart version tags when pushing to a registry and back to
a plus (+) when pulling from a registry.`

var errDeprecatedRemote = errors.New("providing github.com/containerd/containerd/remotes.Resolver via ClientOptResolver is no longer suported")

type (
	// RemoteClient shadows the ORAS remote.Client interface
	// (hiding the ORAS type from Helm client visibility)
	// https://pkg.go.dev/oras.land/oras-go/pkg/registry/remote#Client
	RemoteClient interface {
		Do(req *http.Request) (*http.Response, error)
	}

	// Client works with OCI-compliant registries
	Client struct {
		debug       bool
		enableCache bool
		// path to repository config file e.g. ~/.docker/config.json
		credentialsFile    string
		username           string
		password           string
		out                io.Writer
		authorizer         *auth.Client
		registryAuthorizer RemoteClient
		credentialsStore   credentials.Store
		httpClient         *http.Client
		plainHTTP          bool
		err                error // pass any errors from the ClientOption functions
	}

	// ClientOption allows specifying various settings configurable by the user for overriding the defaults
	// used when creating a new default client
	ClientOption func(*Client)
)

// NewClient returns a new registry client with config
func NewClient(options ...ClientOption) (*Client, error) {
	client := &Client{
		out: io.Discard,
	}
	for _, option := range options {
		option(client)
		if client.err != nil {
			return nil, client.err
		}
	}
	if client.credentialsFile == "" {
		client.credentialsFile = helmpath.ConfigPath(CredentialsFileBasename)
	}
	if client.httpClient == nil {
		type cloner[T any] interface {
			Clone() T
		}

		// try to copy (clone) the http.DefaultTransport so any mutations we
		// perform on it (e.g. TLS config) are not reflected globally
		// follow https://github.com/golang/go/issues/39299 for a more elegant
		// solution in the future
		transport := http.DefaultTransport
		if t, ok := transport.(cloner[*http.Transport]); ok {
			transport = t.Clone()
		} else if t, ok := transport.(cloner[http.RoundTripper]); ok {
			// this branch will not be used with go 1.20, it was added
			// optimistically to try to clone if the http.DefaultTransport
			// implementation changes, still the Clone method in that case
			// might not return http.RoundTripper...
			transport = t.Clone()
		}

		client.httpClient = &http.Client{
			Transport: retry.NewTransport(transport),
		}
	}

	storeOptions := credentials.StoreOptions{
		AllowPlaintextPut:        true,
		DetectDefaultNativeStore: true,
	}
	store, err := credentials.NewStore(client.credentialsFile, storeOptions)
	if err != nil {
		return nil, err
	}
	dockerStore, err := credentials.NewStoreFromDocker(storeOptions)
	if err != nil {
		// should only fail if user home directory can't be determined
		client.credentialsStore = store
	} else {
		// use Helm credentials with fallback to Docker
		client.credentialsStore = credentials.NewStoreWithFallbacks(store, dockerStore)
	}

	if client.authorizer == nil {
		authorizer := auth.Client{
			Client: client.httpClient,
		}
		authorizer.SetUserAgent(version.GetUserAgent())

		authorizer.Credential = credentials.Credential(client.credentialsStore)

		if client.enableCache {
			authorizer.Cache = auth.NewCache()
		}

		client.authorizer = &authorizer
	}

	return client, nil
}

// ClientOptDebug returns a function that sets the debug setting on client options set
func ClientOptDebug(debug bool) ClientOption {
	return func(client *Client) {
		client.debug = debug
	}
}

// ClientOptEnableCache returns a function that sets the enableCache setting on a client options set
func ClientOptEnableCache(enableCache bool) ClientOption {
	return func(client *Client) {
		client.enableCache = enableCache
	}
}

// ClientOptBasicAuth returns a function that sets the username and password setting on client options set
func ClientOptBasicAuth(username, password string) ClientOption {
	return func(client *Client) {
		client.username = username
		client.password = password
	}
}

// ClientOptWriter returns a function that sets the writer setting on client options set
func ClientOptWriter(out io.Writer) ClientOption {
	return func(client *Client) {
		client.out = out
	}
}

// ClientOptAuthorizer returns a function that sets the authorizer setting on a client options set. This
// can be used to override the default authorization mechanism.
//
// Depending on the use-case you may need to set both ClientOptAuthorizer and ClientOptRegistryAuthorizer.
func ClientOptAuthorizer(authorizer auth.Client) ClientOption {
	return func(client *Client) {
		client.authorizer = &authorizer
	}
}

// ClientOptRegistryAuthorizer returns a function that sets the registry authorizer setting on a client options set. This
// can be used to override the default authorization mechanism.
//
// Depending on the use-case you may need to set both ClientOptAuthorizer and ClientOptRegistryAuthorizer.
func ClientOptRegistryAuthorizer(registryAuthorizer RemoteClient) ClientOption {
	return func(client *Client) {
		client.registryAuthorizer = registryAuthorizer
	}
}

// ClientOptCredentialsFile returns a function that sets the credentialsFile setting on a client options set
func ClientOptCredentialsFile(credentialsFile string) ClientOption {
	return func(client *Client) {
		client.credentialsFile = credentialsFile
	}
}

// ClientOptHTTPClient returns a function that sets the httpClient setting on a client options set
func ClientOptHTTPClient(httpClient *http.Client) ClientOption {
	return func(client *Client) {
		client.httpClient = httpClient
	}
}

func ClientOptPlainHTTP() ClientOption {
	return func(c *Client) {
		c.plainHTTP = true
	}
}

func ClientOptResolver(_ remotes.Resolver) ClientOption {
	return func(c *Client) {
		c.err = errDeprecatedRemote
	}
}

type (
	// LoginOption allows specifying various settings on login
	LoginOption func(*loginOperation)

	loginOperation struct {
		host   string
		client *Client
	}
)

// Login logs into a registry
func (c *Client) Login(host string, options ...LoginOption) error {
	for _, option := range options {
		option(&loginOperation{host, c})
	}

	reg, err := remote.NewRegistry(host)
	if err != nil {
		return err
	}
	reg.PlainHTTP = c.plainHTTP
	reg.Client = c.authorizer

	ctx := context.Background()
	cred, err := c.authorizer.Credential(ctx, host)
	if err != nil {
		return fmt.Errorf("fetching credentials for %q: %w", host, err)
	}

	if err := reg.Ping(ctx); err != nil {
		return fmt.Errorf("authenticating to %q: %w", host, err)
	}

	key := credentials.ServerAddressFromRegistry(host)
	if err := c.credentialsStore.Put(ctx, key, cred); err != nil {
		return err
	}

	fmt.Fprintln(c.out, "Login Succeeded")
	return nil
}

// LoginOptBasicAuth returns a function that sets the username/password settings on login
func LoginOptBasicAuth(username string, password string) LoginOption {
	return func(o *loginOperation) {
		o.client.username = username
		o.client.password = password
		o.client.authorizer.Credential = auth.StaticCredential(o.host, auth.Credential{Username: username, Password: password})
	}
}

// LoginOptPlainText returns a function that allows plaintext (HTTP) login
func LoginOptPlainText(isPlainText bool) LoginOption {
	return func(o *loginOperation) {
		o.client.plainHTTP = isPlainText
	}
}

func ensureTLSConfig(client *auth.Client) (*tls.Config, error) {
	var transport *http.Transport

	switch t := client.Client.Transport.(type) {
	case *http.Transport:
		transport = t
	case *retry.Transport:
		switch t := t.Base.(type) {
		case *http.Transport:
			transport = t
		}
	}

	if transport == nil {
		// we don't know how to access the http.Transport, most likely the
		// auth.Client.Client was provided by API user
		return nil, fmt.Errorf("unable to access TLS client configuration, the provided HTTP Transport is not supported, given: %T", client.Client.Transport)
	}

	if transport.TLSClientConfig == nil {
		transport.TLSClientConfig = &tls.Config{}
	}

	return transport.TLSClientConfig, nil
}

// LoginOptInsecure returns a function that sets the insecure setting on login
func LoginOptInsecure(insecure bool) LoginOption {
	return func(o *loginOperation) {
		tlsConfig, err := ensureTLSConfig(o.client.authorizer)

		if err != nil {
			panic(err)
		}

		tlsConfig.InsecureSkipVerify = insecure
	}
}

// LoginOptTLSClientConfig returns a function that sets the TLS settings on login.
func LoginOptTLSClientConfig(certFile, keyFile, caFile string) LoginOption {
	return func(o *loginOperation) {
		if (certFile == "" || keyFile == "") && caFile == "" {
			return
		}
		tlsConfig, err := ensureTLSConfig(o.client.authorizer)
		if err != nil {
			panic(err)
		}

		if certFile != "" && keyFile != "" {
			authCert, err := tls.LoadX509KeyPair(certFile, keyFile)
			if err != nil {
				panic(err)
			}
			tlsConfig.Certificates = []tls.Certificate{authCert}
		}

		if caFile != "" {
			certPool := x509.NewCertPool()
			ca, err := os.ReadFile(caFile)
			if err != nil {
				panic(err)
			}
			if !certPool.AppendCertsFromPEM(ca) {
				panic(fmt.Errorf("unable to parse CA file: %q", caFile))
			}
			tlsConfig.RootCAs = certPool
		}
	}
}

type (
	// LogoutOption allows specifying various settings on logout
	LogoutOption func(*logoutOperation)

	logoutOperation struct{}
)

// Logout logs out of a registry
func (c *Client) Logout(host string, opts ...LogoutOption) error {
	operation := &logoutOperation{}
	for _, opt := range opts {
		opt(operation)
	}

	if err := credentials.Logout(context.Background(), c.credentialsStore, host); err != nil {
		return err
	}
	fmt.Fprintf(c.out, "Removing login credentials for %s\n", host)
	return nil
}

type (
	// PullOption allows specifying various settings on pull
	PullOption func(*pullOperation)

	// PullResult is the result returned upon successful pull.
	PullResult struct {
		Manifest *DescriptorPullSummary         `json:"manifest"`
		Config   *DescriptorPullSummary         `json:"config"`
		Chart    *DescriptorPullSummaryWithMeta `json:"chart"`
		Prov     *DescriptorPullSummary         `json:"prov"`
		Ref      string                         `json:"ref"`
	}

	DescriptorPullSummary struct {
		Data   []byte `json:"-"`
		Digest string `json:"digest"`
		Size   int64  `json:"size"`
	}

	DescriptorPullSummaryWithMeta struct {
		DescriptorPullSummary
		Meta *chart.Metadata `json:"meta"`
	}

	pullOperation struct {
		withChart         bool
		withProv          bool
		ignoreMissingProv bool
	}
)

// Pull downloads a chart from a registry
func (c *Client) Pull(ref string, options ...PullOption) (*PullResult, error) {
	parsedRef, err := newReference(ref)
	if err != nil {
		return nil, err
	}

	operation := &pullOperation{
		withChart: true, // By default, always download the chart layer
	}
	for _, option := range options {
		option(operation)
	}
	if !operation.withChart && !operation.withProv {
		return nil, errors.New(
			"must specify at least one layer to pull (chart/prov)")
	}
	memoryStore := memory.New()
	allowedMediaTypes := []string{
		ocispec.MediaTypeImageManifest,
		ConfigMediaType,
	}
	minNumDescriptors := 1 // 1 for the config
	if operation.withChart {
		minNumDescriptors++
		allowedMediaTypes = append(allowedMediaTypes, ChartLayerMediaType, LegacyChartLayerMediaType)
	}
	if operation.withProv {
		if !operation.ignoreMissingProv {
			minNumDescriptors++
		}
		allowedMediaTypes = append(allowedMediaTypes, ProvLayerMediaType)
	}

	var descriptors, layers []ocispec.Descriptor

	repository, err := remote.NewRepository(parsedRef.String())
	if err != nil {
		return nil, err
	}
	repository.PlainHTTP = c.plainHTTP
	repository.Client = c.authorizer

	ctx := context.Background()

	sort.Strings(allowedMediaTypes)

	var mu sync.Mutex
	manifest, err := oras.Copy(ctx, repository, parsedRef.String(), memoryStore, "", oras.CopyOptions{
		CopyGraphOptions: oras.CopyGraphOptions{
			PreCopy: func(_ context.Context, desc ocispec.Descriptor) error {
				mediaType := desc.MediaType
				if i := sort.SearchStrings(allowedMediaTypes, mediaType); i >= len(allowedMediaTypes) || allowedMediaTypes[i] != mediaType {
					return errors.Errorf("media type %q is not allowed, found in descriptor with digest: %q", mediaType, desc.Digest)
				}

				mu.Lock()
				layers = append(layers, desc)
				mu.Unlock()
				return nil
			},
		},
	})
	if err != nil {
		return nil, err
	}

	descriptors = append(descriptors, manifest)
	descriptors = append(descriptors, layers...)

	numDescriptors := len(descriptors)
	if numDescriptors < minNumDescriptors {
		return nil, fmt.Errorf("manifest does not contain minimum number of descriptors (%d), descriptors found: %d",
			minNumDescriptors, numDescriptors)
	}
	var configDescriptor *ocispec.Descriptor
	var chartDescriptor *ocispec.Descriptor
	var provDescriptor *ocispec.Descriptor
	for _, descriptor := range descriptors {
		d := descriptor
		switch d.MediaType {
		case ConfigMediaType:
			configDescriptor = &d
		case ChartLayerMediaType:
			chartDescriptor = &d
		case ProvLayerMediaType:
			provDescriptor = &d
		case LegacyChartLayerMediaType:
			chartDescriptor = &d
			fmt.Fprintf(c.out, "Warning: chart media type %s is deprecated\n", LegacyChartLayerMediaType)
		}
	}
	if configDescriptor == nil {
		return nil, fmt.Errorf("could not load config with mediatype %s", ConfigMediaType)
	}
	if operation.withChart && chartDescriptor == nil {
		return nil, fmt.Errorf("manifest does not contain a layer with mediatype %s",
			ChartLayerMediaType)
	}
	var provMissing bool
	if operation.withProv && provDescriptor == nil {
		if operation.ignoreMissingProv {
			provMissing = true
		} else {
			return nil, fmt.Errorf("manifest does not contain a layer with mediatype %s",
				ProvLayerMediaType)
		}
	}
	result := &PullResult{
		Manifest: &DescriptorPullSummary{
			Digest: manifest.Digest.String(),
			Size:   manifest.Size,
		},
		Config: &DescriptorPullSummary{
			Digest: configDescriptor.Digest.String(),
			Size:   configDescriptor.Size,
		},
		Chart: &DescriptorPullSummaryWithMeta{},
		Prov:  &DescriptorPullSummary{},
		Ref:   parsedRef.String(),
	}

	result.Manifest.Data, err = content.FetchAll(ctx, memoryStore, manifest)
	if err != nil {
		return nil, fmt.Errorf("unable to retrieve blob with digest %s: %w", manifest.Digest, err)
	}

	result.Config.Data, err = content.FetchAll(ctx, memoryStore, *configDescriptor)
	if err != nil {
		return nil, fmt.Errorf("unable to retrieve blob with digest %s: %w", configDescriptor.Digest, err)
	}

	if err := json.Unmarshal(result.Config.Data, &result.Chart.Meta); err != nil {
		return nil, err
	}

	if operation.withChart {
		result.Chart.Data, err = content.FetchAll(ctx, memoryStore, *chartDescriptor)
		if err != nil {
			return nil, fmt.Errorf("unable to retrieve blob with digest %s: %w", chartDescriptor.Digest, err)
		}
		result.Chart.Digest = chartDescriptor.Digest.String()
		result.Chart.Size = chartDescriptor.Size
	}

	if operation.withProv && !provMissing {
		result.Prov.Data, err = content.FetchAll(ctx, memoryStore, *provDescriptor)
		if err != nil {
			return nil, fmt.Errorf("unable to retrieve blob with digest %s: %w", provDescriptor.Digest, err)
		}
		result.Prov.Digest = provDescriptor.Digest.String()
		result.Prov.Size = provDescriptor.Size
	}

	fmt.Fprintf(c.out, "Pulled: %s\n", result.Ref)
	fmt.Fprintf(c.out, "Digest: %s\n", result.Manifest.Digest)

	if strings.Contains(result.Ref, "_") {
		fmt.Fprintf(c.out, "%s contains an underscore.\n", result.Ref)
		fmt.Fprint(c.out, registryUnderscoreMessage+"\n")
	}

	return result, nil
}

// PullOptWithChart returns a function that sets the withChart setting on pull
func PullOptWithChart(withChart bool) PullOption {
	return func(operation *pullOperation) {
		operation.withChart = withChart
	}
}

// PullOptWithProv returns a function that sets the withProv setting on pull
func PullOptWithProv(withProv bool) PullOption {
	return func(operation *pullOperation) {
		operation.withProv = withProv
	}
}

// PullOptIgnoreMissingProv returns a function that sets the ignoreMissingProv setting on pull
func PullOptIgnoreMissingProv(ignoreMissingProv bool) PullOption {
	return func(operation *pullOperation) {
		operation.ignoreMissingProv = ignoreMissingProv
	}
}

type (
	// PushOption allows specifying various settings on push
	PushOption func(*pushOperation)

	// PushResult is the result returned upon successful push.
	PushResult struct {
		Manifest *descriptorPushSummary         `json:"manifest"`
		Config   *descriptorPushSummary         `json:"config"`
		Chart    *descriptorPushSummaryWithMeta `json:"chart"`
		Prov     *descriptorPushSummary         `json:"prov"`
		Ref      string                         `json:"ref"`
	}

	descriptorPushSummary struct {
		Digest string `json:"digest"`
		Size   int64  `json:"size"`
	}

	descriptorPushSummaryWithMeta struct {
		descriptorPushSummary
		Meta *chart.Metadata `json:"meta"`
	}

	pushOperation struct {
		provData     []byte
		strictMode   bool
		creationTime string
	}
)

// Push uploads a chart to a registry.
func (c *Client) Push(data []byte, ref string, options ...PushOption) (*PushResult, error) {
	parsedRef, err := newReference(ref)
	if err != nil {
		return nil, err
	}

	operation := &pushOperation{
		strictMode: true, // By default, enable strict mode
	}
	for _, option := range options {
		option(operation)
	}
	meta, err := extractChartMeta(data)
	if err != nil {
		return nil, err
	}
	if operation.strictMode {
		if !strings.HasSuffix(ref, fmt.Sprintf("/%s:%s", meta.Name, meta.Version)) {
			return nil, errors.New(
				"strict mode enabled, ref basename and tag must match the chart name and version")
		}
	}

	ctx := context.Background()

	memoryStore := memory.New()
	chartDescriptor, err := oras.PushBytes(ctx, memoryStore, ChartLayerMediaType, data)
	if err != nil {
		return nil, err
	}

	configData, err := json.Marshal(meta)
	if err != nil {
		return nil, err
	}

	configDescriptor, err := oras.PushBytes(ctx, memoryStore, ConfigMediaType, configData)
	if err != nil {
		return nil, err
	}

	layers := []ocispec.Descriptor{chartDescriptor}
	var provDescriptor ocispec.Descriptor
	if operation.provData != nil {
		provDescriptor, err = oras.PushBytes(ctx, memoryStore, ProvLayerMediaType, operation.provData)
		if err != nil {
			return nil, err
		}

		layers = append(layers, provDescriptor)
	}

	// sort layers for determinism, similar to how ORAS v1 does it
	sort.Slice(layers, func(i, j int) bool {
		return layers[i].Digest < layers[j].Digest
	})

	ociAnnotations := generateOCIAnnotations(meta, operation.creationTime)
	manifest := ocispec.Manifest{
		Versioned:   specs.Versioned{SchemaVersion: 2},
		Config:      configDescriptor,
		Layers:      layers,
		Annotations: ociAnnotations,
	}

	manifestData, err := json.Marshal(manifest)
	if err != nil {
		return nil, err
	}

	manifestDescriptor, err := oras.TagBytes(ctx, memoryStore, ocispec.MediaTypeImageManifest, manifestData, ref)
	if err != nil {
		return nil, err
	}

	repository, err := remote.NewRepository(parsedRef.String())
	if err != nil {
		return nil, err
	}
	repository.PlainHTTP = c.plainHTTP
	repository.Client = c.authorizer

	manifestDescriptor, err = oras.ExtendedCopy(ctx, memoryStore, parsedRef.String(), repository, parsedRef.String(), oras.DefaultExtendedCopyOptions)
	if err != nil {
		return nil, err
	}

	chartSummary := &descriptorPushSummaryWithMeta{
		Meta: meta,
	}
	chartSummary.Digest = chartDescriptor.Digest.String()
	chartSummary.Size = chartDescriptor.Size
	result := &PushResult{
		Manifest: &descriptorPushSummary{
			Digest: manifestDescriptor.Digest.String(),
			Size:   manifestDescriptor.Size,
		},
		Config: &descriptorPushSummary{
			Digest: configDescriptor.Digest.String(),
			Size:   configDescriptor.Size,
		},
		Chart: chartSummary,
		Prov:  &descriptorPushSummary{}, // prevent nil references
		Ref:   parsedRef.String(),
	}
	if operation.provData != nil {
		result.Prov = &descriptorPushSummary{
			Digest: provDescriptor.Digest.String(),
			Size:   provDescriptor.Size,
		}
	}
	fmt.Fprintf(c.out, "Pushed: %s\n", result.Ref)
	fmt.Fprintf(c.out, "Digest: %s\n", result.Manifest.Digest)
	if strings.Contains(parsedRef.orasReference.Reference, "_") {
		fmt.Fprintf(c.out, "%s contains an underscore.\n", result.Ref)
		fmt.Fprint(c.out, registryUnderscoreMessage+"\n")
	}

	return result, err
}

// PushOptProvData returns a function that sets the prov bytes setting on push
func PushOptProvData(provData []byte) PushOption {
	return func(operation *pushOperation) {
		operation.provData = provData
	}
}

// PushOptStrictMode returns a function that sets the strictMode setting on push
func PushOptStrictMode(strictMode bool) PushOption {
	return func(operation *pushOperation) {
		operation.strictMode = strictMode
	}
}

// PushOptCreationDate returns a function that sets the creation time
func PushOptCreationTime(creationTime string) PushOption {
	return func(operation *pushOperation) {
		operation.creationTime = creationTime
	}
}

// Tags provides a sorted list all semver compliant tags for a given repository
func (c *Client) Tags(ref string) ([]string, error) {
	parsedReference, err := registry.ParseReference(ref)
	if err != nil {
		return nil, err
	}

	ctx := context.Background()
	repository, err := remote.NewRepository(parsedReference.String())
	if err != nil {
		return nil, err
	}
	repository.PlainHTTP = c.plainHTTP
	repository.Client = c.authorizer

	var tagVersions []*semver.Version
	err = repository.Tags(ctx, "", func(tags []string) error {
		for _, tag := range tags {
			// Change underscore (_) back to plus (+) for Helm
			// See https://github.com/helm/helm/issues/10166
			tagVersion, err := semver.StrictNewVersion(strings.ReplaceAll(tag, "_", "+"))
			if err == nil {
				tagVersions = append(tagVersions, tagVersion)
			}
		}

		return nil
	})
	if err != nil {
		return nil, err
	}

	// Sort the collection
	sort.Sort(sort.Reverse(semver.Collection(tagVersions)))

	tags := make([]string, len(tagVersions))

	for iTv, tv := range tagVersions {
		tags[iTv] = tv.String()
	}

	return tags, nil

}

// Resolve a reference to a descriptor.
func (c *Client) Resolve(ref string) (desc ocispec.Descriptor, err error) {
	remoteRepository, err := remote.NewRepository(ref)
	if err != nil {
		return desc, err
	}
	remoteRepository.PlainHTTP = c.plainHTTP

	parsedReference, err := newReference(ref)
	if err != nil {
		return desc, err
	}

	ctx := context.Background()
	parsedString := parsedReference.String()
	return remoteRepository.Resolve(ctx, parsedString)
}

// ValidateReference for path and version
func (c *Client) ValidateReference(ref, version string, u *url.URL) (*url.URL, error) {
	var tag string

	registryReference, err := newReference(u.Host + u.Path)
	if err != nil {
		return nil, err
	}

	if version == "" {
		// Use OCI URI tag as default
		version = registryReference.Tag
	} else {
		if registryReference.Tag != "" && registryReference.Tag != version {
			return nil, errors.Errorf("chart reference and version mismatch: %s is not %s", version, registryReference.Tag)
		}
	}

	if registryReference.Digest != "" {
		if version == "" {
			// Install by digest only
			return u, nil
		}
		u.Path = fmt.Sprintf("%s@%s", registryReference.Repository, registryReference.Digest)

		// Validate the tag if it was specified
		path := registryReference.Registry + "/" + registryReference.Repository + ":" + version
		desc, err := c.Resolve(path)
		if err != nil {
			// The resource does not have to be tagged when digest is specified
			return u, nil
		}
		if desc.Digest.String() != registryReference.Digest {
			return nil, errors.Errorf("chart reference digest mismatch: %s is not %s", desc.Digest.String(), registryReference.Digest)
		}
		return u, nil
	}

	// Evaluate whether an explicit version has been provided. Otherwise, determine version to use
	_, errSemVer := semver.NewVersion(version)
	if errSemVer == nil {
		tag = version
	} else {
		// Retrieve list of repository tags
		tags, err := c.Tags(strings.TrimPrefix(ref, fmt.Sprintf("%s://", OCIScheme)))
		if err != nil {
			return nil, err
		}
		if len(tags) == 0 {
			return nil, errors.Errorf("Unable to locate any tags in provided repository: %s", ref)
		}

		// Determine if version provided
		// If empty, try to get the highest available tag
		// If exact version, try to find it
		// If semver constraint string, try to find a match
		tag, err = GetTagMatchingVersionOrConstraint(tags, version)
		if err != nil {
			return nil, err
		}
	}

	u.Path = fmt.Sprintf("%s:%s", registryReference.Repository, tag)

	return u, err
}