func v2auth(client *gophercloud.ProviderClient, endpoint string, options gophercloud.AuthOptions) error {
	v2Client := NewIdentityV2(client)
	if endpoint != "" {
		v2Client.Endpoint = endpoint
	}

	result := tokens2.Create(v2Client, tokens2.AuthOptions{AuthOptions: options})

	token, err := result.ExtractToken()
	if err != nil {
		return err
	}

	catalog, err := result.ExtractServiceCatalog()
	if err != nil {
		return err
	}

	if options.AllowReauth {
		client.ReauthFunc = func() error {
			client.TokenID = ""
			return AuthenticateV2(client, options)
		}
	}
	client.TokenID = token.ID
	client.EndpointLocator = func(opts gophercloud.EndpointOpts) (string, error) {
		return V2EndpointURL(catalog, opts)
	}

	return nil
}

// NewDBV1 creates a ServiceClient that may be used to access the v1 DB service.
func NewDBV1(client *gophercloud.ProviderClient, eo gophercloud.EndpointOpts) (*gophercloud.ServiceClient, error) {
	eo.ApplyDefaults("database")
	url, err := client.EndpointLocator(eo)
	if err != nil {
		return nil, err
	}
	return &gophercloud.ServiceClient{ProviderClient: client, Endpoint: url}, nil
}

// NewRackConnectV3 creates a ServiceClient that may be used to access the v3 RackConnect service.
func NewRackConnectV3(client *gophercloud.ProviderClient, eo gophercloud.EndpointOpts) (*gophercloud.ServiceClient, error) {
	eo.ApplyDefaults("rax:rackconnect")
	url, err := client.EndpointLocator(eo)
	if err != nil {
		return nil, err
	}
	return &gophercloud.ServiceClient{ProviderClient: client, Endpoint: url}, nil
}

// NewNetworkV2 creates a ServiceClient that may be used with the v2 network package.
func NewNetworkV2(client *gophercloud.ProviderClient, eo gophercloud.EndpointOpts) (*gophercloud.ServiceClient, error) {
	eo.ApplyDefaults("network")
	url, err := client.EndpointLocator(eo)
	if err != nil {
		return nil, err
	}
	return &gophercloud.ServiceClient{
		ProviderClient: client,
		Endpoint:       url,
		ResourceBase:   url + "v2.0/",
	}, nil
}

func v3auth(client *gophercloud.ProviderClient, endpoint string, options gophercloud.AuthOptions) error {
	// Override the generated service endpoint with the one returned by the version endpoint.
	v3Client := NewIdentityV3(client)
	if endpoint != "" {
		v3Client.Endpoint = endpoint
	}

	var scope *tokens3.Scope
	if options.TenantID != "" {
		scope = &tokens3.Scope{
			ProjectID: options.TenantID,
		}
		options.TenantID = ""
		options.TenantName = ""
	} else {
		if options.TenantName != "" {
			scope = &tokens3.Scope{
				ProjectName: options.TenantName,
				DomainID:    options.DomainID,
				DomainName:  options.DomainName,
			}
			options.TenantName = ""
		}
	}

	result := tokens3.Create(v3Client, options, scope)

	token, err := result.ExtractToken()
	if err != nil {
		return err
	}

	catalog, err := result.ExtractServiceCatalog()
	if err != nil {
		return err
	}

	client.TokenID = token.ID

	if options.AllowReauth {
		client.ReauthFunc = func() error {
			return AuthenticateV3(client, options)
		}
	}
	client.EndpointLocator = func(opts gophercloud.EndpointOpts) (string, error) {
		return V3EndpointURL(catalog, opts)
	}

	return nil
}

// ChooseVersion queries the base endpoint of an API to choose the most recent non-experimental alternative from a service's
// published versions.
// It returns the highest-Priority Version among the alternatives that are provided, as well as its corresponding endpoint.
func ChooseVersion(client *gophercloud.ProviderClient, recognized []*Version) (*Version, string, error) {
	type linkResp struct {
		Href string `json:"href"`
		Rel  string `json:"rel"`
	}

	type valueResp struct {
		ID     string     `json:"id"`
		Status string     `json:"status"`
		Links  []linkResp `json:"links"`
	}

	type versionsResp struct {
		Values []valueResp `json:"values"`
	}

	type response struct {
		Versions versionsResp `json:"versions"`
	}

	normalize := func(endpoint string) string {
		if !strings.HasSuffix(endpoint, "/") {
			return endpoint + "/"
		}
		return endpoint
	}
	identityEndpoint := normalize(client.IdentityEndpoint)

	// If a full endpoint is specified, check version suffixes for a match first.
	for _, v := range recognized {
		if strings.HasSuffix(identityEndpoint, v.Suffix) {
			return v, identityEndpoint, nil
		}
	}

	var resp response
	_, err := client.Request("GET", client.IdentityBase, gophercloud.RequestOpts{
		JSONResponse: &resp,
		OkCodes:      []int{200, 300},
	})

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

	byID := make(map[string]*Version)
	for _, version := range recognized {
		byID[version.ID] = version
	}

	var highest *Version
	var endpoint string

	for _, value := range resp.Versions.Values {
		href := ""
		for _, link := range value.Links {
			if link.Rel == "self" {
				href = normalize(link.Href)
			}
		}

		if matching, ok := byID[value.ID]; ok {
			// Prefer a version that exactly matches the provided endpoint.
			if href == identityEndpoint {
				if href == "" {
					return nil, "", fmt.Errorf("Endpoint missing in version %s response from %s", value.ID, client.IdentityBase)
				}
				return matching, href, nil
			}

			// Otherwise, find the highest-priority version with a whitelisted status.
			if goodStatus[strings.ToLower(value.Status)] {
				if highest == nil || matching.Priority > highest.Priority {
					highest = matching
					endpoint = href
				}
			}
		}
	}

	if highest == nil {
		return nil, "", fmt.Errorf("No supported version available from endpoint %s", client.IdentityBase)
	}
	if endpoint == "" {
		return nil, "", fmt.Errorf("Endpoint missing in version %s response from %s", highest.ID, client.IdentityBase)
	}

	return highest, endpoint, nil
}