Add config.NewExternalNameFrom that makes the existing ExternalName c…

…onfigurations

reusable via compositions.

- Format the doc comments for the config.TemplatedStringAsIdentifier function.

Signed-off-by: Alper Rifat Ulucinar <[email protected]>

pkg/config/externalname.go

@@ -70,34 +70,38 @@ func ParameterAsIdentifier(param string) ExternalName {
 // TemplatedStringAsIdentifier accepts a template as the shape of the Terraform
 // ID and lets you provide a field path for the argument you're using as external
 // name. The available variables you can use in the template are as follows:
-// parameters: A tree of parameters that you'd normally see in a Terraform HCL
 //
-//	file. You can use TF registry documentation of given resource to
-//	see what's available.
+// parameters: A tree of parameters that you'd normally see in a Terraform HCL
+// file. You can use TF registry documentation of given resource to
+// see what's available.
 //
 // setup.configuration: The Terraform configuration object of the provider. You can
-//
-//	take a look at the TF registry provider configuration object
-//	to see what's available. Not to be confused with ProviderConfig
-//	custom resource of the Crossplane provider.
+// take a look at the TF registry provider configuration object
+// to see what's available. Not to be confused with ProviderConfig
+// custom resource of the Crossplane provider.
 //
 // setup.client_metadata: The Terraform client metadata available for the provider,
-//
-//	such as the AWS account ID for the AWS provider.
+// such as the AWS account ID for the AWS provider.
 //
 // external_name: The value of external name annotation of the custom resource.
-//
-//	It is required to use this as part of the template.
+// It is required to use this as part of the template.
 //
 // The following template functions are available:
+//
 // ToLower: Converts the contents of the pipeline to lower-case
+//
 // ToUpper: Converts the contents of the pipeline to upper-case
+//
 // Please note that it's currently *not* possible to use
 // the template functions on the .external_name template variable.
 // Example usages:
+//
 // TemplatedStringAsIdentifier("index_name", "/subscriptions/{{ .setup.configuration.subscription }}/{{ .external_name }}")
+//
 // TemplatedStringAsIdentifier("index_name", "/resource/{{ .external_name }}/static")
+//
 // TemplatedStringAsIdentifier("index_name", "{{ .parameters.cluster_id }}:{{ .parameters.node_id }}:{{ .external_name }}")
+//
 // TemplatedStringAsIdentifier("", "arn:aws:network-firewall:{{ .setup.configuration.region }}:{{ .setup.client_metadata.account_id }}:{{ .parameters.type | ToLower }}-rulegroup/{{ .external_name }}")
 func TemplatedStringAsIdentifier(nameFieldPath, tmpl string) ExternalName {
 	t, err := template.New("getid").Funcs(template.FuncMap{
@@ -205,3 +209,96 @@ func GetExternalNameFromTemplated(tmpl, val string) (string, error) { //nolint:g
 	}
 	return "", errors.Errorf("unhandled case with template %s and value %s", tmpl, val)
 }
+
+// ExternalNameFrom is an ExternalName configuration which uses a parent
+// configuration as its base and modifies any of the GetIDFn,
+// GetExternalNameFn or SetIdentifierArgumentsFn. This enables us to reuse
+// the existing ExternalName configurations with modifications in their
+// behaviors via compositions.
+type ExternalNameFrom struct {
+	ExternalName
+	getIDFn                 func(GetIDFn, context.Context, string, map[string]any, map[string]any) (string, error)
+	getExternalNameFn       func(GetExternalNameFn, map[string]any) (string, error)
+	setIdentifierArgumentFn func(SetIdentifierArgumentsFn, map[string]any, string)
+}
+
+// ExternalNameFromOption is an option that modifies the behavior of an
+// ExternalNameFrom external-name configuration.
+type ExternalNameFromOption func(from *ExternalNameFrom)
+
+// WithGetIDFn sets the GetIDFn for the ExternalNameFrom configuration.
+// The function parameter fn receives the parent ExternalName's GetIDFn, and
+// implementations may invoke the parent's GetIDFn via this
+// parameter. For the description of the rest of the parameters and return
+// values, please see the documentation of GetIDFn.
+func WithGetIDFn(fn func(fn GetIDFn, ctx context.Context, externalName string, parameters map[string]any, terraformProviderConfig map[string]any) (string, error)) ExternalNameFromOption {
+	return func(ec *ExternalNameFrom) {
+		ec.getIDFn = fn
+	}
+}
+
+// WithGetExternalNameFn sets the GetExternalNameFn for the ExternalNameFrom
+// configuration. The function parameter fn receives the parent ExternalName's
+// GetExternalNameFn, and implementations may invoke the parent's
+// GetExternalNameFn via this parameter. For the description of the rest
+// of the parameters and return values, please see the documentation of
+// GetExternalNameFn.
+func WithGetExternalNameFn(fn func(fn GetExternalNameFn, tfstate map[string]any) (string, error)) ExternalNameFromOption {
+	return func(ec *ExternalNameFrom) {
+		ec.getExternalNameFn = fn
+	}
+}
+
+// WithSetIdentifierArgumentsFn sets the SetIdentifierArgumentsFn for the
+// ExternalNameFrom configuration. The function parameter fn receives the
+// parent ExternalName's SetIdentifierArgumentsFn, and implementations may
+// invoke the parent's SetIdentifierArgumentsFn via this
+// parameter. For the description of the rest of the parameters and return
+// values, please see the documentation of SetIdentifierArgumentsFn.
+func WithSetIdentifierArgumentsFn(fn func(fn SetIdentifierArgumentsFn, base map[string]any, externalName string)) ExternalNameFromOption {
+	return func(ec *ExternalNameFrom) {
+		ec.setIdentifierArgumentFn = fn
+	}
+}
+
+// NewExternalNameFrom initializes a new ExternalNameFrom with the given parent
+// and with the given options. An example configuration that uses a
+// TemplatedStringAsIdentifier as its parent (base) and sets a default value
+// for the external-name if the external-name is yet not populated is as
+// follows:
+//
+// config.NewExternalNameFrom(config.TemplatedStringAsIdentifier("", "{{ .parameters.type }}/{{ .setup.client_metadata.account_id }}/{{ .external_name }}"),
+//
+//	config.WithGetIDFn(func(fn config.GetIDFn, ctx context.Context, externalName string, parameters map[string]any, terraformProviderConfig map[string]any) (string, error) {
+//		if externalName == "" {
+//			externalName = "some random string"
+//		}
+//		return fn(ctx, externalName, parameters, terraformProviderConfig)
+//	}))
+func NewExternalNameFrom(parent ExternalName, opts ...ExternalNameFromOption) ExternalName {
+	ec := &ExternalNameFrom{}
+	for _, o := range opts {
+		o(ec)
+	}
+
+	ec.ExternalName.GetIDFn = func(ctx context.Context, externalName string, parameters map[string]any, terraformProviderConfig map[string]any) (string, error) {
+		if ec.getIDFn == nil {
+			return parent.GetIDFn(ctx, externalName, parameters, terraformProviderConfig)
+		}
+		return ec.getIDFn(parent.GetIDFn, ctx, externalName, parameters, terraformProviderConfig)
+	}
+	ec.ExternalName.GetExternalNameFn = func(tfstate map[string]any) (string, error) {
+		if ec.getExternalNameFn == nil {
+			return parent.GetExternalNameFn(tfstate)
+		}
+		return ec.getExternalNameFn(parent.GetExternalNameFn, tfstate)
+	}
+	ec.ExternalName.SetIdentifierArgumentFn = func(base map[string]any, externalName string) {
+		if ec.setIdentifierArgumentFn == nil {
+			parent.SetIdentifierArgumentFn(base, externalName)
+			return
+		}
+		ec.setIdentifierArgumentFn(parent.SetIdentifierArgumentFn, base, externalName)
+	}
+	return ec.ExternalName
+}