Add a layer of safety around required ActivityPub Actor fields (#4703)

* fix(ap): add safe constructors, getters, and validators to ActivityPub actors to address #4701

* chore: replace nil check with the new Validate() method

* chore(test): added test to verify the values extracted from actors

* fix: return the specific error type + test for it

* fix(ap): add recovery for each AP inbox worker for a worst case scenario

* fix(ap): add additional safe accessor methods to other AP entities other than actors

* chore(tests): add tests for the new safe accessors

* fix(ap): handle empty public keys in AP actors

activitypub/apmodels/utils.go

@@ -2,6 +2,7 @@ package apmodels
 
 import (
 	"encoding/json"
+	"fmt"
 	"net/url"
 	"path"
 	"path/filepath"
@@ -118,3 +119,149 @@ func GetLogoType() string {
 	}
 	return logoType
 }
+
+// ErrMissingIRI is returned when an IRI cannot be extracted from an ActivityStreams property.
+var ErrMissingIRI = fmt.Errorf("missing IRI")
+
+// GetIRIFromActorProperty safely extracts the IRI from an ActivityStreamsActorProperty.
+// Returns the IRI and nil error on success, or nil and an error if the IRI cannot be extracted.
+func GetIRIFromActorProperty(actor vocab.ActivityStreamsActorProperty) (*url.URL, error) {
+	if actor == nil || actor.Empty() || actor.Len() == 0 {
+		return nil, fmt.Errorf("%w: actor property is empty or nil", ErrMissingIRI)
+	}
+	first := actor.At(0)
+	if first == nil {
+		return nil, fmt.Errorf("%w: actor property first element is nil", ErrMissingIRI)
+	}
+	iri := first.GetIRI()
+	if iri == nil {
+		return nil, fmt.Errorf("%w: actor IRI is nil", ErrMissingIRI)
+	}
+	return iri, nil
+}
+
+// GetIRIStringFromActorProperty safely extracts the IRI string from an ActivityStreamsActorProperty.
+// Returns the IRI string and nil error on success, or empty string and an error if extraction fails.
+func GetIRIStringFromActorProperty(actor vocab.ActivityStreamsActorProperty) (string, error) {
+	iri, err := GetIRIFromActorProperty(actor)
+	if err != nil {
+		return "", err
+	}
+	return iri.String(), nil
+}
+
+// GetIRIFromObjectProperty safely extracts the IRI from an ActivityStreamsObjectProperty.
+// Returns the IRI and nil error on success, or nil and an error if the IRI cannot be extracted.
+func GetIRIFromObjectProperty(object vocab.ActivityStreamsObjectProperty) (*url.URL, error) {
+	if object == nil || object.Len() == 0 {
+		return nil, fmt.Errorf("%w: object property is empty or nil", ErrMissingIRI)
+	}
+	first := object.At(0)
+	if first == nil {
+		return nil, fmt.Errorf("%w: object property first element is nil", ErrMissingIRI)
+	}
+	iri := first.GetIRI()
+	if iri == nil {
+		return nil, fmt.Errorf("%w: object IRI is nil", ErrMissingIRI)
+	}
+	return iri, nil
+}
+
+// GetIRIStringFromObjectProperty safely extracts the IRI string from an ActivityStreamsObjectProperty.
+// Returns the IRI string and nil error on success, or empty string and an error if extraction fails.
+func GetIRIStringFromObjectProperty(object vocab.ActivityStreamsObjectProperty) (string, error) {
+	iri, err := GetIRIFromObjectProperty(object)
+	if err != nil {
+		return "", err
+	}
+	return iri.String(), nil
+}
+
+// GetIRIFromJSONLDIdProperty safely extracts the IRI from a JSONLDIdProperty.
+// Returns the IRI and nil error on success, or nil and an error if the IRI cannot be extracted.
+func GetIRIFromJSONLDIdProperty(id vocab.JSONLDIdProperty) (*url.URL, error) {
+	if id == nil {
+		return nil, fmt.Errorf("%w: JSONLD id property is nil", ErrMissingIRI)
+	}
+	iri := id.GetIRI()
+	if iri == nil {
+		return nil, fmt.Errorf("%w: JSONLD id IRI is nil", ErrMissingIRI)
+	}
+	return iri, nil
+}
+
+// GetIRIStringFromJSONLDIdProperty safely extracts the IRI string from a JSONLDIdProperty.
+// Returns the IRI string and nil error on success, or empty string and an error if extraction fails.
+func GetIRIStringFromJSONLDIdProperty(id vocab.JSONLDIdProperty) (string, error) {
+	iri, err := GetIRIFromJSONLDIdProperty(id)
+	if err != nil {
+		return "", err
+	}
+	return iri.String(), nil
+}
+
+// GetPublicKeyPem safely extracts the public key PEM from a W3IDSecurityV1PublicKey.
+// Returns the PEM string and nil error on success, or empty string and an error if extraction fails.
+func GetPublicKeyPem(publicKey vocab.W3IDSecurityV1PublicKey) (string, error) {
+	if publicKey == nil {
+		return "", fmt.Errorf("public key is nil")
+	}
+	pemProp := publicKey.GetW3IDSecurityV1PublicKeyPem()
+	if pemProp == nil {
+		return "", fmt.Errorf("public key PEM property is nil")
+	}
+	return pemProp.Get(), nil
+}
+
+// IsFirstObjectActivityStreamsPerson safely checks if the first element of an
+// ActivityStreamsObjectProperty is an ActivityStreamsPerson.
+// Returns false if the object is nil, empty, or the first element is not a Person.
+func IsFirstObjectActivityStreamsPerson(object vocab.ActivityStreamsObjectProperty) bool {
+	if object == nil || object.Len() == 0 {
+		return false
+	}
+	first := object.At(0)
+	if first == nil {
+		return false
+	}
+	return first.IsActivityStreamsPerson()
+}
+
+// GetImageFromIcon safely extracts the image URL from an ActivityStreamsIconProperty.
+// Returns the URL and nil error on success, or nil and nil if the icon is not present or invalid.
+// This handles the common pattern of icon -> image -> url -> iri.
+func GetImageFromIcon(icon vocab.ActivityStreamsIconProperty) *url.URL {
+	if icon == nil || icon.Empty() {
+		return nil
+	}
+	first := icon.At(0)
+	if first == nil {
+		return nil
+	}
+	image := first.GetActivityStreamsImage()
+	if image == nil {
+		return nil
+	}
+	urlProp := image.GetActivityStreamsUrl()
+	if urlProp == nil {
+		return nil
+	}
+	begin := urlProp.Begin()
+	if begin == nil {
+		return nil
+	}
+	return begin.GetIRI()
+}
+
+// GetHostnameFromJSONLDId safely extracts the hostname from a JSONLDIdProperty.
+// Returns the hostname string, or empty string if extraction fails.
+func GetHostnameFromJSONLDId(id vocab.JSONLDIdProperty) string {
+	if id == nil {
+		return ""
+	}
+	iri := id.GetIRI()
+	if iri == nil {
+		return ""
+	}
+	return iri.Hostname()
+}