[bugfix] support both CollectionPage AND OrderedCollectionPage in status replies (#2220)

internal/federation/dereferencing/collectionpage.go

@@ -20,49 +20,115 @@ package dereferencing
 import (
 	"context"
 	"encoding/json"
-	"errors"
-	"fmt"
 	"net/url"
 
 	"github.com/superseriousbusiness/activity/streams"
 	"github.com/superseriousbusiness/activity/streams/vocab"
 	"github.com/superseriousbusiness/gotosocial/internal/ap"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/log"
 )
 
 // dereferenceCollectionPage returns the activitystreams CollectionPage at the specified IRI, or an error if something goes wrong.
-func (d *deref) dereferenceCollectionPage(ctx context.Context, username string, pageIRI *url.URL) (ap.CollectionPageable, error) {
+func (d *deref) dereferenceCollectionPage(ctx context.Context, username string, pageIRI *url.URL) (ap.CollectionPageIterator, error) {
 	if blocked, err := d.state.DB.IsDomainBlocked(ctx, pageIRI.Host); blocked || err != nil {
-		return nil, fmt.Errorf("DereferenceCollectionPage: domain %s is blocked", pageIRI.Host)
+		return nil, gtserror.Newf("domain %s is blocked", pageIRI.Host)
 	}
 
 	transport, err := d.transportController.NewTransportForUsername(ctx, username)
 	if err != nil {
-		return nil, fmt.Errorf("DereferenceCollectionPage: error creating transport: %s", err)
+		return nil, gtserror.Newf("error creating transport: %w", err)
 	}
 
 	b, err := transport.Dereference(ctx, pageIRI)
 	if err != nil {
-		return nil, fmt.Errorf("DereferenceCollectionPage: error deferencing %s: %s", pageIRI.String(), err)
+		return nil, gtserror.Newf("error deferencing %s: %w", pageIRI.String(), err)
 	}
 
 	m := make(map[string]interface{})
 	if err := json.Unmarshal(b, &m); err != nil {
-		return nil, fmt.Errorf("DereferenceCollectionPage: error unmarshalling bytes into json: %s", err)
+		return nil, gtserror.Newf("error unmarshalling bytes into json: %w", err)
 	}
 
 	t, err := streams.ToType(ctx, m)
 	if err != nil {
-		return nil, fmt.Errorf("DereferenceCollectionPage: error resolving json into ap vocab type: %s", err)
+		return nil, gtserror.Newf("error resolving json into ap vocab type: %w", err)
 	}
 
-	if t.GetTypeName() != ap.ObjectCollectionPage {
-		return nil, fmt.Errorf("DereferenceCollectionPage: type name %s not supported", t.GetTypeName())
+	page, err := ap.ToCollectionPageIterator(t)
+	if err != nil {
+		return nil, gtserror.Newf("error resolving vocab type as page: %w", err)
 	}
 
-	p, ok := t.(vocab.ActivityStreamsCollectionPage)
-	if !ok {
-		return nil, errors.New("DereferenceCollectionPage: error resolving type as activitystreams collection page")
-	}
-
-	return p, nil
+	return page, nil
+}
+
+// getAttachedStatusCollection is a small utility function to fetch the first page of an
+// attached activity streams collection from a provided statusable object, along with a URI.
+func getAttachedStatusCollectionPage(status ap.Statusable) (ap.CollectionPageIterator, string) { //nolint:gocritic
+	// Look for an attached status replies (as collection)
+	replies := status.GetActivityStreamsReplies()
+	if replies == nil {
+		return nil, ""
+	}
+
+	// Look for an attached collection page, wrap and return.
+	if page := getRepliesCollectionPage(replies); page != nil {
+		return ap.WrapCollectionPage(page), getIDString(page)
+	}
+
+	// Look for an attached ordered collection page, wrap and return.
+	if page := getRepliesOrderedCollectionPage(replies); page != nil {
+		return ap.WrapOrderedCollectionPage(page), getIDString(page)
+	}
+
+	log.Warnf(nil, "replies without collection page: %s", getIDString(status))
+	return nil, ""
+}
+
+func getRepliesCollectionPage(replies vocab.ActivityStreamsRepliesProperty) vocab.ActivityStreamsCollectionPage {
+	// Get the status replies collection
+	collection := replies.GetActivityStreamsCollection()
+	if collection == nil {
+		return nil
+	}
+
+	// Get the "first" property of the replies collection
+	first := collection.GetActivityStreamsFirst()
+	if first == nil {
+		return nil
+	}
+
+	// Return the first activity stream collection page
+	return first.GetActivityStreamsCollectionPage()
+}
+
+func getRepliesOrderedCollectionPage(replies vocab.ActivityStreamsRepliesProperty) vocab.ActivityStreamsOrderedCollectionPage {
+	// Get the status replies collection
+	collection := replies.GetActivityStreamsOrderedCollection()
+	if collection == nil {
+		return nil
+	}
+
+	// Get the "first" property of the replies collection
+	first := collection.GetActivityStreamsFirst()
+	if first == nil {
+		return nil
+	}
+
+	// Return the first activity stream collection page
+	return first.GetActivityStreamsOrderedCollectionPage()
+}
+
+// getIDString is shorthand to fetch an ID URI string from AP type with attached JSONLDId.
+func getIDString(a ap.WithJSONLDId) string {
+	id := a.GetJSONLDId()
+	if id == nil {
+		return ""
+	}
+	uri := id.Get()
+	if uri == nil {
+		return ""
+	}
+	return uri.String()
 }