GoToSocial/internal/ap/serialize.go

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// GoToSocial
// Copyright (C) GoToSocial Authors admin@gotosocial.org
// SPDX-License-Identifier: AGPL-3.0-or-later
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package ap
import (
"fmt"
"github.com/superseriousbusiness/activity/streams"
"github.com/superseriousbusiness/activity/streams/vocab"
)
// Serialize is a custom serializer for ActivityStreams types.
//
// In most cases, it will simply call the go-fed streams.Serialize function under the hood.
// However, if custom serialization is required on a specific type (eg for inter-implementation
// compatibility), it can be inserted into the switch as necessary.
//
// Callers should always call this function instead of streams.Serialize, unless there's a
// very good reason to do otherwise.
//
// Currently, the following things will be custom serialized:
//
// - OrderedCollection: 'orderedItems' property will always be made into an array.
// - Any Accountable type: 'attachment' property will always be made into an array.
// - Update: any Accountable 'object's set on an update will be custom serialized as above.
func Serialize(t vocab.Type) (m map[string]interface{}, e error) {
switch t.GetTypeName() {
case ObjectOrderedCollection:
return serializeOrderedCollection(t)
case ActorApplication, ActorGroup, ActorOrganization, ActorPerson, ActorService:
return serializeAccountable(t, true)
case ActivityUpdate:
return serializeWithObject(t)
default:
// No custom serializer necessary.
return streams.Serialize(t)
}
}
// serializeOrderedCollection is a custom serializer for an ActivityStreamsOrderedCollection.
// Unlike the standard streams.Serialize function, this serializer normalizes the orderedItems
// value to always be an array/slice, regardless of how many items are contained therein.
//
// TODO: Remove this function if we can fix the underlying issue in Go-Fed.
//
// See:
// - https://github.com/go-fed/activity/issues/139
// - https://github.com/mastodon/mastodon/issues/24225
func serializeOrderedCollection(orderedCollection vocab.Type) (map[string]interface{}, error) {
data, err := streams.Serialize(orderedCollection)
if err != nil {
return nil, err
}
orderedItems, ok := data["orderedItems"]
if !ok {
// No 'orderedItems', nothing to change.
return data, nil
}
if _, ok := orderedItems.([]interface{}); ok {
// Already slice.
return data, nil
}
// Coerce single-object to slice.
data["orderedItems"] = []interface{}{orderedItems}
return data, nil
}
// SerializeAccountable is a custom serializer for any Accountable type.
// This serializer rewrites the 'attachment' value of the Accountable, if
// present, to always be an array/slice.
//
// While this is not strictly necessary in json-ld terms, most other fedi
// implementations look for attachment to be an array of PropertyValue (field)
// entries, and will not parse single-entry, non-array attachments on accounts
// properly.
//
// If the accountable is being serialized as a top-level object (eg., for serving
// in response to an account dereference request), then includeContext should be
// set to true, so as to include the json-ld '@context' entries in the data.
// If the accountable is being serialized as part of another object (eg., as the
// object of an activity), then includeContext should be set to false, as the
// @context entry should be included on the top-level/wrapping activity/object.
func serializeAccountable(accountable vocab.Type, includeContext bool) (map[string]interface{}, error) {
var (
data map[string]interface{}
err error
)
if includeContext {
data, err = streams.Serialize(accountable)
} else {
data, err = accountable.Serialize()
}
if err != nil {
return nil, err
}
attachment, ok := data["attachment"]
if !ok {
// No 'attachment', nothing to change.
return data, nil
}
if _, ok := attachment.([]interface{}); ok {
// Already slice.
return data, nil
}
// Coerce single-object to slice.
data["attachment"] = []interface{}{attachment}
return data, nil
}
func serializeWithObject(t vocab.Type) (map[string]interface{}, error) {
withObject, ok := t.(WithObject)
if !ok {
return nil, fmt.Errorf("serializeWithObject: could not resolve %T to WithObject", t)
}
data, err := streams.Serialize(t)
if err != nil {
return nil, err
}
object := withObject.GetActivityStreamsObject()
if object == nil {
// Nothing to do, bail early.
return data, nil
}
objectLen := object.Len()
if objectLen == 0 {
// Nothing to do, bail early.
return data, nil
}
// The thing we already serialized has objects
// on it, so we should see if we need to custom
// serialize any of those objects, and replace
// them on the data map as necessary.
objects := make([]interface{}, 0, objectLen)
for iter := object.Begin(); iter != object.End(); iter = iter.Next() {
if iter.IsIRI() {
// Plain IRIs don't need custom serialization.
objects = append(objects, iter.GetIRI().String())
continue
}
var (
objectType = iter.GetType()
objectSer map[string]interface{}
)
if objectType == nil {
// This is awkward.
return nil, fmt.Errorf("serializeWithObject: could not resolve object iter %T to vocab.Type", iter)
}
switch objectType.GetTypeName() {
case ActorApplication, ActorGroup, ActorOrganization, ActorPerson, ActorService:
// @context will be included in wrapping type already,
// we don't need to include it in the object itself.
objectSer, err = serializeAccountable(objectType, false)
default:
// No custom serializer for this type; serialize as normal.
objectSer, err = objectType.Serialize()
}
if err != nil {
return nil, err
}
objects = append(objects, objectSer)
}
if objectLen == 1 {
// Unnest single object.
data["object"] = objects[0]
} else {
// Array of objects.
data["object"] = objects
}
return data, nil
}