activitypub/activitystreams/object.go

package activitystreams

import (
	"encoding/json"
	"fmt"
	"sort"
	"strings"
	"time"

	"github.com/buger/jsonparser"
)

// ObjectID designates an unique global identifier.
// All Objects in [ActivityStreams] should have unique global identifiers.
// ActivityPub extends this requirement; all objects distributed by the ActivityPub protocol MUST
// have unique global identifiers, unless they are intentionally transient
// (short lived activities that are not intended to be able to be looked up,
// such as some kinds of chat messages or game notifications).
// These identifiers must fall into one of the following groups:
//
// 1. Publicly dereferencable URIs, such as HTTPS URIs, with their authority belonging
// to that of their originating server. (Publicly facing content SHOULD use HTTPS URIs).
// 2. An ID explicitly specified as the JSON null object, which implies an anonymous object
// (a part of its parent context)
type ObjectID IRI

const (
	// ActivityBaseURI the basic URI for the activity streams namespaces
	ActivityBaseURI                                  = IRI("https://www.w3.org/ns/activitystreams")
	ObjectType                ActivityVocabularyType = "Object"
	LinkType                  ActivityVocabularyType = "Link"
	ActivityType              ActivityVocabularyType = "Activity"
	IntransitiveActivityType  ActivityVocabularyType = "IntransitiveActivity"
	ActorType                 ActivityVocabularyType = "Actor"
	CollectionType            ActivityVocabularyType = "Collection"
	OrderedCollectionType     ActivityVocabularyType = "OrderedCollection"
	CollectionPageType        ActivityVocabularyType = "CollectionPage"
	OrderedCollectionPageType ActivityVocabularyType = "OrderedCollectionPage"

	// Activity Pub Object Types
	ArticleType      ActivityVocabularyType = "Article"
	AudioType        ActivityVocabularyType = "Audio"
	DocumentType     ActivityVocabularyType = "Document"
	EventType        ActivityVocabularyType = "Event"
	ImageType        ActivityVocabularyType = "Image"
	NoteType         ActivityVocabularyType = "Note"
	PageType         ActivityVocabularyType = "Page"
	PlaceType        ActivityVocabularyType = "Place"
	ProfileType      ActivityVocabularyType = "Profile"
	RelationshipType ActivityVocabularyType = "Relationship"
	TombstoneType    ActivityVocabularyType = "Tombstone"
	VideoType        ActivityVocabularyType = "Video"

	// MentionType is a link type for @mentions
	MentionType ActivityVocabularyType = "Mention"
)

const (
	NilLangRef LangRef = "-"
)

var validGenericObjectTypes = [...]ActivityVocabularyType{
	ActivityType,
	IntransitiveActivityType,
	ObjectType,
	ActorType,
	CollectionType,
	OrderedCollectionType,
}

var validGenericLinkTypes = [...]ActivityVocabularyType{
	LinkType,
}

var validGenericTypes = append(validGenericObjectTypes[:], validGenericLinkTypes[:]...)

var validObjectTypes = [...]ActivityVocabularyType{
	ArticleType,
	AudioType,
	DocumentType,
	EventType,
	ImageType,
	NoteType,
	PageType,
	PlaceType,
	ProfileType,
	RelationshipType,
	TombstoneType,
	VideoType,
}

type (
	// ActivityVocabularyType is the data type for an Activity type object
	ActivityVocabularyType string
	// ActivityObject is a subtype of Object that describes some form of action that may happen,
	// is currently happening, or has already happened
	ActivityObject interface {
		GetID() *ObjectID
	}
	// Item describes an object of any kind.
	ObjectOrLink interface {
		ActivityObject
		LinkOrURI
		GetType() ActivityVocabularyType
		IsLink() bool
		IsObject() bool
		//UnmarshalJSON([]byte) error
	}
	// LinkOrURI is an interface that Object and Link structs implement, and at the same time
	// they are kept disjointed
	LinkOrURI interface {
		GetLink() IRI
	}
	// MimeType is the type for MIME types
	MimeType string
	// LangRef is the type for a language reference, should be ISO 639-1 language specifier.
	LangRef string

	LangRefValue struct {
		Ref   LangRef
		Value string
	}
	// NaturalLanguageValue is a mapping for multiple language values
	NaturalLanguageValue []LangRefValue
)

func NaturalLanguageValueNew() NaturalLanguageValue {
	return make(NaturalLanguageValue, 0)
}

func (n NaturalLanguageValue) Get(ref LangRef) string {
	for _, val := range n {
		if val.Ref == ref {
			return val.Value
		}
	}
	return ""
}

func (n *NaturalLanguageValue) Set(ref LangRef, v string) error {
	t := append(*n, LangRefValue{ref, v})
	*n = t
	return nil
}

// IsLink validates if currentActivity Pub Object is a Link
func (o Object) IsLink() bool {
	return false
}

// IsObject validates if currentActivity Pub Object is an Object
func (o Object) IsObject() bool {
	return true
}

// MarshalJSON serializes the NaturalLanguageValue into JSON
func (n NaturalLanguageValue) MarshalJSON() ([]byte, error) {
	if len(n) == 0 {
		return json.Marshal(nil)
	}
	if len(n) == 1 {
		for _, v := range n {
			return json.Marshal(v.Value)
		}
	}
	mm := make(map[LangRef]string)
	for _, val := range n {
		mm[val.Ref] = val.Value
	}

	return json.Marshal(mm)
}

// First returns the first element in the map
func (n NaturalLanguageValue) First() string {
	for _, v := range n {
		return v.Value
	}
	return ""
}

// MarshalText serializes the NaturalLanguageValue into Text
func (n NaturalLanguageValue) MarshalText() ([]byte, error) {
	for _, v := range n {
		return []byte(fmt.Sprintf("%q", v)), nil
	}
	return nil, nil
}

// Append is syntactic sugar for resizing the NaturalLanguageValue map
// and appending an element
func (n *NaturalLanguageValue) Append(lang LangRef, value string) error {
	var t NaturalLanguageValue
	if len(*n) == 0 {
		t = make(NaturalLanguageValue, 1)
	} else {
		t = *n
	}
	t = append(*n, LangRefValue{lang, value})
	*n = t

	return nil
}

// UnmarshalJSON tries to load the NaturalLanguage array from the incoming json value
func (l *LangRef) UnmarshalJSON(data []byte) error {
	return l.UnmarshalText(data)
}

// UnmarshalText tries to load the NaturalLanguage array from the incoming Text value
func (l *LangRef) UnmarshalText(data []byte) error {
	*l = LangRef("")
	if len(data) == 0 {
		return nil
	}
	if len(data) > 2 {
		if data[0] == '"' && data[len(data)-1] == '"' {
			*l = LangRef(data[1 : len(data)-1])
		}
	} else {
		*l = LangRef(data)
	}
	return nil
}

// UnmarshalJSON tries to load the NaturalLanguage array from the incoming json value
func (n *NaturalLanguageValue) UnmarshalJSON(data []byte) error {
	val, typ, _, err := jsonparser.Get(data)
	if err != nil {
		return nil
	}
	switch typ {
	case jsonparser.Object:
		jsonparser.ObjectEach(data, func(key []byte, value []byte, dataType jsonparser.ValueType, offset int) error {
			n.Append(LangRef(key), string(value))
			return err
		})
	case jsonparser.String:
		n.Append(NilLangRef, string(val))
	}

	return nil
}

// UnmarshalText tries to load the NaturalLanguage array from the incoming Text value
func (n *NaturalLanguageValue) UnmarshalText(data []byte) error {
	if data[0] == '"' {
		// a quoted string - loading it to c.URL
		if data[len(data)-1] != '"' {
			return fmt.Errorf("invalid string value when unmarshalling %T value", n)
		}
		n.Append(LangRef(NilLangRef), string(data[1:len(data)-1]))
	}
	return nil
}

// Describes an object of any kind.
// The Activity Pub Object type serves as the base type for most of the other kinds of objects defined in the Activity Vocabulary,
// including other Core types such as Activity, IntransitiveActivity, Collection and OrderedCollection.
type Object struct {
	// ID provides the globally unique identifier for anActivity Pub Object or Link.
	ID ObjectID `jsonld:"id,omitempty"`
	// Type identifies the Activity Pub Object or Link type. Multiple values may be specified.
	Type ActivityVocabularyType `jsonld:"type,omitempty"`
	// Name a simple, human-readable, plain-text name for the object.
	// HTML markup MUST NOT be included. The name MAY be expressed using multiple language-tagged values.
	Name NaturalLanguageValue `jsonld:"name,omitempty,collapsible"`
	// Attachment identifies a resource attached or related to an object that potentially requires special handling.
	// The intent is to provide a model that is at least semantically similar to attachments in email.
	Attachment Item `jsonld:"attachment,omitempty"`
	// AttributedTo identifies one or more entities to which this object is attributed. The attributed entities might not be Actors.
	// For instance, an object might be attributed to the completion of another activity.
	AttributedTo Item `jsonld:"attributedTo,omitempty"`
	// Audience identifies one or more entities that represent the total population of entities
	// for which the object can considered to be relevant.
	Audience Item `jsonld:"audience,omitempty"`
	// Content or textual representation of the Activity Pub Object encoded as a JSON string.
	// By default, the value of content is HTML.
	// The mediaType property can be used in the object to indicate a different content type.
	// (The content MAY be expressed using multiple language-tagged values.)
	Content NaturalLanguageValue `jsonld:"content,omitempty,collapsible"`
	// Context identifies the context within which the object exists or an activity was performed.
	// The notion of "context" used is intentionally vague.
	// The intended function is to serve as a means of grouping objects and activities that share a
	// common originating context or purpose. An example could be all activities relating to a common project or event.
	Context Item `jsonld:"context,omitempty"`
	// MediaType when used on an Object, identifies the MIME media type of the value of the content property.
	// If not specified, the content property is assumed to contain text/html content.
	MediaType MimeType `jsonld:"mediaType,omitempty"`
	// EndTime the date and time describing the actual or expected ending time of the object.
	// When used with an Activity object, for instance, the endTime property specifies the moment
	// the activity concluded or is expected to conclude.
	EndTime time.Time `jsonld:"endTime,omitempty"`
	// Generator identifies the entity (e.g. an application) that generated the object.
	Generator Item `jsonld:"generator,omitempty"`
	// Icon indicates an entity that describes an icon for this object.
	// The image should have an aspect ratio of one (horizontal) to one (vertical)
	// and should be suitable for presentation at a small size.
	Icon Item `jsonld:"icon,omitempty"`
	// Image indicates an entity that describes an image for this object.
	// Unlike the icon property, there are no aspect ratio or display size limitations assumed.
	Image Item `jsonld:"image,omitempty"`
	// InReplyTo indicates one or more entities for which this object is considered a response.
	InReplyTo Item `jsonld:"inReplyTo,omitempty"`
	// Location indicates one or more physical or logical locations associated with the object.
	Location Item `jsonld:"location,omitempty"`
	// Preview identifies an entity that provides a preview of this object.
	Preview Item `jsonld:"preview,omitempty"`
	// Published the date and time at which the object was published
	Published time.Time `jsonld:"published,omitempty"`
	// Replies identifies a Collection containing objects considered to be responses to this object.
	Replies Item `jsonld:"replies,omitempty"`
	// StartTime the date and time describing the actual or expected starting time of the object.
	// When used with an Activity object, for instance, the startTime property specifies
	// the moment the activity began or is scheduled to begin.
	StartTime time.Time `jsonld:"startTime,omitempty"`
	// Summary a natural language summarization of the object encoded as HTML.
	// *Multiple language tagged summaries may be provided.)
	Summary NaturalLanguageValue `jsonld:"summary,omitempty,collapsible"`
	// Tag one or more "tags" that have been associated with an objects. A tag can be any kind of Activity Pub Object.
	// The key difference between attachment and tag is that the former implies association by inclusion,
	// while the latter implies associated by reference.
	Tag ItemCollection `jsonld:"tag,omitempty"`
	// Updated the date and time at which the object was updated
	Updated time.Time `jsonld:"updated,omitempty"`
	// URL identifies one or more links to representations of the object
	URL LinkOrURI `jsonld:"url,omitempty"`
	// To identifies an entity considered to be part of the public primary audience of an Activity Pub Object
	To ItemCollection `jsonld:"to,omitempty"`
	// Bto identifies anActivity Pub Object that is part of the private primary audience of this Activity Pub Object.
	Bto ItemCollection `jsonld:"bto,omitempty"`
	// CC identifies anActivity Pub Object that is part of the public secondary audience of this Activity Pub Object.
	CC ItemCollection `jsonld:"cc,omitempty"`
	// BCC identifies one or more Objects that are part of the private secondary audience of this Activity Pub Object.
	BCC ItemCollection `jsonld:"bcc,omitempty"`
	// Duration when the object describes a time-bound resource, such as an audio or video, a meeting, etc,
	// the duration property indicates the object's approximate duration.
	// The value must be expressed as an xsd:duration as defined by [ xmlschema11-2],
	// section 3.3.6 (e.g. a period of 5 seconds is represented as "PT5S").
	Duration time.Duration `jsonld:"duration,omitempty"`
}

type (
	// Article represents any kind of multi-paragraph written work.
	Article Object
	// Audio represents an audio document of any kind.
	Audio Document
	// Document represents a document of any kind.
	Document Object
	// Event represents any kind of event.
	Event Object
	// Image An image document of any kind
	Image Document
	// Note represents a short written work typically less than a single paragraph in length.
	Note Object
	// Page represents a Web Page.
	Page Document
	// Video represents a video document of any kind
	Video Document
)

// Place represents a logical or physical location. See 5.3 Representing Places for additional information.
type Place struct {
	Object
	// Accuracy indicates the accuracy of position coordinates on a Place objects.
	// Expressed in properties of percentage. e.g. "94.0" means "94.0% accurate".
	Accuracy float32
	// Altitude indicates the altitude of a place. The measurement units is indicated using the units property.
	// If units is not specified, the default is assumed to be "m" indicating meters.
	Altitude float32
	// Latitude the latitude of a place
	Latitude float32
	// Longitude the longitude of a place
	Longitude float32
	// Radius the radius from the given latitude and longitude for a Place.
	// The units is expressed by the units property. If units is not specified,
	// the default is assumed to be "m" indicating "meters".
	Radius int
	// Specifies the measurement units for the radius and altitude properties on a Place object.
	// If not specified, the default is assumed to be "m" for "meters".
	// Values "cm" | " feet" | " inches" | " km" | " m" | " miles" | xsd:anyURI
	Units string
}

// Profile a Profile is a content object that describes another Object,
// typically used to describe Actor Type objects.
// The describes property is used to reference the object being described by the profile.
type Profile struct {
	Object
	// Describes On a Profile object, the describes property identifies the object described by the Profile.
	Describes Item `jsonld:"describes,omitempty"`
}

// Relationship describes a relationship between two individuals.
// The subject and object properties are used to identify the connected individuals.
//See 5.2 Representing Relationships Between Entities for additional information.
// 5.2: The relationship property specifies the kind of relationship that exists between the two individuals identified
// by the subject and object properties. Used together, these three properties form what is commonly known
// as a "reified statement" where subject identifies the subject, relationship identifies the predicate,
// and object identifies the object.
type Relationship struct {
	// ID provides the globally unique identifier for anActivity Pub Object or Link.
	ID ObjectID `jsonld:"id,omitempty"`
	// Type identifies the Activity Pub Object or Link type. Multiple values may be specified.
	Type ActivityVocabularyType `jsonld:"type,omitempty"`
	// Name a simple, human-readable, plain-text name for the object.
	// HTML markup MUST NOT be included. The name MAY be expressed using multiple language-tagged values.
	Name NaturalLanguageValue `jsonld:"name,omitempty,collapsible"`
	// Attachment identifies a resource attached or related to an object that potentially requires special handling.
	// The intent is to provide a model that is at least semantically similar to attachments in email.
	Attachment Item `jsonld:"attachment,omitempty"`
	// AttributedTo identifies one or more entities to which this object is attributed. The attributed entities might not be Actors.
	// For instance, an object might be attributed to the completion of another activity.
	AttributedTo Item `jsonld:"attributedTo,omitempty"`
	// Audience identifies one or more entities that represent the total population of entities
	// for which the object can considered to be relevant.
	Audience Item `jsonld:"audience,omitempty"`
	// Content the content or textual representation of the Activity Pub Object encoded as a JSON string.
	// By default, the value of content is HTML.
	// The mediaType property can be used in the object to indicate a different content type.
	// (The content MAY be expressed using multiple language-tagged values.)
	Content NaturalLanguageValue `jsonld:"content,omitempty,collapsible"`
	// Context identifies the context within which the object exists or an activity was performed.
	// The notion of "context" used is intentionally vague.
	// The intended function is to serve as a means of grouping objects and activities that share a
	// common originating context or purpose. An example could be all activities relating to a common project or event.
	Context Item `jsonld:"context,omitempty"`
	// MediaType when used on an Object, identifies the MIME media type of the value of the content property.
	// If not specified, the content property is assumed to contain text/html content.
	MediaType MimeType `jsonld:"mediaType,omitempty"`
	// EndTime the date and time describing the actual or expected ending time of the object.
	// When used with an Activity object, for instance, the endTime property specifies the moment
	// the activity concluded or is expected to conclude.
	EndTime time.Time `jsonld:"endTime,omitempty"`
	// Generator identifies the entity (e.g. an application) that generated the object.
	Generator Item `jsonld:"generator,omitempty"`
	// Icon indicates an entity that describes an icon for this object.
	// The image should have an aspect ratio of one (horizontal) to one (vertical)
	// and should be suitable for presentation at a small size.
	Icon Item `jsonld:"icon,omitempty"`
	// Image indicates an entity that describes an image for this object.
	// Unlike the icon property, there are no aspect ratio or display size limitations assumed.
	Image Item `jsonld:"image,omitempty"`
	// InReplyTo indicates one or more entities for which this object is considered a response.
	InReplyTo Item `jsonld:"inReplyTo,omitempty"`
	// Location indicates one or more physical or logical locations associated with the object.
	Location Item `jsonld:"location,omitempty"`
	// Preview identifies an entity that provides a preview of this object.
	Preview Item `jsonld:"preview,omitempty"`
	// Published the date and time at which the object was published
	Published time.Time `jsonld:"published,omitempty"`
	// Replies identifies a Collection containing objects considered to be responses to this object.
	Replies Item `jsonld:"replies,omitempty"`
	// StartTime the date and time describing the actual or expected starting time of the object.
	// When used with an Activity object, for instance, the startTime property specifies
	// the moment the activity began or is scheduled to begin.
	StartTime time.Time `jsonld:"startTime,omitempty"`
	// Summary a natural language summarization of the object encoded as HTML.
	// *Multiple language tagged summaries may be provided.)
	Summary NaturalLanguageValue `jsonld:"summary,omitempty,collapsible"`
	// Tag one or more "tags" that have been associated with an objects. A tag can be any kind of Activity Pub Object.
	// The key difference between attachment and tag is that the former implies association by inclusion,
	// while the latter implies associated by reference.
	Tag ItemCollection `jsonld:"tag,omitempty"`
	// Updated the date and time at which the object was updated
	Updated time.Time `jsonld:"updated,omitempty"`
	// URL identifies one or more links to representations of the object
	URL LinkOrURI `jsonld:"url,omitempty"`
	// To identifies an entity considered to be part of the public primary audience of an Activity Pub Object
	To ItemCollection `jsonld:"to,omitempty"`
	// Bto identifies anActivity Pub Object that is part of the private primary audience of this Activity Pub Object.
	Bto ItemCollection `jsonld:"bto,omitempty"`
	// CC identifies anActivity Pub Object that is part of the public secondary audience of this Activity Pub Object.
	CC ItemCollection `jsonld:"cc,omitempty"`
	// BCC identifies one or more Objects that are part of the private secondary audience of this Activity Pub Object.
	BCC ItemCollection `jsonld:"bcc,omitempty"`
	// Duration when the object describes a time-bound resource, such as an audio or video, a meeting, etc,
	// the duration property indicates the object's approximate duration.
	// The value must be expressed as an xsd:duration as defined by [ xmlschema11-2],
	// section 3.3.6 (e.g. a period of 5 seconds is represented as "PT5S").
	Duration time.Duration `jsonld:"duration,omitempty"`
	// Subject Subject On a Relationship object, the subject property identifies one of the connected individuals.
	// For instance, for a Relationship object describing "John is related to Sally", subject would refer to John.
	Subject Item
	// Object
	Object Item
	// Relationship On a Relationship object, the relationship property identifies the kind
	// of relationship that exists between subject and object.
	Relationship Item
}

// Tombstone a Tombstone represents a content object that has been deleted.
// It can be used in Collections to signify that there used to be an object at this position,
// but it has been deleted.
type Tombstone struct {
	Object
	// FormerType On a Tombstone object, the formerType property identifies the type of the object that was deleted.
	FormerType Item
	// Deleted On a Tombstone object, the deleted property is a timestamp for when the object was deleted.
	Deleted time.Time
}

// ContentType represents the content type for a Source object
type ContentType string

// ValidGenericType validates the type against the valid generic object types
func ValidGenericType(typ ActivityVocabularyType) bool {
	for _, v := range validGenericObjectTypes {
		if v == typ {
			return true
		}
	}
	return false
}

// ValidObjectType validates the type against the valid object types
func ValidObjectType(typ ActivityVocabularyType) bool {
	for _, v := range validObjectTypes {
		if v == typ {
			return true
		}
	}
	return ValidActivityType(typ) || ValidActorType(typ) || ValidCollectionType(typ) || ValidGenericType(typ)
}

// ObjectNew initializes a new Object
func ObjectNew(typ ActivityVocabularyType) *Object {
	if !(ValidObjectType(typ)) {
		typ = ObjectType
	}
	o := Object{Type: typ}
	o.Name = NaturalLanguageValueNew()
	o.Content = NaturalLanguageValueNew()
	return &o
}

// GetID returns the ObjectID corresponding to the current object
func (o Object) GetID() *ObjectID {
	return &o.ID
}

// GetLink returns the IRI corresponding to the current object
func (o Object) GetLink() IRI {
	return IRI(o.ID)
}

// Link returns the Link corresponding to the current object
func (o Object) GetType() ActivityVocabularyType {
	return o.Type
}

// recipientsDeduplication normalizes the received arguments lists
func recipientsDeduplication(recArgs ...*ItemCollection) error {
	recIds := make([]ObjectID, 0)

	for _, recList := range recArgs {
		if recList == nil {
			continue
		}

		toRemove := make([]int, 0)
		for i, rec := range *recList {
			save := true
			if rec == nil {
				continue
			}
			var testId ObjectID
			if rec.IsObject() {
				testId = *rec.GetID()
			} else if rec.IsLink() {
				testId = ObjectID(rec.(IRI))
			} else {
				continue
			}
			for _, id := range recIds {
				if testId == id {
					// mark the element for removal
					toRemove = append(toRemove, i)
					save = false
				}
			}
			if save {
				recIds = append(recIds, testId)
			}
		}

		sort.Sort(sort.Reverse(sort.IntSlice(toRemove)))
		for _, idx := range toRemove {
			*recList = append((*recList)[:idx], (*recList)[idx+1:]...)
		}
	}
	return nil
}

// UnmarshalJSON
func (i *ObjectID) UnmarshalJSON(data []byte) error {
	*i = ObjectID(strings.Trim(string(data), "\""))
	return nil
}

// UnmarshalJSON
func (c *ContentType) UnmarshalJSON(data []byte) error {
	*c = ContentType(strings.Trim(string(data), "\""))
	return nil
}

// UnmarshalJSON
func (o *Object) UnmarshalJSON(data []byte) error {
	o.ID = getAPObjectID(data)
	o.Type = getAPType(data)
	o.Name = getAPNaturalLanguageField(data, "name")
	o.Content = getAPNaturalLanguageField(data, "content")
	o.Context = getAPItem(data, "context")
	o.URL = getURIField(data, "url")
	o.MediaType = MimeType(getAPString(data, "mediaType"))
	o.Generator = getAPItem(data, "generator")
	o.AttributedTo = getAPItem(data, "attributedTo")
	o.InReplyTo = getAPItem(data, "inReplyTo")
	o.Published = getAPTime(data, "published")
	o.StartTime = getAPTime(data, "startTime")
	o.Updated = getAPTime(data, "updated")
	to := getAPItemCollection(data, "to")
	if to != nil {
		o.To = to
	}
	if v, _, _, err := jsonparser.Get(data, "replies"); err == nil {
		r := Collection{}
		if r.UnmarshalJSON(v) == nil {
			o.Replies = &r
		}
	}
	tag := getAPItemCollection(data, "tag")
	if tag != nil {
		o.Tag = tag
	}
	return nil
}