1 // apub is an implementation of the ActivityPub protocol.
2 //
3 // https://www.w3.org/TR/activitypub/
4 // https://www.w3.org/TR/activitystreams-core/
5 // https://www.w3.org/TR/activitystreams-vocabulary/
6 package apub
7 
8 import (
9 	"bytes"
10 	"encoding/json"
11 	"errors"
12 	"fmt"
13 	"io"
14 	"net/mail"
15 	"strings"
16 	"time"
17 )
18 
19 // @context
20 const AtContext string = "https://www.w3.org/ns/activitystreams"
21 
22 const ContentType string = "application/activity+json"
23 
24 const AcceptMediaType string = `application/activity+json; profile="https://www.w3.org/ns/activitystreams"`
25 
26 const ToEveryone string = "https://www.w3.org/ns/activitystreams#Public"
27 
28 var ErrNotExist = errors.New("no such activity")
29 
30 type Activity struct {
31 	AtContext    string     `json:"@context"`
32 	ID           string     `json:"id"`
33 	Type         string     `json:"type"`
34 	Name         string     `json:"name,omitempty"`
35 	Actor        string     `json:"actor,omitempty"`
36 	Username     string     `json:"preferredUsername,omitempty"`
37 	Summary      string     `json:"summary"`
38 	Inbox        string     `json:"inbox,omitempty"`
39 	Outbox       string     `json:"outbox,omitempty"`
40 	To           []string   `json:"to,omitempty"`
41 	CC           []string   `json:"cc,omitempty"`
42 	InReplyTo    string     `json:"inReplyTo,omitempty"`
43 	Published    *time.Time `json:"published,omitempty"`
44 	AttributedTo string     `json:"attributedTo,omitempty"`
45 	Content      string     `json:"content,omitempty"`
46 	MediaType    string     `json:"mediaType,omitempty"`
47 	Source       struct {
48 		Content   string `json:"content,omitempty"`
49 		MediaType string `json:"mediaType,omitempty"`
50 	} `json:"source,omitempty"`
51 	Audience string          `json:"audience,omitempty"`
52 	Object   json.RawMessage `json:"object,omitempty"`
53 }
54 
55 func (act *Activity) UnmarshalJSON(b []byte) error {
56 	type Alias Activity
57 	aux := &struct {
58 		AtContext interface{} `json:"@context"`
59 		Object    interface{}
60 		*Alias
61 	}{
62 		Alias: (*Alias)(act),
63 	}
64 	if err := json.Unmarshal(b, &aux); err != nil {
65 		return err
66 	}
67 	switch v := aux.AtContext.(type) {
68 	case string:
69 		act.AtContext = v
70 	case []interface{}:
71 		if vv, ok := v[0].(string); ok {
72 			act.AtContext = vv
73 		}
74 	}
75 	return nil
76 }
77 
78 func (act *Activity) Unwrap(client *Client) (*Activity, error) {
79 	if act.Object == nil {
80 		return nil, errors.New("no wrapped activity")
81 	}
82 
83 	var buf io.Reader
84 	buf = bytes.NewReader(act.Object)
85 	if strings.HasPrefix(string(act.Object), "https") {
86 		if client == nil {
87 			return Lookup(string(act.Object))
88 		}
89 		return client.Lookup(string(act.Object))
90 	}
91 	return Decode(buf)
92 }
93 
94 func Decode(r io.Reader) (*Activity, error) {
95 	var a Activity
96 	if err := json.NewDecoder(r).Decode(&a); err != nil {
97 		return nil, fmt.Errorf("decode activity: %w", err)
98 	}
99 	return &a, nil
100 }
101 
102 func DecodeActor(r io.Reader) (*Actor, error) {
103 	a, err := Decode(r)
104 	if err != nil {
105 		return nil, err
106 	}
107 	return activityToActor(a), nil
108 }
109 
110 type Actor struct {
111 	AtContext string     `json:"@context"`
112 	ID        string     `json:"id"`
113 	Type      string     `json:"type"`
114 	Name      string     `json:"name"`
115 	Username  string     `json:"preferredUsername"`
116 	Summary   string     `json:"summary"`
117 	Inbox     string     `json:"inbox"`
118 	Outbox    string     `json:"outbox"`
119 	Published *time.Time `json:"published,omitempty"`
120 	PublicKey PublicKey  `json:"publicKey"`
121 }
122 
123 type PublicKey struct {
124 	ID           string `json:"id"`
125 	Owner        string `json:"owner"`
126 	PublicKeyPEM string `json:"publicKeyPem"`
127 }
128 
129 func (a *Actor) Address() *mail.Address {
130 	if a.Username == "" && a.Name == "" {
131 		return &mail.Address{"", a.ID}
132 	}
133 	trimmed := strings.TrimPrefix(a.ID, "https://")
134 	host, _, _ := strings.Cut(trimmed, "/")
135 	addr := fmt.Sprintf("%s@%s", a.Username, host)
136 	return &mail.Address{a.Name, addr}
137 }