1 package apub
2 
3 import (
4 	"bytes"
5 	"fmt"
6 	"io"
7 	"net/mail"
8 	"net/smtp"
9 	"strings"
10 	"time"
11 )
12 
13 func MarshalMail(activity *Activity, client *Client) ([]byte, error) {
14 	msg, err := marshalMail(activity, client)
15 	if err != nil {
16 		return nil, err
17 	}
18 	return encodeMsg(msg), nil
19 }
20 
21 func marshalMail(activity *Activity, client *Client) (*mail.Message, error) {
22 	if client == nil {
23 		client = &DefaultClient
24 	}
25 
26 	msg := new(mail.Message)
27 	msg.Header = make(mail.Header)
28 	var actors []Actor
29 	from, err := client.LookupActor(activity.AttributedTo)
30 	if err != nil {
31 		return nil, fmt.Errorf("build From: lookup actor %s: %w", activity.AttributedTo, err)
32 	}
33 	actors = append(actors, *from)
34 	msg.Header["From"] = []string{from.Address().String()}
35 
36 	var addrs, collections []string
37 	for _, id := range activity.To {
38 		if id == PublicCollection {
39 			continue
40 		}
41 
42 		a, err := client.LookupActor(id)
43 		if err != nil {
44 			return nil, fmt.Errorf("build To: lookup actor %s: %w", id, err)
45 		}
46 		if a.Type == "Collection" || a.Type == "OrderedCollection" {
47 			collections = append(collections, a.ID)
48 		} else {
49 			addrs = append(addrs, a.Address().String())
50 			actors = append(actors, *a)
51 		}
52 	}
53 	for _, id := range collections {
54 		if i := indexFollowers(actors, id); i >= 0 {
55 			addrs = append(addrs, actors[i].FollowersAddress().String())
56 		}
57 	}
58 	msg.Header["To"] = addrs
59 
60 	addrs, collections = []string{}, []string{}
61 	for _, id := range activity.CC {
62 		if id == PublicCollection {
63 			continue
64 		}
65 
66 		a, err := client.LookupActor(id)
67 		if err != nil {
68 			return nil, fmt.Errorf("build CC: lookup actor %s: %w", id, err)
69 		}
70 		if a.Type == "Collection" || a.Type == "OrderedCollection" {
71 			collections = append(collections, a.ID)
72 			continue
73 		}
74 		addrs = append(addrs, a.Address().String())
75 		actors = append(actors, *a)
76 	}
77 	for _, id := range collections {
78 		if i := indexFollowers(actors, id); i >= 0 {
79 			addrs = append(addrs, actors[i].FollowersAddress().String())
80 		}
81 	}
82 	msg.Header["CC"] = addrs
83 
84 	msg.Header["Date"] = []string{activity.Published.Format(time.RFC1123Z)}
85 	msg.Header["Message-ID"] = []string{"<" + activity.ID + ">"}
86 	msg.Header["Subject"] = []string{activity.Name}
87 	if activity.Audience != "" {
88 		msg.Header["List-ID"] = []string{"<" + activity.Audience + ">"}
89 	}
90 	if activity.InReplyTo != "" {
91 		msg.Header["In-Reply-To"] = []string{"<" + activity.InReplyTo + ">"}
92 	}
93 
94 	msg.Body = strings.NewReader(activity.Content)
95 	msg.Header["Content-Type"] = []string{"text/html; charset=utf-8"}
96 	if activity.Source.Content != "" && activity.Source.MediaType == "text/markdown" {
97 		msg.Body = strings.NewReader(activity.Source.Content)
98 		msg.Header["Content-Type"] = []string{"text/plain; charset=utf-8"}
99 	} else if activity.MediaType == "text/markdown" {
100 		msg.Header["Content-Type"] = []string{"text/plain; charset=utf-8"}
101 	}
102 	return msg, nil
103 }
104 
105 func indexFollowers(actors []Actor, id string) int {
106 	for i := range actors {
107 		if actors[i].Followers == id {
108 			return i
109 		}
110 	}
111 	return -1
112 }
113 
114 func UnmarshalMail(msg *mail.Message, client *Client) (*Activity, error) {
115 	if client == nil {
116 		client = &DefaultClient
117 	}
118 	ct := msg.Header.Get("Content-Type")
119 	if strings.HasPrefix(ct, "multipart") {
120 		return nil, fmt.Errorf("cannot unmarshal from multipart message")
121 	}
122 	enc := msg.Header.Get("Content-Transfer-Encoding")
123 	if enc == "quoted-printable" {
124 		return nil, fmt.Errorf("cannot decode message with transfer encoding: %s", enc)
125 	}
126 
127 	date, err := msg.Header.Date()
128 	if err != nil {
129 		return nil, fmt.Errorf("parse message date: %w", err)
130 	}
131 	from, err := msg.Header.AddressList("From")
132 	if err != nil {
133 		return nil, fmt.Errorf("parse From: %w", err)
134 	}
135 	wfrom, err := client.Finger(from[0].Address)
136 	if err != nil {
137 		return nil, fmt.Errorf("webfinger From: %w", err)
138 	}
139 
140 	var wto, wcc []string
141 	var tags []Activity
142 	if msg.Header.Get("To") != "" {
143 		to, err := msg.Header.AddressList("To")
144 		// ignore missing To line. Some ActivityPub servers only have the
145 		// PublicCollection listed, which we don't care about.
146 		if err != nil {
147 			return nil, fmt.Errorf("parse To address list: %w", err)
148 		}
149 		actors, err := client.fingerAll(to)
150 		if err != nil {
151 			return nil, fmt.Errorf("webfinger To addresses: %w", err)
152 		}
153 		wto = make([]string, len(actors))
154 		for i, a := range actors {
155 			addr := strings.Trim(to[i].Address, "<>")
156 			if strings.Contains(addr, "+followers") {
157 				wto[i] = a.Followers
158 				continue
159 			}
160 			tags = append(tags, Activity{Type: "Mention", Href: a.ID, Name: "@" + addr})
161 			wto[i] = a.ID
162 		}
163 	}
164 	if msg.Header.Get("CC") != "" {
165 		cc, err := msg.Header.AddressList("CC")
166 		if err != nil {
167 			return nil, fmt.Errorf("parse CC address list: %w", err)
168 		}
169 		actors, err := client.fingerAll(cc)
170 		if err != nil {
171 			return nil, fmt.Errorf("webfinger CC addresses: %w", err)
172 		}
173 		wcc = make([]string, len(actors))
174 		for i, a := range actors {
175 			if strings.Contains(cc[i].Address, "+followers") {
176 				wcc[i] = a.Followers
177 				continue
178 			}
179 			wcc[i] = a.ID
180 		}
181 	}
182 
183 	buf := &bytes.Buffer{}
184 	if _, err := io.Copy(buf, msg.Body); err != nil {
185 		return nil, fmt.Errorf("read message body: %v", err)
186 	}
187 	content := strings.TrimSpace(strings.ReplaceAll(buf.String(), "\r", ""))
188 
189 	return &Activity{
190 		AtContext:    NormContext,
191 		Type:         "Note",
192 		AttributedTo: wfrom.ID,
193 		To:           wto,
194 		CC:           wcc,
195 		MediaType:    "text/markdown",
196 		Name:         strings.TrimSpace(msg.Header.Get("Subject")),
197 		Content:      content,
198 		InReplyTo:    strings.Trim(msg.Header.Get("In-Reply-To"), "<>"),
199 		Published:    &date,
200 		Tag:          tags,
201 	}, nil
202 }
203 
204 func SendMail(addr string, auth smtp.Auth, from string, to []string, activity *Activity) error {
205 	msg, err := MarshalMail(activity, nil)
206 	if err != nil {
207 		return fmt.Errorf("marshal to mail message: %w", err)
208 	}
209 	return smtp.SendMail(addr, auth, from, to, msg)
210 }
211 
212 func encodeMsg(msg *mail.Message) []byte {
213 	buf := &bytes.Buffer{}
214 	// Lead with "From", end with "Subject" to make some mail clients happy.
215 	fmt.Fprintln(buf, "From:", msg.Header.Get("From"))
216 	for k, v := range msg.Header {
217 		switch k {
218 		case "Subject", "From":
219 			continue
220 		default:
221 			fmt.Fprintf(buf, "%s: %s\n", k, strings.Join(v, ", "))
222 		}
223 	}
224 	fmt.Fprintln(buf, "Subject:", msg.Header.Get("Subject"))
225 	fmt.Fprintln(buf)
226 	io.Copy(buf, msg.Body)
227 	return buf.Bytes()
228 }