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) ([]byte, error) {
14 	buf := &bytes.Buffer{}
15 
16 	from, err := LookupActor(activity.AttributedTo)
17 	if err != nil {
18 		return nil, fmt.Errorf("lookup actor %s: %w", activity.AttributedTo, err)
19 	}
20 	fmt.Fprintf(buf, "From: %s\n", from.Address())
21 
22 	var rcpt []string
23 	for _, u := range activity.To {
24 		if u == PublicCollection {
25 			continue
26 		}
27 		actor, err := LookupActor(u)
28 		if err != nil {
29 			return nil, fmt.Errorf("lookup actor %s: %w", u, err)
30 		}
31 		rcpt = append(rcpt, actor.Address().String())
32 	}
33 	fmt.Fprintln(buf, "To:", strings.Join(rcpt, ", "))
34 
35 	var rcptcc []string
36 	if activity.CC != nil {
37 		for _, u := range activity.CC {
38 			if u == PublicCollection {
39 				continue
40 			} else if u == from.Followers {
41 				rcptcc = append(rcptcc, from.FollowersAddress().String())
42 				continue
43 			}
44 			actor, err := LookupActor(u)
45 			if err != nil {
46 				return nil, fmt.Errorf("lookup actor %s: %w", u, err)
47 			}
48 			rcptcc = append(rcptcc, actor.Address().String())
49 		}
50 		fmt.Fprintln(buf, "CC:", strings.Join(rcptcc, ", "))
51 	}
52 
53 	fmt.Fprintf(buf, "Date: %s\n", activity.Published.Format(time.RFC822))
54 	fmt.Fprintf(buf, "Message-ID: <%s>\n", activity.ID)
55 	if activity.Audience != "" {
56 		fmt.Fprintf(buf, "List-ID: <%s>\n", activity.Audience)
57 	}
58 	if activity.InReplyTo != "" {
59 		fmt.Fprintf(buf, "References: <%s>\n", activity.InReplyTo)
60 	}
61 
62 	if activity.Source.Content != "" && activity.Source.MediaType == "text/markdown" {
63 		fmt.Fprintln(buf, "Content-Type: text/plain; charset=utf-8")
64 	} else if activity.MediaType != "" {
65 		fmt.Fprintln(buf, "Content-Type:", activity.MediaType)
66 	} else {
67 		fmt.Fprintln(buf, "Content-Type:", "text/html; charset=utf-8")
68 	}
69 	fmt.Fprintln(buf, "Subject:", activity.Name)
70 	fmt.Fprintln(buf)
71 	if activity.Source.Content != "" && activity.Source.MediaType == "text/markdown" {
72 		fmt.Fprintln(buf, activity.Source.Content)
73 	} else {
74 		fmt.Fprintln(buf, activity.Content)
75 	}
76 	_, err = mail.ReadMessage(bytes.NewReader(buf.Bytes()))
77 	return buf.Bytes(), err
78 }
79 
80 func UnmarshalMail(msg *mail.Message) (*Activity, error) {
81 	date, err := msg.Header.Date()
82 	if err != nil {
83 		return nil, fmt.Errorf("parse message date: %w", err)
84 	}
85 	from, err := msg.Header.AddressList("From")
86 	if err != nil {
87 		return nil, fmt.Errorf("parse From: %w", err)
88 	}
89 	wfrom, err := Finger(from[0].Address)
90 	if err != nil {
91 		return nil, fmt.Errorf("webfinger From: %w", err)
92 	}
93 
94 	var wto, wcc []string
95 	var tags []Activity
96 	if msg.Header.Get("To") != "" {
97 		to, err := msg.Header.AddressList("To")
98 		// ignore missing To line. Some ActivityPub servers only have the
99 		// PublicCollection listed, which we don't care about.
100 		if err != nil {
101 			return nil, fmt.Errorf("parse To address list: %w", err)
102 		}
103 		actors, err := fingerAll(to)
104 		if err != nil {
105 			return nil, fmt.Errorf("webfinger To addresses: %w", err)
106 		}
107 		wto = make([]string, len(actors))
108 		tags = make([]Activity, len(actors))
109 		for i, a := range actors {
110 			addr := strings.Trim(to[i].Address, "<>")
111 			tags[i] = Activity{Type: "Mention", Href: a.ID, Name: "@" + addr}
112 			wto[i] = a.ID
113 		}
114 	}
115 	if msg.Header.Get("CC") != "" {
116 		cc, err := msg.Header.AddressList("CC")
117 		if err != nil {
118 			return nil, fmt.Errorf("parse CC address list: %w", err)
119 		}
120 		actors, err := fingerAll(cc)
121 		if err != nil {
122 			return nil, fmt.Errorf("webfinger CC addresses: %w", err)
123 		}
124 		wcc = make([]string, len(actors))
125 		for i, a := range actors {
126 			wcc[i] = a.ID
127 		}
128 	}
129 
130 	buf := &bytes.Buffer{}
131 	if _, err := io.Copy(buf, msg.Body); err != nil {
132 		return nil, fmt.Errorf("read message body: %v", err)
133 	}
134 
135 	return &Activity{
136 		AtContext:    NormContext,
137 		Type:         "Note",
138 		AttributedTo: wfrom.ID,
139 		To:           wto,
140 		CC:           wcc,
141 		MediaType:    "text/markdown",
142 		Name:         strings.TrimSpace(msg.Header.Get("Subject")),
143 		Content:      strings.TrimSpace(buf.String()),
144 		InReplyTo:    strings.Trim(msg.Header.Get("In-Reply-To"), "<>"),
145 		Published:    &date,
146 		Tag:          tags,
147 	}, nil
148 }
149 
150 func SendMail(addr string, auth smtp.Auth, from string, to []string, activity *Activity) error {
151 	msg, err := MarshalMail(activity)
152 	if err != nil {
153 		return fmt.Errorf("marshal to mail message: %w", err)
154 	}
155 	return smtp.SendMail(addr, auth, from, to, msg)
156 }