refactoring, created email package

email/email.go

@@ -0,0 +1,210 @@
+package email
+
+import (
+	"crypto"
+	"crypto/x509"
+	"encoding/pem"
+	"strings"
+
+	"github.com/emersion/go-msgauth/dkim"
+	"github.com/jhillyerd/enmime"
+	"maunium.net/go/mautrix/event"
+	"maunium.net/go/mautrix/format"
+	"maunium.net/go/mautrix/id"
+
+	"gitlab.com/etke.cc/postmoogle/utils"
+)
+
+// Email object
+type Email struct {
+	Date       string
+	MessageID  string
+	InReplyTo  string
+	References string
+	From       string
+	To         string
+	RcptTo     string
+	CC         string
+	Subject    string
+	Text       string
+	HTML       string
+	Files      []*utils.File
+}
+
+// New constructs Email object
+func New(messageID, inReplyTo, references, subject, from, to, text, html string, files []*utils.File) *Email {
+	email := &Email{
+		Date:       dateNow(),
+		MessageID:  messageID,
+		InReplyTo:  inReplyTo,
+		References: references,
+		From:       from,
+		To:         to,
+		RcptTo:     to,
+		Subject:    subject,
+		Text:       text,
+		HTML:       html,
+		Files:      files,
+	}
+
+	if html != "" {
+		html = styleRegex.ReplaceAllString(html, "")
+		email.HTML = html
+	}
+
+	return email
+}
+
+// FromEnvelope constructs Email object from envelope
+func FromEnvelope(rcptto string, envelope *enmime.Envelope) *Email {
+	datetime, _ := envelope.Date() //nolint:errcheck // handled in dateNow()
+	date := dateNow(datetime)
+
+	var html string
+	if envelope.HTML != "" {
+		html = styleRegex.ReplaceAllString(envelope.HTML, "")
+	}
+
+	files := make([]*utils.File, 0, len(envelope.Attachments))
+	for _, attachment := range envelope.Attachments {
+		file := utils.NewFile(attachment.FileName, attachment.Content)
+		files = append(files, file)
+	}
+
+	email := &Email{
+		Date:       date,
+		MessageID:  envelope.GetHeader("Message-Id"),
+		InReplyTo:  envelope.GetHeader("In-Reply-To"),
+		References: envelope.GetHeader("References"),
+		From:       envelope.GetHeader("From"),
+		To:         envelope.GetHeader("To"),
+		RcptTo:     rcptto,
+		CC:         envelope.GetHeader("Cc"),
+		Subject:    envelope.GetHeader("Subject"),
+		Text:       envelope.Text,
+		HTML:       html,
+		Files:      files,
+	}
+
+	return email
+}
+
+// Mailbox returns postmoogle's mailbox, parsing it from FROM (if incoming=false) or TO (incoming=true)
+func (e *Email) Mailbox(incoming bool) string {
+	if incoming {
+		return utils.Mailbox(e.RcptTo)
+	}
+	return utils.Mailbox(e.From)
+}
+
+// Content converts the email object to a Matrix event content
+func (e *Email) Content(threadID id.EventID, options *ContentOptions) *event.Content {
+	var text strings.Builder
+	if options.Sender {
+		text.WriteString(e.From)
+	}
+	if options.Recipient {
+		text.WriteString(" ➡️ ")
+		text.WriteString(e.To)
+	}
+	if options.Sender || options.Recipient {
+		text.WriteString("\n\n")
+	}
+	if options.Subject && threadID == "" {
+		text.WriteString("# ")
+		text.WriteString(e.Subject)
+		text.WriteString("\n\n")
+	}
+	if e.HTML != "" && options.HTML {
+		text.WriteString(format.HTMLToMarkdown(e.HTML))
+	} else {
+		text.WriteString(e.Text)
+	}
+
+	parsed := format.RenderMarkdown(text.String(), true, true)
+	parsed.RelatesTo = utils.RelatesTo(options.Threads, threadID)
+
+	content := event.Content{
+		Raw: map[string]interface{}{
+			options.MessageIDKey:  e.MessageID,
+			options.InReplyToKey:  e.InReplyTo,
+			options.ReferencesKey: e.References,
+			options.SubjectKey:    e.Subject,
+			options.RcptToKey:     e.RcptTo,
+			options.FromKey:       e.From,
+			options.ToKey:         e.To,
+			options.CcKey:         e.CC,
+		},
+		Parsed: &parsed,
+	}
+	return &content
+}
+
+// Compose converts the email object to a string (to be used for delivery via SMTP) and possibly DKIM-signs it
+func (e *Email) Compose(privkey string) string {
+	textSize := len(e.Text)
+	htmlSize := len(e.HTML)
+	if textSize == 0 && htmlSize == 0 {
+		return ""
+	}
+
+	mail := enmime.Builder().
+		From("", e.From).
+		To("", e.To).
+		Header("Message-Id", e.MessageID).
+		Subject(e.Subject)
+	if textSize > 0 {
+		mail = mail.Text([]byte(e.Text))
+	}
+	if htmlSize > 0 {
+		mail = mail.HTML([]byte(e.HTML))
+	}
+	if e.InReplyTo != "" {
+		mail = mail.Header("In-Reply-To", e.InReplyTo)
+	}
+	if e.References != "" {
+		mail = mail.Header("References", e.References)
+	}
+
+	root, err := mail.Build()
+	if err != nil {
+		return ""
+	}
+	var data strings.Builder
+	err = root.Encode(&data)
+	if err != nil {
+		return ""
+	}
+
+	domain := strings.SplitN(e.From, "@", 2)[1]
+	return e.sign(domain, privkey, data)
+}
+
+func (e *Email) sign(domain, privkey string, data strings.Builder) string {
+	if privkey == "" {
+		return data.String()
+	}
+	pemblock, _ := pem.Decode([]byte(privkey))
+	if pemblock == nil {
+		return data.String()
+	}
+	parsedkey, err := x509.ParsePKCS8PrivateKey(pemblock.Bytes)
+	if err != nil {
+		return data.String()
+	}
+	signer := parsedkey.(crypto.Signer)
+
+	options := &dkim.SignOptions{
+		Domain:   domain,
+		Selector: "postmoogle",
+		Signer:   signer,
+	}
+
+	var msg strings.Builder
+	err = dkim.Sign(&msg, strings.NewReader(data.String()), options)
+	if err != nil {
+		return data.String()
+	}
+
+	return msg.String()
+}

email/options.go

@@ -0,0 +1,28 @@
+package email
+
+// IncomingFilteringOptions for incoming mail
+type IncomingFilteringOptions interface {
+	SpamcheckSMTP() bool
+	SpamcheckMX() bool
+	Spamlist() []string
+}
+
+// ContentOptions represents settings that specify how an email is to be converted to a Matrix message
+type ContentOptions struct {
+	// On/Off
+	Sender    bool
+	Recipient bool
+	Subject   bool
+	HTML      bool
+	Threads   bool
+
+	// Keys
+	MessageIDKey  string
+	InReplyToKey  string
+	ReferencesKey string
+	SubjectKey    string
+	FromKey       string
+	ToKey         string
+	CcKey         string
+	RcptToKey     string
+}

email/utils.go

@@ -0,0 +1,33 @@
+package email
+
+import (
+	"fmt"
+	"net/mail"
+	"regexp"
+	"time"
+
+	"maunium.net/go/mautrix/id"
+)
+
+var styleRegex = regexp.MustCompile("<style((.|\n|\r)*?)<\\/style>")
+
+// AddressValid checks if email address is valid
+func AddressValid(email string) bool {
+	_, err := mail.ParseAddress(email)
+	return err == nil
+}
+
+// MessageID generates email Message-Id from matrix event ID
+func MessageID(eventID id.EventID, domain string) string {
+	return fmt.Sprintf("<%s@%s>", eventID, domain)
+}
+
+// dateNow returns Date in RFC1123 with numeric timezone
+func dateNow(original ...time.Time) string {
+	now := time.Now().UTC()
+	if len(original) > 0 && !original[0].IsZero() {
+		now = original[0]
+	}
+
+	return now.Format(time.RFC1123Z)
+}