invites: reply with accept, accept-tentative or decline

Reply to iCalendar invitations with three commands: :accept,
:accept-tentative or :decline. Parse a text/calendar request, create a
reply and append it to the composer.

Suggested-by: Ondřej Synáček <ondrej@synacek.org>
Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

commands/msg/invite.go

@@ -0,0 +1,190 @@
+package msg
+
+import (
+	"errors"
+	"fmt"
+	"io"
+
+	"git.sr.ht/~rjarry/aerc/lib"
+	"git.sr.ht/~rjarry/aerc/lib/calendar"
+	"git.sr.ht/~rjarry/aerc/lib/format"
+	"git.sr.ht/~rjarry/aerc/models"
+	"git.sr.ht/~rjarry/aerc/widgets"
+	"github.com/emersion/go-message/mail"
+)
+
+type invite struct{}
+
+func init() {
+	register(invite{})
+}
+
+func (invite) Aliases() []string {
+	return []string{"accept", "accept-tentative", "decline"}
+}
+
+func (invite) Complete(aerc *widgets.Aerc, args []string) []string {
+	return nil
+}
+
+func (invite) Execute(aerc *widgets.Aerc, args []string) error {
+
+	acct := aerc.SelectedAccount()
+	if acct == nil {
+		return errors.New("no account selected")
+	}
+	store := acct.Store()
+	if store == nil {
+		return errors.New("cannot perform action: messages still loading")
+	}
+	msg, err := acct.SelectedMessage()
+	if err != nil {
+		return err
+	}
+
+	part := lib.FindCalendartext(msg.BodyStructure, nil)
+	if part == nil {
+		return fmt.Errorf("no invitation found (missing text/calendar)")
+	}
+
+	subject := trimLocalizedRe(msg.Envelope.Subject)
+	switch args[0] {
+	case "accept":
+		subject = "Accepted: " + subject
+	case "accept-tentative":
+		subject = "Tentatively Accepted: " + subject
+	case "decline":
+		subject = "Declined: " + subject
+	default:
+		return fmt.Errorf("no participation status defined")
+	}
+
+	conf := acct.AccountConfig()
+	from, err := mail.ParseAddress(conf.From)
+	if err != nil {
+		return err
+	}
+	var aliases []*mail.Address
+	if conf.Aliases != "" {
+		aliases, err = mail.ParseAddressList(conf.Aliases)
+		if err != nil {
+			return err
+		}
+	}
+
+	// figure out the sending from address if we have aliases
+	if len(aliases) != 0 {
+		rec := newAddrSet()
+		rec.AddList(msg.Envelope.To)
+		rec.AddList(msg.Envelope.Cc)
+		// test the from first, it has priority over any present alias
+		if rec.Contains(from) {
+			// do nothing
+		} else {
+			for _, a := range aliases {
+				if rec.Contains(a) {
+					from = a
+					break
+				}
+			}
+		}
+	}
+
+	var (
+		to []*mail.Address
+	)
+
+	if len(msg.Envelope.ReplyTo) != 0 {
+		to = msg.Envelope.ReplyTo
+	} else {
+		to = msg.Envelope.From
+	}
+
+	if !aerc.Config().Compose.ReplyToSelf {
+		for i, v := range to {
+			if v.Address == from.Address {
+				to = append(to[:i], to[i+1:]...)
+				break
+			}
+		}
+		if len(to) == 0 {
+			to = msg.Envelope.To
+		}
+	}
+
+	recSet := newAddrSet() // used for de-duping
+	recSet.AddList(to)
+
+	h := &mail.Header{}
+	h.SetAddressList("from", []*mail.Address{from})
+	h.SetSubject(subject)
+	h.SetMsgIDList("in-reply-to", []string{msg.Envelope.MessageId})
+	err = setReferencesHeader(h, msg.RFC822Headers)
+	if err != nil {
+		aerc.PushError(fmt.Sprintf("could not set references: %v", err))
+	}
+	original := models.OriginalMail{
+		From:          format.FormatAddresses(msg.Envelope.From),
+		Date:          msg.Envelope.Date,
+		RFC822Headers: msg.RFC822Headers,
+	}
+
+	handleInvite := func(reader io.Reader) (*calendar.Reply, error) {
+		cr, err := calendar.CreateReply(reader, from, args[0])
+		if err != nil {
+			return nil, err
+		}
+		for _, org := range cr.Organizers {
+			organizer, err := mail.ParseAddress(org)
+			if err != nil {
+				continue
+			}
+			if !recSet.Contains(organizer) {
+				to = append(to, organizer)
+			}
+		}
+		h.SetAddressList("to", to)
+		return cr, nil
+	}
+
+	addTab := func(cr *calendar.Reply) error {
+		composer, err := widgets.NewComposer(aerc, acct, aerc.Config(),
+			acct.AccountConfig(), acct.Worker(), "", h, original)
+		if err != nil {
+			aerc.PushError("Error: " + err.Error())
+			return err
+		}
+
+		composer.SetContents(cr.PlainText)
+		composer.AppendPart(cr.MimeType, cr.Params, cr.CalendarText)
+		composer.FocusTerminal()
+
+		tab := aerc.NewTab(composer, subject)
+		composer.OnHeaderChange("Subject", func(subject string) {
+			if subject == "" {
+				tab.Name = "New email"
+			} else {
+				tab.Name = subject
+			}
+			tab.Content.Invalidate()
+		})
+
+		composer.OnClose(func(c *widgets.Composer) {
+			if c.Sent() {
+				store.Answered([]uint32{msg.Uid}, true, nil)
+			}
+		})
+
+		return nil
+	}
+
+	store.FetchBodyPart(msg.Uid, part, func(reader io.Reader) {
+		if cr, err := handleInvite(reader); err != nil {
+			aerc.PushError(err.Error())
+			return
+		} else {
+			addTab(cr)
+		}
+	})
+	return nil
+}

doc/aerc.1.scd

@@ -112,9 +112,18 @@ message list, the message in the message viewer, etc).
 
 	*month*: Messages are stored in folders per year and subfolders per month
 
+*accept*
+	Accepts an iCalendar meeting invitation.
+
+*accept-tentative*
+	Accepts an iCalendar meeting invitation tentatively.
+
 *copy* <target>
 	Copies the selected message to the target folder.
 
+*decline*
+	Declines an iCalendar meeting invitation.
+
 *delete*
 	Deletes the selected message.
 

go.mod

@@ -5,6 +5,7 @@ go 1.13
 require (
 	git.sr.ht/~sircmpwn/getopt v1.0.0
 	github.com/ProtonMail/go-crypto v0.0.0-20211221144345-a4f6767435ab
+	github.com/arran4/golang-ical v0.0.0-20220517104411-fd89fefb0182 // indirect
 	github.com/creack/pty v1.1.17
 	github.com/danwakefield/fnmatch v0.0.0-20160403171240-cbb64ac3d964
 	github.com/ddevault/go-libvterm v0.0.0-20190526194226-b7d861da3810
@@ -32,7 +33,7 @@ require (
 	github.com/mitchellh/go-homedir v1.1.0
 	github.com/pkg/errors v0.9.1
 	github.com/riywo/loginshell v0.0.0-20200815045211-7d26008be1ab
-	github.com/stretchr/testify v1.4.0
+	github.com/stretchr/testify v1.7.1
 	github.com/xo/terminfo v0.0.0-20210125001918-ca9a967f8778 // indirect
 	github.com/zenhack/go.notmuch v0.0.0-20211022191430-4d57e8ad2a8b
 	golang.org/x/crypto v0.0.0-20211215153901-e495a2d5b3d3 // indirect
@@ -42,6 +43,7 @@ require (
 	golang.org/x/term v0.0.0-20210927222741-03fcf44c2211 // indirect
 	google.golang.org/appengine v1.6.7 // indirect
 	google.golang.org/protobuf v1.27.1 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20220512140231-539c8e751b99 // indirect
 )
 
 replace golang.org/x/crypto => github.com/ProtonMail/crypto v0.0.0-20200420072808-71bec3603bf3

go.sum

@@ -40,6 +40,8 @@ github.com/ProtonMail/crypto v0.0.0-20200420072808-71bec3603bf3/go.mod h1:Pxr7w4
 github.com/ProtonMail/go-crypto v0.0.0-20211112122917-428f8eabeeb3/go.mod h1:z4/9nQmJSSwwds7ejkxaJwO37dru3geImFUdJlaLzQo=
 github.com/ProtonMail/go-crypto v0.0.0-20211221144345-a4f6767435ab h1:5FiL/TCaiKCss/BLMIACDxxadYrx767l9kh0qYX+sLQ=
 github.com/ProtonMail/go-crypto v0.0.0-20211221144345-a4f6767435ab/go.mod h1:z4/9nQmJSSwwds7ejkxaJwO37dru3geImFUdJlaLzQo=
+github.com/arran4/golang-ical v0.0.0-20220517104411-fd89fefb0182 h1:mUsKridvWp4dgfkO/QWtgGwuLtZYpjKgsm15JRRik3o=
+github.com/arran4/golang-ical v0.0.0-20220517104411-fd89fefb0182/go.mod h1:BSTTrYHuM12oAL8jDdcmPdw02SBThKYWNFHQlvEG6b0=
 github.com/brunnre8/go.notmuch v0.0.0-20201126061756-caa2daf7093c h1:dh58QrW3/S/aCnQPFoeRRE9zMauKooDFd5zh1dLtxXs=
 github.com/brunnre8/go.notmuch v0.0.0-20201126061756-caa2daf7093c/go.mod h1:zJtFvR3NinVdmBiLyB4MyXKmqyVfZEb2cK97ISfTgV8=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
@@ -49,6 +51,7 @@ github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5P
 github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=
 github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
 github.com/cncf/udpa/go v0.0.0-20191209042840-269d4d468f6f/go.mod h1:M8M6+tZqaGXZJjfX53e64911xZQV5JYwmTeXPW+k8Sc=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/creack/pty v1.1.17 h1:QeVUsEDNrLBW4tMgZHvxy18sKtr6VI492kBhUfhDJNI=
 github.com/creack/pty v1.1.17/go.mod h1:MOBLtS5ELjhRRrroQr9kyvTxUAFNvYEK993ew/Vr4O4=
 github.com/danwakefield/fnmatch v0.0.0-20160403171240-cbb64ac3d964 h1:y5HC9v93H5EPKqaS1UYVg1uYah5Xf51mBfIoWehClUQ=
@@ -166,6 +169,7 @@ github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORN
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/kyoh86/xdg v1.2.0 h1:CERuT/ShdTDj+A2UaX3hQ3mOV369+Sj+wyn2nIRIIkI=
 github.com/kyoh86/xdg v1.2.0/go.mod h1:/mg8zwu1+qe76oTFUBnyS7rJzk7LLC0VGEzJyJ19DHs=
 github.com/lithammer/fuzzysearch v1.1.3 h1:+t5SevHLfi3IHcTx7LT3S+od4OcUmjzxD1xmnvtgG38=
@@ -188,6 +192,7 @@ github.com/miolini/datacounter v1.0.2 h1:mGTL0vqEAtH7mwNJS1JIpd6jwTAP6cBQQ2P8apa
 github.com/miolini/datacounter v1.0.2/go.mod h1:C45dc2hBumHjDpEU64IqPwR6TDyPVpzOqqRTN7zmBUA=
 github.com/mitchellh/go-homedir v1.1.0 h1:lukF9ziXFxDFPkA1vsr5zpc1XuPDn/wFntq5mG+4E0Y=
 github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrkLzIz1N1q0pr0=
+github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e/go.mod h1:zD1mROLANZcx1PVRCS0qkT7pwLkGfwJo4zjcN/Tysno=
 github.com/olekukonko/tablewriter v0.0.5/go.mod h1:hPp6KlRPjbx+hW8ykQs1w3UBbZlj6HuIJcUGPhkA7kY=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
@@ -206,6 +211,9 @@ github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.7.1 h1:5TQK59W5E3v0r2duFAb7P95B6hEeOyEnHRa8MjYSMTY=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/xo/terminfo v0.0.0-20210125001918-ca9a967f8778 h1:QldyIu/L63oPpyvQmHgvgickp1Yw510KJOqX7H24mg8=
 github.com/xo/terminfo v0.0.0-20210125001918-ca9a967f8778/go.mod h1:2MuV+tbUrU1zIOPMxZ5EncGwgmMJsa+9ucAQZXxsObs=
 github.com/yuin/goldmark v1.1.25/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
@@ -467,10 +475,15 @@ google.golang.org/protobuf v1.27.1/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQ
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/errgo.v2 v2.1.0/go.mod h1:hNsd1EY+bozCKY1Ytp96fpM3vjJbqLJn88ws8XvfDNI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.3.0 h1:clyUAQHOM3G0M3f5vQj7LuJrETvjVot3Z5el9nffUtU=
 gopkg.in/yaml.v2 v2.3.0/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.0-20220512140231-539c8e751b99 h1:dbuHpmKjkDzSOMKAWl10QNlgaZUd3V1q99xc81tt2Kc=
+gopkg.in/yaml.v3 v3.0.0-20220512140231-539c8e751b99/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.0-20190106161140-3f1c8253044a/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
 honnef.co/go/tools v0.0.0-20190418001031-e561f6794a2a/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=

lib/calendar/calendar.go

@@ -0,0 +1,201 @@
+package calendar
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net/mail"
+	"regexp"
+	"strings"
+	"time"
+
+	ics "github.com/arran4/golang-ical"
+)
+
+type Reply struct {
+	MimeType     string
+	Params       map[string]string
+	CalendarText io.ReadWriter
+	PlainText    io.ReadWriter
+	Organizers   []string
+}
+
+func (cr *Reply) AddOrganizer(o string) {
+	cr.Organizers = append(cr.Organizers, o)
+}
+
+// CreateReply parses a ics request and return a ics reply (RFC 2446, Section 3.2.3)
+func CreateReply(reader io.Reader, from *mail.Address, partstat string) (*Reply, error) {
+
+	cr := Reply{
+		MimeType: "text/calendar",
+		Params: map[string]string{
+			"charset": "UTF-8",
+			"method":  "REPLY",
+		},
+		CalendarText: &bytes.Buffer{},
+		PlainText:    &bytes.Buffer{},
+	}
+
+	var (
+		status ics.ParticipationStatus
+		action string
+	)
+
+	switch partstat {
+	case "accept":
+		status = ics.ParticipationStatusAccepted
+		action = "accepted"
+	case "accept-tentative":
+		status = ics.ParticipationStatusTentative
+		action = "tentatively accepted"
+	case "decline":
+		status = ics.ParticipationStatusDeclined
+		action = "declined"
+	default:
+		return nil, fmt.Errorf("participation status %s is not implemented", partstat)
+	}
+
+	name := from.Name
+	if name == "" {
+		name = from.Address
+	}
+	fmt.Fprintf(cr.PlainText, "%s has %s this invitation.", name, action)
+
+	invite, err := parse(reader)
+	if err != nil {
+		return nil, err
+	}
+
+	if ok := invite.request(); !ok {
+		return nil, fmt.Errorf("no reply is requested")
+	}
+
+	// update invite as a reply
+	reply := invite
+	reply.SetMethod(ics.MethodReply)
+	reply.SetProductId("aerc")
+
+	// check all events
+	for _, vevent := range reply.Events() {
+		e := event{vevent}
+
+		// check if we should answer
+		if err := e.isReplyRequested(from.Address); err != nil {
+			return nil, err
+		}
+
+		// make sure we send our reply to the meeting organizer
+		if organizer := e.GetProperty(ics.ComponentPropertyOrganizer); organizer != nil {
+			cr.AddOrganizer(organizer.Value)
+		}
+
+		// update attendee participation status
+		e.updateAttendees(status, from.Address)
+
+		// update timestamp
+		e.SetDtStampTime(time.Now())
+
+		// remove any subcomponents of event
+		e.Components = nil
+	}
+
+	// keep only timezone and event components
+	reply.clean()
+
+	if len(reply.Events()) == 0 {
+		return nil, fmt.Errorf("no events to respond to")
+	}
+
+	if err := reply.SerializeTo(cr.CalendarText); err != nil {
+		return nil, err
+	}
+	return &cr, nil
+}
+
+type calendar struct {
+	*ics.Calendar
+}
+
+func parse(reader io.Reader) (*calendar, error) {
+	// fix capitalized mailto for parsing of ics file
+	var sb strings.Builder
+	io.Copy(&sb, reader)
+	re := regexp.MustCompile("MAILTO:(.+@)")
+	str := re.ReplaceAllString(sb.String(), "mailto:${1}")
+
+	// parse calendar
+	invite, err := ics.ParseCalendar(strings.NewReader(str))
+	if err != nil {
+		return nil, err
+	}
+	return &calendar{invite}, nil
+}
+
+func (cal *calendar) request() (ok bool) {
+	ok = false
+	for i := range cal.CalendarProperties {
+		if cal.CalendarProperties[i].IANAToken == string(ics.PropertyMethod) {
+			if cal.CalendarProperties[i].Value == string(ics.MethodRequest) {
+				ok = true
+				return
+			}
+		}
+	}
+	return
+}
+
+func (cal *calendar) clean() {
+	var clean []ics.Component
+	for _, comp := range cal.Components {
+		switch comp.(type) {
+		case *ics.VTimezone, *ics.VEvent:
+			clean = append(clean, comp)
+		default:
+			continue
+		}
+	}
+	cal.Components = clean
+}
+
+type event struct {
+	*ics.VEvent
+}
+
+func (e *event) isReplyRequested(from string) error {
+	var present bool = false
+	var rsvp bool = false
+	for _, a := range e.Attendees() {
+		if a.Email() == from {
+			present = true
+			if r, ok := a.ICalParameters[string(ics.ParameterRsvp)]; ok {
+				if len(r) > 0 && strings.ToLower(r[0]) == "true" {
+					rsvp = true
+				}
+			}
+		}
+	}
+	if !present {
+		return fmt.Errorf("we are not invited")
+	}
+	if !rsvp {
+		return fmt.Errorf("we don't have to rsvp")
+	}
+	return nil
+}
+
+func (e *event) updateAttendees(status ics.ParticipationStatus, from string) {
+	var clean []ics.IANAProperty
+	for _, prop := range e.Properties {
+		if prop.IANAToken == string(ics.ComponentPropertyAttendee) {
+			att := ics.Attendee{prop}
+			if att.Email() != from {
+				continue
+			}
+			prop.ICalParameters[string(ics.ParameterParticipationStatus)] = []string{string(status)}
+			delete(prop.ICalParameters, string(ics.ParameterRsvp))
+		}
+		clean = append(clean, prop)
+	}
+	e.Properties = clean
+}

lib/structure_helpers.go

@@ -22,6 +22,22 @@ func FindPlaintext(bs *models.BodyStructure, path []int) []int {
 	return nil
 }
 
+func FindCalendartext(bs *models.BodyStructure, path []int) []int {
+	for i, part := range bs.Parts {
+		cur := append(path, i+1)
+		if strings.ToLower(part.MIMEType) == "text" &&
+			strings.ToLower(part.MIMESubType) == "calendar" {
+			return cur
+		}
+		if strings.ToLower(part.MIMEType) == "multipart" {
+			if path := FindCalendartext(part, cur); path != nil {
+				return path
+			}
+		}
+	}
+	return nil
+}
+
 func FindFirstNonMultipart(bs *models.BodyStructure, path []int) []int {
 	for i, part := range bs.Parts {
 		cur := append(path, i+1)