Let caller pass in custom headers to compose

commands/compose/send.go

@@ -53,7 +53,7 @@ func SendMessage(aerc *widgets.Aerc, args []string) error {
 		return fmt.Errorf("Unknown transfer protocol %s", uri.Scheme)
 	}
 
-	header, rcpts, err := composer.Header()
+	header, rcpts, err := composer.PrepareHeader()
 	if err != nil {
 		return err
 	}
@@ -188,7 +188,7 @@ func SendMessage(aerc *widgets.Aerc, args []string) error {
 					composer.Close()
 				}
 			})
-			header, _, _ := composer.Header()
+			header, _, _ := composer.PrepareHeader()
 			composer.WriteMessage(header, w)
 			w.Close()
 		} else {

lib/ui/textinput.go

@@ -40,6 +40,10 @@ func (ti *TextInput) String() string {
 	return string(ti.text)
 }
 
+func (ti *TextInput) Set(value string) {
+	ti.text = []rune(value)
+}
+
 func (ti *TextInput) Invalidate() {
 	ti.DoInvalidate(ti)
 }

widgets/compose.go

@@ -27,6 +27,7 @@ type Composer struct {
 
 	config *config.AccountConfig
 
+	defaults map[string]string
 	editor   *Terminal
 	email    *os.File
 	grid     *ui.Grid
@@ -104,6 +105,24 @@ func NewComposer(conf *config.AercConfig,
 	return c
 }
 
+// Sets additional headers to be added to the outgoing email (e.g. In-Reply-To)
+func (c *Composer) Defaults(defaults map[string]string) *Composer {
+	c.defaults = defaults
+	if to, ok := defaults["To"]; ok {
+		c.headers.to.input.Set(to)
+		delete(defaults, "To")
+	}
+	if from, ok := defaults["From"]; ok {
+		c.headers.from.input.Set(from)
+		delete(defaults, "From")
+	}
+	if subject, ok := defaults["Subject"]; ok {
+		c.headers.subject.input.Set(subject)
+		delete(defaults, "Subject")
+	}
+	return c
+}
+
 func (c *Composer) OnSubjectChange(fn func(subject string)) {
 	c.headers.subject.OnChange(func() {
 		fn(c.headers.subject.input.String())
@@ -163,7 +182,7 @@ func (c *Composer) Worker() *types.Worker {
 	return c.worker
 }
 
-func (c *Composer) Header() (*mail.Header, []string, error) {
+func (c *Composer) PrepareHeader() (*mail.Header, []string, error) {
 	// Extract headers from the email, if present
 	c.email.Seek(0, os.SEEK_SET)
 	var (
@@ -209,6 +228,13 @@ func (c *Composer) Header() (*mail.Header, []string, error) {
 			rcpts = append(rcpts, addr.Address)
 		}
 	}
+	// Merge in additional headers
+	txthdr := mhdr.Header
+	for key, value := range c.defaults {
+		if !txthdr.Has(key) {
+			mhdr.SetText(key, value)
+		}
+	}
 	// TODO: Add cc, bcc to rcpts
 	return &header, rcpts, nil
 }