Add parsing of attachment fallback text

cmd/delegatebot/service/slack/message_parser.go

@@ -49,20 +49,29 @@ func (p *MessageParser) ParseMessage(msg slack.Msg) (*message.Message, error) {
 		Text:            msg.Text,
 	}
 
+	// include attachments
+	for _, attachment := range msg.Attachments {
+		if attachment.Fallback == "" {
+			continue
+		}
+
+		incoming.Text = fmt.Sprintf("%s\n\n---\n\n%s", incoming.Text, attachment.Fallback)
+	}
+
 	if msg.Channel[0] == 'D' { // TODO better way to detect if this is our bot DM?
-		matches := reChannelMention.FindStringSubmatch(msg.Text)
+		matches := reChannelMention.FindStringSubmatch(incoming.Text)
 		if len(matches) > 0 {
 			incoming.InterruptTarget = matches[1]
 		}
 
 		incoming.OriginType = message.DirectMessageOriginType
 
 		return incoming, nil
-	} else if !p.reMention.MatchString(msg.Text) {
+	} else if !p.reMention.MatchString(incoming.Text) {
 		return nil, nil
 	}
 
-	matches := p.reChannelMention.FindStringSubmatch(msg.Text)
+	matches := p.reChannelMention.FindStringSubmatch(incoming.Text)
 	if len(matches) > 0 {
 		incoming.InterruptTarget = matches[1]
 	}

cmd/delegatebot/service/slack/message_parser_test.go

@@ -69,6 +69,21 @@ var _ = Describe("MessageParser", func() {
 			Expect(res).To(BeNil())
 		})
 
+		It("parses attachment fallback", func() {
+			msg.Attachments = []slack.Attachment{
+				{
+					Fallback: msg.Text,
+				},
+			}
+
+			msg.Text = "something else entirely"
+
+			res, err := subject.ParseMessage(msg)
+			Expect(err).NotTo(HaveOccurred())
+			Expect(res).ToNot(BeNil())
+			Expect(res.Text).To(Equal("something else entirely\n\n---\n\nhelp me, <@U1234567> you're my only hope."))
+		})
+
 		Context("direct messages", func() {
 			BeforeEach(func() {
 				msg.Channel = "D1234567"