Publish Discord inbound replies on the post event bus (#19)

Inbound publishes PostCreated after saving the Discord link. Outbound skips already-linked posts so the bot does not echo. Mail uses the existing subscriber.

Reviewed-on: #19
Co-authored-by: codegirl-007 <s.raide@gmail.com>

internal/discord/bot_test.go

@@ -161,6 +161,36 @@ func TestOutboundSkipsReplyWithoutRootLink(t *testing.T) {
 	}
 }
 
+func TestOutboundSkipsAlreadyLinkedPost(t *testing.T) {
+	t.Parallel()
+
+	links := newMemoryLinks()
+	api := &fakeAPI{}
+	bot := New("channel-1", links, api)
+	if err := links.Upsert(context.Background(), store.DiscordLink{
+		PostID:    "reply-1",
+		MessageID: "d-reply-1",
+	}); err != nil {
+		t.Fatal(err)
+	}
+	if err := links.Upsert(context.Background(), store.DiscordLink{
+		PostID:    "root-1",
+		MessageID: "d-root",
+		ThreadID:  "thread-1",
+	}); err != nil {
+		t.Fatal(err)
+	}
+	bot.Handle(context.Background(), events.PostCreated{PostEvent: events.PostEvent{
+		PostID:   "reply-1",
+		RootID:   "root-1",
+		ParentID: "root-1",
+		Body:     "Already on Discord.",
+	}})
+	if len(api.sends) != 0 {
+		t.Fatalf("echoed already-linked reply: %+v", api.sends)
+	}
+}
+
 func TestOutboundUpdateWithoutLinkCreates(t *testing.T) {
 	t.Parallel()
 
@@ -218,7 +248,7 @@ func TestFormatMessage(t *testing.T) {
 func TestFromEnvDisabled(t *testing.T) {
 	t.Setenv("DISCORD_BOT_TOKEN", "")
 	t.Setenv("DISCORD_CHANNEL_ID", "")
-	bot, err := FromEnv(newMemoryLinks(), nil, nil, nil)
+	bot, err := FromEnv(newMemoryLinks(), nil, nil)
 	if err != nil || bot != nil {
 		t.Fatalf("disabled FromEnv = (%v, %v)", bot, err)
 	}
@@ -227,12 +257,12 @@ func TestFromEnvDisabled(t *testing.T) {
 func TestFromEnvRequiresBoth(t *testing.T) {
 	t.Setenv("DISCORD_BOT_TOKEN", "token")
 	t.Setenv("DISCORD_CHANNEL_ID", "")
-	if _, err := FromEnv(newMemoryLinks(), nil, nil, nil); err == nil {
+	if _, err := FromEnv(newMemoryLinks(), nil, nil); err == nil {
 		t.Fatal("expected error when channel is missing")
 	}
 	t.Setenv("DISCORD_BOT_TOKEN", "")
 	t.Setenv("DISCORD_CHANNEL_ID", "channel")
-	if _, err := FromEnv(newMemoryLinks(), nil, nil, nil); err == nil {
+	if _, err := FromEnv(newMemoryLinks(), nil, nil); err == nil {
 		t.Fatal("expected error when token is missing")
 	}
 }