Add an in-process post event bus.

internal/events/bus_test.go

@@ -0,0 +1,104 @@
+package events
+
+import (
+	"context"
+	"sync"
+	"testing"
+	"time"
+)
+
+func TestPermalink(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		base, root, post, want string
+	}{
+		{"", "root-1", "post-2", "/questions/root-1#post-post-2"},
+		{"https://www.askaplumberfirst.com/", "root-1", "post-2", "https://www.askaplumberfirst.com/questions/root-1#post-post-2"},
+		{"https://www.askaplumberfirst.com", "a b", "c/d", "https://www.askaplumberfirst.com/questions/a%20b#post-c%2Fd"},
+	}
+	for _, tc := range tests {
+		if got := Permalink(tc.base, tc.root, tc.post); got != tc.want {
+			t.Fatalf("Permalink(%q, %q, %q) = %q, want %q", tc.base, tc.root, tc.post, got, tc.want)
+		}
+	}
+}
+
+func TestNopAndRecording(t *testing.T) {
+	t.Parallel()
+
+	Nop{}.Publish(context.Background(), PostCreated{})
+
+	rec := &Recording{}
+	rec.Publish(context.Background(), PostCreated{PostEvent: PostEvent{PostID: "a"}})
+	rec.Publish(context.Background(), PostUpdated{PostEvent: PostEvent{PostID: "b"}})
+	if rec.Len() != 2 {
+		t.Fatalf("len = %d", rec.Len())
+	}
+	got := rec.Snapshot()
+	created, ok := got[0].(PostCreated)
+	if !ok || created.PostID != "a" {
+		t.Fatalf("first = %#v", got[0])
+	}
+	updated, ok := got[1].(PostUpdated)
+	if !ok || updated.PostID != "b" {
+		t.Fatalf("second = %#v", got[1])
+	}
+}
+
+func TestBusDeliversInOrder(t *testing.T) {
+	t.Parallel()
+
+	bus := New()
+	defer bus.Close()
+
+	var mu sync.Mutex
+	var got []string
+	done := make(chan struct{})
+	bus.Subscribe(func(_ context.Context, ev any) {
+		mu.Lock()
+		got = append(got, ev.(string))
+		if len(got) == 3 {
+			close(done)
+		}
+		mu.Unlock()
+	})
+
+	ctx := context.Background()
+	bus.Publish(ctx, "one")
+	bus.Publish(ctx, "two")
+	bus.Publish(ctx, "three")
+
+	select {
+	case <-done:
+	case <-time.After(time.Second):
+		t.Fatal("timed out waiting for events")
+	}
+	mu.Lock()
+	defer mu.Unlock()
+	if len(got) != 3 || got[0] != "one" || got[1] != "two" || got[2] != "three" {
+		t.Fatalf("got %v", got)
+	}
+}
+
+func TestBusDropsWhenFull(t *testing.T) {
+	t.Parallel()
+
+	bus := newBus(1, false)
+	bus.Publish(context.Background(), "kept")
+	bus.Publish(context.Background(), "dropped")
+
+	select {
+	case ev := <-bus.ch:
+		if ev != "kept" {
+			t.Fatalf("got %v", ev)
+		}
+	default:
+		t.Fatal("expected buffered event")
+	}
+	select {
+	case ev := <-bus.ch:
+		t.Fatalf("unexpected extra event %v", ev)
+	default:
+	}
+}