Published an OpportunityMarksUpdated event when an opportunity's marks change over the API

internal/api/api.go

@@ -3,6 +3,7 @@ package api
 import (
 	"github.com/go-chi/chi/v5"
 
+	"git.avsdev.uk/Go/job-search/internal/events"
 	"git.avsdev.uk/Go/job-search/internal/store"
 )
 
@@ -11,7 +12,8 @@ import (
 // server applies the API's middleware (CSRF, NoStore, RequireJSON, rate
 // limits); the API only registers handlers.
 type API struct {
-	store *store.Store // nil: no opportunity routes
+	store  *store.Store // nil: no opportunity routes
+	events *events.Bus  // nil: nothing is published
 }
 
 // Option configures the API.
@@ -25,6 +27,14 @@ func WithStore(opportunityStore *store.Store) Option {
 	}
 }
 
+// WithEvents makes the API publish its changes to bus, such as an
+// events.OpportunityMarksUpdated event when an opportunity's marks change.
+func WithEvents(bus *events.Bus) Option {
+	return func(a *API) {
+		a.events = bus
+	}
+}
+
 // New returns the API.
 func New(opts ...Option) *API {
 	api := &API{}
@@ -40,6 +50,6 @@ func New(opts ...Option) *API {
 func (a *API) Routes(router chi.Router) {
 	docsRoutes(router)
 	if a.store != nil {
-		newOpportunityRoutes(a.store).Routes(router)
+		newOpportunityRoutes(a.store, a.events).Routes(router)
 	}
 }

internal/api/opportunities.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/go-chi/chi/v5"
 
+	"git.avsdev.uk/Go/job-search/internal/events"
 	"git.avsdev.uk/Go/job-search/internal/httpx"
 	"git.avsdev.uk/Go/job-search/internal/store"
 	"git.avsdev.uk/Go/job-search/internal/types"
@@ -33,7 +34,8 @@ type OpportunityPage struct {
 // opportunityRoutes wires HTTP handlers to the opportunity store.
 // Opportunities are read-only; only their marks can be changed.
 type opportunityRoutes struct {
-	store *store.Store
+	store  *store.Store
+	events *events.Bus // nil: nothing is published
 
 	// marksMu makes changing one mark (read the marks, change one, write
 	// them all back) atomic, so concurrent changes to different marks of an
@@ -42,10 +44,13 @@ type opportunityRoutes struct {
 }
 
 // newOpportunityRoutes returns the opportunity handlers for
-// opportunityStore.
-func newOpportunityRoutes(opportunityStore *store.Store) *opportunityRoutes {
+// opportunityStore, publishing mark changes to bus if it isn't nil.
+func newOpportunityRoutes(
+	opportunityStore *store.Store, bus *events.Bus,
+) *opportunityRoutes {
 	return &opportunityRoutes{
-		store: opportunityStore,
+		store:  opportunityStore,
+		events: bus,
 	}
 }
 
@@ -179,7 +184,9 @@ func (h *opportunityRoutes) clearMark(w http.ResponseWriter, r *http.Request) {
 
 // changeMark sets the mark named in the URL to value, keeping the
 // opportunity's other marks, and responds with all of its marks. Setting won
-// while lost is set, or lost while won is, is refused with 409 Conflict.
+// while lost is set, or lost while won is, is refused with 409 Conflict. A
+// change is published as an events.OpportunityMarksUpdated event; one that
+// changes nothing is neither stored nor published.
 func (h *opportunityRoutes) changeMark(
 	w http.ResponseWriter, r *http.Request, value bool,
 ) {
@@ -196,6 +203,7 @@ func (h *opportunityRoutes) changeMark(
 
 	marks := opportunity.Marks
 	marks.UUID = uuid
+	before := marks
 	if !setMark(&marks, name, value) {
 		httpx.WriteProblem(
 			w,
@@ -205,6 +213,10 @@ func (h *opportunityRoutes) changeMark(
 		)
 		return
 	}
+	if marks == before {
+		httpx.WriteJSON(w, http.StatusOK, marks)
+		return
+	}
 
 	err = h.store.SetMarks(r.Context(), marks)
 	if err != nil {
@@ -213,6 +225,15 @@ func (h *opportunityRoutes) changeMark(
 	}
 
 	httpx.WriteJSON(w, http.StatusOK, marks)
+
+	// Still under marksMu, so events are published in the order the
+	// changes were made.
+	if h.events != nil {
+		h.events.Publish(events.Event{
+			Type:    events.OpportunityMarksUpdated,
+			Payload: marks,
+		})
+	}
 }
 
 // findMarks returns the marks of types.OpportunityMarks: every bool field,

internal/api/opportunities_test.go

@@ -14,13 +14,15 @@ import (
 
 	"github.com/go-chi/chi/v5"
 
+	"git.avsdev.uk/Go/job-search/internal/events"
 	"git.avsdev.uk/Go/job-search/internal/store"
 	"git.avsdev.uk/Go/job-search/internal/types"
 )
 
-// opportunitiesServer serves the opportunity routes over a store holding
-// count opportunities, ocds-1 the oldest, and returns its URL.
-func opportunitiesServer(t *testing.T, count int) string {
+// opportunitiesServer serves the API, given opts as well as its store, over
+// a store holding count opportunities, ocds-1 the oldest, and returns its
+// URL.
+func opportunitiesServer(t *testing.T, count int, opts ...Option) string {
 	t.Helper()
 	opportunityStore, err := store.Open(
 		context.Background(),
@@ -57,7 +59,7 @@ func opportunitiesServer(t *testing.T, count int) string {
 	}
 
 	router := chi.NewRouter()
-	New(WithStore(opportunityStore)).Routes(router)
+	New(append([]Option{WithStore(opportunityStore)}, opts...)...).Routes(router)
 	server := httptest.NewServer(router)
 	t.Cleanup(server.Close)
 	return server.URL
@@ -302,3 +304,55 @@ func TestFindMarks(t *testing.T) {
 		t.Error("setMark accepted a name that isn't a mark")
 	}
 }
+
+// A change to a mark is published with all the marks; a change that changes
+// nothing, or is refused, isn't.
+func TestChangeMarkPublishes(t *testing.T) {
+	var bus events.Bus
+	var mu sync.Mutex
+	var published []types.OpportunityMarks
+	bus.Subscribe(func(event events.Event) {
+		if event.Type != events.OpportunityMarksUpdated {
+			t.Errorf("event type %q", event.Type)
+		}
+		mu.Lock()
+		defer mu.Unlock()
+		published = append(published, event.Payload.(types.OpportunityMarks))
+	})
+	url := opportunitiesServer(t, 1, WithEvents(&bus))
+	marks := url + "/opportunities/ocds-1/marks/"
+
+	request(t, "PUT", marks+"interested", nil)    // published
+	request(t, "PUT", marks+"interested", nil)    // already set: not published
+	request(t, "DELETE", marks+"skipped", nil)    // not set: not published
+	request(t, "PUT", marks+"shiny", nil)         // no such mark: refused
+	request(t, "PUT", marks+"won", nil)           // published
+	request(t, "PUT", marks+"lost", nil)          // won and lost: refused
+	request(t, "DELETE", marks+"interested", nil) // published
+
+	mu.Lock()
+	defer mu.Unlock()
+	want := []types.OpportunityMarks{
+		{
+			UUID:       "ocds-1",
+			Interested: true,
+		},
+		{
+			UUID:       "ocds-1",
+			Interested: true,
+			Won:        true,
+		},
+		{
+			UUID: "ocds-1",
+			Won:  true,
+		},
+	}
+	if len(published) != len(want) {
+		t.Fatalf("published %+v; want %+v", published, want)
+	}
+	for i := range want {
+		if published[i] != want[i] {
+			t.Errorf("event %d: %+v; want %+v", i, published[i], want[i])
+		}
+	}
+}