snapshot of https://github.com/ThreeDotsLabs/watermill.git (master, 2026-09-15; blobs > 131072B omitted)

_examples/real-world-examples/server-sent-events-htmx/http.go

@@ -0,0 +1,267 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"main/views"
+	"net/http"
+	"strconv"
+	"sync/atomic"
+	"time"
+
+	watermillhttp "github.com/ThreeDotsLabs/watermill-http/v2/pkg/http"
+	"github.com/ThreeDotsLabs/watermill/components/cqrs"
+	"github.com/ThreeDotsLabs/watermill/message"
+	"github.com/labstack/echo/v4"
+	"github.com/labstack/echo/v4/middleware"
+)
+
+type Handler struct {
+	repo     *Repository
+	eventBus *cqrs.EventBus
+}
+
+func NewHandler(repo *Repository, eventBus *cqrs.EventBus, sseRouter watermillhttp.SSERouter) *echo.Echo {
+	h := Handler{
+		repo:     repo,
+		eventBus: eventBus,
+	}
+
+	marshaler := cqrs.JSONMarshaler{}
+	topic := marshaler.Name(PostStatsUpdated{})
+	statsHandler := sseRouter.AddHandler(topic, &statsStream{repo: repo})
+
+	e := echo.New()
+	e.Use(middleware.Recover())
+	e.Use(middleware.Logger())
+
+	counter := sseHandlersCounter{}
+
+	e.GET("/", h.Index)
+	e.GET("/posts", h.Posts)
+	e.GET("/idle", h.Idle)
+	e.POST("/posts/:id/reactions", h.AddReaction)
+	e.GET("/posts/:id/stats", func(c echo.Context) error {
+		postID := c.Param("id")
+		c.Request().SetPathValue("id", postID)
+
+		statsHandler(c.Response(), c.Request())
+		return nil
+	}, counter.Middleware)
+
+	go func() {
+		for {
+			fmt.Println("SSE handlers count:", counter.Count.Load())
+			time.Sleep(60 * time.Second)
+		}
+	}()
+
+	return e
+}
+
+func (h Handler) Index(c echo.Context) error {
+	posts, err := h.allPosts(c)
+	if err != nil {
+		return err
+	}
+
+	return views.Index(posts).Render(c.Request().Context(), c.Response())
+}
+
+func (h Handler) Posts(c echo.Context) error {
+	posts, err := h.allPosts(c)
+	if err != nil {
+		return err
+	}
+
+	return views.Posts(posts).Render(c.Request().Context(), c.Response())
+}
+
+func (h Handler) Idle(c echo.Context) error {
+	return views.Idle().Render(c.Request().Context(), c.Response())
+}
+
+func (h Handler) allPosts(c echo.Context) ([]views.Post, error) {
+	posts, err := h.repo.AllPosts(c.Request().Context())
+	if err != nil {
+		return nil, err
+	}
+
+	for _, post := range posts {
+		event := PostViewed{
+			PostID: post.ID,
+		}
+
+		err = h.eventBus.Publish(c.Request().Context(), event)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	var postViews []views.Post
+	for _, post := range posts {
+		postViews = append(postViews, newPostView(post))
+	}
+
+	return postViews, nil
+}
+
+func (h Handler) AddReaction(c echo.Context) error {
+	postID, err := strconv.Atoi(c.Param("id"))
+	if err != nil {
+		return err
+	}
+
+	reactionID := c.FormValue("reaction_id")
+
+	var found bool
+	for _, r := range allReactions {
+		if r.ID == reactionID {
+			found = true
+			break
+		}
+	}
+
+	if !found {
+		return c.String(http.StatusBadRequest, "invalid reaction ID")
+	}
+
+	event := PostReactionAdded{
+		PostID:     postID,
+		ReactionID: reactionID,
+	}
+
+	err = h.eventBus.Publish(c.Request().Context(), event)
+	if err != nil {
+		return err
+	}
+
+	reaction := mustReactionByID(reactionID)
+
+	return views.UpdatedButton(reaction.Label).Render(c.Request().Context(), c.Response())
+}
+
+type statsStream struct {
+	repo *Repository
+}
+
+func (s *statsStream) InitialStreamResponse(w http.ResponseWriter, r *http.Request) (response interface{}, ok bool) {
+	postIDStr := r.PathValue("id")
+	postID, err := strconv.Atoi(postIDStr)
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		w.Write([]byte("invalid post ID"))
+		return nil, false
+	}
+
+	post, err := s.repo.PostByID(r.Context(), postID)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte("could not get post"))
+		return nil, false
+	}
+
+	stats := PostStats{
+		ID:        post.ID,
+		Views:     post.Views,
+		Reactions: post.Reactions,
+	}
+
+	resp, err := newPostStatsView(r.Context(), stats)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Write([]byte(err.Error()))
+		return nil, false
+	}
+
+	return resp, true
+}
+
+func (s *statsStream) NextStreamResponse(r *http.Request, msg *message.Message) (response interface{}, ok bool) {
+	postIDStr := r.PathValue("id")
+	postID, err := strconv.Atoi(postIDStr)
+	if err != nil {
+		fmt.Println("invalid post ID")
+		return nil, false
+	}
+
+	var event PostStatsUpdated
+	err = json.Unmarshal(msg.Payload, &event)
+	if err != nil {
+		fmt.Println("cannot unmarshal: " + err.Error())
+		return "", false
+	}
+
+	if event.PostID != postID {
+		return "", false
+	}
+
+	stats := PostStats{
+		ID:              event.PostID,
+		Views:           event.Views,
+		ViewsUpdated:    event.ViewsUpdated,
+		Reactions:       event.Reactions,
+		ReactionUpdated: event.ReactionUpdated,
+	}
+
+	resp, err := newPostStatsView(r.Context(), stats)
+	if err != nil {
+		fmt.Println("could not get response: " + err.Error())
+		return nil, false
+	}
+
+	return resp, true
+}
+
+func newPostStatsView(ctx context.Context, stats PostStats) (interface{}, error) {
+	var reactions []views.Reaction
+
+	for _, r := range allReactions {
+		reactions = append(reactions, views.Reaction{
+			ID:          r.ID,
+			Label:       r.Label,
+			Count:       fmt.Sprint(stats.Reactions[r.ID]),
+			JustChanged: stats.ReactionUpdated != nil && *stats.ReactionUpdated == r.ID,
+		})
+	}
+
+	view := views.PostStats{
+		PostID: fmt.Sprint(stats.ID),
+		Views: views.PostViews{
+			Count:       fmt.Sprint(stats.Views),
+			JustChanged: stats.ViewsUpdated,
+		},
+		Reactions: reactions,
+	}
+
+	var buffer bytes.Buffer
+	err := views.PostStatsView(view).Render(ctx, &buffer)
+	if err != nil {
+		return nil, err
+	}
+
+	return buffer.String(), nil
+}
+
+func newPostView(p Post) views.Post {
+	return views.Post{
+		ID:      fmt.Sprint(p.ID),
+		Content: p.Content,
+		Author:  p.Author,
+		Date:    p.CreatedAt.Format("02 Jan 2006 15:04"),
+	}
+}
+
+type sseHandlersCounter struct {
+	Count atomic.Int64
+}
+
+func (s *sseHandlersCounter) Middleware(next echo.HandlerFunc) echo.HandlerFunc {
+	return func(c echo.Context) error {
+		s.Count.Add(1)
+		defer s.Count.Add(-1)
+		return next(c)
+	}
+}