feat: add NATS chatroom example with embedded server
Demonstrates pub/sub messaging as an alternative to custom Rooms implementation. Uses delaneyj/toolbelt/embeddednats to run NATS with JetStream inside the binary - no external server required.
This commit is contained in:
Ryan Hamamura
409
internal/examples/nats-chatroom/main.go
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409
internal/examples/nats-chatroom/main.go
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@@ -0,0 +1,409 @@
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package main
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import (
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"context"
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"encoding/json"
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"log"
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"math/rand"
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"sync"
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"time"
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"github.com/delaneyj/toolbelt/embeddednats"
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"github.com/nats-io/nats.go"
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"github.com/ryanhamamura/via"
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"github.com/ryanhamamura/via/h"
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)
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var (
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WithSignal = via.WithSignal
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)
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// ChatMessage represents a message in a chat room
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type ChatMessage struct {
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User UserInfo `json:"user"`
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Message string `json:"message"`
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Time int64 `json:"time"`
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}
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// UserInfo identifies a chat participant
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type UserInfo struct {
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Name string `json:"name"`
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Emoji string `json:"emoji"`
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}
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func (u *UserInfo) Avatar() h.H {
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return h.Div(h.Class("avatar"), h.Attr("title", u.Name), h.Text(u.Emoji))
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}
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// NATSChatroom manages NATS connections and per-context subscriptions
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type NATSChatroom struct {
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nc *nats.Conn
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js nats.JetStreamContext
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subs map[string]*nats.Subscription
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mu sync.RWMutex
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}
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func NewNATSChatroom(nc *nats.Conn) (*NATSChatroom, error) {
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js, err := nc.JetStream()
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if err != nil {
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return nil, err
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}
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// Create or update the CHAT stream for durability
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_, err = js.AddStream(&nats.StreamConfig{
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Name: "CHAT",
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Subjects: []string{"chat.>"},
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Retention: nats.LimitsPolicy,
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MaxMsgs: 1000, // Keep last 1000 messages per room
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MaxAge: 24 * time.Hour,
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})
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if err != nil && err != nats.ErrStreamNameAlreadyInUse {
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// Stream might already exist, that's fine
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log.Printf("Note: stream creation returned: %v", err)
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}
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return &NATSChatroom{
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nc: nc,
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js: js,
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subs: make(map[string]*nats.Subscription),
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}, nil
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}
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// Subscribe creates a subscription for a context to a room
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func (chat *NATSChatroom) Subscribe(ctxID, room string, handler func(msg *ChatMessage)) error {
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subject := "chat.room." + room
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sub, err := chat.nc.Subscribe(subject, func(m *nats.Msg) {
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var msg ChatMessage
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if err := json.Unmarshal(m.Data, &msg); err != nil {
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log.Printf("Failed to unmarshal message: %v", err)
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return
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}
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handler(&msg)
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})
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if err != nil {
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return err
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}
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chat.mu.Lock()
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// Clean up old subscription if exists
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if old, exists := chat.subs[ctxID]; exists {
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old.Unsubscribe()
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}
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chat.subs[ctxID] = sub
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chat.mu.Unlock()
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return nil
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}
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// Unsubscribe removes a context's subscription
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func (chat *NATSChatroom) Unsubscribe(ctxID string) {
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chat.mu.Lock()
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defer chat.mu.Unlock()
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if sub, exists := chat.subs[ctxID]; exists {
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sub.Unsubscribe()
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delete(chat.subs, ctxID)
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}
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}
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// Publish sends a message to a room
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func (chat *NATSChatroom) Publish(room string, msg ChatMessage) error {
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subject := "chat.room." + room
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data, err := json.Marshal(msg)
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if err != nil {
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return err
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}
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return chat.nc.Publish(subject, data)
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}
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// GetHistory retrieves recent messages from JetStream
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func (chat *NATSChatroom) GetHistory(room string, limit int) ([]ChatMessage, error) {
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subject := "chat.room." + room
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// Create an ephemeral consumer to replay messages
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sub, err := chat.js.SubscribeSync(subject, nats.DeliverLast())
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if err != nil {
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// No messages yet
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return nil, nil
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}
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defer sub.Unsubscribe()
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var messages []ChatMessage
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for i := 0; i < limit; i++ {
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msg, err := sub.NextMsg(100 * time.Millisecond)
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if err != nil {
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break
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}
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var chatMsg ChatMessage
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if err := json.Unmarshal(msg.Data, &chatMsg); err == nil {
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messages = append(messages, chatMsg)
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}
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}
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return messages, nil
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}
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func (chat *NATSChatroom) Close() {
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chat.mu.Lock()
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for _, sub := range chat.subs {
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sub.Unsubscribe()
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}
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chat.mu.Unlock()
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chat.nc.Close()
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}
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var roomNames = []string{"Go", "Rust", "Python", "JavaScript", "Clojure"}
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func main() {
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ctx := context.Background()
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// Start embedded NATS server (JetStream enabled by default)
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ns, err := embeddednats.New(ctx,
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embeddednats.WithDirectory("./data/nats"),
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)
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if err != nil {
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log.Fatalf("Failed to start embedded NATS: %v", err)
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}
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ns.WaitForServer()
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// Get client connection to embedded server
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nc, err := ns.Client()
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if err != nil {
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log.Fatalf("Failed to connect to embedded NATS: %v", err)
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}
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chat, err := NewNATSChatroom(nc)
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if err != nil {
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log.Fatalf("Failed to initialize chatroom: %v", err)
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}
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defer chat.Close()
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v := via.New()
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v.Config(via.Options{
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DevMode: true,
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DocumentTitle: "NATS Chat",
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LogLvl: via.LogLevelInfo,
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ServerAddress: ":7331",
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})
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v.AppendToHead(
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h.Link(h.Rel("stylesheet"), h.Href("https://cdn.jsdelivr.net/npm/@picocss/pico@2/css/pico.min.css")),
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h.StyleEl(h.Raw(`
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body { margin: 0; }
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main {
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display: flex;
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flex-direction: column;
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height: 100vh;
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}
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nav[role="tab-control"] ul li a[aria-current="page"] {
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background-color: var(--pico-primary-background);
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color: var(--pico-primary-inverse);
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border-bottom: 2px solid var(--pico-primary);
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}
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.chat-message { display: flex; gap: 0.75rem; margin-bottom: 0.5rem; }
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.avatar {
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width: 2rem;
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height: 2rem;
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border-radius: 50%;
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background: var(--pico-muted-border-color);
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display: grid;
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place-items: center;
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font-size: 1.5rem;
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flex-shrink: 0;
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}
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.bubble { flex: 1; }
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.bubble p { margin: 0; }
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.chat-history {
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flex: 1;
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overflow-y: auto;
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padding: 1rem;
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padding-bottom: calc(88px + env(safe-area-inset-bottom));
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}
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.chat-input {
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position: fixed;
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left: 0;
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right: 0;
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bottom: 0;
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background: var(--pico-background-color);
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display: flex;
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align-items: center;
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gap: 0.75rem;
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padding: 0.75rem 1rem calc(0.75rem + env(safe-area-inset-bottom));
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border-top: 1px solid var(--pico-muted-border-color);
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}
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.chat-input fieldset {
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flex: 1;
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margin: 0;
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}
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.nats-badge {
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background: #27AAE1;
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color: white;
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padding: 0.25rem 0.5rem;
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border-radius: 4px;
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font-size: 0.75rem;
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margin-left: auto;
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}
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`)),
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h.Script(h.Raw(`
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function scrollChatToBottom() {
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const chatHistory = document.querySelector('.chat-history');
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if (chatHistory) chatHistory.scrollTop = chatHistory.scrollHeight;
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}
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`)),
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)
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v.Page("/", func(c *via.Context) {
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currentUser := randUser()
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roomSignal := c.Signal("Go")
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statement := c.Signal("")
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// Local message cache for this context
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var messages []ChatMessage
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var messagesMu sync.Mutex
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currentRoom := "Go"
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// Context ID for subscription management
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ctxID := randID()
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// Subscribe to current room
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subscribeToRoom := func(room string) {
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chat.Subscribe(ctxID, room, func(msg *ChatMessage) {
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messagesMu.Lock()
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messages = append(messages, *msg)
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// Keep only last 50 messages
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if len(messages) > 50 {
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messages = messages[len(messages)-50:]
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}
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messagesMu.Unlock()
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c.Sync()
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})
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currentRoom = room
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}
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subscribeToRoom("Go")
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switchRoom := c.Action(func() {
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newRoom := roomSignal.String()
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if newRoom != currentRoom {
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messagesMu.Lock()
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messages = nil // Clear messages for new room
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messagesMu.Unlock()
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subscribeToRoom(newRoom)
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c.Sync()
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}
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})
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say := c.Action(func() {
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msg := statement.String()
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if msg == "" {
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msg = randomDevQuote()
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}
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statement.SetValue("")
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chat.Publish(currentRoom, ChatMessage{
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User: currentUser,
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Message: msg,
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Time: time.Now().UnixMilli(),
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})
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})
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c.View(func() h.H {
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// Build room tabs
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var tabs []h.H
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for _, name := range roomNames {
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isCurrent := name == currentRoom
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tabs = append(tabs, h.Li(
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h.A(
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h.If(isCurrent, h.Attr("aria-current", "page")),
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h.Text(name),
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switchRoom.OnClick(WithSignal(roomSignal, name)),
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),
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))
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}
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// Build message list
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messagesMu.Lock()
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chatHistoryChildren := []h.H{
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h.Class("chat-history"),
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h.Script(h.Raw(`new MutationObserver(()=>scrollChatToBottom()).observe(document.querySelector('.chat-history'), {childList:true})`)),
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}
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for _, msg := range messages {
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chatHistoryChildren = append(chatHistoryChildren,
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h.Div(h.Class("chat-message"),
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h.Div(h.Class("avatar"), h.Attr("title", msg.User.Name), h.Text(msg.User.Emoji)),
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h.Div(h.Class("bubble"),
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h.P(h.Text(msg.Message)),
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),
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),
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)
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}
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messagesMu.Unlock()
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return h.Main(h.Class("container"),
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h.Nav(
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h.Attr("role", "tab-control"),
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h.Ul(tabs...),
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h.Span(h.Class("nats-badge"), h.Text("NATS")),
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),
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h.Div(chatHistoryChildren...),
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h.Div(
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h.Class("chat-input"),
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currentUser.Avatar(),
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h.FieldSet(
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h.Attr("role", "group"),
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h.Input(
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h.Type("text"),
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h.Placeholder(currentUser.Name+" says..."),
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statement.Bind(),
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h.Attr("autofocus"),
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say.OnKeyDown("Enter"),
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),
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h.Button(h.Text("Send"), say.OnClick()),
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),
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),
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)
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})
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})
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log.Println("Starting NATS chatroom on :7331 (embedded NATS server)")
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v.Start()
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}
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func randUser() UserInfo {
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adjectives := []string{"Happy", "Clever", "Brave", "Swift", "Gentle", "Wise", "Bold", "Calm", "Eager", "Fierce"}
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animals := []string{"Panda", "Tiger", "Eagle", "Dolphin", "Fox", "Wolf", "Bear", "Hawk", "Otter", "Lion"}
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emojis := []string{"🐼", "🐯", "🦅", "🐬", "🦊", "🐺", "🐻", "🦅", "🦦", "🦁"}
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idx := rand.Intn(len(animals))
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return UserInfo{
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Name: adjectives[rand.Intn(len(adjectives))] + " " + animals[idx],
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Emoji: emojis[idx],
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}
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}
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func randID() string {
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const chars = "abcdefghijklmnopqrstuvwxyz0123456789"
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b := make([]byte, 8)
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for i := range b {
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b[i] = chars[rand.Intn(len(chars))]
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}
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return string(b)
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}
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var quoteIdx = rand.Intn(len(devQuotes))
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var devQuotes = []string{
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"Just use NATS.",
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"Pub/sub all the things!",
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"Messages are the new API.",
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"JetStream for durability.",
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"No more polling.",
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"Event-driven architecture FTW.",
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"Decouple everything.",
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"NATS is fast.",
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"Subjects are like topics.",
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"Request-reply is cool.",
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}
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func randomDevQuote() string {
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quoteIdx = (quoteIdx + 1) % len(devQuotes)
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return devQuotes[quoteIdx]
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}
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Reference in New Issue
Block a user