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.
2026-01-16 00:50:05 -10:00
parent 82a3314089
commit 88bd0f31df
5 changed files with 585 additions and 11 deletions
--- a/.gitignore
+++ b/.gitignore
@@ -47,3 +47,7 @@ internal/examples/picocss/picocss
 internal/examples/plugins/plugins
 internal/examples/realtimechart/realtimechart
 internal/examples/shakespeare/shakespeare
+internal/examples/nats-chatroom/nats-chatroom
+
+# NATS data directory
+data/
--- a/go.mod
+++ b/go.mod
@@ -8,17 +8,32 @@ require (
 	github.com/DATA-DOG/go-sqlmock v1.5.2
 	github.com/alexedwards/scs/sqlite3store v0.0.0-20251002162104-209de6e426de
 	github.com/alexedwards/scs/v2 v2.9.0
+	github.com/delaneyj/toolbelt v0.9.1
 	github.com/mattn/go-sqlite3 v1.14.32
+	github.com/nats-io/nats.go v1.48.0
 	github.com/starfederation/datastar-go v1.0.3
-	github.com/stretchr/testify v1.10.0
+	github.com/stretchr/testify v1.11.1
 )

 require (
 	github.com/CAFxX/httpcompression v0.0.9 // indirect
 	github.com/andybalholm/brotli v1.2.0 // indirect
-	github.com/davecgh/go-spew v1.1.1 // indirect
-	github.com/klauspost/compress v1.18.0 // indirect
-	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/antithesishq/antithesis-sdk-go v0.5.0 // indirect
+	github.com/cenkalti/backoff v2.2.1+incompatible // indirect
+	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect
+	github.com/google/go-tpm v0.9.7 // indirect
+	github.com/klauspost/compress v1.18.2 // indirect
+	github.com/kr/text v0.2.0 // indirect
+	github.com/minio/highwayhash v1.0.4-0.20251030100505-070ab1a87a76 // indirect
+	github.com/nats-io/jwt/v2 v2.8.0 // indirect
+	github.com/nats-io/nats-server/v2 v2.12.2 // indirect
+	github.com/nats-io/nkeys v0.4.12 // indirect
+	github.com/nats-io/nuid v1.0.1 // indirect
+	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
+	github.com/rogpeppe/go-internal v1.14.1 // indirect
 	github.com/valyala/bytebufferpool v1.0.0 // indirect
+	golang.org/x/crypto v0.45.0 // indirect
+	golang.org/x/sys v0.38.0 // indirect
+	golang.org/x/time v0.14.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
--- a/go.sum
+++ b/go.sum
@@ -9,23 +9,52 @@ github.com/alexedwards/scs/v2 v2.9.0/go.mod h1:ToaROZxyKukJKT/xLcVQAChi5k6+Pn1Gv
 github.com/andybalholm/brotli v1.0.5/go.mod h1:fO7iG3H7G2nSZ7m0zPUDn85XEX2GTukHGRSepvi9Eig=
 github.com/andybalholm/brotli v1.2.0 h1:ukwgCxwYrmACq68yiUqwIWnGY0cTPox/M94sVwToPjQ=
 github.com/andybalholm/brotli v1.2.0/go.mod h1:rzTDkvFWvIrjDXZHkuS16NPggd91W3kUSvPlQ1pLaKY=
+github.com/antithesishq/antithesis-sdk-go v0.5.0 h1:cudCFF83pDDANcXFzkQPUHHedfnnIbUO3JMr9fqwFJs=
+github.com/antithesishq/antithesis-sdk-go v0.5.0/go.mod h1:IUpT2DPAKh6i/YhSbt6Gl3v2yvUZjmKncl7U91fup7E=
+github.com/cenkalti/backoff v2.2.1+incompatible h1:tNowT99t7UNflLxfYYSlKYsBpXdEet03Pg2g16Swow4=
+github.com/cenkalti/backoff v2.2.1+incompatible/go.mod h1:90ReRw6GdpyfrHakVjL/QHaoyV4aDUVVkXQJJJ3NXXM=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
+github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/delaneyj/toolbelt v0.9.1 h1:QJComn2qoaQ4azl5uRkGpdHSO9e+JtoxDTXCiQHvH8o=
+github.com/delaneyj/toolbelt v0.9.1/go.mod h1:eNXpPuThjTD4tpRNCBl4JEz9jdg9LpyzNuyG+stnIbs=
 github.com/google/brotli/go/cbrotli v0.0.0-20230829110029-ed738e842d2f h1:jopqB+UTSdJGEJT8tEqYyE29zN91fi2827oLET8tl7k=
 github.com/google/brotli/go/cbrotli v0.0.0-20230829110029-ed738e842d2f/go.mod h1:nOPhAkwVliJdNTkj3gXpljmWhjc4wCaVqbMJcPKWP4s=
+github.com/google/go-tpm v0.9.7 h1:u89J4tUUeDTlH8xxC3CTW7OHZjbjKoHdQ9W7gCUhtxA=
+github.com/google/go-tpm v0.9.7/go.mod h1:h9jEsEECg7gtLis0upRBQU+GhYVH6jMjrFxI8u6bVUY=
 github.com/kisielk/sqlstruct v0.0.0-20201105191214-5f3e10d3ab46/go.mod h1:yyMNCyc/Ib3bDTKd379tNMpB/7/H5TjM2Y9QJ5THLbE=
 github.com/klauspost/compress v1.16.7/go.mod h1:ntbaceVETuRiXiv4DpjP66DpAtAGkEQskQzEyD//IeE=
-github.com/klauspost/compress v1.18.0 h1:c/Cqfb0r+Yi+JtIEq73FWXVkRonBlf0CRNYc8Zttxdo=
-github.com/klauspost/compress v1.18.0/go.mod h1:2Pp+KzxcywXVXMr50+X0Q/Lsb43OQHYWRCY2AiWywWQ=
+github.com/klauspost/compress v1.18.2 h1:iiPHWW0YrcFgpBYhsA6D1+fqHssJscY/Tm/y2Uqnapk=
+github.com/klauspost/compress v1.18.2/go.mod h1:R0h/fSBs8DE4ENlcrlib3PsXS61voFxhIs2DeRhCvJ4=
 github.com/klauspost/pgzip v1.2.6/go.mod h1:Ch1tH69qFZu15pkjo5kYi6mth2Zzwzt50oCQKQE9RUs=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/mattn/go-sqlite3 v1.14.6/go.mod h1:NyWgC/yNuGj7Q9rpYnZvas74GogHl5/Z4A/KQRfk6bU=
 github.com/mattn/go-sqlite3 v1.14.32 h1:JD12Ag3oLy1zQA+BNn74xRgaBbdhbNIDYvQUEuuErjs=
 github.com/mattn/go-sqlite3 v1.14.32/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=
+github.com/minio/highwayhash v1.0.4-0.20251030100505-070ab1a87a76 h1:KGuD/pM2JpL9FAYvBrnBBeENKZNh6eNtjqytV6TYjnk=
+github.com/minio/highwayhash v1.0.4-0.20251030100505-070ab1a87a76/go.mod h1:GGYsuwP/fPD6Y9hMiXuapVvlIUEhFhMTh0rxU3ik1LQ=
+github.com/nats-io/jwt/v2 v2.8.0 h1:K7uzyz50+yGZDO5o772eRE7atlcSEENpL7P+b74JV1g=
+github.com/nats-io/jwt/v2 v2.8.0/go.mod h1:me11pOkwObtcBNR8AiMrUbtVOUGkqYjMQZ6jnSdVUIA=
+github.com/nats-io/nats-server/v2 v2.12.2 h1:4TEQd0Y4zvcW0IsVxjlXnRso1hBkQl3TS0BI+SxgPhE=
+github.com/nats-io/nats-server/v2 v2.12.2/go.mod h1:j1AAttYeu7WnvD8HLJ+WWKNMSyxsqmZ160pNtCQRMyE=
+github.com/nats-io/nats.go v1.48.0 h1:pSFyXApG+yWU/TgbKCjmm5K4wrHu86231/w84qRVR+U=
+github.com/nats-io/nats.go v1.48.0/go.mod h1:iRWIPokVIFbVijxuMQq4y9ttaBTMe0SFdlZfMDd+33g=
+github.com/nats-io/nkeys v0.4.12 h1:nssm7JKOG9/x4J8II47VWCL1Ds29avyiQDRn0ckMvDc=
+github.com/nats-io/nkeys v0.4.12/go.mod h1:MT59A1HYcjIcyQDJStTfaOY6vhy9XTUjOFo+SVsvpBg=
+github.com/nats-io/nuid v1.0.1 h1:5iA8DT8V7q8WK2EScv2padNa/rTESc1KdnPw4TC2paw=
+github.com/nats-io/nuid v1.0.1/go.mod h1:19wcPz3Ph3q0Jbyiqsd0kePYG7A95tJPxeL+1OSON2c=
 github.com/pierrec/lz4/v4 v4.1.18 h1:xaKrnTkyoqfh1YItXl56+6KJNVYWlEEPuAQW9xsplYQ=
 github.com/pierrec/lz4/v4 v4.1.18/go.mod h1:gZWDp/Ze/IJXGXf23ltt2EXimqmTUXEy0GFuRQyBid4=
-github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
+github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/rogpeppe/go-internal v1.14.1 h1:UQB4HGPB6osV0SQTLymcB4TgvyWu6ZyliaW0tI/otEQ=
+github.com/rogpeppe/go-internal v1.14.1/go.mod h1:MaRKkUm5W0goXpeCfT7UZI6fk/L7L7so1lCWt35ZSgc=
 github.com/starfederation/datastar-go v1.0.3 h1:DnzgsJ6tDHDM6y5Nxsk0AGW/m8SyKch2vQg3P1xGTcU=
 github.com/starfederation/datastar-go v1.0.3/go.mod h1:stm83LQkhZkwa5GzzdPEN6dLuu8FVwxIv0w1DYkbD3w=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
@@ -34,8 +63,8 @@ github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpE
 github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
-github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
-github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
 github.com/ulikunitz/xz v0.5.11/go.mod h1:nbz6k7qbPmH4IRqmfOplQw/tblSgqTqBwxkY0oWt/14=
 github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6KllzawFIhcdPw=
 github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
@@ -43,8 +72,16 @@ github.com/valyala/gozstd v1.20.1 h1:xPnnnvjmaDDitMFfDxmQ4vpx0+3CdTg2o3lALvXTU/g
 github.com/valyala/gozstd v1.20.1/go.mod h1:y5Ew47GLlP37EkTB+B4s7r6A5rdaeB7ftbl9zoYiIPQ=
 github.com/xyproto/randomstring v1.0.5 h1:YtlWPoRdgMu3NZtP45drfy1GKoojuR7hmRcnhZqKjWU=
 github.com/xyproto/randomstring v1.0.5/go.mod h1:rgmS5DeNXLivK7YprL0pY+lTuhNQW3iGxZ18UQApw/E=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+golang.org/x/crypto v0.45.0 h1:jMBrvKuj23MTlT0bQEOBcAE0mjg8mK9RXFhRH6nyF3Q=
+golang.org/x/crypto v0.45.0/go.mod h1:XTGrrkGJve7CYK7J8PEww4aY7gM3qMCElcJQ8n8JdX4=
+golang.org/x/sys v0.21.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
+golang.org/x/sys v0.38.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/time v0.14.0 h1:MRx4UaLrDotUKUdCIqzPC48t1Y9hANFKIRpNx+Te8PI=
+golang.org/x/time v0.14.0/go.mod h1:eL/Oa2bBBK0TkX57Fyni+NgnyQQN4LitPmob2Hjnqw4=
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+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c h1:Hei/4ADfdWqJk1ZMxUNpqntNwaWcugrBjAiHlqqRiVk=
+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
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--- a/internal/examples/nats-chatroom/README.md
+++ b/internal/examples/nats-chatroom/README.md
@@ -0,0 +1,109 @@
+# NATS Chatroom Example (Embedded)
+
+A chatroom built with Via and an **embedded NATS server**, demonstrating pub/sub messaging as an alternative to the custom `Rooms` implementation in `../chatroom`.
+
+Uses `delaneyj/toolbelt/embeddednats` to run NATS inside the same binary - no external server required.
+
+## Key Differences from Original Chatroom
+
+| Aspect | Original (`../chatroom`) | This Example |
+|--------|-------------------------|--------------|
+| Pub/sub | Custom `Rooms` struct (~160 lines) | NATS subjects |
+| Member tracking | Manual `map[TU]Syncable` | NATS handles subscribers |
+| Publish timing | Ticker every 100ms + dirty flag | Instant delivery |
+| Durability | None (in-memory) | JetStream persists to disk |
+| Multi-instance | Not supported | Works across server instances |
+| External deps | None | **None** (NATS embedded in binary) |
+
+## Run the Example
+
+```bash
+go run ./internal/examples/nats-chatroom
+```
+
+That's it. No separate NATS server needed.
+
+Open multiple browser tabs at http://localhost:7331 to see messages broadcast across all clients.
+
+## How Embedded NATS Works
+
+```go
+// Start embedded NATS server (JetStream enabled by default)
+ns, err := embeddednats.New(ctx,
+    embeddednats.WithDirectory("./data/nats"),
+)
+ns.WaitForServer()
+
+// Get client connection to embedded server
+nc, err := ns.Client()
+```
+
+Data is persisted to `./data/nats/` for JetStream durability.
+
+## Architecture
+
+```
+┌─────────────────────────────────────────────────────────┐
+│                    Single Binary                         │
+│                                                          │
+│  Browser A          Embedded NATS         Browser B      │
+│      │                   │                    │          │
+│      │-- Via Action ---> │                    │          │
+│      │   (Send msg)      │                    │          │
+│      │                   │                    │          │
+│      │              nc.Publish()              │          │
+│      │              "chat.room.Go"            │          │
+│      │                   │                    │          │
+│      │<-- Subscribe -----|---- Subscribe --->│          │
+│      │    callback       │    callback        │          │
+│      │                   │                    │          │
+│      │-- c.Sync() ------>│<--- c.Sync() -----|          │
+│      │   (SSE)           │     (SSE)          │          │
+│                                                          │
+└─────────────────────────────────────────────────────────┘
+```
+
+## JetStream Durability
+
+Messages persist to disk via JetStream:
+
+```go
+js.AddStream(&nats.StreamConfig{
+    Name:      "CHAT",
+    Subjects:  []string{"chat.>"},
+    MaxMsgs:   1000,  // Keep last 1000 messages
+    MaxAge:    24 * time.Hour,
+})
+```
+
+Stop and restart the app - chat history survives.
+
+## Code Comparison
+
+**Original chatroom - 160+ lines of custom pub/sub:**
+- `Rooms` struct with named rooms
+- `Room` with member tracking, mutex, dirty flag
+- Ticker-based publish loop
+- Manual join/leave channels
+
+**This example - ~60 lines of NATS integration:**
+- `embeddednats.New()` starts the server
+- `nc.Subscribe(subject, handler)` for receiving
+- `nc.Publish(subject, data)` for sending
+- NATS handles delivery, no polling
+
+## Next Steps
+
+If this pattern proves useful, it could be promoted to a Via plugin:
+
+```go
+// Hypothetical future API
+v.Config(via.WithEmbeddedNATS("./data/nats"))
+
+// In page init
+c.Subscribe("events.user.*", func(data []byte) {
+    c.Sync()
+})
+
+c.Publish("events.user.login", userData)
+```
--- a/internal/examples/nats-chatroom/main.go
+++ b/internal/examples/nats-chatroom/main.go
@@ -0,0 +1,409 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"log"
+	"math/rand"
+	"sync"
+	"time"
+
+	"github.com/delaneyj/toolbelt/embeddednats"
+	"github.com/nats-io/nats.go"
+	"github.com/ryanhamamura/via"
+	"github.com/ryanhamamura/via/h"
+)
+
+var (
+	WithSignal = via.WithSignal
+)
+
+// ChatMessage represents a message in a chat room
+type ChatMessage struct {
+	User    UserInfo `json:"user"`
+	Message string   `json:"message"`
+	Time    int64    `json:"time"`
+}
+
+// UserInfo identifies a chat participant
+type UserInfo struct {
+	Name  string `json:"name"`
+	Emoji string `json:"emoji"`
+}
+
+func (u *UserInfo) Avatar() h.H {
+	return h.Div(h.Class("avatar"), h.Attr("title", u.Name), h.Text(u.Emoji))
+}
+
+// NATSChatroom manages NATS connections and per-context subscriptions
+type NATSChatroom struct {
+	nc   *nats.Conn
+	js   nats.JetStreamContext
+	subs map[string]*nats.Subscription
+	mu   sync.RWMutex
+}
+
+func NewNATSChatroom(nc *nats.Conn) (*NATSChatroom, error) {
+	js, err := nc.JetStream()
+	if err != nil {
+		return nil, err
+	}
+
+	// Create or update the CHAT stream for durability
+	_, err = js.AddStream(&nats.StreamConfig{
+		Name:      "CHAT",
+		Subjects:  []string{"chat.>"},
+		Retention: nats.LimitsPolicy,
+		MaxMsgs:   1000, // Keep last 1000 messages per room
+		MaxAge:    24 * time.Hour,
+	})
+	if err != nil && err != nats.ErrStreamNameAlreadyInUse {
+		// Stream might already exist, that's fine
+		log.Printf("Note: stream creation returned: %v", err)
+	}
+
+	return &NATSChatroom{
+		nc:   nc,
+		js:   js,
+		subs: make(map[string]*nats.Subscription),
+	}, nil
+}
+
+// Subscribe creates a subscription for a context to a room
+func (chat *NATSChatroom) Subscribe(ctxID, room string, handler func(msg *ChatMessage)) error {
+	subject := "chat.room." + room
+
+	sub, err := chat.nc.Subscribe(subject, func(m *nats.Msg) {
+		var msg ChatMessage
+		if err := json.Unmarshal(m.Data, &msg); err != nil {
+			log.Printf("Failed to unmarshal message: %v", err)
+			return
+		}
+		handler(&msg)
+	})
+	if err != nil {
+		return err
+	}
+
+	chat.mu.Lock()
+	// Clean up old subscription if exists
+	if old, exists := chat.subs[ctxID]; exists {
+		old.Unsubscribe()
+	}
+	chat.subs[ctxID] = sub
+	chat.mu.Unlock()
+
+	return nil
+}
+
+// Unsubscribe removes a context's subscription
+func (chat *NATSChatroom) Unsubscribe(ctxID string) {
+	chat.mu.Lock()
+	defer chat.mu.Unlock()
+	if sub, exists := chat.subs[ctxID]; exists {
+		sub.Unsubscribe()
+		delete(chat.subs, ctxID)
+	}
+}
+
+// Publish sends a message to a room
+func (chat *NATSChatroom) Publish(room string, msg ChatMessage) error {
+	subject := "chat.room." + room
+	data, err := json.Marshal(msg)
+	if err != nil {
+		return err
+	}
+	return chat.nc.Publish(subject, data)
+}
+
+// GetHistory retrieves recent messages from JetStream
+func (chat *NATSChatroom) GetHistory(room string, limit int) ([]ChatMessage, error) {
+	subject := "chat.room." + room
+
+	// Create an ephemeral consumer to replay messages
+	sub, err := chat.js.SubscribeSync(subject, nats.DeliverLast())
+	if err != nil {
+		// No messages yet
+		return nil, nil
+	}
+	defer sub.Unsubscribe()
+
+	var messages []ChatMessage
+	for i := 0; i < limit; i++ {
+		msg, err := sub.NextMsg(100 * time.Millisecond)
+		if err != nil {
+			break
+		}
+		var chatMsg ChatMessage
+		if err := json.Unmarshal(msg.Data, &chatMsg); err == nil {
+			messages = append(messages, chatMsg)
+		}
+	}
+	return messages, nil
+}
+
+func (chat *NATSChatroom) Close() {
+	chat.mu.Lock()
+	for _, sub := range chat.subs {
+		sub.Unsubscribe()
+	}
+	chat.mu.Unlock()
+	chat.nc.Close()
+}
+
+var roomNames = []string{"Go", "Rust", "Python", "JavaScript", "Clojure"}
+
+func main() {
+	ctx := context.Background()
+
+	// Start embedded NATS server (JetStream enabled by default)
+	ns, err := embeddednats.New(ctx,
+		embeddednats.WithDirectory("./data/nats"),
+	)
+	if err != nil {
+		log.Fatalf("Failed to start embedded NATS: %v", err)
+	}
+	ns.WaitForServer()
+
+	// Get client connection to embedded server
+	nc, err := ns.Client()
+	if err != nil {
+		log.Fatalf("Failed to connect to embedded NATS: %v", err)
+	}
+
+	chat, err := NewNATSChatroom(nc)
+	if err != nil {
+		log.Fatalf("Failed to initialize chatroom: %v", err)
+	}
+	defer chat.Close()
+
+	v := via.New()
+	v.Config(via.Options{
+		DevMode:       true,
+		DocumentTitle: "NATS Chat",
+		LogLvl:        via.LogLevelInfo,
+		ServerAddress: ":7331",
+	})
+
+	v.AppendToHead(
+		h.Link(h.Rel("stylesheet"), h.Href("https://cdn.jsdelivr.net/npm/@picocss/pico@2/css/pico.min.css")),
+		h.StyleEl(h.Raw(`
+			body { margin: 0; }
+			main {
+				display: flex;
+				flex-direction: column;
+				height: 100vh;
+			}
+			nav[role="tab-control"] ul li a[aria-current="page"] {
+				background-color: var(--pico-primary-background);
+				color: var(--pico-primary-inverse);
+				border-bottom: 2px solid var(--pico-primary);
+			}
+			.chat-message { display: flex; gap: 0.75rem; margin-bottom: 0.5rem; }
+			.avatar {
+				width: 2rem;
+				height: 2rem;
+				border-radius: 50%;
+				background: var(--pico-muted-border-color);
+				display: grid;
+				place-items: center;
+				font-size: 1.5rem;
+				flex-shrink: 0;
+			}
+			.bubble { flex: 1; }
+			.bubble p { margin: 0; }
+			.chat-history {
+				flex: 1;
+				overflow-y: auto;
+				padding: 1rem;
+				padding-bottom: calc(88px + env(safe-area-inset-bottom));
+			}
+			.chat-input {
+				position: fixed;
+				left: 0;
+				right: 0;
+				bottom: 0;
+				background: var(--pico-background-color);
+				display: flex;
+				align-items: center;
+				gap: 0.75rem;
+				padding: 0.75rem 1rem calc(0.75rem + env(safe-area-inset-bottom));
+				border-top: 1px solid var(--pico-muted-border-color);
+			}
+			.chat-input fieldset {
+				flex: 1;
+				margin: 0;
+			}
+			.nats-badge {
+				background: #27AAE1;
+				color: white;
+				padding: 0.25rem 0.5rem;
+				border-radius: 4px;
+				font-size: 0.75rem;
+				margin-left: auto;
+			}
+		`)),
+		h.Script(h.Raw(`
+			function scrollChatToBottom() {
+				const chatHistory = document.querySelector('.chat-history');
+				if (chatHistory) chatHistory.scrollTop = chatHistory.scrollHeight;
+			}
+		`)),
+	)
+
+	v.Page("/", func(c *via.Context) {
+		currentUser := randUser()
+		roomSignal := c.Signal("Go")
+		statement := c.Signal("")
+
+		// Local message cache for this context
+		var messages []ChatMessage
+		var messagesMu sync.Mutex
+		currentRoom := "Go"
+
+		// Context ID for subscription management
+		ctxID := randID()
+
+		// Subscribe to current room
+		subscribeToRoom := func(room string) {
+			chat.Subscribe(ctxID, room, func(msg *ChatMessage) {
+				messagesMu.Lock()
+				messages = append(messages, *msg)
+				// Keep only last 50 messages
+				if len(messages) > 50 {
+					messages = messages[len(messages)-50:]
+				}
+				messagesMu.Unlock()
+				c.Sync()
+			})
+			currentRoom = room
+		}
+
+		subscribeToRoom("Go")
+
+		switchRoom := c.Action(func() {
+			newRoom := roomSignal.String()
+			if newRoom != currentRoom {
+				messagesMu.Lock()
+				messages = nil // Clear messages for new room
+				messagesMu.Unlock()
+				subscribeToRoom(newRoom)
+				c.Sync()
+			}
+		})
+
+		say := c.Action(func() {
+			msg := statement.String()
+			if msg == "" {
+				msg = randomDevQuote()
+			}
+			statement.SetValue("")
+
+			chat.Publish(currentRoom, ChatMessage{
+				User:    currentUser,
+				Message: msg,
+				Time:    time.Now().UnixMilli(),
+			})
+		})
+
+		c.View(func() h.H {
+			// Build room tabs
+			var tabs []h.H
+			for _, name := range roomNames {
+				isCurrent := name == currentRoom
+				tabs = append(tabs, h.Li(
+					h.A(
+						h.If(isCurrent, h.Attr("aria-current", "page")),
+						h.Text(name),
+						switchRoom.OnClick(WithSignal(roomSignal, name)),
+					),
+				))
+			}
+
+			// Build message list
+			messagesMu.Lock()
+			chatHistoryChildren := []h.H{
+				h.Class("chat-history"),
+				h.Script(h.Raw(`new MutationObserver(()=>scrollChatToBottom()).observe(document.querySelector('.chat-history'), {childList:true})`)),
+			}
+			for _, msg := range messages {
+				chatHistoryChildren = append(chatHistoryChildren,
+					h.Div(h.Class("chat-message"),
+						h.Div(h.Class("avatar"), h.Attr("title", msg.User.Name), h.Text(msg.User.Emoji)),
+						h.Div(h.Class("bubble"),
+							h.P(h.Text(msg.Message)),
+						),
+					),
+				)
+			}
+			messagesMu.Unlock()
+
+			return h.Main(h.Class("container"),
+				h.Nav(
+					h.Attr("role", "tab-control"),
+					h.Ul(tabs...),
+					h.Span(h.Class("nats-badge"), h.Text("NATS")),
+				),
+				h.Div(chatHistoryChildren...),
+				h.Div(
+					h.Class("chat-input"),
+					currentUser.Avatar(),
+					h.FieldSet(
+						h.Attr("role", "group"),
+						h.Input(
+							h.Type("text"),
+							h.Placeholder(currentUser.Name+" says..."),
+							statement.Bind(),
+							h.Attr("autofocus"),
+							say.OnKeyDown("Enter"),
+						),
+						h.Button(h.Text("Send"), say.OnClick()),
+					),
+				),
+			)
+		})
+	})
+
+	log.Println("Starting NATS chatroom on :7331 (embedded NATS server)")
+	v.Start()
+}
+
+func randUser() UserInfo {
+	adjectives := []string{"Happy", "Clever", "Brave", "Swift", "Gentle", "Wise", "Bold", "Calm", "Eager", "Fierce"}
+	animals := []string{"Panda", "Tiger", "Eagle", "Dolphin", "Fox", "Wolf", "Bear", "Hawk", "Otter", "Lion"}
+	emojis := []string{"🐼", "🐯", "🦅", "🐬", "🦊", "🐺", "🐻", "🦅", "🦦", "🦁"}
+
+	idx := rand.Intn(len(animals))
+	return UserInfo{
+		Name:  adjectives[rand.Intn(len(adjectives))] + " " + animals[idx],
+		Emoji: emojis[idx],
+	}
+}
+
+func randID() string {
+	const chars = "abcdefghijklmnopqrstuvwxyz0123456789"
+	b := make([]byte, 8)
+	for i := range b {
+		b[i] = chars[rand.Intn(len(chars))]
+	}
+	return string(b)
+}
+
+var quoteIdx = rand.Intn(len(devQuotes))
+var devQuotes = []string{
+	"Just use NATS.",
+	"Pub/sub all the things!",
+	"Messages are the new API.",
+	"JetStream for durability.",
+	"No more polling.",
+	"Event-driven architecture FTW.",
+	"Decouple everything.",
+	"NATS is fast.",
+	"Subjects are like topics.",
+	"Request-reply is cool.",
+}
+
+func randomDevQuote() string {
+	quoteIdx = (quoteIdx + 1) % len(devQuotes)
+	return devQuotes[quoteIdx]
+}