feat: Added simple demo app.

This was just for the screenshot, but it can be a fun proof of concept.

internal/cli/demo.go

@@ -0,0 +1,197 @@
+package cli
+
+import (
+	"net/http"
+	"net/url"
+	"time"
+
+	"github.com/google/uuid"
+	"termtap.dev/internal/model"
+	"termtap.dev/internal/tui"
+)
+
+func runDemo() {
+	events := demoEvents()
+	ch := make(chan model.Event, len(events)+8)
+	for _, ev := range events {
+		ch <- ev
+	}
+
+	if err := runTUIFn(ch, tui.Controls{}); err != nil {
+		fatalExit(err)
+	}
+}
+
+func demoEvents() []model.Event {
+	base := time.Now().Add(-12 * time.Second)
+	request := func(method, host, path string, status int, duration time.Duration, reqBody, respBody string, reqHeaders, respHeaders http.Header) []model.Event {
+		id := uuid.New()
+		startedAt := base
+		base = base.Add(850 * time.Millisecond)
+
+		requestURL := (&url.URL{Scheme: "https", Host: host, Path: path}).String()
+		start := model.Event{
+			Time: startedAt,
+			Type: model.EventTypeRequestStarted,
+			Request: model.Request{
+				ID:             id,
+				Method:         method,
+				Host:           host,
+				URL:            path,
+				RawURL:         requestURL,
+				QueryString:    "",
+				Pending:        true,
+				StartTime:      startedAt,
+				RequestData:    []byte(reqBody),
+				RequestHeaders: reqHeaders,
+			},
+		}
+
+		finish := model.Event{
+			Time: startedAt.Add(duration),
+			Type: model.EventTypeRequestFinished,
+			Request: model.Request{
+				ID:              id,
+				Method:          method,
+				Host:            host,
+				URL:             path,
+				RawURL:          requestURL,
+				Status:          status,
+				Duration:        duration,
+				Pending:         false,
+				StartTime:       startedAt,
+				RequestData:     []byte(reqBody),
+				ResponseData:    []byte(respBody),
+				RequestHeaders:  reqHeaders,
+				ResponseHeaders: respHeaders,
+			},
+		}
+
+		return []model.Event{start, finish}
+	}
+
+	events := []model.Event{
+		{Time: base, Type: model.EventTypeSessionStarted, Body: "demo session started"},
+		{Time: base.Add(100 * time.Millisecond), Type: model.EventTypeProxyStarting, Body: "proxy warming up"},
+		{Time: base.Add(200 * time.Millisecond), Type: model.EventTypeProxyStarted, Body: "proxy listening on 127.0.0.1:8080"},
+		{Time: base.Add(300 * time.Millisecond), Type: model.EventTypeProcessStarting, Body: "starting demo app: go run ."},
+		{Time: base.Add(450 * time.Millisecond), Type: model.EventTypeProcessStarted, PID: 48213, Body: "demo app pid 48213"},
+		{Time: base.Add(500 * time.Millisecond), Type: model.EventTypeProcessStdout, Body: "tap • 12 requests captured"},
+		{Time: base.Add(650 * time.Millisecond), Type: model.EventTypeProcessStdout, Body: "tap • replay mode enabled"},
+		{Time: base.Add(800 * time.Millisecond), Type: model.EventTypeProcessStderr, Body: "tap • upstream 429s detected"},
+	}
+
+	events = append(events, request(
+		"POST",
+		"api.stripe.com",
+		"/v1/payment_intents",
+		200,
+		183*time.Millisecond,
+		`{"amount":4900,"currency":"usd","payment_method":"pm_card_visa"}`,
+		`{"id":"pi_3NtDemo","status":"succeeded"}`,
+		http.Header{"Authorization": []string{"Bearer sk_demo_123"}, "Content-Type": []string{"application/json"}},
+		http.Header{"Content-Type": []string{"application/json"}},
+	)...)
+	events = append(events, request(
+		"GET",
+		"api.github.com",
+		"/repos/lovable/tap/pulls",
+		200,
+		245*time.Millisecond,
+		"",
+		`[{"number":12,"title":"Add demo mode"}]`,
+		http.Header{"Accept": []string{"application/vnd.github+json"}},
+		http.Header{"Content-Type": []string{"application/json"}},
+	)...)
+	events = append(events, request(
+		"POST",
+		"api.openai.com",
+		"/v1/chat/completions",
+		200,
+		1832*time.Millisecond,
+		`{"model":"gpt-4.1-mini","stream":true}`,
+		`{"id":"chatcmpl_demo","choices":[{"delta":{"content":"hello"}}]}`,
+		http.Header{"Authorization": []string{"Bearer sk-openai-demo"}},
+		http.Header{"Content-Type": []string{"application/json"}},
+	)...)
+	events = append(events, request(
+		"GET",
+		"api.example.com",
+		"/v2/users/42/preferences",
+		500,
+		2105*time.Millisecond,
+		"",
+		`{"error":"internal_server_error"}`,
+		http.Header{},
+		http.Header{"Content-Type": []string{"application/json"}},
+	)...)
+	events = append(events, request(
+		"GET",
+		"hooks.slack.com",
+		"/services/T0B/xxx",
+		200,
+		312*time.Millisecond,
+		"",
+		`{"ok":true}`,
+		http.Header{},
+		http.Header{"Content-Type": []string{"application/json"}},
+	)...)
+	events = append(events, request(
+		"PUT",
+		"api.example.com",
+		"/v2/users/42/preferences",
+		404,
+		89*time.Millisecond,
+		`{"theme":"terminal"}`,
+		`{"error":"not_found"}`,
+		http.Header{"Content-Type": []string{"application/json"}},
+		http.Header{"Content-Type": []string{"application/json"}},
+	)...)
+	events = append(events, request(
+		"DELETE",
+		"api.stripe.com",
+		"/v1/subscriptions/sub_xyz",
+		200,
+		156*time.Millisecond,
+		"",
+		`{"status":"canceled"}`,
+		http.Header{},
+		http.Header{"Content-Type": {"application/json"}},
+	)...)
+	events = append(events, request(
+		"PATCH",
+		"api.openai.com",
+		"/v1/fine_tuning/jobs",
+		429,
+		423*time.Millisecond,
+		`{"suffix":"demo","hyperparameters":{"n_epochs":3}}`,
+		`{"error":"rate_limit_exceeded"}`,
+		http.Header{"Authorization": []string{"Bearer sk-openai-demo"}},
+		http.Header{"Retry-After": []string{"2"}},
+	)...)
+	events = append(events, request(
+		"POST",
+		"api.resend.com",
+		"/emails",
+		422,
+		67*time.Millisecond,
+		`{"to":"demo@example.com"}`,
+		`{"error":"unprocessable_entity"}`,
+		http.Header{"Content-Type": []string{"application/json"}},
+		http.Header{"Content-Type": []string{"application/json"}},
+	)...)
+	events = append(events, request(
+		"GET",
+		"cdn.jsdelivr.net",
+		"/npm/lodash@4.17.21/lodash.min.js",
+		200,
+		23*time.Millisecond,
+		"",
+		"/* minified js */",
+		http.Header{},
+		http.Header{"Content-Type": []string{"application/javascript"}},
+	)...)
+	events = append(events, model.Event{Time: base.Add(1200 * time.Millisecond), Type: model.EventTypeProcessStdout, Body: "tap • demo ready • press q to quit"})
+
+	return events
+}

internal/cli/run.go

@@ -39,6 +39,10 @@ func Run(args []string) {
 		runCert()
 		return
 	}
+	if len(args) >= 2 && args[1] == "demo" {
+		runDemo()
+		return
+	}
 
 	cmd, ok := parseCommand(args)
 	if !ok {
@@ -83,6 +87,7 @@ func parseCommand(args []string) (model.Command, bool) {
 func displayHelp() {
 	helpText := `
 usage:
+	tap demo
 	tap cert
 	tap run -- <command> [args...]
 `

internal/cli/run_test.go

@@ -55,7 +55,7 @@ func TestDisplayHelpWritesToStderr(t *testing.T) {
 		displayHelp()
 	})
 
-	if !strings.Contains(stderr, "tap cert") || !strings.Contains(stderr, "tap run --") {
+	if !strings.Contains(stderr, "tap demo") || !strings.Contains(stderr, "tap cert") || !strings.Contains(stderr, "tap run --") {
 		t.Fatalf("stderr missing usage text: %q", stderr)
 	}
 }
@@ -83,6 +83,36 @@ func TestRun_RoutesCertCommand(t *testing.T) {
 	}
 }
 
+func TestRun_RoutesDemoCommand(t *testing.T) {
+	restore := installRunSeams(t)
+	defer restore()
+
+	called := installFatalSpy(t)
+	seen := 0
+	runTUIFn = func(ch <-chan model.Event, _ tui.Controls) error {
+		for i := 0; i < 3; i++ {
+			select {
+			case ev := <-ch:
+				seen++
+				if seen == 1 && ev.Type != model.EventTypeSessionStarted {
+					t.Fatalf("first demo event = %s, want %s", ev.Type, model.EventTypeSessionStarted)
+				}
+			default:
+				return nil
+			}
+		}
+		return nil
+	}
+
+	Run([]string{"tap", "demo"})
+	if *called {
+		t.Fatal("fatalExit should not be called for demo command")
+	}
+	if seen == 0 {
+		t.Fatal("expected demo event stream to be seeded")
+	}
+}
+
 func TestRun_StartSessionFailureCallsFatalExit(t *testing.T) {
 	restore := installRunSeams(t)
 	defer restore()