flamegraph: add live HTTP server entrypoint

1 files changed, 51 insertions, 0 deletions

diff --git a/internal/flamegraph/liveserver.go b/internal/flamegraph/liveserver.go
index d7a48cf..6b964a1 100644
--- a/internal/flamegraph/liveserver.go
+++ b/internal/flamegraph/liveserver.go
@@ -1,11 +1,62 @@
 package flamegraph
 
 import (
+	"context"
 	"fmt"
 	"net/http"
 	"time"
 )
 
+// ServeLive starts the live flamegraph HTTP server and blocks until ctx is canceled.
+func ServeLive(ctx context.Context, lt *LiveTrie, interval time.Duration) error {
+	mux := http.NewServeMux()
+	mux.HandleFunc("/", handleLivePage())
+	mux.HandleFunc("/events", handleSSE(lt, interval))
+	srv := &http.Server{Handler: mux}
+
+	listener, err := listenRandomPort()
+	if err != nil {
+		return err
+	}
+	defer listener.Close()
+
+	hostname, port := serverHostPort(listener)
+	fmt.Printf("Live flamegraph available at http://%s:%d/\n", hostname, port)
+
+	errCh := make(chan error, 1)
+	go func() {
+		errCh <- srv.Serve(listener)
+	}()
+
+	select {
+	case <-ctx.Done():
+	case serveErr := <-errCh:
+		if serveErr != nil && serveErr != http.ErrServerClosed {
+			return serveErr
+		}
+		return nil
+	}
+
+	shutdownCtx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+	if err := srv.Shutdown(shutdownCtx); err != nil {
+		return fmt.Errorf("shutdown live web server: %w", err)
+	}
+
+	serveErr := <-errCh
+	if serveErr != nil && serveErr != http.ErrServerClosed {
+		return serveErr
+	}
+	return nil
+}
+
+func handleLivePage() http.HandlerFunc {
+	return func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "text/html; charset=utf-8")
+		_, _ = w.Write([]byte(liveHTML))
+	}
+}
+
 func handleSSE(lt *LiveTrie, interval time.Duration) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		flusher, ok := w.(http.Flusher)