From ad0cc92e16aa98ee10bead846c0ff4c74c5244d6 Mon Sep 17 00:00:00 2001
From: Paul Buetow <paul@buetow.org>
Date: Mon, 27 Apr 2026 08:40:32 +0300
Subject: generator: lazy-init themeSet and navDefs with sync.Once

---
 internal/generator/doc.go            |  2 +-
 internal/generator/generator.go      |  2 +-
 internal/generator/generator_test.go | 12 +++++------
 internal/generator/shared.go         | 23 +++++++++++++-------
 internal/generator/templates.go      |  2 +-
 internal/generator/themes.go         | 42 +++++++++++++++++++++---------------
 6 files changed, 49 insertions(+), 34 deletions(-)

diff --git a/internal/generator/doc.go b/internal/generator/doc.go
index be82bdc..8eaf4db 100644
--- a/internal/generator/doc.go
+++ b/internal/generator/doc.go
@@ -8,7 +8,7 @@
 //     shared.css/shared.js and per-theme assets, then call atom.Generate.
 //   - themes.go — ListThemes / validThemeName helpers backed by the embedded FS.
 //   - shared.go — navDefs: shared {{define}} blocks (splashGate, navhints,
-//     navmodal) merged at parse time with shell.tmpl so a single html/template
+//     navSharedCSS) merged at parse time with shell.tmpl so a single html/template
 //     parse sees every name.
 //   - theme_sounds.go — Per-theme Web Audio parameters; one file is written per
 //     theme to dist/themes/<name>/sounds.json and the default theme's preset is
diff --git a/internal/generator/generator.go b/internal/generator/generator.go
index 0b51edd..db9531b 100644
--- a/internal/generator/generator.go
+++ b/internal/generator/generator.go
@@ -99,7 +99,7 @@ func Run(cfg *config.Config) error {
 	if err != nil {
 		return fmt.Errorf("load shell template: %w", err)
 	}
-	combined := shellSrc + "\n" + navDefs
+	combined := shellSrc + "\n" + getNavDefs()
 	tmpl, err := template.New("page").Parse(combined)
 	if err != nil {
 		return fmt.Errorf("parse page template: %w", err)
diff --git a/internal/generator/generator_test.go b/internal/generator/generator_test.go
index 0e3708b..56542a3 100644
--- a/internal/generator/generator_test.go
+++ b/internal/generator/generator_test.go
@@ -93,7 +93,7 @@ func TestJSONStringOrNull(t *testing.T) {
 
 func TestThemeSoundPresetsMatchRegistry(t *testing.T) {
 	t.Parallel()
-	for name := range themeSet {
+	for name := range getThemeSet() {
 		if _, ok := themeSoundPresets[name]; !ok {
 			t.Errorf("theme %q has no sound preset in themeSoundPresets", name)
 		}
@@ -112,7 +112,7 @@ func TestThemeSoundsJSON_ambientSchema(t *testing.T) {
 	t.Parallel()
 
 	// Verify the ambient schema is present and valid for every registered theme.
-	for name := range themeSet {
+	for name := range getThemeSet() {
 		j := themeSoundsJSON(name)
 		if len(j) < 50 {
 			t.Fatalf("themeSoundsJSON(%q) too short: %q", name, j)
@@ -148,7 +148,7 @@ func TestThemeSoundsJSON_ambientSchema(t *testing.T) {
 func TestThemeSoundPresetsAmbientPopulated(t *testing.T) {
 	t.Parallel()
 
-	for name := range themeSet {
+	for name := range getThemeSet() {
 		preset, ok := themeSoundPresets[name]
 		if !ok {
 			t.Errorf("theme %q missing from themeSoundPresets", name)
@@ -170,7 +170,7 @@ func TestThemeSoundPresetsAmbientPopulated(t *testing.T) {
 func TestThemeSoundPresetsAmbientValuesBounded(t *testing.T) {
 	t.Parallel()
 
-	for name := range themeSet {
+	for name := range getThemeSet() {
 		preset, ok := themeSoundPresets[name]
 		if !ok {
 			continue
@@ -384,8 +384,8 @@ func TestLoadThemeMeta_neonHasFields(t *testing.T) {
 func TestListThemes_sortedAndComplete(t *testing.T) {
 	t.Parallel()
 	names := ListThemes()
-	if len(names) != len(themeSet) {
-		t.Fatalf("len=%d, want %d", len(names), len(themeSet))
+	if len(names) != len(getThemeSet()) {
+		t.Fatalf("len=%d, want %d", len(names), len(getThemeSet()))
 	}
 	for i := 1; i < len(names); i++ {
 		if names[i] <= names[i-1] {
diff --git a/internal/generator/shared.go b/internal/generator/shared.go
index d0badb8..378a01f 100644
--- a/internal/generator/shared.go
+++ b/internal/generator/shared.go
@@ -2,6 +2,7 @@ package generator
 
 import (
 	"log"
+	"sync"
 
 	"codeberg.org/snonux/snonux/internal/generator/templates"
 )
@@ -18,13 +19,19 @@ import (
 // Each theme ends its <style> with {{template "navSharedCSSInner"}} then calls
 // {{template "splashGate"}}, {{template "navhints" .}}, {{template "navmodal" .}},
 // and {{template "navscript" .}} at the appropriate points in its HTML.
-var navDefs = loadNavDefs()
+var (
+	navDefsCache string
+	navDefsOnce  sync.Once
+)
 
-func loadNavDefs() string {
-	s, err := templates.Shared("nav")
-	if err != nil {
-		log.Printf("warning: could not load shared nav template: %v", err)
-		return ""
-	}
-	return s
+func getNavDefs() string {
+	navDefsOnce.Do(func() {
+		s, err := templates.Shared("nav")
+		if err != nil {
+			log.Printf("warning: could not load shared nav template: %v", err)
+			return
+		}
+		navDefsCache = s
+	})
+	return navDefsCache
 }
diff --git a/internal/generator/templates.go b/internal/generator/templates.go
index df854ab..fcb15f5 100644
--- a/internal/generator/templates.go
+++ b/internal/generator/templates.go
@@ -5,6 +5,6 @@ package generator
 // binary via embed.FS; see internal/generator/templates/embed.go.
 //
 // themes.go exposes ListThemes()/validThemeName().
-// shared.go loads templates/shared/nav.tmpl into navDefs (splashGate, navhints,
+// shared.go loads templates/shared/nav.tmpl into getNavDefs() (splashGate, navhints,
 // navmodal partials called from shell.tmpl).
 // favicon.go generates the favicon.ico binary written into each output dir.
diff --git a/internal/generator/themes.go b/internal/generator/themes.go
index a3a9881..c0ba7ea 100644
--- a/internal/generator/themes.go
+++ b/internal/generator/themes.go
@@ -2,6 +2,7 @@ package generator
 
 import (
 	"log"
+	"sync"
 
 	"codeberg.org/snonux/snonux/internal/generator/templates"
 )
@@ -12,30 +13,37 @@ const fallbackThemeName = "neon"
 
 // themeSet caches the list of theme names available in the embedded template FS
 // so ListThemes does not re-read the directory on every call.
-var themeSet = loadThemeSet()
-
-func loadThemeSet() map[string]struct{} {
-	names, err := templates.ThemeNames()
-	if err != nil {
-		// At build time the embed //go:embed directive guarantees the FS is
-		// populated, so this should never happen; log and continue with an
-		// empty set so callers can fall back cleanly.
-		log.Printf("warning: could not enumerate themes from embedded FS: %v", err)
-		return map[string]struct{}{}
-	}
+var (
+	themeSetCache map[string]struct{}
+	themeSetOnce  sync.Once
+)
 
-	out := make(map[string]struct{}, len(names))
-	for _, n := range names {
-		out[n] = struct{}{}
-	}
-	return out
+func getThemeSet() map[string]struct{} {
+	themeSetOnce.Do(func() {
+		names, err := templates.ThemeNames()
+		if err != nil {
+			// At build time the embed //go:embed directive guarantees the FS is
+			// populated, so this should never happen; log and continue with an
+			// empty set so callers can fall back cleanly.
+			log.Printf("warning: could not enumerate themes from embedded FS: %v", err)
+			themeSetCache = map[string]struct{}{}
+			return
+		}
+
+		out := make(map[string]struct{}, len(names))
+		for _, n := range names {
+			out[n] = struct{}{}
+		}
+		themeSetCache = out
+	})
+	return themeSetCache
 }
 
 // validThemeName returns name if it is a known theme, otherwise the fallback.
 // Callers use this to coerce CLI input ("--theme random" already resolves
 // upstream) so downstream lookups never miss.
 func validThemeName(name string) string {
-	if _, ok := themeSet[name]; ok {
+	if _, ok := getThemeSet()[name]; ok {
 		return name
 	}
 	return fallbackThemeName
-- 
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