From d71c372080e4008551db79f4d92a2fbdfcde19cc Mon Sep 17 00:00:00 2001
From: Minecon724 <minecon724@noreply.git.m724.eu>
Date: Sun, 16 Mar 2025 12:59:37 +0100
Subject: [PATCH] Dynamic theme loading

Signed-off-by: Minecon724 <minecon724@noreply.git.m724.eu>
---
 modules/theme/theme.go              | 80 +++++++++++++++++++++++++++++
 routers/web/user/setting/profile.go | 10 ++++
 2 files changed, 90 insertions(+)
 create mode 100644 modules/theme/theme.go

diff --git a/modules/theme/theme.go b/modules/theme/theme.go
new file mode 100644
index 0000000000..762926d78f
--- /dev/null
+++ b/modules/theme/theme.go
@@ -0,0 +1,80 @@
+package theme
+
+import (
+	"fmt"
+	"strings"
+
+	"code.gitea.io/gitea/modules/assetfs"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/public"
+	"code.gitea.io/gitea/modules/setting"
+
+	"golang.org/x/sync/singleflight"
+)
+
+const (
+	key string = "load-themes"
+)
+
+var (
+	group   singleflight.Group
+	assetFs *assetfs.LayeredFS
+	loaded  bool
+)
+
+// LoadThemes loads installed themes
+//
+// Note that you can't just run this during init, because webpack mightn't have completed yet.
+// Hence, we're loading on first demand.
+func LoadThemes() error {
+	if loaded {
+		return nil
+	}
+
+	if assetFs == nil {
+		assetFs = public.AssetFS()
+	}
+
+	_, err, _ := group.Do(key, func() (interface{}, error) {
+		themes, err := loadThemesInner(assetFs)
+
+		if err != nil {
+			group.Forget(key)
+		} else {
+			setting.UI.Themes = themes
+			loaded = true
+		}
+
+		return nil, err
+	})
+
+	return err
+}
+
+func loadThemesInner(assetFs *assetfs.LayeredFS) ([]string, error) {
+	entries, err := assetFs.ListFiles("assets/css")
+
+	if err != nil {
+		return nil, err
+	}
+
+	var themes []string
+
+	for _, entry := range entries {
+		if !(strings.HasPrefix(entry, "theme-") && strings.HasSuffix(entry, ".css")) {
+			continue
+		}
+
+		theme := entry[6 : len(entry)-4]
+		themes = append(themes, theme)
+
+		log.Info("Found theme: %s", theme)
+	}
+
+	if len(themes) > 0 {
+		log.Info("Loaded %d themes", len(themes))
+		return themes, nil
+	} else {
+		return nil, fmt.Errorf("no themes found")
+	}
+}
diff --git a/routers/web/user/setting/profile.go b/routers/web/user/setting/profile.go
index 271621872f..1dee0d641f 100644
--- a/routers/web/user/setting/profile.go
+++ b/routers/web/user/setting/profile.go
@@ -24,6 +24,7 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/optional"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/theme"
 	"code.gitea.io/gitea/modules/translation"
 	"code.gitea.io/gitea/modules/typesniffer"
 	"code.gitea.io/gitea/modules/util"
@@ -327,6 +328,15 @@ func Repos(ctx *context.Context) {
 
 // Appearance render user's appearance settings
 func Appearance(ctx *context.Context) {
+	err := theme.LoadThemes()
+
+	if err != nil {
+		ctx.ServerError("Failed to load themes", err)
+		return
+	}
+
+	ctx.Data["AllThemes"] = setting.UI.Themes
+
 	ctx.Data["Title"] = ctx.Tr("settings.appearance")
 	ctx.Data["PageIsSettingsAppearance"] = true
 	ctx.Data["AllThemes"] = setting.UI.Themes