Theme: Added the ability to add views before/after existing ones

Adds a registration system via the logical theme system, to tell
BookStack about views to render before or after a specific template
is included in the system.

app/App/Providers/ThemeServiceProvider.php

@@ -4,7 +4,9 @@ namespace BookStack\App\Providers;
 
 use BookStack\Theming\ThemeEvents;
 use BookStack\Theming\ThemeService;
+use Illuminate\Support\Facades\Blade;
 use Illuminate\Support\ServiceProvider;
+use Illuminate\View\View;
 
 class ThemeServiceProvider extends ServiceProvider
 {
@@ -24,8 +26,17 @@ class ThemeServiceProvider extends ServiceProvider
     {
         // Boot up the theme system
         $themeService = $this->app->make(ThemeService::class);
-        $themeService->registerViewPathsForTheme($this->app->make('view')->getFinder());
-        $themeService->readThemeActions();
-        $themeService->dispatch(ThemeEvents::APP_BOOT, $this->app);
+
+        $viewFactory = $this->app->make('view');
+        $themeService->registerViewPathsForTheme($viewFactory->getFinder());
+
+        if ($themeService->logicalThemeIsActive()) {
+            $themeService->readThemeActions();
+            $themeService->dispatch(ThemeEvents::APP_BOOT, $this->app);
+            $viewFactory->share('__theme', $themeService);
+            Blade::directive('include', function ($expression) {
+                return "<?php echo \$__theme->handleViewInclude({$expression}, array_diff_key(get_defined_vars(), ['__data' => 1, '__path' => 1])); ?>";
+            });
+        }
     }
 }

app/Theming/ThemeService.php

@@ -16,6 +16,16 @@ class ThemeService
      */
     protected array $listeners = [];
 
+    /**
+     * @var array<string, array<string, int>>
+     */
+    protected array $beforeViews = [];
+
+    /**
+     * @var array<string, array<string, int>>
+     */
+    protected array $afterViews = [];
+
     /**
      * Get the currently configured theme.
      * Returns an empty string if not configured.
@@ -82,15 +92,22 @@ class ThemeService
     public function readThemeActions(): void
     {
         $themeActionsFile = theme_path('functions.php');
-        if ($themeActionsFile && file_exists($themeActionsFile)) {
-            try {
-                require $themeActionsFile;
-            } catch (\Error $exception) {
-                throw new ThemeException("Failed loading theme functions file at \"{$themeActionsFile}\" with error: {$exception->getMessage()}");
-            }
+        try {
+            require $themeActionsFile;
+        } catch (\Error $exception) {
+            throw new ThemeException("Failed loading theme functions file at \"{$themeActionsFile}\" with error: {$exception->getMessage()}");
         }
     }
 
+    /**
+     * Check if a logical theme is active.
+     */
+    public function logicalThemeIsActive(): bool
+    {
+        $themeActionsFile = theme_path('functions.php');
+        return $themeActionsFile && file_exists($themeActionsFile);
+    }
+
     /**
      * Register any extra paths for where we may expect views to be located
      * with the provided FileViewFinder, to make custom views available for use.
@@ -108,4 +125,63 @@ class ThemeService
         $driverManager = app()->make(SocialDriverManager::class);
         $driverManager->addSocialDriver($driverName, $config, $socialiteHandler, $configureForRedirect);
     }
+
+    /**
+     * Provide the response for a blade template view include.
+     */
+    public function handleViewInclude(string $viewPath, array $data = []): string
+    {
+        $viewsContent = [
+            ...$this->renderViewSets($this->beforeViews[$viewPath] ?? [], $data),
+            view()->make($viewPath, $data)->render(),
+            ...$this->renderViewSets($this->afterViews[$viewPath] ?? [], $data),
+        ];
+
+        return implode("\n", $viewsContent);
+    }
+
+    /**
+     * Register a custom view to be rendered before the given target view is included in the template system.
+     */
+    public function registerViewRenderBefore(string $targetView, string $localView, int $priority = 50): void
+    {
+        $this->registerAdjacentView($this->beforeViews, $targetView, $localView, $priority);
+    }
+
+    /**
+     * Register a custom view to be rendered after the given target view is included in the template system.
+     */
+    public function registerViewRenderAfter(string $targetView, string $localView, int $priority = 50): void
+    {
+        $this->registerAdjacentView($this->afterViews, $targetView, $localView, $priority);
+    }
+
+    protected function registerAdjacentView(array &$location, string $targetView, string $localView, int $priority = 50): void
+    {
+        $viewPath = theme_path($localView . '.blade.php');
+        if (!file_exists($viewPath)) {
+            throw new ThemeException("Expected registered view file at \"{$viewPath}\" does not exist");
+        }
+
+        if (!isset($location[$targetView])) {
+            $location[$targetView] = [];
+        }
+        $location[$targetView][$viewPath] = $priority;
+    }
+
+    /**
+     * @param array<string, int> $viewSet
+     * @return string[]
+     */
+    protected function renderViewSets(array $viewSet, array $data): array
+    {
+        $paths = array_keys($viewSet);
+        usort($paths, function (string $a, string $b) use ($viewSet) {
+            return $viewSet[$a] <=> $viewSet[$b];
+        });
+
+        return array_map(function (string $viewPath) use ($data) {
+            return view()->file($viewPath, $data)->render();
+        }, $paths);
+    }
 }