Add brush UI service boundary

src/app_core/brush_ui.h

@@ -37,6 +37,16 @@ struct BrushUiPlan {
     bool update_brush_ui = false;
 };
 
+class BrushUiServices {
+public:
+    virtual ~BrushUiServices() = default;
+
+    virtual void set_tip_color(float r, float g, float b, float a) = 0;
+    virtual void set_texture(BrushUiTextureSlot slot, std::string_view path, std::string_view thumbnail_path) = 0;
+    virtual void replace_brush_from_preset(bool preserve_existing_color, bool load_resources) = 0;
+    virtual void refresh_brush_ui(bool update_color_ui, bool update_brush_ui) = 0;
+};
+
 [[nodiscard]] inline pp::foundation::Status validate_brush_ui_color_channel(float value) noexcept
 {
     if (!std::isfinite(value) || value < 0.0F || value > 1.0F) {
@@ -119,4 +129,43 @@ struct BrushUiPlan {
     return plan;
 }
 
+[[nodiscard]] inline pp::foundation::Status execute_brush_ui_plan(
+    const BrushUiPlan& plan,
+    BrushUiServices& services)
+{
+    switch (plan.operation) {
+    case BrushUiOperation::set_tip_color:
+    {
+        for (const auto value : { plan.r, plan.g, plan.b, plan.a }) {
+            const auto channel_status = validate_brush_ui_color_channel(value);
+            if (!channel_status.ok()) {
+                return channel_status;
+            }
+        }
+        services.set_tip_color(plan.r, plan.g, plan.b, plan.a);
+        services.refresh_brush_ui(plan.update_color_ui, plan.update_brush_ui);
+        return pp::foundation::Status::success();
+    }
+
+    case BrushUiOperation::set_texture:
+        if (plan.path.empty()) {
+            return pp::foundation::Status::invalid_argument("brush texture path must not be empty");
+        }
+        services.set_texture(plan.texture_slot, plan.path, plan.thumbnail_path);
+        services.refresh_brush_ui(plan.update_color_ui, plan.update_brush_ui);
+        return pp::foundation::Status::success();
+
+    case BrushUiOperation::replace_brush_from_preset:
+        services.replace_brush_from_preset(plan.preserves_existing_color, plan.loads_brush_resources);
+        services.refresh_brush_ui(plan.update_color_ui, plan.update_brush_ui);
+        return pp::foundation::Status::success();
+
+    case BrushUiOperation::stroke_settings_changed:
+        services.refresh_brush_ui(plan.update_color_ui, plan.update_brush_ui);
+        return pp::foundation::Status::success();
+    }
+
+    return pp::foundation::Status::invalid_argument("unknown brush UI operation");
+}
+
 } // namespace pp::app