Reject duplicate document snapshot payloads

src/document/document.cpp

@@ -1,6 +1,7 @@
 #include "document/document.h"
 
 #include <algorithm>
+#include <array>
 #include <cmath>
 #include <limits>
 #include <string>
@@ -238,11 +239,18 @@ namespace {
     std::uint32_t document_height) noexcept
 {
     for (const auto& frame : frames) {
+        std::array<bool, cube_face_count> seen_faces {};
         for (const auto& pixels : frame.face_pixels) {
             const auto pixels_status = validate_face_pixels(pixels, document_width, document_height);
             if (!pixels_status.ok()) {
                 return pixels_status;
             }
+
+            if (seen_faces[pixels.face_index]) {
+                return pp::foundation::Status::invalid_argument(
+                    "snapshot contains duplicate face pixel payloads for a cube face");
+            }
+            seen_faces[pixels.face_index] = true;
         }
     }
 
@@ -366,11 +374,19 @@ pp::foundation::Result<CanvasDocument> CanvasDocument::create_from_snapshot(Docu
         document.frames_.push_back(frame_config);
     }
 
+    std::array<bool, cube_face_count> seen_selection_masks {};
     for (const auto& mask : config.selection_masks) {
         const auto mask_status = validate_selection_mask(mask, document.width_, document.height_);
         if (!mask_status.ok()) {
             return pp::foundation::Result<CanvasDocument>::failure(mask_status);
         }
+
+        if (seen_selection_masks[mask.face_index]) {
+            return pp::foundation::Result<CanvasDocument>::failure(
+                pp::foundation::Status::invalid_argument(
+                    "snapshot contains duplicate selection masks for a cube face"));
+        }
+        seen_selection_masks[mask.face_index] = true;
         document.selection_masks_.push_back(mask);
     }