PalUIExtension/Api/PanelWidget.hpp

#pragma once

#include <vector>

#include "Widget.hpp"
#include "PanelSlot.hpp"

namespace PalUIExtension::Api
{
    class PanelWidget : public Widget
    {
    public:
        static auto ClassPath() -> const TCHAR* { return STR("/Script/UMG.PanelWidget"); }
        static auto DebugTag()  -> const TCHAR* { return STR("PanelWidget"); }

        PanelWidget() = default;
        explicit PanelWidget(UObject* Obj)
            : Widget(Obj, ClassOf<PanelWidget>(), DebugTag()) {}

        auto GetChildrenCount() -> std::optional<int32>
        {
            return CallForReturn<int32>(STR("GetChildrenCount"));
        }
        auto HasAnyChildren() -> std::optional<bool>
        {
            return CallForReturn<bool>(STR("HasAnyChildren"));
        }

        auto GetChildAt(int32 Index) -> Widget
        {
            struct P { int32 Index; UObject* ReturnValue; } p{ Index, nullptr };
            auto Result = CallForReturn(STR("GetChildAt"), p, &P::ReturnValue);
            return (Result && *Result) ? Widget{ *Result } : Widget{};
        }

        auto GetChildIndex(UObject* Content) -> std::optional<int32>
        {
            struct P { UObject* Content; int32 ReturnValue; } p{ Content, -1 };
            return CallForReturn(STR("GetChildIndex"), p, &P::ReturnValue);
        }

        auto HasChild(UObject* Content) -> std::optional<bool>
        {
            struct P { UObject* Content; bool ReturnValue; } p{ Content, false };
            return CallForReturn(STR("HasChild"), p, &P::ReturnValue);
        }

        auto AddChild(UObject* Content) -> PanelSlot
        {
            struct P { UObject* Content; UObject* ReturnValue; } p{ Content, nullptr };
            auto Result = CallForReturn(STR("AddChild"), p, &P::ReturnValue);
            return (Result && *Result) ? PanelSlot{ *Result } : PanelSlot{};
        }

        auto RemoveChild(UObject* Content) -> std::optional<bool>
        {
            struct P { UObject* Content; bool ReturnValue; } p{ Content, false };
            return CallForReturn(STR("RemoveChild"), p, &P::ReturnValue);
        }

        auto RemoveChildAt(int32 Index) -> std::optional<bool>
        {
            struct P { int32 Index; bool ReturnValue; } p{ Index, false };
            return CallForReturn(STR("RemoveChildAt"), p, &P::ReturnValue);
        }

        auto ClearChildren() -> bool { return CallVoid(STR("ClearChildren")); }

        // ------------------------------------------------------------------
        // Deliberately NOT a wrapper around the engine's GetAllChildren.
        //
        // That UFUNCTION returns TArray<UWidget*> by value. ProcessEvent
        // constructs that array into the frame with the engine's allocator
        // and then hands you ownership of the allocation. Getting that
        // wrong is either a leak on every call or a free across a module
        // boundary, and neither shows up as a crash near the cause.
        //
        // The count + index loop is two extra ProcessEvent calls per child
        // and zero ownership questions. If you are calling this per-frame
        // over a large panel, cache the result; if you are calling it once
        // in a Construct hook, the cost is irrelevant.
        // ------------------------------------------------------------------
        auto GetAllChildren() -> std::vector<Widget>
        {
            std::vector<Widget> Children;

            auto Count = GetChildrenCount();
            if (!Count || *Count <= 0) return Children;

            Children.reserve(static_cast<size_t>(*Count));
            for (int32 i = 0; i < *Count; ++i)
            {
                Widget Child = GetChildAt(i);
                if (Child) Children.push_back(Child);
            }
            return Children;
        }

        // ------------------------------------------------------------------
        // Children WITHOUT ProcessEvent.
        //
        // GetAllChildren() above costs 1 + N ProcessEvent calls. That is
        // fine once in a Construct hook and not fine as the inner loop of a
        // whole-tree walk, where it becomes 1 + N per PANEL.
        //
        // UPanelWidget::Slots is a TArray<UPanelSlot*> UPROPERTY (confirmed
        // in the dump: UHTHeaderDump/UMG/Public/PanelWidget.h line 14), and
        // UPanelSlot::Content is a UPROPERTY too. So the full child list is
        // reachable as pure memory reads. Slot order is child order -- the
        // engine's own GetChildAt(i) is Slots[i]->Content.
        //
        // Nothing here is copied out of engine memory except the pointers
        // themselves, which is what makes reading the TArray safe; see the
        // TArrayRead_ comment in UmgTypes.hpp for where that line is.
        //
        // Returns false if Slots could not be read or looked implausible,
        // WITHOUT touching Out -- so a caller can fall back to
        // GetAllChildren() and know it isn't double-appending.
        // ------------------------------------------------------------------
        static constexpr int32 kMaxPlausibleChildren = 4096;

        auto TryGetChildObjects(std::vector<UObject*>& Out) const -> bool
        {
            auto* Slots = TryPropertyPtr<TArrayRead_<UObject*>>(STR("Slots"));
            if (!Slots) return false;

            if (!Slots->IsPlausible(kMaxPlausibleChildren))
            {
                Output::send<LogLevel::Warning>(
                    STR("[{}] 'Slots' does not look like a live TArray ")
                    STR("(Num={}, Max={}, Data={}) -- falling back to ProcessEvent\n"),
                    m_tag, Slots->Num, Slots->Max,
                    Slots->Data ? STR("set") : STR("null"));
                return false;
            }

            Out.reserve(Out.size() + static_cast<size_t>(Slots->Num));
            for (int32 i = 0; i < Slots->Num; ++i)
            {
                UObject* Slot = Slots->Data[i];
                if (!Slot) continue;

                // Read Content off the slot directly rather than through the
                // PanelSlot wrapper: the wrapper's IsA check would log on
                // anything unexpected, and this runs once per node of a
                // whole-tree walk.
                if (UObject* Content = RawObject{ Slot, STR("PanelSlot") }.TryObjectProperty(STR("Content")))
                {
                    Out.push_back(Content);
                }
            }
            return true;
        }

        // Property read first, ProcessEvent second. Use this anywhere you
        // just want the children and don't care which route produced them.
        auto GetChildObjects() -> std::vector<UObject*>
        {
            std::vector<UObject*> Out;
            if (TryGetChildObjects(Out)) return Out;

            for (Widget& Child : GetAllChildren())
            {
                if (UObject* O = Child.Get()) Out.push_back(O);
            }
            return Out;
        }

    protected:
        PanelWidget(UObject* Obj, UClass* Expected, const TCHAR* Tag)
            : Widget(Obj, Expected, Tag) {}
    };
}