#include "RadialMenu.h"
#include "Rendering/DrawElements.h"
#include "Engine/Texture2D.h"
#include "Styling/SlateBrush.h"
#include "Widgets/SLeafWidget.h"


TArray<FRadialMenuItem> FRadialMenuItem::Calculate(const FRadialMenuConfig &Config)
{
    TArray<FRadialMenuItem> Items;
    if (Config.NumItems < 0) return Items;

    int32 NumRight = (Config.NumItems / 2);
    int32 NumLeft = Config.NumItems - NumRight;
    Items.SetNum(Config.NumItems);

    View LeftItems(Items.GetData(), NumLeft);
    View RightItems(Items.GetData() + NumLeft, NumRight);

    CalculateSpokes(LeftItems, Config.NumItems, Config.ItemHeight, Config.InnerRadius, Config.MinSpoke);
    CalculateSpokes(RightItems, Config.NumItems, Config.ItemHeight, Config.InnerRadius, Config.MinSpoke);
    double LeftWidth = WidestSpoke(LeftItems);
    double RightWidth = WidestSpoke(RightItems);
    double HalfWidth = FMath::Max(LeftWidth, RightWidth) + Config.Spread;
    CalculateSpread(LeftItems, HalfWidth - LeftWidth);
    CalculateSpread(RightItems, HalfWidth - RightWidth);

    FlipHorizontal(LeftItems);
    return Items;
}

FVector2D FRadialMenuItem::SpokeVector(int32 I, int32 NSide, int32 NTotal)
{
    double SpokeAngle = 1.0 / NTotal;
    double OffsetAngle = 0.5 * (0.5 - ((NSide - 1) * SpokeAngle));
    double Revolutions = (I * SpokeAngle) + OffsetAngle;
    double Radians = (Revolutions * 2.0 * UE_PI);
    return FVector2D(FMath::Sin(Radians), -FMath::Cos(Radians));
}

void FRadialMenuItem::FlipHorizontal(View V)
{
    for (FRadialMenuItem& Item : V)
    {
        Item.Point1.X = -Item.Point1.X;
        Item.Point2.X = -Item.Point2.X;
        Item.Point3.X = -Item.Point3.X;
        Item.RightSide = !Item.RightSide;
    }
}

double FRadialMenuItem::WidestSpoke(View V)
{
    double Result = 0.0;
    for (const FRadialMenuItem &Item : V)
    {
        Result = FMath::Max(Item.Point2.X, Result);
    }
    return Result;
}

void FRadialMenuItem::CalculateSpread(View V, double Offset)
{
    for (FRadialMenuItem &Item : V)
    {
        Item.Point3 = Item.Point2 + FVector2D(Offset, 0.0);
    }
}

void FRadialMenuItem::CalculateSpokes(View V, int32 TotalItems, float ItemHeight, float InnerRadius, float MinSpoke)
{
    if (V.Num() == 0) return;

    // RightSide is always initialized to true, it may get
    // reversed by FlipHorizontal.
    for (int32 I = 0; I < V.Num(); I++)
    {
        V[I].RightSide = true;
        V[I].Point1 = SpokeVector(I, V.Num(), TotalItems) * InnerRadius;
    }

    // Calculate point2 for all spokes.
    double NextLineMin = ItemHeight * 0.5;
    int32 Mid = (V.Num() / 2);
    if (V.Num() & 1)
    {
        V[Mid].Point2 = FVector2D(InnerRadius + MinSpoke, 0.0);
        NextLineMin = ItemHeight;
        Mid += 1;
    }
    for (int32 I = Mid; I < V.Num(); I++)
    {
        FVector2D UnitVec = SpokeVector(I, V.Num(), TotalItems);
        double Y = (UnitVec.Y * (InnerRadius + MinSpoke));
        if (Y < NextLineMin) Y = NextLineMin;
        NextLineMin = Y + ItemHeight;
        FVector2D Point2 = UnitVec * (Y / UnitVec.Y);
        V[I].Point2 = Point2;
        V[V.Num() - 1 - I].Point2 = Point2 * FVector2D(1.0,-1.0);
    }

    // The middle spoke is calculated using a different formula,
    // which may result in a short spoke.  If so, fix it to make
    // it at least as long as the adjacent spoke.
    if ((V.Num() & 1) && (V.Num() >= 3))
    {
        Mid = V.Num() / 2;
        if (V[Mid].Point2.X < V[Mid + 1].Point2.X)
            V[Mid].Point2.X = V[Mid + 1].Point2.X;
    }
}


// Slate widget that paints the radial menu's polylines.
class SRadialMenu : public SLeafWidget
{
public:
    SLATE_BEGIN_ARGS(SRadialMenu) {}
    SLATE_END_ARGS()

    void Construct(const FArguments& InArgs, const FRadialMenuConfig& InConfig)
    {
        Config = InConfig;
    }

    void SetConfig(const FRadialMenuConfig& NewConfig)
    {
        Config = NewConfig;
        Items = FRadialMenuItem::Calculate(Config);
        Invalidate(EInvalidateWidgetReason::Layout);
    }

protected:
    virtual FVector2D ComputeDesiredSize(float) const override
    {
        FVector2D Min(0.0, 0.0);
        FVector2D Max(0.0, 0.0);
        for (const FRadialMenuItem &Item : Items)
        {
            for (const FVector2D &P : { Item.Point1, Item.Point2, Item.Point3 })
            {
                Min.X = FMath::Min(Min.X, P.X);
                Min.Y = FMath::Min(Min.Y, P.Y);
                Max.X = FMath::Max(Max.X, P.X);
                Max.Y = FMath::Max(Max.Y, P.Y);
            }
        }
        // Symmetric around the origin so the menu draws centered.
        double HalfW = FMath::Max(FMath::Abs(Min.X), FMath::Abs(Max.X));
        double HalfH = FMath::Max(FMath::Abs(Min.Y), FMath::Abs(Max.Y));
        return FVector2D(HalfW * 2.0, HalfH * 2.0);
    }

    virtual int32 OnPaint(const FPaintArgs& Args, const FGeometry& AllottedGeometry,
        const FSlateRect& MyCullingRect, FSlateWindowElementList& OutDrawElements,
        int32 LayerId, const FWidgetStyle& InWidgetStyle, bool bParentEnabled) const override
    {
        const FVector2D Center = AllottedGeometry.GetLocalSize() * 0.5;
        const FPaintGeometry PaintGeom = AllottedGeometry.ToPaintGeometry();

        for (int32 I = 0; I < Items.Num(); I++)
        {
            const FRadialMenuItem& Item = Items[I];
            const bool bSelected = (I == Config.SelectedItem);
            const FLinearColor& Color = bSelected ? Config.SelectedColor : Config.LineColor;
            const float Thickness = bSelected ? Config.SelectedThickness : Config.LineThickness;
            TArray<FVector2D> Points;
            Points.Add(Center + Item.Point1);
            Points.Add(Center + Item.Point2);
            Points.Add(Center + Item.Point3);
            FSlateDrawElement::MakeLines(OutDrawElements, LayerId, PaintGeom, Points, ESlateDrawEffect::None, Color, true, Thickness);
        }

        if (Config.DotRadius <= 0.0f) return LayerId;
        if (Config.DotTexture == nullptr) return LayerId;

        FSlateBrush DotBrush;
        DotBrush.SetResourceObject(Config.DotTexture);
        const FVector2D DotSize(Config.DotRadius * 2.0f);
        for (int32 I = 0; I < Items.Num(); I++)
        {
            const FRadialMenuItem& Item = Items[I];
            const bool bSelected = (I == Config.SelectedItem);
            const FLinearColor& Color = bSelected ? Config.SelectedColor : Config.LineColor;
            for (const FVector2D& Point : { Item.Point1, Item.Point3 })
            {
                const FVector2D LocalPoint = Center + Point;
                FSlateDrawElement::MakeBox(
                    OutDrawElements,
                    LayerId,
                    AllottedGeometry.ToPaintGeometry(DotSize, FSlateLayoutTransform(LocalPoint - FVector2D(Config.DotRadius))),
                    &DotBrush,
                    ESlateDrawEffect::None,
                    Color);
            }
        }
        return LayerId;
    }

private:
    FRadialMenuConfig Config;

    TArray<FRadialMenuItem> Items;
};


void URadialMenuWidget::SetNumItems(int32 NewNumItems)
{
    if (Config.NumItems == NewNumItems) return;

    Config.NumItems = NewNumItems;
    SynchronizeProperties();
}

void URadialMenuWidget::SetItemHeight(float NewItemHeight)
{
    if (Config.ItemHeight == NewItemHeight) return;

    Config.ItemHeight = NewItemHeight;
    SynchronizeProperties();
}

void URadialMenuWidget::SetInnerRadius(float NewInnerRadius)
{
    if (Config.InnerRadius == NewInnerRadius) return;

    Config.InnerRadius = NewInnerRadius;
    SynchronizeProperties();
}

void URadialMenuWidget::SetMinSpoke(float NewMinSpoke)
{
    if (Config.MinSpoke == NewMinSpoke) return;

    Config.MinSpoke = NewMinSpoke;
    SynchronizeProperties();
}

void URadialMenuWidget::SetSpread(float NewSpread)
{
    if (Config.Spread == NewSpread) return;

    Config.Spread = NewSpread;
    SynchronizeProperties();
}

void URadialMenuWidget::SetLineThickness(float NewLineThickness)
{
    if (Config.LineThickness == NewLineThickness) return;

    Config.LineThickness = NewLineThickness;
    SynchronizeProperties();
}

void URadialMenuWidget::SetLineColor(FLinearColor NewLineColor)
{
    if (Config.LineColor == NewLineColor) return;

    Config.LineColor = NewLineColor;
    SynchronizeProperties();
}

void URadialMenuWidget::SetDotTexture(UTexture2D* NewDotTexture)
{
    if (Config.DotTexture == NewDotTexture) return;

    Config.DotTexture = NewDotTexture;
    SynchronizeProperties();
}

void URadialMenuWidget::SetDotRadius(float NewDotRadius)
{
    if (Config.DotRadius == NewDotRadius) return;

    Config.DotRadius = NewDotRadius;
    SynchronizeProperties();
}

bool URadialMenuWidget::SetSelectedItem(int32 NewSelectedItem)
{
    if (Config.SelectedItem == NewSelectedItem) return false;

    Config.SelectedItem = NewSelectedItem;
    SynchronizeProperties();
    return true;
}

void URadialMenuWidget::SetSelectedColor(FLinearColor NewSelectedColor)
{
    if (Config.SelectedColor == NewSelectedColor) return;

    Config.SelectedColor = NewSelectedColor;
    SynchronizeProperties();
}

void URadialMenuWidget::SetSelectedThickness(float NewSelectedThickness)
{
    if (Config.SelectedThickness == NewSelectedThickness) return;

    Config.SelectedThickness = NewSelectedThickness;
    SynchronizeProperties();
}

void URadialMenuWidget::SynchronizeProperties()
{
    Super::SynchronizeProperties();

    Items = FRadialMenuItem::Calculate(Config);
    if (Items.Num() == 0)
    {
        PointerVector = FVector2D(0,0);
    }
    if (MySlateWidget.IsValid())
    {
        MySlateWidget->SetConfig(Config);
    }
}

bool URadialMenuWidget::AddPointer(FVector2D Direction, float Scale)
{
    if (!IsVisible())
    {
        return false;
    }
    
    if (Items.Num() == 0)
    {
        return false;
    }

    PointerVector += (Direction * Scale);

    if (PointerVector.Length() < 0.5)
    {
        return SetSelectedItem(-1);
    }

    if (PointerVector.Length() > 1.0)
    {
        PointerVector.Normalize();
    }

    int32 BestIndex = -1;
    double BestDot = -2.0;
    for (int32 I = 0; I < Items.Num(); I++)
    {
        FVector2D SpokeDir = Items[I].Point1;
        if (!SpokeDir.Normalize()) continue;
        double Dot = FVector2D::DotProduct(SpokeDir, PointerVector);
        if (Dot <= BestDot) continue;
        BestDot = Dot;
        BestIndex = I;
    }
    return SetSelectedItem(BestIndex);
}

FLinearColor URadialMenuWidget::GetItemColor(int N) const
{
    return (N == Config.SelectedItem) ? Config.SelectedColor : Config.LineColor;
}


TSharedRef<SWidget> URadialMenuWidget::RebuildWidget()
{
    MySlateWidget = SNew(SRadialMenu, Config);
    return MySlateWidget.ToSharedRef();
}

void URadialMenuWidget::ReleaseSlateResources(bool bReleaseChildren)
{
    Super::ReleaseSlateResources(bReleaseChildren);
    MySlateWidget.Reset();
}
