// Copyright Epic Games, Inc. All Rights Reserved.

#include "AIGraphConnectionDrawingPolicy.h"
#include "Rendering/DrawElements.h"

FAIGraphConnectionDrawingPolicy::FAIGraphConnectionDrawingPolicy(int32 InBackLayerID, int32 InFrontLayerID, float ZoomFactor, const FSlateRect& InClippingRect, FSlateWindowElementList& InDrawElements, UEdGraph* InGraphObj)
	: FConnectionDrawingPolicy(InBackLayerID, InFrontLayerID, ZoomFactor, InClippingRect, InDrawElements)
	, GraphObj(InGraphObj)
{
}

void FAIGraphConnectionDrawingPolicy::DetermineWiringStyle(UEdGraphPin* OutputPin, UEdGraphPin* InputPin, /*inout*/ FConnectionParams& Params)
{
	Params.AssociatedPin1 = OutputPin;
	Params.AssociatedPin2 = InputPin;
	Params.WireThickness = 1.5f;

	const bool bDeemphasizeUnhoveredPins = HoveredPins.Num() > 0;
	if (bDeemphasizeUnhoveredPins)
	{
		ApplyHoverDeemphasis(OutputPin, InputPin, /*inout*/ Params.WireThickness, /*inout*/ Params.WireColor);
	}
}

void FAIGraphConnectionDrawingPolicy::Draw(TMap<TSharedRef<SWidget>, FArrangedWidget>& InPinGeometries, FArrangedChildren& ArrangedNodes)
{
	// Build an acceleration structure to quickly find geometry for the nodes
	NodeWidgetMap.Empty();
	for (int32 NodeIndex = 0; NodeIndex < ArrangedNodes.Num(); ++NodeIndex)
	{
		FArrangedWidget& CurWidget = ArrangedNodes[NodeIndex];
		TSharedRef<SGraphNode> ChildNode = StaticCastSharedRef<SGraphNode>(CurWidget.Widget);
		NodeWidgetMap.Add(ChildNode->GetNodeObj(), NodeIndex);
	}

	// Now draw
	FConnectionDrawingPolicy::Draw(InPinGeometries, ArrangedNodes);
}

void FAIGraphConnectionDrawingPolicy::DrawPreviewConnector(const FGeometry& PinGeometry, const FVector2D& StartPoint, const FVector2D& EndPoint, UEdGraphPin* Pin)
{
	FConnectionParams Params;
	DetermineWiringStyle(Pin, nullptr, /*inout*/ Params);

	if (Pin->Direction == EEdGraphPinDirection::EGPD_Output)
	{
		DrawSplineWithArrow(FGeometryHelper::FindClosestPointOnGeom(PinGeometry, EndPoint), EndPoint, Params);
	}
	else
	{
		DrawSplineWithArrow(FGeometryHelper::FindClosestPointOnGeom(PinGeometry, StartPoint), StartPoint, Params);
	}
}

void FAIGraphConnectionDrawingPolicy::DrawSplineWithArrow(const FVector2D& StartAnchorPoint, const FVector2D& EndAnchorPoint, const FConnectionParams& Params)
{
	// bUserFlag1 indicates that we need to reverse the direction of connection (used by debugger)
	const FVector2D& P0 = Params.bUserFlag1 ? EndAnchorPoint : StartAnchorPoint;
	const FVector2D& P1 = Params.bUserFlag1 ? StartAnchorPoint : EndAnchorPoint;

	Internal_DrawLineWithArrow(P0, P1, Params);
}

void FAIGraphConnectionDrawingPolicy::Internal_DrawLineWithArrow(const FVector2D& StartAnchorPoint, const FVector2D& EndAnchorPoint, const FConnectionParams& Params)
{
	//@TODO: Should this be scaled by zoom factor?
	const float LineSeparationAmount = 4.5f;

	const FVector2D DeltaPos = EndAnchorPoint - StartAnchorPoint;
	const FVector2D UnitDelta = DeltaPos.GetSafeNormal();
	const FVector2D Normal = FVector2D(DeltaPos.Y, -DeltaPos.X).GetSafeNormal();

	// Come up with the final start/end points
	const FVector2D DirectionBias = Normal * LineSeparationAmount;
	const FVector2D LengthBias = ArrowRadius.X * UnitDelta;
	const FVector2D StartPoint = StartAnchorPoint + DirectionBias + LengthBias;
	const FVector2D EndPoint = EndAnchorPoint + DirectionBias - LengthBias;

	// Draw a line/spline
	DrawConnection(WireLayerID, StartPoint, EndPoint, Params);

	// Draw the arrow
	const FVector2D ArrowDrawPos = EndPoint - ArrowRadius;
	const float AngleInRadians = FMath::Atan2(DeltaPos.Y, DeltaPos.X);

	FSlateDrawElement::MakeRotatedBox(
		DrawElementsList,
		ArrowLayerID,
		FPaintGeometry(ArrowDrawPos, ArrowImage->ImageSize * ZoomFactor, ZoomFactor),
		ArrowImage,
		ESlateDrawEffect::None,
		AngleInRadians,
		TOptional<FVector2D>(),
		FSlateDrawElement::RelativeToElement,
		Params.WireColor
		);
}

void FAIGraphConnectionDrawingPolicy::DrawSplineWithArrow(const FGeometry& StartGeom, const FGeometry& EndGeom, const FConnectionParams& Params)
{
	// Get a reasonable seed point (halfway between the boxes)
	const FVector2D StartCenter = FGeometryHelper::CenterOf(StartGeom);
	const FVector2D EndCenter = FGeometryHelper::CenterOf(EndGeom);
	const FVector2D SeedPoint = (StartCenter + EndCenter) * 0.5f;

	// Find the (approximate) closest points between the two boxes
	const FVector2D StartAnchorPoint = FGeometryHelper::FindClosestPointOnGeom(StartGeom, SeedPoint);
	const FVector2D EndAnchorPoint = FGeometryHelper::FindClosestPointOnGeom(EndGeom, SeedPoint);

	DrawSplineWithArrow(StartAnchorPoint, EndAnchorPoint, Params);
}

FVector2D FAIGraphConnectionDrawingPolicy::ComputeSplineTangent(const FVector2D& Start, const FVector2D& End) const
{
	const FVector2D Delta = End - Start;
	const FVector2D NormDelta = Delta.GetSafeNormal();

	return NormDelta;
}