#include "World/DescentShear.h"
#include "World/DescentSDF.h"
#include "Core/DescentMath.h"
#include "Core/Tuning/DescentTune_World.h"

namespace WTune = Descent::Tune::World;

namespace Descent::World
{
	FVector FDescentShear::VelocityAt(const FVector& P)
	{
		const double H = P.Z - WTune::ShearBaseZ;
		if (H <= 0.0)
		{
			return FVector::ZeroVector;
		}
		// Horizontal distance from the canyon's centreline (the canyon runs X -250..850 along Yc(X)); beyond its ends
		// the nearest end point stands in for the polyline.
		const double Xc = FMath::Clamp(P.X, WTune::CanyonX0, WTune::CanyonX1);
		const double Yc = FDescentSDF::CanyonCentre(Xc);
		const double Dx = Xc - P.X, Dy = Yc - P.Y;
		const double Dist = FMath::Sqrt(Dx * Dx + Dy * Dy);
		const double A = Dist - WTune::ShearLatOffset;
		const double S = FMath::Clamp(H / WTune::ShearVertRamp, 0.0, WTune::ShearMaxPart) + FMath::Clamp(A / WTune::ShearLatRamp, 0.0, WTune::ShearMaxPart);
		FVector Dir(0.0, 0.0, -1.0);
		if (Dist > 1e-3)
		{
			Dir = FVector(Dx / Dist * WTune::ShearToward, Dy / Dist * WTune::ShearToward, -WTune::ShearDown).GetSafeNormal();
		}
		return Dir * S;
	}

	bool FDescentShear::IsWarning(const FVector& P)
	{
		return P.Z >= WTune::ShearWarnZ;
	}
}