// 
//---------------------------------------------------------------------------
//
// Copyright(C) 2002-2016 Christoph Oelckers
// All rights reserved.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with this program.  If not, see http://www.gnu.org/licenses/
//
//--------------------------------------------------------------------------
//
/*
** gl_light.cpp
** Light level / fog management / dynamic lights
**
*/

#include "c_dispatch.h"
#include "a_dynlight.h" 
#include "p_local.h"
#include "p_effect.h"
#include "g_level.h"
#include "g_levellocals.h"
#include "actorinlines.h"
#include "hw_drawcontext.h"
#include "hw_dynlightdata.h"
#include "hw_shadowmap.h"
#include "hwrenderer/scene/hw_drawinfo.h"
#include "hwrenderer/scene/hw_drawstructs.h"
#include "models.h"
#include <cmath>	// needed for std::floor on mac

template<class T>
T smoothstep(const T edge0, const T edge1, const T x)
{
	auto t = clamp((x - edge0) / (edge1 - edge0), 0.0, 1.0);
	return t * t * (3.0 - 2.0 * t);
}

class ActorTraceStaticLight
{
public:
	ActorTraceStaticLight(AActor* actor) : Actor(actor)
	{
		if (Actor && (Actor->Pos() != Actor->StaticLightsTraceCache.Pos || (Actor->Sector && (Actor->Sector->Flags & SECF_LM_DYNAMIC) && lm_dynamic)))
		{
			Actor->StaticLightsTraceCache.Pos = Actor->Pos();
			Actor->StaticLightsTraceCache.Bits = 0;
			ActorMoved = true;
		}
	}

	bool TraceLightVisbility(FLightNode* node, const FVector3& L, float dist)
	{
		FDynamicLight* light = node->lightsource;
		if (!light->TraceActors() || !level.levelMesh || !Actor)
			return true;

		if (!ActorMoved && CurrentBit < 64)
		{
			bool traceResult = (Actor->StaticLightsTraceCache.Bits >> CurrentBit) & 1;
			CurrentBit++;
			return traceResult;
		}
		else
		{
			bool traceResult = !level.levelMesh->Trace(FVector3((float)light->Pos.X, (float)light->Pos.Y, (float)light->Pos.Z), FVector3(-L.X, -L.Y, -L.Z), dist);
			Actor->StaticLightsTraceCache.Bits |= ((uint64_t)traceResult) << CurrentBit;
			CurrentBit++;
			return traceResult;
		}
	}

	bool TraceSunVisibility(float x, float y, float z)
	{
		if (!level.lightmaps || !Actor)
			return false;

		if (!ActorMoved && CurrentBit < 64)
		{
			bool traceResult = (Actor->StaticLightsTraceCache.Bits >> CurrentBit) & 1;
			CurrentBit++;
			return traceResult;
		}
		else
		{
			bool traceResult = level.levelMesh->TraceSky(FVector3(x, y, z), level.SunDirection, 65536.0f);
			Actor->StaticLightsTraceCache.Bits |= ((uint64_t)traceResult) << CurrentBit;
			CurrentBit++;
			return traceResult;
		}
	}

	AActor* Actor;
	bool ActorMoved = false;
	int CurrentBit = 0;
};

//==========================================================================
//
// Sets a single light value from all dynamic lights affecting the specified location
//
//==========================================================================


float inverseSquareAttenuation(float dist, float radius, float strength)
{
	float a = dist / radius;
	float b = clamp(1.0 - a * a * a * a, 0.0, 1.0);
	return (b * b) / (dist * dist + 1.0) * strength;
}

void HWDrawInfo::GetDynSpriteLight(AActor *self, float x, float y, float z, FLightNode *node, int portalgroup, float *out, bool fullbright)
{
	if (fullbright)
		return;

	FDynamicLight *light;
	float frac, lr, lg, lb;
	float radius;
	
	out[0] = out[1] = out[2] = 0.f;

	ActorTraceStaticLight staticLight(self);

	if (staticLight.TraceSunVisibility(x, y, z))
	{
		out[0] = Level->SunColor.X;
		out[1] = Level->SunColor.Y;
		out[2] = Level->SunColor.Z;
	}

	// Go through both light lists
	while (node)
	{
		light=node->lightsource;
		if (light->ShouldLightActor(self))
		{
			float dist;
			FVector3 L;

			// This is a performance critical section of code where we cannot afford to let the compiler decide whether to inline the function or not.
			// This will do the calculations explicitly rather than calling one of AActor's utility functions.
			if (Level->Displacements.size > 0)
			{
				int fromgroup = light->Sector->PortalGroup;
				int togroup = portalgroup;
				if (fromgroup == togroup || fromgroup == 0 || togroup == 0) goto direct;

				DVector2 offset = Level->Displacements.getOffset(fromgroup, togroup);
				L = FVector3(x - (float)(light->X() + offset.X), y - (float)(light->Y() + offset.Y), z - (float)light->Z());
			}
			else
			{
			direct:
				L = FVector3(x - (float)light->X(), y - (float)light->Y(), z - (float)light->Z());
			}

			dist = (float)L.LengthSquared();
			radius = light->GetRadius();

			if (radius > 0 && dist < radius * radius)
			{
				dist = sqrtf(dist);	// only calculate the square root if we really need it.

				if (light->IsSpot() || light->Trace())
					L *= -1.0f / dist;

				if (staticLight.TraceLightVisbility(node, L, dist))
				{
					if(level.info->lightattenuationmode == ELightAttenuationMode::INVERSE_SQUARE)
					{
						frac = (inverseSquareAttenuation(std::max(dist, sqrt(radius) * 2), radius, light->GetStrength()));
					}
					else
					{
						frac = 1.0f - (dist / radius);
					}

					if (light->IsSpot())
					{
						DAngle negPitch = -*light->pPitch;
						DAngle Angle = light->target->Angles.Yaw;
						double xyLen = negPitch.Cos();
						double spotDirX = -Angle.Cos() * xyLen;
						double spotDirY = -Angle.Sin() * xyLen;
						double spotDirZ = -negPitch.Sin();
						double cosDir = L.X * spotDirX + L.Y * spotDirY + L.Z * spotDirZ;
						frac *= (float)smoothstep(light->pSpotOuterAngle->Cos(), light->pSpotInnerAngle->Cos(), cosDir);
					}

					if (frac > 0 && (!light->shadowmapped || (self && light->Trace()) || screen->mShadowMap->ShadowTest(light->Pos, { x, y, z })))
					{
						lr = light->GetRed() / 255.0f;
						lg = light->GetGreen() / 255.0f;
						lb = light->GetBlue() / 255.0f;

						if (light->target)
						{
							float alpha = (float)light->target->Alpha;
							lr *= alpha;
							lg *= alpha;
							lb *= alpha;
						}

						if (light->IsSubtractive())
						{
							float bright = (float)FVector3(lr, lg, lb).Length();
							FVector3 lightColor(lr, lg, lb);
							lr = (bright - lr) * -1;
							lg = (bright - lg) * -1;
							lb = (bright - lb) * -1;
						}

						out[0] += lr * frac;
						out[1] += lg * frac;
						out[2] += lb * frac;
					}
				}
			}
		}
		node = node->nextLight;
	}
}

void HWDrawInfo::GetDynSpriteLight(AActor *thing, particle_t *particle, float *out)
{
	if (thing != NULL)
	{
		GetDynSpriteLight(thing, (float)thing->X(), (float)thing->Y(), (float)thing->Center(), thing->section->lighthead, thing->Sector->PortalGroup, out, (thing->flags5 & MF5_BRIGHT));
	}
	else if (particle != NULL)
	{
		GetDynSpriteLight(NULL, (float)particle->Pos.X, (float)particle->Pos.Y, (float)particle->Pos.Z, particle->subsector->section->lighthead, particle->subsector->sector->PortalGroup, out, (particle->flags & SPF_FULLBRIGHT));
	}
}


void hw_GetDynModelLight(HWDrawContext* drawctx, AActor *self, FDynLightData &modellightdata)
{
	modellightdata.Clear();

	if (self)
	{
		if ((self->flags5 & MF5_BRIGHT))
			return;

		auto &addedLights = drawctx->addedLightsArray;

		addedLights.Clear();

		float x = (float)self->X();
		float y = (float)self->Y();
		float z = (float)self->Center();
		float actorradius = (float)self->RenderRadius();
		float radiusSquared = actorradius * actorradius;
		dl_validcount++;

		ActorTraceStaticLight staticLight(self);

		if (staticLight.TraceSunVisibility(x, y, z))
		{
			AddSunLightToList(modellightdata, x, y, z, self->Level->SunDirection, self->Level->SunColor);
		}

		BSPWalkCircle(self->Level, x, y, radiusSquared, [&](subsector_t *subsector) // Iterate through all subsectors potentially touched by actor
		{
			auto section = subsector->section;
			if (section->validcount == dl_validcount) return;	// already done from a previous subsector.
			FLightNode * node = section->lighthead;
			while (node) // check all lights touching a subsector
			{
				FDynamicLight *light = node->lightsource;
				if (light->ShouldLightActor(self))
				{
					int group = subsector->sector->PortalGroup;
					DVector3 pos = light->PosRelative(group);
					float radius = (float)(light->GetRadius() + actorradius);
					double dx = pos.X - x;
					double dy = pos.Y - y;
					double dz = pos.Z - z;
					double distSquared = dx * dx + dy * dy + dz * dz;
					if (distSquared < radius * radius) // Light and actor touches
					{
						if (std::find(addedLights.begin(), addedLights.end(), light) == addedLights.end()) // Check if we already added this light from a different subsector
						{
							FVector3 L(dx, dy, dz);
							float dist = sqrtf(distSquared);
							if (light->Trace())
								L *= 1.0f / dist;

							if (staticLight.TraceLightVisbility(node, L, dist))
							{
								AddLightToList(modellightdata, group, light, true);
							}

							addedLights.Push(light);
						}
					}
				}
				node = node->nextLight;
			}
		});
	}
}