/*
 * OpenClonk, http://www.openclonk.org
 *
 * Copyright (c) 2014-2015, The OpenClonk Team and contributors
 *
 * Distributed under the terms of the ISC license; see accompanying file
 * "COPYING" for details.
 *
 * "Clonk" is a registered trademark of Matthes Bender, used with permission.
 * See accompanying file "TRADEMARK" for details.
 *
 * To redistribute this file separately, substitute the full license texts
 * for the above references.
 */

#include "C4Include.h"
#include "C4FoWLight.h"
#include "C4FoWLightSection.h"
#include "C4FoWBeamTriangle.h"
#include "C4FoWDrawStrategy.h"
#include "C4FoWRegion.h"
#include "C4PlayerList.h"
#include "C4Player.h"

#include <vector>

C4FoWLight::C4FoWLight(C4Object *pObj)
	: iX(fixtoi(pObj->fix_x)),
	  iY(fixtoi(pObj->fix_y)),
	  iReach(pObj->lightRange),
	  iFadeout(pObj->lightFadeoutRange),
	  iSize(20),
	  pNext(NULL),
	  pObj(pObj),
	  sections(4)
{
	sections[0] = new C4FoWLightSection(this,0);
	sections[1] = new C4FoWLightSection(this,90);
	sections[2] = new C4FoWLightSection(this,180);
	sections[3] = new C4FoWLightSection(this,270);
}

C4FoWLight::~C4FoWLight()
{
	for(size_t i = 0; i < sections.size(); ++i )
		delete sections[i];
}

void C4FoWLight::Invalidate(C4Rect r)
{
	for(size_t i = 0; i < sections.size(); ++i )
		sections[i]->Invalidate(r);
}

void C4FoWLight::SetReach(int32_t iReach2, int32_t iFadeout2)
{
	// Fadeout changes don't matter
	iFadeout = iFadeout2;

	if (iReach == iReach2) return;

	if (iReach2 < iReach)
	{
		// Reach decreased? Prune beams
		iReach = iReach2;
		for(size_t i = 0; i < sections.size(); ++i )
			sections[i]->Prune(iReach);

	} else {

		// Reach increased? Dirty beams that might get longer now
		iReach = iReach2;
		for(size_t i = 0; i < sections.size(); ++i )
			sections[i]->Dirty(iReach);
	}
}

void C4FoWLight::Update(C4Rect Rec)
{
	// Update position from object. Clear if we moved in any way
	int32_t iNX = fixtoi(pObj->fix_x), iNY = fixtoi(pObj->fix_y);
	if (iNX != iX || iNY != iY)
	{
		for(size_t i = 0; i < sections.size(); ++i )
			sections[i]->Prune(0);
		iX = iNX; iY = iNY;
	}

	for(size_t i = 0; i < sections.size(); ++i )
		sections[i]->Update(Rec);
}

void C4FoWLight::Render(C4FoWRegion *region, const C4TargetFacet *onScreen)
{
	TriangleList triangles;

	bool clip = false;

	iX = 199; iY = 579;
	iReach = 300;
	iFadeout = 80;
	iSize = 20;
	StdStrBuf test;
	assert(FileExists("light_section_assertion.txt"));
	test.LoadFromFile("light_section_assertion.txt");
	CompileFromBuf<StdCompilerINIRead>(mkNamingAdapt(*sections[0], "LightSection"), test);
	region->Update(C4Rect(0, 0, 1000, 1000), FLOAT_RECT());
	sections[0]->CalculateTriangles(region);
	
	for(size_t i = 0; i < sections.size(); ++i )
	{
		TriangleList sectionTriangles = sections[i]->CalculateTriangles(region);

		// if the triangles of one section are clipped completely, the neighbouring triangles
		// must be marked as clipped
		if(!triangles.empty()) triangles.rbegin()->clipRight |= clip;
		if(!sectionTriangles.empty()) sectionTriangles.begin()->clipLeft |= clip;

		clip = sectionTriangles.empty();
		triangles.splice(triangles.end(), sectionTriangles);
	}

	CalculateFanMaxed(triangles);
	CalculateIntermediateFadeTriangles(triangles);

	// Here's the master plan for updating the lights texture. We
	// want to add intensity (R channel) as well as the normal (GB channels).
	// Normals are obviously meant to be though of as signed, though,
	// so the equation we want would be something like
	//
	//  R_new = Clamp(R_old + R,       0.0, 1.0)
	//  G_new = Clamp(G_old + G - 0.5, 0.0, 1.0)
	//  B_new = Clamp(B_old + B - 0.5, 0.0, 1.0)
	//
	// It seems we can't get that directly though - glBlendFunc only talks
	// about two operands. Even if we make two passes, we have to take
	// care that that we don't over- or underflow in the intermediate pass.
	//
	// Therefore, we store G/1.5 instead of G, losing a bit of accuracy,
	// but allowing us to formulate the following approximation without
	// overflows:
	//
	//  G_new = Clamp(Clamp(G_old + G / 1.5), 0.0, 1.0) - 0.5 / 1.5, 0.0, 1.0)
	//  B_new = Clamp(Clamp(B_old + B / 1.5), 0.0, 1.0) - 0.5 / 1.5, 0.0, 1.0)

	C4FoWDrawStrategy* pen;
	if (onScreen) pen = new C4FoWDrawWireframeStrategy(this, onScreen);
	else          pen = new C4FoWDrawLightTextureStrategy(this, region);

	for(int pass = 0; pass < pen->GetRequestedPasses(); pass++)
	{  
		pen->Begin(pass);

		DrawFan(pen, triangles);
		DrawFanMaxed(pen, triangles);
		DrawFade(pen, triangles);
		DrawIntermediateFadeTriangles(pen, triangles);

		pen->End(pass);
	}

	delete pen;
}

void C4FoWLight::CalculateFanMaxed(TriangleList &triangles) const
{
	for (TriangleList::iterator it = triangles.begin(); it != triangles.end(); ++it)
	{
		C4FoWBeamTriangle &tri = *it;

		// Is the left point close enough that normals don't max out?
		float dist = sqrt(GetSquaredDistanceTo(tri.fanLX, tri.fanLY));
		if (dist <= getNormalSize()) {
			tri.nfanLX = tri.fanLX;
			tri.nfanLY = tri.fanLY;
		} else {
			// Otherwise, calculate point where they do. We will add a seperate
			// triangle/quad later on to capture that.
			float f = float(getNormalSize() / dist);
			tri.nfanLX = f * tri.fanLX + (1.0f - f) * getX();
			tri.nfanLY = f * tri.fanLY + (1.0f - f) * getY();
		}

		// Same for the right point
		dist = sqrt(GetSquaredDistanceTo(tri.fanRX, tri.fanRY));
		if (dist <= getNormalSize()) {
			tri.nfanRX = tri.fanRX;
			tri.nfanRY = tri.fanRY;
		} else {
			float f = float(getNormalSize()) / dist;
			tri.nfanRX = f * tri.fanRX + (1.0f - f) * getX();
			tri.nfanRY = f * tri.fanRY + (1.0f - f) * getY();
		}
	}
}

void C4FoWLight::ProjectPointOutward(float &x, float &y, float maxDistance) const
{
	float distanceDifference = Min(maxDistance, (float) getTotalReach()) / sqrt((x - getX()) * (x - getX()) + (y - getY()) * (y - getY()));

	x = getX() + distanceDifference * (x-getX());
	y = getY() + distanceDifference * (y-getY());
}

void C4FoWLight::CalculateIntermediateFadeTriangles(TriangleList &triangles) const
{
	for (TriangleList::iterator it = triangles.begin(), nextIt = it; it != triangles.end(); ++it)
	{
		// wrap around
		++nextIt;
		if(nextIt == triangles.end()) nextIt = triangles.begin();

		C4FoWBeamTriangle &tri = *it, &nextTri = *nextIt; // just for convenience

		// don't calculate if it should not be drawn anyway
		if (tri.clipRight || nextTri.clipLeft) continue;

		float distFadeR = GetSquaredDistanceTo(tri.fadeRX, tri.fadeRY);
		float distNextFadeL = GetSquaredDistanceTo(nextTri.fadeLX, nextTri.fadeLY);
		float distFanR = GetSquaredDistanceTo(tri.fanRX, tri.fanRY);
		float distNextFanL = GetSquaredDistanceTo(nextTri.fanLX, nextTri.fanLY);
				
		// an extra intermediate fade point is only necessary on cliffs
		tri.descending = distFanR > distNextFanL;
		if (tri.descending) {
			if (distFanR < distNextFadeL)
			{
				tri.fadeIX = nextTri.fadeLX;
				tri.fadeIY = nextTri.fadeLY;
			}
			else
			{
				tri.fadeIX = (tri.fanRX + nextTri.fadeLX) / 2;
				tri.fadeIY = (tri.fanRY + nextTri.fadeLY) / 2;
				ProjectPointOutward(tri.fadeIX, tri.fadeIY, sqrt(distFadeR));
			}
		}
		else
		{
			if (distNextFanL < distFadeR)
			{
				tri.fadeIX = tri.fadeRX;
				tri.fadeIY = tri.fadeRY;
			}
			else
			{
				tri.fadeIX = (tri.fadeRX + nextTri.fanLX) / 2;
				tri.fadeIY = (tri.fadeRY + nextTri.fanLY) / 2;
				ProjectPointOutward(tri.fadeIX, tri.fadeIY, sqrt(distNextFadeL));
			}
		}
		
	}
}


void C4FoWLight::DrawFan(C4FoWDrawStrategy* pen, TriangleList &triangles) const
{
	pen->BeginFan();
	pen->DrawLightVertex(getX(), getY());

	for (TriangleList::iterator it = triangles.begin(), nextIt = it; it != triangles.end(); ++it)
	{
		// wrap around
		++nextIt;
		if(nextIt == triangles.end()) nextIt = triangles.begin();

		C4FoWBeamTriangle &tri = *it, &nextTri = *nextIt; // just for convenience

		pen->DrawLightVertex(tri.nfanLX, tri.nfanLY);

		if(nextIt == triangles.begin() || nextTri.nfanLX != tri.nfanRX || nextTri.nfanLY != tri.nfanRY)
			pen->DrawLightVertex(tri.nfanRX, tri.nfanRY);
	}
	pen->EndFan();
}

void C4FoWLight::DrawFanMaxed(C4FoWDrawStrategy* pen, TriangleList &triangles) const
{
	pen->BeginFanMaxed();
	for (TriangleList::iterator it = triangles.begin(), nextIt = it; it != triangles.end(); ++it)
	{
		// Wrap around for next triangle
		++nextIt; if(nextIt == triangles.end()) nextIt = triangles.begin();
		C4FoWBeamTriangle &tri = *it, &nextTri = *nextIt;

		// First for the current beam
		if (tri.nfanLX != tri.nfanRX || tri.nfanLY != tri.nfanRY)
		{
			pen->DrawLightVertex(tri.nfanLX, tri.nfanLY);
			pen->DrawLightVertex(tri.nfanRX, tri.nfanRY);
			pen->DrawLightVertex(tri.fanRX, tri.fanRY);
			pen->DrawLightVertex(tri.fanLX, tri.fanLY);
		}
		// Then for the space in-between
		if (tri.nfanRX != nextTri.nfanLX || tri.nfanRY != nextTri.nfanLY)
		{
			pen->DrawLightVertex(tri.nfanRX, tri.nfanRY);
			pen->DrawLightVertex(nextTri.nfanLX, nextTri.nfanLY);
			pen->DrawLightVertex(nextTri.fanLX, nextTri.fanLY);
			pen->DrawLightVertex(tri.fanRX, tri.fanRY);
		}
	}
	pen->EndFanMaxed();
}

void C4FoWLight::DrawFade(C4FoWDrawStrategy* pen, TriangleList &triangles) const
{
	pen->BeginFade();

	for (TriangleList::iterator it = triangles.begin(); it != triangles.end(); ++it)
	{
		C4FoWBeamTriangle &tri = *it; // just for convenience

		// The quad will be empty if fan points match
		if (tri.fanLX == tri.fanRX && tri.fanLY == tri.fanRY) continue;

		pen->DrawLightVertex(tri.fanLX, tri.fanLY);
		pen->DrawLightVertex(tri.fanRX, tri.fanRY);
		pen->DrawDarkVertex(tri.fadeRX, tri.fadeRY);
		pen->DrawDarkVertex(tri.fadeLX, tri.fadeLY);
	}
	pen->EndFade();
}

void C4FoWLight::DrawIntermediateFadeTriangles(C4FoWDrawStrategy* pen, TriangleList &triangles) const
{

	for (TriangleList::iterator it = triangles.begin(), nextIt = it; it != triangles.end(); ++it)
	{
		// wrap around
		++nextIt;
		if(nextIt == triangles.end()) nextIt = triangles.begin();

		C4FoWBeamTriangle &tri = *it, &nextTri = *nextIt; // just for convenience
			
		// no inter-fade triangles when it should be clipped
		if (tri.clipRight || nextTri.clipLeft) continue;

		pen->BeginIntermediateFade();

		if (tri.descending) {

			pen->DrawLightVertex(tri.fanRX, tri.fanRY);
			pen->DrawLightVertex(nextTri.fanLX, nextTri.fanLY);
			pen->DrawDarkVertex(nextTri.fadeLX, nextTri.fadeLY);

			// if necessary
			if (tri.fadeIY != nextTri.fadeLY || tri.fadeIX != nextTri.fadeLX) {
				pen->DrawDarkVertex(tri.fadeIX, tri.fadeIY);
			}

			pen->DrawDarkVertex(tri.fadeRX, tri.fadeRY);

		} else {

			pen->DrawLightVertex(nextTri.fanLX, nextTri.fanLY);
			pen->DrawDarkVertex(nextTri.fadeLX, nextTri.fadeLY);

			// if necessary
			if (tri.fadeIY != tri.fadeRY || tri.fadeIX != tri.fadeRX) {
				pen->DrawDarkVertex(tri.fadeIX, tri.fadeIY);
			}

			pen->DrawDarkVertex(tri.fadeRX, tri.fadeRY);
			pen->DrawLightVertex(tri.fanRX, tri.fanRY);			
		}

		pen->EndIntermediateFade();
	}
}

bool C4FoWLight::IsVisibleForPlayer(C4Player *player) const
{
	// check if attached to an object that is not hostile to the given player
	if (!pObj || !player) return true;
	return !::Hostile(pObj->Owner,player->Number);
}