/*
 * Adapted from Open Shading Language with this license:
 *
 * Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
 * All Rights Reserved.
 *
 * Modifications Copyright 2011, Blender Foundation.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * * Neither the name of Sony Pictures Imageworks nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <OpenImageIO/fmath.h>

#include <OSL/genclosure.h>

#include "osl_closures.h"

#include "util_math.h"

CCL_NAMESPACE_BEGIN

using namespace OSL;

class WestinBackscatterClosure : public BSDFClosure {
public:
	Vec3 m_N;
	float m_roughness;
	float m_invroughness;
	WestinBackscatterClosure() : BSDFClosure(Labels::GLOSSY) {}

	void setup()
	{
		m_roughness = clamp(m_roughness, 1e-5f, 1.0f);
		m_invroughness = m_roughness > 0 ? 1 / m_roughness : 0;
	}

	bool mergeable(const ClosurePrimitive *other) const {
		const WestinBackscatterClosure *comp = (const WestinBackscatterClosure *)other;
		return m_N == comp->m_N && m_roughness == comp->m_roughness &&
		       BSDFClosure::mergeable(other);
	}

	size_t memsize() const { return sizeof(*this); }

	const char *name() const { return "westin_backscatter"; }

	void print_on(std::ostream &out) const
	{
		out << name() << " (";
		out << "(" << m_N[0] << ", " << m_N[1] << ", " << m_N[2] << "), ";
		out << m_roughness;
		out << ")";
	}

	float albedo(const Vec3 &omega_out) const
	{
		return 1.0f;
	}

	Color3 eval_reflect(const Vec3 &omega_out, const Vec3 &omega_in, float &pdf) const
	{
		// pdf is implicitly 0 (no indirect sampling)
		float cosNO = m_N.dot(omega_out);
		float cosNI = m_N.dot(omega_in);
		if (cosNO > 0 && cosNI > 0) {
			float cosine = omega_out.dot(omega_in);
			pdf = cosine > 0 ? (m_invroughness + 1) * powf(cosine, m_invroughness) : 0;
			pdf *= 0.5f * float(M_1_PI);
			return Color3(pdf, pdf, pdf);
		}
		return Color3(0, 0, 0);
	}

	Color3 eval_transmit(const Vec3 &omega_out, const Vec3 &omega_in, float &pdf) const
	{
		return Color3(0, 0, 0);
	}

	ustring sample(const Vec3 &Ng,
	               const Vec3 &omega_out, const Vec3 &domega_out_dx, const Vec3 &domega_out_dy,
	               float randu, float randv,
	               Vec3 &omega_in, Vec3 &domega_in_dx, Vec3 &domega_in_dy,
	               float &pdf, Color3 &eval) const
	{
		float cosNO = m_N.dot(omega_out);
		if (cosNO > 0) {
			domega_in_dx = domega_out_dx;
			domega_in_dy = domega_out_dy;
			Vec3 T, B;
			make_orthonormals(omega_out, T, B);
			float phi = 2 * (float) M_PI * randu;
			float cosTheta = powf(randv, 1 / (m_invroughness + 1));
			float sinTheta2 = 1 - cosTheta * cosTheta;
			float sinTheta = sinTheta2 > 0 ? sqrtf(sinTheta2) : 0;
			omega_in = (cosf(phi) * sinTheta) * T +
			           (sinf(phi) * sinTheta) * B +
			           (cosTheta) * omega_out;
			if (Ng.dot(omega_in) > 0)
			{
				// common terms for pdf and eval
				float cosNI = m_N.dot(omega_in);
				// make sure the direction we chose is still in the right hemisphere
				if (cosNI > 0)
				{
					pdf = 0.5f * (float) M_1_PI * powf(cosTheta, m_invroughness);
					pdf = (m_invroughness + 1) * pdf;
					eval.setValue(pdf, pdf, pdf);
					// Since there is some blur to this reflection, make the
					// derivatives a bit bigger. In theory this varies with the
					// exponent but the exact relationship is complex and
					// requires more ops than are practical.
					domega_in_dx *= 10;
					domega_in_dy *= 10;
				}
			}
		}
		return Labels::REFLECT;
	}

};


class WestinSheenClosure : public BSDFClosure {
public:
	Vec3 m_N;
	float m_edginess;
//    float m_normalization;
	WestinSheenClosure() : BSDFClosure(Labels::DIFFUSE) {}

	void setup() {};

	bool mergeable(const ClosurePrimitive *other) const {
		const WestinSheenClosure *comp = (const WestinSheenClosure *)other;
		return m_N == comp->m_N && m_edginess == comp->m_edginess &&
		       BSDFClosure::mergeable(other);
	}

	size_t memsize() const { return sizeof(*this); }

	const char *name() const { return "westin_sheen"; }

	void print_on(std::ostream &out) const
	{
		out << name() << " (";
		out << "(" << m_N[0] << ", " << m_N[1] << ", " << m_N[2] << "), ";
		out << m_edginess;
		out << ")";
	}

	float albedo(const Vec3 &omega_out) const
	{
		return 1.0f;
	}

	Color3 eval_reflect(const Vec3 &omega_out, const Vec3 &omega_in, float &pdf) const
	{
		// pdf is implicitly 0 (no indirect sampling)
		float cosNO = m_N.dot(omega_out);
		float cosNI = m_N.dot(omega_in);
		if (cosNO > 0 && cosNI > 0) {
			float sinNO2 = 1 - cosNO * cosNO;
			pdf = cosNI * float(M_1_PI);
			float westin = sinNO2 > 0 ? powf(sinNO2, 0.5f * m_edginess) * pdf : 0;
			return Color3(westin, westin, westin);
		}
		return Color3(0, 0, 0);
	}

	Color3 eval_transmit(const Vec3 &omega_out, const Vec3 &omega_in, float &pdf) const
	{
		return Color3(0, 0, 0);
	}

	ustring sample(const Vec3 &Ng,
	               const Vec3 &omega_out, const Vec3 &domega_out_dx, const Vec3 &domega_out_dy,
	               float randu, float randv,
	               Vec3 &omega_in, Vec3 &domega_in_dx, Vec3 &domega_in_dy,
	               float &pdf, Color3 &eval) const
	{
		// we are viewing the surface from the right side - send a ray out with cosine
		// distribution over the hemisphere
		sample_cos_hemisphere(m_N, omega_out, randu, randv, omega_in, pdf);
		if (Ng.dot(omega_in) > 0) {
			// TODO: account for sheen when sampling
			float cosNO = m_N.dot(omega_out);
			float sinNO2 = 1 - cosNO * cosNO;
			float westin = sinNO2 > 0 ? powf(sinNO2, 0.5f * m_edginess) * pdf : 0;
			eval.setValue(westin, westin, westin);
			// TODO: find a better approximation for the diffuse bounce
			domega_in_dx = (2 * m_N.dot(domega_out_dx)) * m_N - domega_out_dx;
			domega_in_dy = (2 * m_N.dot(domega_out_dy)) * m_N - domega_out_dy;
			domega_in_dx *= 125;
			domega_in_dy *= 125;
		}
		else {
			pdf = 0;
		}
		return Labels::REFLECT;
	}
};



ClosureParam bsdf_westin_backscatter_params[] = {
	CLOSURE_VECTOR_PARAM(WestinBackscatterClosure, m_N),
	CLOSURE_FLOAT_PARAM(WestinBackscatterClosure, m_roughness),
	CLOSURE_STRING_KEYPARAM("label"),
	CLOSURE_FINISH_PARAM(WestinBackscatterClosure)
};

ClosureParam bsdf_westin_sheen_params[] = {
	CLOSURE_VECTOR_PARAM(WestinSheenClosure, m_N),
	CLOSURE_FLOAT_PARAM(WestinSheenClosure, m_edginess),
	CLOSURE_STRING_KEYPARAM("label"),
	CLOSURE_FINISH_PARAM(WestinSheenClosure)
};

CLOSURE_PREPARE(bsdf_westin_backscatter_prepare, WestinBackscatterClosure)
CLOSURE_PREPARE(bsdf_westin_sheen_prepare,        WestinSheenClosure)

CCL_NAMESPACE_END