/*
 * Adapted from Open Shading Language with this license:
 *
 * Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
 * All Rights Reserved.
 *
 * Modifications Copyright 2012, 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;

// vanilla phong - leaks energy at grazing angles
// see Global Illumination Compendium entry (66) 
class PhongClosure : public BSDFClosure {
public:
    Vec3 m_N;
    float m_exponent;
    PhongClosure() : BSDFClosure(Labels::GLOSSY) { }

    void setup() {};

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

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

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

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

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

    Color3 eval_reflect (const Vec3 &omega_out, const Vec3 &omega_in, float& pdf) const
    {
        float cosNI = m_N.dot(omega_in);
        float cosNO = m_N.dot(omega_out);
        if (cosNI > 0 && cosNO > 0) {
           // reflect the view vector
           Vec3 R = (2 * cosNO) * m_N - omega_out;
           float cosRI = R.dot(omega_in);
           if (cosRI > 0) {
               float common = 0.5f * (float) M_1_PI * powf(cosRI, m_exponent);
               float out = cosNI * (m_exponent + 2) * common;
               pdf = (m_exponent + 1) * common;
               return Color3 (out, out, out);
           }
        }
        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) {
            // reflect the view vector
            Vec3 R = (2 * cosNO) * m_N - omega_out;
            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;
            Vec3 T, B;
            make_orthonormals (R, T, B);
            float phi = 2 * (float) M_PI * randu;
            float cosTheta = powf(randv, 1 / (m_exponent + 1));
            float sinTheta2 = 1 - cosTheta * cosTheta;
            float sinTheta = sinTheta2 > 0 ? sqrtf(sinTheta2) : 0;
            omega_in = (cosf(phi) * sinTheta) * T +
                       (sinf(phi) * sinTheta) * B +
                       (            cosTheta) * R;
            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)
                {
                    float common = 0.5f * (float) M_1_PI * powf(cosTheta, m_exponent);
                    pdf = (m_exponent + 1) * common;
                    float out = cosNI * (m_exponent + 2) * common;
                    eval.setValue(out, out, out);
                    // 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 PhongRampClosure : public BSDFClosure {
public:
    static const int MAXCOLORS = 8;
    Vec3 m_N;
    float m_exponent;
    Color3 m_colors[MAXCOLORS];
    PhongRampClosure() : BSDFClosure(Labels::GLOSSY) { }

    void setup() {};

    bool mergeable (const ClosurePrimitive *other) const {
        const PhongRampClosure *comp = (const PhongRampClosure *)other;
        if (! (m_N == comp->m_N && m_exponent == comp->m_exponent && 
               BSDFClosure::mergeable(other)))
            return false;
        for (int i = 0;  i < MAXCOLORS;  ++i)
            if (m_colors[i] != comp->m_colors[i])
                return false;
        return true;
    }

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

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

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

    Color3 get_color (float pos) const
    {
        float npos = pos * (float)(MAXCOLORS - 1);
        int ipos = (int)npos;
        if (ipos >= (MAXCOLORS - 1))
            return m_colors[MAXCOLORS - 1];
        float offset = npos - (float)ipos;
        return m_colors[ipos] * (1.0f - offset) + m_colors[ipos+1] * offset;
    }

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

    Color3 eval_reflect (const Vec3 &omega_out, const Vec3 &omega_in, float& pdf) const
    {
        float cosNI = m_N.dot(omega_in);
        float cosNO = m_N.dot(omega_out);
        if (cosNI > 0 && cosNO > 0) {
            // reflect the view vector
            Vec3 R = (2 * cosNO) * m_N - omega_out;
            float cosRI = R.dot(omega_in);
            if (cosRI > 0) {
                float cosp = powf(cosRI, m_exponent);
                float common = 0.5f * (float) M_1_PI * cosp;
                float out = cosNI * (m_exponent + 2) * common;
                pdf = (m_exponent + 1) * common;
                return get_color(cosp) * out;
            }
        }
        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) {
            // reflect the view vector
            Vec3 R = (2 * cosNO) * m_N - omega_out;
            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;
            Vec3 T, B;
            make_orthonormals (R, T, B);
            float phi = 2 * (float) M_PI * randu;
            float cosTheta = powf(randv, 1 / (m_exponent + 1));
            float sinTheta2 = 1 - cosTheta * cosTheta;
            float sinTheta = sinTheta2 > 0 ? sqrtf(sinTheta2) : 0;
            omega_in = (cosf(phi) * sinTheta) * T +
                       (sinf(phi) * sinTheta) * B +
                       (            cosTheta) * R;
            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)
                {
                    float cosp = powf(cosTheta, m_exponent);
                    float common = 0.5f * (float) M_1_PI * cosp;
                    pdf = (m_exponent + 1) * common;
                    float out = cosNI * (m_exponent + 2) * common;
                    eval = get_color(cosp) * out;
                    // 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;
    }
};



ClosureParam bsdf_phong_params[] = {
    CLOSURE_VECTOR_PARAM(PhongClosure, m_N),
    CLOSURE_FLOAT_PARAM (PhongClosure, m_exponent),
    CLOSURE_STRING_KEYPARAM("label"),
    CLOSURE_FINISH_PARAM(PhongClosure) };

ClosureParam bsdf_phong_ramp_params[] = {
    CLOSURE_VECTOR_PARAM     (PhongRampClosure, m_N),
    CLOSURE_FLOAT_PARAM      (PhongRampClosure, m_exponent),
    CLOSURE_COLOR_ARRAY_PARAM(PhongRampClosure, m_colors, PhongRampClosure::MAXCOLORS),
    CLOSURE_STRING_KEYPARAM("label"),
    CLOSURE_FINISH_PARAM     (PhongRampClosure) };

CLOSURE_PREPARE(bsdf_phong_prepare, PhongClosure)
CLOSURE_PREPARE(bsdf_phong_ramp_prepare, PhongRampClosure)

CCL_NAMESPACE_END