// Copyright 2009-2021 Intel Corporation
// SPDX-License-Identifier: Apache-2.0

#include "light.h"
#include <sampling.hpp>
#include <math/linearspace3.h>
#include "helper.hpp"

namespace embree {
    struct AmbientLight {
        Light super; //!< inherited light fields

        Vec3fa radiance; //!< RGB color and intensity of light
    };


    // Implementation
    //////////////////////////////////////////////////////////////////////////////

    // XXX importance sampling is only done into the positive hemisphere
    // ==> poor support for translucent materials
    Light_SampleRes AmbientLight_sample(const Light* super,
                                        const Sample& dg,
                                        const Vec2f& s) {
        AmbientLight* self = (AmbientLight *) super;
        Light_SampleRes res;

        const Vec3fa localDir = cosineSampleHemisphere(s);
        res.dir = frame(dg.Ns) * localDir;
        res.pdf = cosineSampleHemispherePDF(localDir);
        res.dist = inf;
        res.weight = self->radiance * rcp(res.pdf);

        return res;
    }

    Light_EvalRes AmbientLight_eval(const Light* super,
                                    const Sample& dg,
                                    const Vec3fa& dir) {
        AmbientLight* self = (AmbientLight *) super;
        Light_EvalRes res;

        res.value = self->radiance;
        res.dist = inf;
        res.pdf = cosineSampleHemispherePDF(max(dot(dg.Ns, dir), 0.f));

        return res;
    }


    void AmbientLight_Constructor(AmbientLight* self,
                                  const Vec3fa& radiance) {
        Light_Constructor(&self->super);
        self->radiance = radiance;
        //self->super.sample = GET_FUNCTION_POINTER(AmbientLight_sample);
        //self->super.eval = GET_FUNCTION_POINTER(AmbientLight_eval);
        self->super.type = LIGHT_AMBIENT;
    }


    // Exports (called from C++)
    //////////////////////////////////////////////////////////////////////////////

    //! Create an ispc-side AmbientLight object
    extern "C" void* AmbientLight_create() {
        AmbientLight* self = (AmbientLight *) alignedUSMMalloc(sizeof(AmbientLight), 16);
        AmbientLight_Constructor(self, Vec3fa(1.f));
        return self;
    }

    //! Set the parameters of an ispc-side AmbientLight object
    extern "C" void AmbientLight_set(void* super,
                                     const Vec3fa& radiance) {
        AmbientLight* self = (AmbientLight *) super;
        self->radiance = radiance;
    }
} // namespace embree