/************************************************************************************

PublicHeader:   OVR_CAPI_Util.c
Copyright   :   Copyright 2014 Oculus VR, LLC All Rights reserved.

Licensed under the Oculus VR Rift SDK License Version 3.2 (the "License"); 
you may not use the Oculus VR Rift SDK except in compliance with the License, 
which is provided at the time of installation or download, or which 
otherwise accompanies this software in either electronic or hard copy form.

You may obtain a copy of the License at

http://www.oculusvr.com/licenses/LICENSE-3.2 

Unless required by applicable law or agreed to in writing, the Oculus VR SDK 
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

*************************************************************************************/


#include <OVR_CAPI_Util.h>
#include "OVR_StereoProjection.h"

#if defined(_MSC_VER)
    #include <emmintrin.h>
    #pragma intrinsic(_mm_pause)
#endif



// Used to generate projection from ovrEyeDesc::Fov
ovrMatrix4f ovrMatrix4f_Projection(ovrFovPort fov, float znear, float zfar, unsigned int projectionModFlags)
{
    bool rightHanded    = (projectionModFlags & ovrProjection_RightHanded) > 0;
    bool flipZ          = (projectionModFlags & ovrProjection_FarLessThanNear) > 0;
    bool farAtInfinity  = (projectionModFlags & ovrProjection_FarClipAtInfinity) > 0;
    bool isOpenGL       = (projectionModFlags & ovrProjection_ClipRangeOpenGL) > 0;

    // TODO: Pass in correct eye to CreateProjection if we want to support canted displays from CAPI
    return OVR::CreateProjection(rightHanded , isOpenGL, fov, OVR::StereoEye_Center, znear, zfar, flipZ, farAtInfinity);
}


ovrMatrix4f ovrMatrix4f_OrthoSubProjection(ovrMatrix4f projection, ovrVector2f orthoScale,
                                                      float orthoDistance, float hmdToEyeViewOffsetX)
{
    ovrMatrix4f ortho;
    float orthoHorizontalOffset = hmdToEyeViewOffsetX / orthoDistance;

    /*
    // Current projection maps real-world vector (x,y,1) to the RT.
    // We want to find the projection that maps the range [-FovPixels/2,FovPixels/2] to
    // the physical [-orthoHalfFov,orthoHalfFov]
    // Note moving the offset from M[0][2]+M[1][2] to M[0][3]+M[1][3] - this means
    // we don't have to feed in Z=1 all the time.
    // The horizontal offset math is a little hinky because the destination is
    // actually [-orthoHalfFov+orthoHorizontalOffset,orthoHalfFov+orthoHorizontalOffset]
    // So we need to first map [-FovPixels/2,FovPixels/2] to
    //                         [-orthoHalfFov+orthoHorizontalOffset,orthoHalfFov+orthoHorizontalOffset]:
    // x1 = x0 * orthoHalfFov/(FovPixels/2) + orthoHorizontalOffset;
    //    = x0 * 2*orthoHalfFov/FovPixels + orthoHorizontalOffset;
    // But then we need the same mapping as the existing projection matrix, i.e.
    // x2 = x1 * Projection.M[0][0] + Projection.M[0][2];
    //    = x0 * (2*orthoHalfFov/FovPixels + orthoHorizontalOffset) * Projection.M[0][0] + Projection.M[0][2];
    //    = x0 * Projection.M[0][0]*2*orthoHalfFov/FovPixels +
    //      orthoHorizontalOffset*Projection.M[0][0] + Projection.M[0][2];
    // So in the new projection matrix we need to scale by Projection.M[0][0]*2*orthoHalfFov/FovPixels and
    // offset by orthoHorizontalOffset*Projection.M[0][0] + Projection.M[0][2].
    */

    ortho.M[0][0] = projection.M[0][0] * orthoScale.x;
    ortho.M[0][1] = 0.0f;
    ortho.M[0][2] = 0.0f;
    ortho.M[0][3] = -projection.M[0][2] + ( orthoHorizontalOffset * projection.M[0][0] );

    ortho.M[1][0] = 0.0f;
    ortho.M[1][1] = -projection.M[1][1] * orthoScale.y;       /* Note sign flip (text rendering uses Y=down). */
    ortho.M[1][2] = 0.0f;
    ortho.M[1][3] = -projection.M[1][2];

    ortho.M[2][0] = 0.0f;
    ortho.M[2][1] = 0.0f;
    ortho.M[2][2] = 0.0f;
    ortho.M[2][3] = 0.0f;

    /* No perspective correction for ortho. */
    ortho.M[3][0] = 0.0f;
    ortho.M[3][1] = 0.0f;
    ortho.M[3][2] = 0.0f;
    ortho.M[3][3] = 1.0f;

    return ortho;
}


double ovr_WaitTillTime(double absTime)
{
    double       initialTime = ovr_GetTimeInSeconds();
    double       newTime     = initialTime;
    
    while(newTime < absTime)
    {
        for (int j = 0; j < 5; j++)
        {
            #if defined(__x86_64__) || defined(_M_AMD64) || defined(__i386__) ||  defined(_M_IX86) // Intel architecture...
                #if defined(__GNUC__) || defined(__clang__)
                    asm volatile("pause" ::: "memory");
                #elif defined(_MSC_VER)
                    _mm_pause();
                #endif
            #endif
        }

        newTime = ovr_GetTimeInSeconds();
    }

    return (newTime - initialTime);
}