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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef GFX_QUATERNION_H
#define GFX_QUATERNION_H

#include "mozilla/gfx/BasePoint4D.h"
#include "mozilla/gfx/Matrix.h"
#include "nsAlgorithm.h"
#include <algorithm>

struct gfxQuaternion
    : public mozilla::gfx::BasePoint4D<gfxFloat, gfxQuaternion> {
  typedef mozilla::gfx::BasePoint4D<gfxFloat, gfxQuaternion> Super;

  gfxQuaternion() : Super() {}
  gfxQuaternion(gfxFloat aX, gfxFloat aY, gfxFloat aZ, gfxFloat aW)
      : Super(aX, aY, aZ, aW) {}

  explicit gfxQuaternion(const mozilla::gfx::Matrix4x4& aMatrix) {
    w = 0.5 *
        sqrt(std::max(1 + aMatrix[0][0] + aMatrix[1][1] + aMatrix[2][2], 0.0f));
    x = 0.5 *
        sqrt(std::max(1 + aMatrix[0][0] - aMatrix[1][1] - aMatrix[2][2], 0.0f));
    y = 0.5 *
        sqrt(std::max(1 - aMatrix[0][0] + aMatrix[1][1] - aMatrix[2][2], 0.0f));
    z = 0.5 *
        sqrt(std::max(1 - aMatrix[0][0] - aMatrix[1][1] + aMatrix[2][2], 0.0f));

    if (aMatrix[2][1] > aMatrix[1][2]) x = -x;
    if (aMatrix[0][2] > aMatrix[2][0]) y = -y;
    if (aMatrix[1][0] > aMatrix[0][1]) z = -z;
  }

  // Convert from |direction axis, angle| pair to gfxQuaternion.
  //
  // Reference:
  // https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation
  //
  // if the direction axis is (x, y, z) = xi + yj + zk,
  // and the angle is |theta|, this formula can be done using
  // an extension of Euler's formula:
  //   q = cos(theta/2) + (xi + yj + zk)(sin(theta/2))
  //     = cos(theta/2) +
  //       x*sin(theta/2)i + y*sin(theta/2)j + z*sin(theta/2)k
  // Note: aDirection should be an unit vector and
  //       the unit of aAngle should be Radian.
  gfxQuaternion(const mozilla::gfx::Point3D& aDirection, gfxFloat aAngle) {
    MOZ_ASSERT(mozilla::gfx::FuzzyEqual(aDirection.Length(), 1.0f),
               "aDirection should be an unit vector");
    x = aDirection.x * sin(aAngle / 2.0);
    y = aDirection.y * sin(aAngle / 2.0);
    z = aDirection.z * sin(aAngle / 2.0);
    w = cos(aAngle / 2.0);
  }

  gfxQuaternion Slerp(const gfxQuaternion& aOther, gfxFloat aCoeff) const {
    gfxFloat dot = mozilla::clamped(DotProduct(aOther), -1.0, 1.0);
    if (dot == 1.0) {
      return *this;
    }

    gfxFloat theta = acos(dot);
    gfxFloat rsintheta = 1 / sqrt(1 - dot * dot);
    gfxFloat rightWeight = sin(aCoeff * theta) * rsintheta;

    gfxQuaternion left = *this;
    gfxQuaternion right = aOther;

    left *= cos(aCoeff * theta) - dot * rightWeight;
    right *= rightWeight;

    return left + right;
  }

  using Super::operator*=;

  // Quaternion multiplication
  // Reference:
  // https://en.wikipedia.org/wiki/Quaternion#Ordered_list_form
  //
  // (w1, x1, y1, z1)(w2, x2, y2, z2) = (w1w2 - x1x2 - y1y2 - z1z2,
  //                                     w1x2 + x1w2 + y1z2 - z1y2,
  //                                     w1y2 - x1z2 + y1w2 + z1x2,
  //                                     w1z2 + x1y2 - y1x2 + z1w2)
  gfxQuaternion operator*(const gfxQuaternion& aOther) const {
    return gfxQuaternion(
        w * aOther.x + x * aOther.w + y * aOther.z - z * aOther.y,
        w * aOther.y - x * aOther.z + y * aOther.w + z * aOther.x,
        w * aOther.z + x * aOther.y - y * aOther.x + z * aOther.w,
        w * aOther.w - x * aOther.x - y * aOther.y - z * aOther.z);
  }
  gfxQuaternion& operator*=(const gfxQuaternion& aOther) {
    *this = *this * aOther;
    return *this;
  }

  mozilla::gfx::Matrix4x4 ToMatrix() const {
    mozilla::gfx::Matrix4x4 temp;

    temp[0][0] = 1 - 2 * (y * y + z * z);
    temp[0][1] = 2 * (x * y + w * z);
    temp[0][2] = 2 * (x * z - w * y);
    temp[1][0] = 2 * (x * y - w * z);
    temp[1][1] = 1 - 2 * (x * x + z * z);
    temp[1][2] = 2 * (y * z + w * x);
    temp[2][0] = 2 * (x * z + w * y);
    temp[2][1] = 2 * (y * z - w * x);
    temp[2][2] = 1 - 2 * (x * x + y * y);

    return temp;
  }
};

#endif /* GFX_QUATERNION_H */