// Ceres Solver - A fast non-linear least squares minimizer
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// Author: sameeragarwal@google.com (Sameer Agarwal)

#include <array>
#include <cmath>
#include <memory>

#include "absl/log/check.h"
#include "benchmark/benchmark.h"
#include "ceres/autodiff_manifold.h"
#include "ceres/manifold.h"
#include "ceres/rotation.h"

namespace ceres::internal {
namespace {

struct QuaternionFunctor {
  static constexpr int kAmbientSize = 4;
  static constexpr int kTangentSize = 3;

  static std::array<double, kAmbientSize> MakeParameter() {
    return {0.5, 0.5, 0.5, 0.5};
  }

  template <typename T>
  bool Plus(const T* x, const T* delta, T* x_plus_delta) const {
    const T squared_norm_delta =
        delta[0] * delta[0] + delta[1] * delta[1] + delta[2] * delta[2];

    T q_delta[4];
    if (squared_norm_delta > T(0.0)) {
      const T norm_delta = sqrt(squared_norm_delta);
      const T sin_delta_by_delta = sin(norm_delta) / norm_delta;
      q_delta[0] = cos(norm_delta);
      q_delta[1] = sin_delta_by_delta * delta[0];
      q_delta[2] = sin_delta_by_delta * delta[1];
      q_delta[3] = sin_delta_by_delta * delta[2];
    } else {
      q_delta[0] = T(1.0);
      q_delta[1] = delta[0];
      q_delta[2] = delta[1];
      q_delta[3] = delta[2];
    }

    QuaternionProduct(q_delta, x, x_plus_delta);
    return true;
  }

  template <typename T>
  bool Minus(const T* y, const T* x, T* y_minus_x) const {
    const T minus_x[4] = {x[0], -x[1], -x[2], -x[3]};
    T ambient_y_minus_x[4];
    QuaternionProduct(y, minus_x, ambient_y_minus_x);
    const T u_sq = ambient_y_minus_x[1] * ambient_y_minus_x[1] +
                   ambient_y_minus_x[2] * ambient_y_minus_x[2] +
                   ambient_y_minus_x[3] * ambient_y_minus_x[3];
    if (u_sq > T(0.0)) {
      const T u_norm = sqrt(u_sq);
      const T theta = atan2(u_norm, ambient_y_minus_x[0]);
      y_minus_x[0] = theta * ambient_y_minus_x[1] / u_norm;
      y_minus_x[1] = theta * ambient_y_minus_x[2] / u_norm;
      y_minus_x[2] = theta * ambient_y_minus_x[3] / u_norm;
    } else {
      y_minus_x[0] = ambient_y_minus_x[1];
      y_minus_x[1] = ambient_y_minus_x[2];
      y_minus_x[2] = ambient_y_minus_x[3];
    }
    return true;
  }
};

struct Pose3Functor {
  static constexpr int kAmbientSize = 7;
  static constexpr int kTangentSize = 6;

  static std::array<double, kAmbientSize> MakeParameter() {
    return {0.5, 0.5, 0.5, 0.5, 1.0, 2.0, 3.0};
  }

  template <typename T>
  bool Plus(const T* x, const T* delta, T* x_plus_delta) const {
    QuaternionFunctor q;
    q.Plus(x, delta, x_plus_delta);
    x_plus_delta[4] = x[4] + delta[3];
    x_plus_delta[5] = x[5] + delta[4];
    x_plus_delta[6] = x[6] + delta[5];
    return true;
  }

  template <typename T>
  bool Minus(const T* y, const T* x, T* y_minus_x) const {
    QuaternionFunctor q;
    q.Minus(y, x, y_minus_x);
    y_minus_x[3] = y[4] - x[4];
    y_minus_x[4] = y[5] - x[5];
    y_minus_x[5] = y[6] - x[6];
    return true;
  }
};

template <typename Functor>
void BM_AutoDiffManifoldPlusJacobian(benchmark::State& state) {
  constexpr int kAmbientSize = Functor::kAmbientSize;
  constexpr int kTangentSize = Functor::kTangentSize;
  const std::unique_ptr<Manifold> manifold =
      std::make_unique<AutoDiffManifold<Functor, kAmbientSize, kTangentSize>>();
  const auto x = Functor::MakeParameter();
  std::array<double, kAmbientSize * kTangentSize> jacobian{};

  CHECK(manifold->PlusJacobian(x.data(), jacobian.data()));

  for (auto _ : state) {
    benchmark::DoNotOptimize(manifold->PlusJacobian(x.data(), jacobian.data()));
    benchmark::DoNotOptimize(jacobian);
  }
}

template <typename Functor>
void BM_AutoDiffManifoldMinusJacobian(benchmark::State& state) {
  constexpr int kAmbientSize = Functor::kAmbientSize;
  constexpr int kTangentSize = Functor::kTangentSize;
  const std::unique_ptr<Manifold> manifold =
      std::make_unique<AutoDiffManifold<Functor, kAmbientSize, kTangentSize>>();
  const auto x = Functor::MakeParameter();
  std::array<double, kTangentSize * kAmbientSize> jacobian{};

  CHECK(manifold->MinusJacobian(x.data(), jacobian.data()));

  for (auto _ : state) {
    benchmark::DoNotOptimize(
        manifold->MinusJacobian(x.data(), jacobian.data()));
    benchmark::DoNotOptimize(jacobian);
  }
}

BENCHMARK_TEMPLATE(BM_AutoDiffManifoldPlusJacobian, QuaternionFunctor);
BENCHMARK_TEMPLATE(BM_AutoDiffManifoldMinusJacobian, QuaternionFunctor);
BENCHMARK_TEMPLATE(BM_AutoDiffManifoldPlusJacobian, Pose3Functor);
BENCHMARK_TEMPLATE(BM_AutoDiffManifoldMinusJacobian, Pose3Functor);

}  // namespace
}  // namespace ceres::internal

BENCHMARK_MAIN();