// Copyright 2021 DeepMind Technologies Limited
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// 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.

// Tests for engine/engine_util_solve.c.

#include <gmock/gmock.h>
#include <gtest/gtest.h>
#include <mujoco/mjdata.h>
#include <mujoco/mujoco.h>
#include "src/engine/engine_util_misc.h"
#include "test/fixture.h"

namespace mujoco {
namespace {

using ::testing::HasSubstr;
using ::testing::DoubleNear;

TEST_F(MujocoTest, PrintsMemoryWarning) {
  EXPECT_THAT(mju_warningText(mjWARN_CNSTRFULL, pow(2, 10)),
              HasSubstr("1K bytes"));
  EXPECT_THAT(mju_warningText(mjWARN_CNSTRFULL, pow(2, 20)),
              HasSubstr("1M bytes"));
  EXPECT_THAT(mju_warningText(mjWARN_CNSTRFULL, pow(2, 30)),
              HasSubstr("1G bytes"));
  EXPECT_THAT(mju_warningText(mjWARN_CNSTRFULL, pow(2, 40)),
              HasSubstr("1T bytes"));
  EXPECT_THAT(mju_warningText(mjWARN_CNSTRFULL, pow(2, 50)),
              HasSubstr("1P bytes"));
  EXPECT_THAT(mju_warningText(mjWARN_CNSTRFULL, pow(2, 60)),
              HasSubstr("1E bytes"));
  EXPECT_THAT(mju_warningText(mjWARN_CNSTRFULL, pow(2, 30) + 1),
              HasSubstr("1073741825 bytes"));
}

TEST_F(MujocoTest, Sigmoid) {
  // function values
  EXPECT_EQ(mju_sigmoid(-1),  0);
  EXPECT_EQ(mju_sigmoid(0),   0);
  EXPECT_EQ(mju_sigmoid(0.5), 0.5);
  EXPECT_EQ(mju_sigmoid(1),   1);
  EXPECT_EQ(mju_sigmoid(2),   1);

  // epsilon for finite-differencing
  const mjtNum dx = 1e-7;

  // derivative at 0
  mjtNum dy_dx_0 = (mju_sigmoid(0 + dx) - mju_sigmoid(0)) / dx;
  EXPECT_THAT(dy_dx_0, DoubleNear(0, dx));

  // derivative at 1
  mjtNum dy_dx_1 = (mju_sigmoid(1) - mju_sigmoid(1 - dx)) / dx;
  EXPECT_THAT(dy_dx_1, DoubleNear(0, dx));

  // derivative at 0.5
  const mjtNum x = 0.5;
  mjtNum dy_dx_0p5 = (mju_sigmoid(x + dx) - mju_sigmoid(x - dx)) / (2*dx);
  mjtNum expected = 30*x*x*x*x - 60*x*x*x + 30*x*x;
  EXPECT_THAT(dy_dx_0p5, DoubleNear(expected, dx));
}

}  // namespace
}  // namespace mujoco