omath/tests/general/unit_test_pred_engine_trait.cpp

// Tests for PredEngineTrait
#include <array>
#include <gtest/gtest.h>
#include <omath/engines/source_engine/traits/pred_engine_trait.hpp>
#include <omath/projectile_prediction/projectile.hpp>
#include <omath/projectile_prediction/target.hpp>

using namespace omath;
using namespace omath::source_engine;

using Projectile = projectile_prediction::Projectile<float>;
using Target     = projectile_prediction::Target<float>;

TEST(PredEngineTrait, PredictProjectilePositionBasic)
{
    Projectile p;
    p.m_origin = {0.f, 0.f, 0.f};
    p.m_launch_speed = 10.f;
    p.m_gravity_scale = 1.f;

    const auto pos = PredEngineTrait::predict_projectile_position(p, /*pitch*/ 0.f, /*yaw*/ 0.f, /*time*/ 1.f,
                                                                  /*gravity*/ 9.81f);
    // With zero pitch and yaw forward vector is along X; expect x ~10, z reduced by gravity*0.5
    EXPECT_NEAR(pos.x, 10.f, 1e-3f);
    EXPECT_NEAR(pos.z, -9.81f * 0.5f, 1e-3f);
}

TEST(PredEngineTrait, PredictTargetPositionAirborne)
{
    Target t;
    t.m_origin = {0.f, 0.f, 10.f};
    t.m_velocity = {1.f, 0.f, 0.f};
    t.m_is_airborne = true;

    const auto pred = PredEngineTrait::predict_target_position(t, 2.f, 9.81f);
    EXPECT_NEAR(pred.x, 2.f, 1e-6f);
    // z should have been reduced by gravity* t^2
    EXPECT_NEAR(pred.z, 10.f - 9.81f * 4.f * 0.5f, 1e-6f);
}

TEST(PredEngineTrait, CalcVector2dDistance)
{
    constexpr Vector3<float> d{3.f, 4.f, 0.f};
    EXPECT_NEAR(PredEngineTrait::calc_vector_2d_distance(d), 5.f, 1e-6f);
}

TEST(PredEngineTrait, CalcViewpointFromAngles)
{
    Projectile p;
    p.m_origin = {0.f, 0.f, 0.f};
    p.m_launch_speed = 10.f;

    constexpr Vector3<float> predicted{10.f, 0.f, 0.f};
    constexpr std::optional<float> pitch = 45.f;
    const auto vp = PredEngineTrait::calc_viewpoint_from_angles(p, predicted, pitch);
    // For 45 degrees, height = delta2d * tan(45deg) = 10 * 1 = 10
    EXPECT_NEAR(vp.z, 10.f, 1e-6f);
}

TEST(PredEngineTrait, PredictProjectilePositionWithLaunchOffset)
{
    Projectile p;
    p.m_origin = {0.f, 0.f, 0.f};
    p.m_launch_offset = {5.f, 3.f, -2.f};
    p.m_launch_speed = 10.f;
    p.m_gravity_scale = 1.f;

    // At time=0, projectile should be at launch_pos = origin + offset
    const auto pos_t0 = PredEngineTrait::predict_projectile_position(p, 0.f, 0.f, 0.f, 9.81f);
    EXPECT_NEAR(pos_t0.x, 5.f, 1e-4f);
    EXPECT_NEAR(pos_t0.y, 3.f, 1e-4f);
    EXPECT_NEAR(pos_t0.z, -2.f, 1e-4f);

    // At time=1 with zero pitch/yaw, should travel along X from the offset position
    const auto pos_t1 = PredEngineTrait::predict_projectile_position(p, 0.f, 0.f, 1.f, 9.81f);
    EXPECT_NEAR(pos_t1.x, 5.f + 10.f, 1e-3f);
    EXPECT_NEAR(pos_t1.y, 3.f, 1e-3f);
    EXPECT_NEAR(pos_t1.z, -2.f - 9.81f * 0.5f, 1e-3f);
}

TEST(PredEngineTrait, PredictProjectilePositionMatchesRotationMatrix)
{
    constexpr Projectile projectile{
            .m_origin = {10.f, -20.f, 30.f},
            .m_launch_offset = {2.f, 3.f, -4.f},
            .m_launch_speed = 750.f,
            .m_gravity_scale = 0.6f,
    };
    struct TestCase
    {
        float pitch;
        float yaw;
        float time;
    };
    constexpr std::array test_cases{
            TestCase{0.f, 0.f, 0.f},
            TestCase{25.f, 45.f, 0.25f},
            TestCase{-60.f, -135.f, 1.5f},
            TestCase{120.f, 540.f, 2.f},
    };
    constexpr float gravity = 9.81f;

    for (const auto& test_case : test_cases)
    {
        const auto launch_position = projectile.m_origin + projectile.m_launch_offset;
        auto expected_position = launch_position
                                 + forward_vector({PitchAngle::from_degrees(-test_case.pitch),
                                                   YawAngle::from_degrees(test_case.yaw), RollAngle::from_degrees(0.f)})
                                           * projectile.m_launch_speed * test_case.time;
        expected_position.z -= gravity * projectile.m_gravity_scale * test_case.time * test_case.time * 0.5f;

        const auto actual_position = PredEngineTrait::predict_projectile_position(
                projectile, test_case.pitch, test_case.yaw, test_case.time, gravity);

        EXPECT_NEAR(actual_position.x, expected_position.x, 1e-5f);
        EXPECT_NEAR(actual_position.y, expected_position.y, 1e-5f);
        EXPECT_NEAR(actual_position.z, expected_position.z, 1e-5f);
    }
}

TEST(PredEngineTrait, ReachabilityCheckUsesDistanceTolerance)
{
    constexpr Projectile projectile{
            .m_origin = {0.f, 0.f, 0.f},
            .m_launch_speed = 100.f,
            .m_gravity_scale = 0.f,
    };

    EXPECT_FALSE(PredEngineTrait::can_projectile_reach_target_at_time(projectile, {100.f, 0.f, 0.f}, 0.5f, 9.81f, 0.f));
    EXPECT_TRUE(PredEngineTrait::can_projectile_reach_target_at_time(projectile, {100.f, 0.f, 0.f}, 1.f, 9.81f, 0.f));
    EXPECT_TRUE(PredEngineTrait::can_projectile_reach_target_at_time(projectile, {101.f, 0.f, 0.f}, 1.f, 9.81f, 1.f));
    EXPECT_TRUE(PredEngineTrait::can_projectile_reach_target_at_time(projectile, {99.f, 0.f, 0.f}, 1.f, 9.81f, 1.f));
    EXPECT_FALSE(PredEngineTrait::can_projectile_reach_target_at_time(projectile, {101.f, 0.f, 0.f}, 1.f, 9.81f, 0.f));
    EXPECT_FALSE(PredEngineTrait::can_projectile_reach_target_at_time(projectile, {98.f, 0.f, 0.f}, 1.f, 9.81f, 1.f));
}

TEST(PredEngineTrait, ReachabilityCheckIncludesFloatingPointError)
{
    constexpr Projectile projectile{
            .m_origin = {1.f, 2.f, 3.f},
            .m_launch_offset = {0.1f, -0.2f, 0.3f},
            .m_launch_speed = 100.f,
            .m_gravity_scale = 1.f,
    };
    constexpr float gravity = 9.81f;
    constexpr float time = 0.3f;
    const auto target_position = PredEngineTrait::predict_projectile_position(projectile, 25.f, 45.f, time, gravity);

    EXPECT_TRUE(PredEngineTrait::can_projectile_reach_target_at_time(projectile, target_position, time, gravity, 0.f));
}

TEST(PredEngineTrait, ZeroLaunchOffsetMatchesOriginalBehavior)
{
    Projectile p;
    p.m_origin = {10.f, 20.f, 30.f};
    p.m_launch_offset = {0.f, 0.f, 0.f};
    p.m_launch_speed = 15.f;
    p.m_gravity_scale = 0.5f;

    Projectile p_no_offset;
    p_no_offset.m_origin = {10.f, 20.f, 30.f};
    p_no_offset.m_launch_speed = 15.f;
    p_no_offset.m_gravity_scale = 0.5f;

    const auto pos1 = PredEngineTrait::predict_projectile_position(p, 30.f, 45.f, 2.f, 9.81f);
    const auto pos2 = PredEngineTrait::predict_projectile_position(p_no_offset, 30.f, 45.f, 2.f, 9.81f);
    EXPECT_NEAR(pos1.x, pos2.x, 1e-6f);
    EXPECT_NEAR(pos1.y, pos2.y, 1e-6f);
    EXPECT_NEAR(pos1.z, pos2.z, 1e-6f);
}

TEST(PredEngineTrait, DirectAngles)
{
    constexpr Vector3<float> origin{0.f, 0.f, 0.f};
    constexpr Vector3<float> target{0.f, 1.f, 1.f};
    // yaw should be 90 degrees (pointing along y)
    EXPECT_NEAR(PredEngineTrait::calc_direct_yaw_angle(origin, target), 90.f, 1e-3f);
    // pitch should be asin(z/distance)
    const float dist = origin.distance_to(target);
    EXPECT_NEAR(PredEngineTrait::calc_direct_pitch_angle(origin, target),
                angles::radians_to_degrees(std::asin((target.z - origin.z) / dist)), 1e-3f);
}