#include <catch2/catch_test_macros.hpp>
#include "../src/physics.h"
#include "../src/bodies.h"
#include "../src/test_utilities.h"
#include <cmath>

TEST_CASE("Energy conservation - Earth circular orbit", "[energy][rk4]") {
    const double TIME_STEP = 60.0;
    const double DAYS_TO_SIMULATE = 10.0;
    const double SECONDS_PER_DAY = 86400.0;

    SimulationState* sim = create_simulation(10, TIME_STEP);

    Vec3 sun_pos = {0, 0, 0};
    Vec3 sun_vel = {0, 0, 0};
    add_body(sim, "Sun", 1.989e30, 6.96e8, sun_pos, sun_vel, -1, 1.0, 1.0, 0.0, 0, 0);

    Vec3 earth_pos = {1.496e11, 0, 0};
    Vec3 earth_vel = {0, 29800, 0};
    add_body(sim, "Earth", 5.972e24, 6.371e6, earth_pos, earth_vel, 0, 0.0, 0.5, 1.0, 0, 1.496e11);

    double initial_energy = calculate_system_total_energy(sim);

    double total_time = DAYS_TO_SIMULATE * SECONDS_PER_DAY;
    while (sim->time < total_time) {
        update_simulation(sim);
    }

    double final_energy = calculate_system_total_energy(sim);
    double energy_drift_percent = fabs((final_energy - initial_energy) / initial_energy) * 100.0;

    INFO("Initial energy: " << initial_energy << " J");
    INFO("Final energy: " << final_energy << " J");
    INFO("Energy drift: " << energy_drift_percent << "%");

    REQUIRE(energy_drift_percent < 5.0);

    destroy_simulation(sim);
}