#include <catch2/catch_test_macros.hpp>
#include <catch2/matchers/catch_matchers_floating_point.hpp>
#include "../src/physics.h"
#include "../src/simulation.h"
#include "../src/config_loader.h"
#include "../src/test_utilities.h"
#include <cmath>

using Catch::Matchers::WithinAbs;

SCENARIO("Energy conservation in circular orbit", "[energy][sanity]") {
    const double TIME_STEP = 60.0;
    const double DAYS_TO_SIMULATE = 10.0;
    const double SECONDS_PER_DAY = 86400.0;

    SimulationState* sim = create_simulation(2, 0, 0, TIME_STEP);
    REQUIRE(load_system_config(sim, "tests/test_energy.toml"));

    const 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);
    }

    const double final_energy = calculate_system_total_energy(sim);
    const double energy_drift = fabs(final_energy - initial_energy) / fabs(initial_energy);

    INFO("Initial energy: " << initial_energy << " J");
    INFO("Final energy: " << final_energy << " J");
    INFO("Relative drift: " << energy_drift << " (fraction)");

    REQUIRE_THAT(energy_drift, WithinAbs(0.0, 1e-12));

    destroy_simulation(sim);
}

SCENARIO("Orbit direction for zero inclination", "[direction][sanity]") {
    const double TIME_STEP = 60.0;
    const int STEPS = 1440; // 1 day at 60s steps

    SimulationState* sim = create_simulation(2, 0, 0, TIME_STEP);
    REQUIRE(load_system_config(sim, "tests/test_energy.toml"));

    CelestialBody* sun = &sim->bodies[0];
    CelestialBody* earth = &sim->bodies[1];

    Vec3 initial_rel = vec3_sub(earth->global_position, sun->global_position);
    const double theta_start = atan2(initial_rel.y, initial_rel.x);

    for (int i = 0; i < STEPS; i++) update_simulation(sim);

    Vec3 final_rel = vec3_sub(earth->global_position, sun->global_position);
    const double delta = atan2(final_rel.y, final_rel.x) - theta_start;

    INFO("Delta: " << delta << " rad");
    REQUIRE_THAT(delta, WithinAbs(0.0172042841, 1e-6));

    destroy_simulation(sim);
}