#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>
#include <vector>
#include <string>

using Catch::Matchers::WithinAbs;

// === Helper: run sim loop, collect failures, assert once at end ===
static std::string fmt_time(double t) {
    char buf[32];
    snprintf(buf, sizeof(buf), "t=%.0fs", t);
    return std::string(buf);
}

static std::string fmt_drift(double d) {
    char buf[32];
    snprintf(buf, sizeof(buf), "drift=%.4f", d);
    return std::string(buf);
}

// === Per-moon period tolerances (0.5% of analytical period, from precalc) ===
static const double MOON_PERIOD_TOL = 11861.4;   // Moon
static const double IO_PERIOD_TOL = 764.6;       // Io
static const double EUROPA_PERIOD_TOL = 1534.5;   // Europa
static const double GANYMEDE_PERIOD_TOL = 3091.1; // Ganymede
static const double CALLISTO_PERIOD_TOL = 7210.6; // Callisto
static const double TITAN_PERIOD_TOL = 6889.9;    // Titan


// === Drift tolerance for distance checks (10% bound) ===
static const double DRIFT_REL_TOL = 0.1;

SCENARIO("Multi-body moon orbital stability and period measurements",
         "[moon][earth][jupiter][saturn][galilean][titan]"
         "[stability][period][integration][inclined][geometry]") {
    // === Fixture ===
    const double TIME_STEP = 60.0;
    const double SECONDS_PER_DAY = 86400.0;

    SimulationState* sim = create_simulation(20, 0, 0, TIME_STEP);
    REQUIRE(load_system_config(sim, "tests/test_moon_orbits.toml"));

    CelestialBody* earth = &sim->bodies[2];
    CelestialBody* moon = &sim->bodies[8];

    struct MoonData {
        int index;
        const char* name;
        double expected_seconds;
        double max_days;
        double min_time_days;
        double period_tol;
        int parent_index;
    };

    const MoonData galilean[] = {
        {9, "Io", 152928.62, 5.0, 1.0, IO_PERIOD_TOL, 4},
        {10, "Europa", 306909.10, 10.0, 2.0, EUROPA_PERIOD_TOL, 4},
        {11, "Ganymede", 618227.12, 15.0, 5.0, GANYMEDE_PERIOD_TOL, 4},
        {12, "Callisto", 1442117.30, 25.0, 10.0, CALLISTO_PERIOD_TOL, 4},
    };

    const MoonData all_moons[] = {
        {8, "Moon", 2372274.33, 35.0, 5.0, MOON_PERIOD_TOL, 2},
        {9, "Io", 152928.62, 5.0, 1.0, IO_PERIOD_TOL, 4},
        {10, "Europa", 306909.10, 10.0, 2.0, EUROPA_PERIOD_TOL, 4},
        {11, "Ganymede", 618227.12, 15.0, 5.0, GANYMEDE_PERIOD_TOL, 4},
        {12, "Callisto", 1442117.30, 25.0, 10.0, CALLISTO_PERIOD_TOL, 4},
        {13, "Titan", 1377976.07, 25.0, 10.0, TITAN_PERIOD_TOL, 5},
    };

    // === Helper lambdas ===
    // Run sim loop without assertions; collect failures; assert once at end.
    // This tests every timestep but produces only 1 assertion per call.
    auto check_parent_stability = [&](CelestialBody* body, int expected_parent,
                                       double max_days) {
        double max_time = max_days * SECONDS_PER_DAY;
        std::vector<std::string> failures;
        while (sim->time < max_time) {
            update_simulation(sim);
            if (body->parent_index != expected_parent) {
                failures.push_back(fmt_time(sim->time) + ": " +
                                   std::string(body->name) +
                                   " parent=" + std::to_string(body->parent_index) +
                                   " (expected " + std::to_string(expected_parent) + ")");
            }
        }
        REQUIRE(failures.empty());
    };

    auto measure_period = [&](int body_index, int parent_index,
                               double max_days, double min_time_days) {
        sim->time = 0.0;
        OrbitTracker* tracker = create_orbit_tracker_with_min_time(
            body_index, min_time_days * SECONDS_PER_DAY);
        double max_time = max_days * SECONDS_PER_DAY;

        while (sim->time < max_time && !tracker->orbit_completed) {
            update_simulation(sim);
            update_orbit_tracker(tracker, &sim->bodies[body_index],
                                 &sim->bodies[parent_index], sim->time);
        }

        double period = tracker->orbit_completed
                        ? tracker->time_at_completion : -1.0;
        destroy_orbit_tracker(tracker);
        return period;
    };

    auto check_distance_drift = [&](CelestialBody* body, int parent_index,
                                     double max_days) {
        CelestialBody* parent = &sim->bodies[parent_index];
        Vec3 initial_rel = vec3_sub(body->global_position, parent->global_position);
        double initial_r = vec3_magnitude(initial_rel);
        double max_time = max_days * SECONDS_PER_DAY;

        std::vector<std::string> failures;
        while (sim->time < max_time) {
            update_simulation(sim);
            Vec3 rel = vec3_sub(body->global_position, parent->global_position);
            double r = vec3_magnitude(rel);
            double drift = std::fabs(r - initial_r) / initial_r;
            if (drift > DRIFT_REL_TOL) {
                failures.push_back(fmt_time(sim->time) + ": " +
                                   std::string(body->name) + " " +
                                   fmt_drift(drift));
            }
        }
        REQUIRE(failures.empty());
    };

    auto wait_for_all_orbits = [&](int count) {
        OrbitTracker* trackers[6] = {};
        for (int i = 0; i < count; i++) {
            trackers[i] = create_orbit_tracker_with_min_time(
                all_moons[i].index, all_moons[i].min_time_days * SECONDS_PER_DAY);
        }

        double max_time = 60.0 * SECONDS_PER_DAY;
        int completed_count = 0;

        while (sim->time < max_time && completed_count < count) {
            update_simulation(sim);
            for (int i = 0; i < count; i++) {
                if (!trackers[i]->orbit_completed) {
                    update_orbit_tracker(trackers[i], &sim->bodies[all_moons[i].index],
                                         &sim->bodies[all_moons[i].parent_index], sim->time);
                    if (trackers[i]->orbit_completed) {
                        completed_count++;
                        double period = trackers[i]->time_at_completion / SECONDS_PER_DAY;
                        INFO(all_moons[i].name << " completed orbit at "
                             << period << " days");
                    }
                }
            }
        }

        for (int i = 0; i < count; i++) {
            REQUIRE(trackers[i]->orbit_completed);
            destroy_orbit_tracker(trackers[i]);
        }
    };

    // === Sections ===

    SECTION("Moon maintains Earth as parent throughout simulation") {
        check_parent_stability(moon, 2, 35.0);
    }

    SECTION("Moon distance from Earth stays within 10% of initial") {
        check_distance_drift(moon, 2, 35.0);
    }

    SECTION("Moon completes orbit in ~27.3 days") {
        double period = measure_period(8, 2, 35.0, 5.0);
        INFO("Measured Moon period: " << period / SECONDS_PER_DAY
             << " days (expected: ~27.3)");
        REQUIRE_THAT(period, WithinAbs(2372274.33, MOON_PERIOD_TOL));
    }

    SECTION("Galilean moons maintain Jupiter as parent") {
        for (const auto& m : galilean) {
            check_parent_stability(&sim->bodies[m.index], 4, 25.0);
        }
    }

    SECTION("Galilean moons complete orbits in expected periods") {
        for (const auto& m : galilean) {
            double period = measure_period(m.index, m.parent_index,
                                           m.max_days, m.min_time_days);
            INFO(m.name << " period: " << period / SECONDS_PER_DAY
                 << " days (expected: " << m.expected_seconds / SECONDS_PER_DAY
                 << ")");
            REQUIRE_THAT(period, WithinAbs(m.expected_seconds, m.period_tol));
        }
    }

    SECTION("Galilean moons stay within 10% of initial distance") {
        for (const auto& m : galilean) {
            check_distance_drift(&sim->bodies[m.index], m.parent_index, 25.0);
        }
    }

    SECTION("Titan maintains Saturn as parent") {
        check_parent_stability(&sim->bodies[13], 5, 25.0);
    }

    SECTION("Titan completes orbit in ~15.95 days") {
        double period = measure_period(13, 5, 25.0, 10.0);
        INFO("Measured Titan period: " << period / SECONDS_PER_DAY
             << " days (expected: ~15.95)");
        REQUIRE_THAT(period, WithinAbs(1377976.07, TITAN_PERIOD_TOL));
    }

    SECTION("Titan distance from Saturn stays within 10%") {
        check_distance_drift(&sim->bodies[13], 5, 25.0);
    }

    SECTION("All moons maintain correct parents over 60-day simulation") {
        double max_time = 60.0 * SECONDS_PER_DAY;
        std::vector<std::string> failures;
        while (sim->time < max_time) {
            update_simulation(sim);
            for (int i = 0; i < 6; i++) {
                int idx = all_moons[i].index;
                int expected = all_moons[i].parent_index;
                if (sim->bodies[idx].parent_index != expected) {
                    failures.push_back(fmt_time(sim->time) + ": " +
                                       std::string(all_moons[i].name) +
                                       " parent=" +
                                       std::to_string(sim->bodies[idx].parent_index) +
                                       " (expected " + std::to_string(expected) + ")");
                }
            }
        }
        REQUIRE(failures.empty());
    }

    SECTION("All moons complete at least one orbit") {
        wait_for_all_orbits(6);
    }

    SECTION("Moon inclined orbit produces non-zero z-coordinate") {
        double max_time = 10.0 * SECONDS_PER_DAY;
        while (sim->time < max_time) {
            update_simulation(sim);
        }

        Vec3 rel = vec3_sub(moon->global_position, earth->global_position);
        double z = rel.z;
        INFO("Moon z-coordinate relative to Earth: " << z << " m");
        INFO("Moon orbital inclination: "
             << (moon->orbit.inclination * 180.0 / M_PI) << " degrees");
        REQUIRE_THAT(z, !WithinAbs(0.0, 10000000.0));
    }

    SECTION("Moon orbital elements loaded correctly from config") {
        REQUIRE_THAT(moon->orbit.eccentricity, WithinAbs(0.055, E_TOL));
        REQUIRE_THAT(moon->orbit.inclination,
                     WithinAbs(5.16 * M_PI / 180.0, ANG_TOL));
        REQUIRE_THAT(moon->orbit.longitude_of_ascending_node,
                     WithinAbs(125.08 * M_PI / 180.0, ANG_TOL));
        REQUIRE_THAT(moon->orbit.argument_of_periapsis,
                     WithinAbs(318.15 * M_PI / 180.0, ANG_TOL));
    }

    destroy_simulation(sim);
}