#include "renderer.h"
#include "raymath.h"
#include <cmath>
#include <cstdio>

// Initialize raylib window
void init_renderer(int width, int height, const char* title) {
    InitWindow(width, height, title);
    SetTargetFPS(60);
}

// Close raylib
void close_renderer() {
    CloseWindow();
}

// Setup the 3D camera
void setup_camera(RenderState* render_state) {
    render_state->camera.position = (Vector3){ 0.0f, 50.0f, 100.0f };
    render_state->camera.target = (Vector3){ 0.0f, 0.0f, 0.0f };
    render_state->camera.up = (Vector3){ 0.0f, 1.0f, 0.0f };
    render_state->camera.fovy = 45.0f;
    render_state->camera.projection = CAMERA_PERSPECTIVE;

    // Set scaling factors (same scale for distances and sizes)
    render_state->distance_scale = 1e-9;  // Meters to scaled units (1 unit = 1 billion meters)
    render_state->size_scale = 1e-9;      // Same scale for body sizes (minimum size still applies)
    render_state->show_info = true;
}

// Update camera with keyboard/mouse controls
void update_camera(RenderState* render_state) {
    // Orbital camera rotation with arrow keys
    float camera_distance = Vector3Distance(render_state->camera.position, render_state->camera.target);
    float angle_speed = 0.02f;

    // Rotate around target
    if (IsKeyDown(KEY_LEFT)) {
        Vector3 pos = render_state->camera.position;
        float angle = angle_speed;
        float x = pos.x * cosf(angle) - pos.z * sinf(angle);
        float z = pos.x * sinf(angle) + pos.z * cosf(angle);
        render_state->camera.position.x = x;
        render_state->camera.position.z = z;
    }
    if (IsKeyDown(KEY_RIGHT)) {
        Vector3 pos = render_state->camera.position;
        float angle = -angle_speed;
        float x = pos.x * cosf(angle) - pos.z * sinf(angle);
        float z = pos.x * sinf(angle) + pos.z * cosf(angle);
        render_state->camera.position.x = x;
        render_state->camera.position.z = z;
    }

    // Zoom in/out with up/down keys
    if (IsKeyDown(KEY_UP) && camera_distance > 10.0f) {
        Vector3 direction = Vector3Subtract(render_state->camera.target, render_state->camera.position);
        direction = Vector3Normalize(direction);
        render_state->camera.position = Vector3Add(render_state->camera.position, Vector3Scale(direction, 2.0f));
    }
    if (IsKeyDown(KEY_DOWN)) {
        Vector3 direction = Vector3Subtract(render_state->camera.position, render_state->camera.target);
        direction = Vector3Normalize(direction);
        render_state->camera.position = Vector3Add(render_state->camera.position, Vector3Scale(direction, 2.0f));
    }

    // Toggle info display with I key
    if (IsKeyPressed(KEY_I)) {
        render_state->show_info = !render_state->show_info;
    }
}

// Transform from simulation coordinates (XY plane) to render coordinates (XZ plane)
// Rotation matrix: 90 degrees around X-axis maps Y -> Z
Vector3 sim_to_render(Vec3 pos, double scale) {
    return (Vector3){
        (float)(pos.x * scale),
        (float)(-pos.z * scale),
        (float)(pos.y * scale)
    };
}

// Scale a radius for rendering (with minimum visible size)
float scale_radius(double radius, double scale) {
    float scaled = (float)(radius * scale);
    float min_radius = 0.5f;  // Minimum visible radius
    return (scaled > min_radius) ? scaled : min_radius;
}

// Render a single celestial body
void render_body(CelestialBody* body, RenderState* render_state) {
    Vector3 position = sim_to_render(body->position, render_state->distance_scale);
    float radius = scale_radius(body->radius, render_state->size_scale);

    Color color = {
        (unsigned char)(body->color[0] * 255),
        (unsigned char)(body->color[1] * 255),
        (unsigned char)(body->color[2] * 255),
        255
    };

    DrawSphereWires(position, radius, 16, 16, color);
}

struct OrbitalBasis {
    Vec3 periapsis_dir;
    Vec3 normal;
    Vec3 q_vec;
};

static OrbitalBasis calculate_orbital_basis(Vec3 r_vec, Vec3 velocity, Vec3 e_vec) {
    OrbitalBasis basis;
    basis.periapsis_dir = vec3_normalize(e_vec);

    Vec3 h_vec = {
        r_vec.y * velocity.z - r_vec.z * velocity.y,
        r_vec.z * velocity.x - r_vec.x * velocity.z,
        r_vec.x * velocity.y - r_vec.y * velocity.x
    };
    basis.normal = vec3_normalize(h_vec);

    basis.q_vec = {
        basis.normal.y * basis.periapsis_dir.z - basis.normal.z * basis.periapsis_dir.y,
        basis.normal.z * basis.periapsis_dir.x - basis.normal.x * basis.periapsis_dir.z,
        basis.normal.x * basis.periapsis_dir.y - basis.normal.y * basis.periapsis_dir.x
    };

    return basis;
}

static Vec3 orbital_to_cartesian(double x, double y, OrbitalBasis basis, Vec3 parent_pos) {
    return {
        basis.periapsis_dir.x * x + basis.q_vec.x * y + parent_pos.x,
        basis.periapsis_dir.y * x + basis.q_vec.y * y + parent_pos.y,
        basis.periapsis_dir.z * x + basis.q_vec.z * y + parent_pos.z
    };
}

static void draw_orbit_segment(double x1, double y1, double x2, double y2,
                               OrbitalBasis basis, Vec3 parent_pos,
                               RenderState* render_state, Color color) {
    Vec3 p1_sim = orbital_to_cartesian(x1, y1, basis, parent_pos);
    Vec3 p2_sim = orbital_to_cartesian(x2, y2, basis, parent_pos);

    Vector3 p1 = sim_to_render(p1_sim, render_state->distance_scale);
    Vector3 p2 = sim_to_render(p2_sim, render_state->distance_scale);

    DrawLine3D(p1, p2, color);
}

static void render_elliptical_orbit(double a, double e, OrbitalBasis basis,
                                   Vec3 parent_pos, RenderState* render_state, Color color) {
    double b = a * sqrt(1.0 - e * e);
    double c = a * e;

    int segments = 100;
    for (int i = 0; i < segments; i++) {
        float theta1 = (float)i / segments * 2.0f * PI;
        float theta2 = (float)(i + 1) / segments * 2.0f * PI;

        double x1 = a * cos(theta1) - c;
        double y1 = b * sin(theta1);
        double x2 = a * cos(theta2) - c;
        double y2 = b * sin(theta2);

        draw_orbit_segment(x1, y1, x2, y2, basis, parent_pos, render_state, color);
    }
}

static void render_hyperbolic_orbit(double p, double e, OrbitalBasis basis,
                                    Vec3 parent_pos, RenderState* render_state, Color color) {
    double max_true_anomaly = (e > 1.01) ? acos(-1.0 / e) * 0.95 : PI * 0.48;

    int segments = 60;
    for (int i = 0; i < segments; i++) {
        float theta1 = -max_true_anomaly + (float)i / segments * 2.0f * max_true_anomaly;
        float theta2 = -max_true_anomaly + (float)(i + 1) / segments * 2.0f * max_true_anomaly;

        double r1 = p / (1.0 + e * cos(theta1));
        double r2 = p / (1.0 + e * cos(theta2));

        double x1 = r1 * cos(theta1);
        double y1 = r1 * sin(theta1);
        double x2 = r2 * cos(theta2);
        double y2 = r2 * sin(theta2);

        draw_orbit_segment(x1, y1, x2, y2, basis, parent_pos, render_state, color);
    }
}

// Render orbit path for a body
void render_orbit(CelestialBody* body, CelestialBody* parent, RenderState* render_state) {
    if (body->parent_index == -1 || parent == NULL) {
        return;
    }

    Vec3 r_vec = vec3_sub(body->position, parent->position);
    double r = vec3_magnitude(r_vec);
    double v = vec3_magnitude(body->velocity);

    if (r < 1.0) return;

    double mu = G * parent->mass;
    double specific_energy = (v * v) / 2.0 - mu / r;

    double v_squared = v * v;
    double r_dot_v = r_vec.x * body->velocity.x + r_vec.y * body->velocity.y + r_vec.z * body->velocity.z;
    Vec3 e_vec = {
        (v_squared - mu / r) * r_vec.x - r_dot_v * body->velocity.x,
        (v_squared - mu / r) * r_vec.y - r_dot_v * body->velocity.y,
        (v_squared - mu / r) * r_vec.z - r_dot_v * body->velocity.z
    };
    double e = vec3_magnitude(e_vec) / mu;

    Color orbit_color = {
        (unsigned char)(body->color[0] * 128),
        (unsigned char)(body->color[1] * 128),
        (unsigned char)(body->color[2] * 128),
        128
    };

    OrbitalBasis basis = calculate_orbital_basis(r_vec, body->velocity, e_vec);

    if (e < 0.98) {
        double a = -mu / (2.0 * specific_energy);
        if (a <= 0.0) return;

        render_elliptical_orbit(a, e, basis, parent->position, render_state, orbit_color);
    } else {
        double a = (e > 1.01) ? mu / (2.0 * (-specific_energy)) : r / (1.0 + e);
        double p = a * (1.0 - e * e);

        if (p <= 0.0) return;

        render_hyperbolic_orbit(p, e, basis, parent->position, render_state, orbit_color);
    }
}

// Render the entire simulation
void render_simulation(SimulationState* sim, RenderState* render_state) {
    BeginDrawing();
    ClearBackground(BLACK);

    BeginMode3D(render_state->camera);

    // Draw a subtle reference grid
    for (int i = -50; i <= 50; i++) {
        if (i == 0) continue;
        DrawLine3D((Vector3){(float)i * 10.0f, 0, -500.0f},
                   (Vector3){(float)i * 10.0f, 0, 500.0f},
                   (Color){20, 20, 20, 255});
        DrawLine3D((Vector3){-500.0f, 0, (float)i * 10.0f},
                   (Vector3){500.0f, 0, (float)i * 10.0f},
                   (Color){20, 20, 20, 255});
    }
    DrawLine3D((Vector3){0, 0, -500.0f}, (Vector3){0, 0, 500.0f}, (Color){40, 40, 40, 255});
    DrawLine3D((Vector3){-500.0f, 0, 0}, (Vector3){500.0f, 0, 0}, (Color){40, 40, 40, 255});

    // Render orbit paths first
    for (int i = 0; i < sim->body_count; i++) {
        CelestialBody* body = &sim->bodies[i];
        if (body->parent_index >= 0 && body->parent_index < sim->body_count) {
            CelestialBody* parent = &sim->bodies[body->parent_index];
            render_orbit(body, parent, render_state);
        }
    }

    // Render all bodies
    for (int i = 0; i < sim->body_count; i++) {
        render_body(&sim->bodies[i], render_state);
    }

    EndMode3D();

    // Render 2D info overlay
    if (render_state->show_info) {
        render_info(sim, "solar_system.txt");
    }

    EndDrawing();
}

// Render simulation information overlay
void render_info(SimulationState* sim, const char* config_name) {
    DrawText("Orbital Mechanics Simulation", 10, 10, 20, WHITE);

    char buffer[256];

    // Simulation time (in days)
    double days = sim->time / 86400.0;  // seconds to days
    snprintf(buffer, sizeof(buffer), "Time: %.2f days", days);
    DrawText(buffer, 10, 40, 16, LIGHTGRAY);

    // Body count
    snprintf(buffer, sizeof(buffer), "Bodies: %d", sim->body_count);
    DrawText(buffer, 10, 60, 16, LIGHTGRAY);

    // Config name
    snprintf(buffer, sizeof(buffer), "Config: %s", config_name);
    DrawText(buffer, 10, 80, 16, LIGHTGRAY);

    // FPS
    snprintf(buffer, sizeof(buffer), "FPS: %d", GetFPS());
    DrawText(buffer, 10, 100, 16, LIGHTGRAY);

    // Controls
    DrawText("Controls:", 10, 130, 16, YELLOW);
    DrawText("  Arrows: Rotate/Zoom camera", 10, 150, 14, LIGHTGRAY);
    DrawText("  Space: Pause/Resume", 10, 170, 14, LIGHTGRAY);
    DrawText("  +/-: Speed up/slow down", 10, 190, 14, LIGHTGRAY);
    DrawText("  I: Toggle info", 10, 210, 14, LIGHTGRAY);
    DrawText("  ESC: Quit", 10, 230, 14, LIGHTGRAY);
}