#include "../marcher.h"
#include "../images/images.h"

#include <limits.h>

static Image* current_image;
static Scene* current_scene;
static Camera* current_camera;

Color march_ray(Point origin, Point direction, Scene* scene);
void camera_iter_callback(Point direction, int x, int y);


Scene scene_new(unsigned int width, unsigned int height, int obj_count) {
    Scene scene;
    scene.height = height;
    scene.width = width;
    scene.max_steps = 32;
    scene.threshold = 0.02;
    scene.object_count = 0;
    scene.objects = malloc(obj_count * sizeof(SceneObject));
    scene.allocated_space = obj_count;
    scene.background = color_new(0,0,0);
    return scene;
}

void scene_add_obj(Scene* scene, SceneObject object) {
    if (scene->object_count >= scene->allocated_space) return; // limit reached
    // TODO realloc

    
    scene->objects[scene->object_count] = object;
    // link containing scene
    scene->objects[scene->object_count].scene = scene;

    scene->object_count++;
}

// render out the scene with threads
// creates a shared image, so destroy with image_destroy_shared then free struct with free_shared_memory
Image* render_scene(Scene *scene, Camera *camera, unsigned int threads) {
    current_image = malloc(sizeof(Image));
    current_scene = scene;
    current_camera= camera;

    // initialize shared pixel buffer
    image_new_shared(scene->width, scene->height, current_image);

    // iterate over the rays
    camera_iterate_rays_const_dist(*camera, scene->width, scene->height, threads, camera_iter_callback);
    // or camera_iterate_rays_const_angle for lense distortion (this might not work correctly tho)

    // return the drawn image
    return current_image;
}

// march the ray, set the color. repeated for each direction generated by the camera
void camera_iter_callback(Point direction, int x, int y) {
    Color c = march_ray(current_camera->location, direction, current_scene);
    image_set_px_c(*current_image, x, y, c);
}



Color march_ray(Point origin, Point direction, Scene* scene) {
    // some local variables
    Point pos = origin;
    double closest_encounter = DBL_MAX;
    double dist = closest_encounter;
    // the closest object we have
    SceneObject* closest_obj = scene->objects;

    // get steps, threshold from scene
    int steps = scene->max_steps;
    double threshold = scene->threshold;

    // as long as we did not max out steps, or got very close to an object
    while (steps > 0 && dist > threshold) {
        dist = 100;

        // find distance to closest object
        for(int i = 0; i < scene->object_count; i++) {
            // get pointer to scene obj
            SceneObject* obj = scene->objects + i;
            double curr_dist = scene->objects[i].distance(pos, obj);

            // if we are close
            if (curr_dist < dist) {
                dist = curr_dist;
                closest_obj = obj;
            }
        }

        // write down our closest encounter
        if (dist < closest_encounter) closest_encounter = dist;

        // scale direction vector to distance, then add it to our position
        Point step_vector = pt_scale(direction, dist);
        pt_add(&pos, step_vector);

        // one step taken...
        steps--;
    }

    // check for a hit
    if (dist <= threshold) {
        // a hit!
        double f = (steps / (double) scene->max_steps);
        f = f * f * f * f;

        Color c = closest_obj->get_color(pos, direction, closest_obj);
        return color_mix(c, color_new(0,0,0), f);

    } else {
        // a miss :(
        // this should be 0!
        return scene->background;
    }
}

void scene_destroy(Scene scene) {
    for (int i = 0; i < scene.object_count; i++) {
        // free args memory
        free(scene.objects[i].args);
    }
    free(scene.objects);

}