#include <raylib.h>
#include <stddef.h>
#include <stdlib.h>

typedef struct Node {
    Rectangle bounds;
    Vector2 entities[4];
    int entity_count;
    struct Node* children[4];
} Node;

Node* create_node(Rectangle bounds) {
    Node* n = calloc(1, sizeof(Node));
    n->bounds = bounds;
    return n;
}

void split_node(Node* n) {
    Rectangle b = n->bounds;
    Vector2 half = (Vector2){ b.width / 2.0f, b.height / 2.0f };
    n->children[0] = create_node((Rectangle){ b.x, b.y, half.x, half.y });
    n->children[1] = create_node((Rectangle){ b.x + half.x, b.y, half.x, half.y });
    n->children[2] = create_node((Rectangle){ b.x, b.y + half.y, half.x, half.y });
    n->children[3] = create_node((Rectangle){ b.x + half.x, b.y + half.y, half.x, half.y });
}

int inside(Node* n, Vector2 p) {
    return p.x > n->bounds.x && p.x < n->bounds.x + n->bounds.width &&
            p.y > n->bounds.y && p.y < n->bounds.y + n->bounds.height;
}

int is_leaf(Node* n) {
    return 
        n->children[0] == NULL &&
        n->children[1] == NULL &&
        n->children[2] == NULL &&
        n->children[3] == NULL;
}

void add(Node* n, Vector2 p) {
    if(n->entity_count >= 4) {
        if(is_leaf(n)) {
            split_node(n);
        }

        int added = 0;
        
        for(int i = 0; i < 4; i++) {
            if(inside(n->children[i], p)) {
                add(n->children[i], p);
                added = 1;
                break;
            }
        }

        if(!added) {
            add(n->children[0], p);
        }
    } else {
        n->entities[n->entity_count++] = p;
    }
}

void draw(Vector2 p, Color c) {
    DrawCircleV(p, 5.0f, c);
}

void visualize(Node* n) {
    //DrawRectangleLinesEx(n->bounds, 1.0f, RED);

    if(!is_leaf(n)) {
        visualize(n->children[0]);
        visualize(n->children[1]);
        visualize(n->children[2]);
        visualize(n->children[3]);
    }

    Vector2 m_pos = GetMousePosition();
    
    if(inside(n, m_pos)) {
        //DrawRectangleLinesEx(n->bounds, 1.0f, BLUE);
        for(int i = 0; i < n->entity_count; i++) {
            if(CheckCollisionCircles(m_pos, 1.0f, n->entities[i], 5.0f)) {
                draw(n->entities[i], GREEN);
            } else {
                draw(n->entities[i], WHITE);
            }
        }
    } else {
        for(int i = 0; i < n->entity_count; i++) {
            draw(n->entities[i], WHITE);
        }
    }
}

int main() {
    const int width = 800;
    const int height = 600;
    InitWindow(width, height, "quadtree");

    Node* root = create_node((Rectangle){ 0.0f, 0.0f, width, height });

    for(int i = 0; i < 5000; i++) {
        add(root, (Vector2){ GetRandomValue(0, width), GetRandomValue(0, height) });
    }

    while(!WindowShouldClose()) {
        /*if(IsMouseButtonPressed(MOUSE_LEFT_BUTTON)) {
            add(root, GetMousePosition());
        }*/

        BeginDrawing();
        {
            ClearBackground(BLACK);
            visualize(root);
            DrawFPS(10, 10);
        }
        EndDrawing();
    }

    CloseWindow();
}