#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>

#define exec(Object, Method) Object->table.Method()

typedef int32_t int32;
typedef uint8_t uint8;

typedef void (*set_fcn_ptr) (void*, int32);
typedef int32 (*get_fcn_ptr) (void*);
typedef void (*display_fcn_ptr) (void);

typedef struct {
    set_fcn_ptr set_x;
    get_fcn_ptr get_x;

    set_fcn_ptr set_y;
    get_fcn_ptr get_y;

    display_fcn_ptr display;
} VTable;

/*
================================================================================
*/

typedef struct {
    VTable table;

    int32 x;
    int32 y;
} Shape;

void shape_set_x(Shape* shape, int32 x) { shape->x = x; }
void shape_set_y(Shape* shape, int32 y) { shape->y = y; }
int32 shape_get_x(Shape* shape) { return shape->x; }
int32 shape_get_y(Shape* shape) { return shape->y; }
void shape_display(Shape* shape) { fputs("Shape", stdout); }

Shape* make_shape(int32 x, int32 y)
{
    Shape* shape = malloc(sizeof(Shape));
    VTable* vtable = &shape->table;

    vtable->set_x = shape_set_x;
    vtable->set_y = shape_set_y;
    vtable->get_x = shape_get_x;
    vtable->get_y = shape_get_y;
    vtable->display = shape_display;

    shape->x = x;
    shape->y = y;
}

/*
================================================================================
*/

typedef struct {
    Shape base;

    size_t width;
    size_t height;
} Rectangle;

void rect_set_x(Rectangle* rect, int32 x) { rect->base.x = x; }
void rect_set_y(Rectangle* rect, int32 y) { rect->base.y = y; }
int32 rect_get_x(Rectangle* rect) { return rect->base.x; }
int32 rect_get_y(Rectangle* rect) { return rect->base.y; }
void rect_display(Rectangle* rect) { fputs("Rectangle", stdout); }

Rectangle* make_rectangle(int32 x, int32 y, size_t w, size_t h)
{
    Rectangle* rect = malloc(sizeof(Rectangle));

    VTable* vtable = &rect->base.table;

    vtable->set_x = rect_set_x;
    vtable->set_y = rect_set_y;
    vtable->get_x = rect_get_x;
    vtable->get_y = rect_get_y;
    vtable->display = rect_display;

    rect->base.x = x;
    rect->base.y = y;
    rect->width = w;
    rect->height = h;
}

/*
================================================================================
*/

int main()
{
    Shape* shapes[4];

    shapes[0] = make_shape(3, 5);
    shapes[1] = make_rectangle(7, 2, 10, 10);
    shapes[2] = make_shape(10, 2);
    shapes[3] = make_rectangle(0, 7, 50, 50);

    for (uint8 i = 0; i < 4; ++i) {
        exec(shapes[i], display);
    }

    return 0;
}