JSClassID JS_NewClassID(JSRuntime *rt, JSClassID *pclass_id);

static JSClassID js_point_class_id;

// During initialization
JS_NewClassID(rt, &js_point_class_id);

typedef struct JSClassDef {
    const char *class_name;
    JSClassFinalizer *finalizer;
    JSClassGCMark *gc_mark;
    JSClassCall *call;
    JSClassExoticMethods *exotic;
} JSClassDef;

typedef void JSClassFinalizer(JSRuntime *rt, JSValueConst val);

typedef void JSClassGCMark(JSRuntime *rt, JSValueConst val,
                          JS_MarkFunc *mark_func);

int JS_NewClass(JSRuntime *rt, JSClassID class_id, const JSClassDef *class_def);

typedef struct {
    int x;
    int y;
} JSPointData;

static void js_point_finalizer(JSRuntime *rt, JSValue val)
{
    JSPointData *s = JS_GetOpaque(val, js_point_class_id);
    /* Note: 's' can be NULL in case JS_SetOpaque() was not called */
    js_free_rt(rt, s);
}

static JSClassDef js_point_class = {
    "Point",
    .finalizer = js_point_finalizer,
};

static int js_point_init(JSContext *ctx, JSModuleDef *m)
{
    JSRuntime *rt = JS_GetRuntime(ctx);
    
    /* create the Point class */
    JS_NewClassID(rt, &js_point_class_id);
    JS_NewClass(rt, js_point_class_id, &js_point_class);
    
    // ... create prototype and constructor
    
    return 0;
}

void JS_SetClassProto(JSContext *ctx, JSClassID class_id, JSValue obj);

JSValue point_proto = JS_NewObject(ctx);
JS_SetPropertyFunctionList(ctx, point_proto, js_point_proto_funcs,
                          countof(js_point_proto_funcs));

JSValue point_class = JS_NewCFunction2(ctx, js_point_ctor, "Point", 2,
                                       JS_CFUNC_constructor, 0);
JS_SetConstructor(ctx, point_class, point_proto);
JS_SetClassProto(ctx, js_point_class_id, point_proto);

JSValue JS_GetClassProto(JSContext *ctx, JSClassID class_id);

int JS_SetOpaque(JSValueConst obj, void *opaque);

void *JS_GetOpaque(JSValueConst obj, JSClassID class_id);

void *JS_GetOpaque2(JSContext *ctx, JSValueConst obj, JSClassID class_id);

static JSValue js_point_get_xy(JSContext *ctx, JSValue this_val, int magic)
{
    JSPointData *s = JS_GetOpaque2(ctx, this_val, js_point_class_id);
    if (!s)
        return JS_EXCEPTION;
    if (magic == 0)
        return JS_NewInt32(ctx, s->x);
    else
        return JS_NewInt32(ctx, s->y);
}

static JSValue js_point_set_xy(JSContext *ctx, JSValue this_val, 
                               JSValue val, int magic)
{
    JSPointData *s = JS_GetOpaque2(ctx, this_val, js_point_class_id);
    int v;
    if (!s)
        return JS_EXCEPTION;
    if (JS_ToInt32(ctx, &v, val))
        return JS_EXCEPTION;
    if (magic == 0)
        s->x = v;
    else
        s->y = v;
    return JS_UNDEFINED;
}

typedef struct {
    int x;
    int y;
} JSPointData;

static JSClassID js_point_class_id;

static void js_point_finalizer(JSRuntime *rt, JSValue val)
{
    JSPointData *s = JS_GetOpaque(val, js_point_class_id);
    js_free_rt(rt, s);
}

static JSValue js_point_norm(JSContext *ctx, JSValue this_val,
                             int argc, JSValue *argv)
{
    JSPointData *s = JS_GetOpaque2(ctx, this_val, js_point_class_id);
    if (!s)
        return JS_EXCEPTION;
    return JS_NewFloat64(ctx, sqrt((double)s->x * s->x + (double)s->y * s->y));
}

static JSClassDef js_point_class = {
    "Point",
    .finalizer = js_point_finalizer,
};

static const JSCFunctionListEntry js_point_proto_funcs[] = {
    JS_CGETSET_MAGIC_DEF("x", js_point_get_xy, js_point_set_xy, 0),
    JS_CGETSET_MAGIC_DEF("y", js_point_get_xy, js_point_set_xy, 1),
    JS_CFUNC_DEF("norm", 0, js_point_norm),
};

static int js_point_init(JSContext *ctx, JSModuleDef *m)
{
    JSRuntime *rt = JS_GetRuntime(ctx);
    
    JS_NewClassID(rt, &js_point_class_id);
    JS_NewClass(rt, js_point_class_id, &js_point_class);
    
    JSValue point_proto = JS_NewObject(ctx);
    JS_SetPropertyFunctionList(ctx, point_proto, js_point_proto_funcs,
                              countof(js_point_proto_funcs));
    
    JSValue point_class = JS_NewCFunction2(ctx, js_point_ctor, "Point", 2,
                                           JS_CFUNC_constructor, 0);
    JS_SetConstructor(ctx, point_class, point_proto);
    JS_SetClassProto(ctx, js_point_class_id, point_proto);
    
    JS_SetModuleExport(ctx, m, "Point", point_class);
    return 0;
}

JSClassID JS_GetClassID(JSValueConst v);

bool JS_IsRegisteredClass(JSRuntime *rt, JSClassID class_id);

JSAtom JS_GetClassName(JSRuntime *rt, JSClassID class_id);