// Class implementing reference counting cache for objects

class RefCountedCache {

constructor() {

// The cache. The key is the object being stored in the cache.

// The value is ref count of the object. When that reaches zero,

// destroy function on the object gets called and object is removed

// from the cache.

this.cache = new Map();

}

// destroy all stored objects

destroy() {

this.cache.forEach((refCount, object) => {

object.destroy();

});

this.cache.clear();

}

// add object reference to the cache

incRef(object) {

const refCount = (this.cache.get(object) || 0) + 1;

this.cache.set(object, refCount);

}

// remove object reference from the cache

decRef(object) {

if (object) {

let refCount = this.cache.get(object);

if (refCount) {

refCount--;

if (refCount === 0) {

// destroy object and remove it from cache

this.cache.delete(object);

object.destroy();

} else {

// update new ref count in the cache

this.cache.set(object, refCount);

}

}

}

}

}

export { RefCountedCache };