class Linkable {
  constructor (_) {
    this._ = _
    this._references = []
    this._refCount = 0
    this._pendingDelete = false
    this._binding = 0
  }

  _link (b) {
    this._references.push(b)
    b._refCount += 1
    return true
  }

  _unlink (b) {
    let idx = this._references.indexOf(b)
    if (idx < 0) {
      return false
    }
    while (idx >= 0) {
      this._references[idx] = this._references[this._references.length - 1]
      this._references.pop()
      b._refCount -= 1
      b._checkDelete()
      idx = this._references.indexOf(b)
    }
    return true
  }

  _linked (b) {
    return this._references.indexOf(b) >= 0
  }

  _checkDelete () {
    if (this._refCount <= 0 &&
      this._pendingDelete &&
      this._ !== 0) {
      while (this._references.length > 0) {
        this._unlink(this._references[0])
      }
      this._performDelete()
      this._ = 0
    }
  }

  _performDelete () {}
}

module.exports = { Linkable }