git ssb

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module.exports = class ReferanceMap {
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  /**
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   * Handle mapping arbitary JS object to ints
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   */
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  constructor () {
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    this.intRefProp = Symbol('int')
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    this._map = []
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  }
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  /**
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   * Adds an object to the referance map returning an int to be used as a
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   * referance
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   * @param {*} obj
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   * @param {*} type - optional
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   * @return {integer}
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   */
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  add (obj, type) {
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    let ref = obj[this.intRefProp]
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    if (ref === undefined) {
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      ref = this._map.push({obj, type}) - 1
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      obj[this.intRefProp] = ref
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    }
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    return ref
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  }
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  /**
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   * gets a POJO given a refernce as an int
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   * @param {integer} ref
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   * @param {Object} type - optional
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   * @return {*}
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   */
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  get (ref, typeCheck) {
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    const {obj, type} = this._map[ref]
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    if (obj === undefined || (typeCheck && type !== typeCheck)) {
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      throw new Error('invalid referance')
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    }
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    return obj
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  }
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  /**
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   * deletes an object given a referance as an int
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   * @param {integer}
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   * @return {boolean} whether or not the object was deleted
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   */
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  delete (ref) {
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    delete this._map[ref].obj[this.intRefProp]
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    delete this._map[ref]
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  }
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  /**
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   * clears the referance map of a objects
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   */
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  clear () {
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    this._map.forEach(el => {
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      delete el.obj[this.intRefProp]
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    })
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    this._map = []
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  }
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  /**
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   * returns the number of items in the refernace map
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   * @return {integer}
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   */
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  get size () {
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    return this._map.length
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  }
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  /**
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   * tests wether a given referance is valid or not
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   * @return {boolean}
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   */
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  has (ref) {
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    const obj = this._map[ref]
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    return obj !== undefined
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  }
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}
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