git ssb

1
module.exports = class ReferanceMap {
2
  /**
3
   * Handle mapping arbitary JS object to ints
4
   */
5
  constructor () {
6
    this.intRefProp = Symbol('int')
7
    this._map = []
8
  }
9
10
  /**
11
   * Adds an object to the referance map returning an int to be used as a
12
   * referance
13
   * @param {*} obj
14
   * @param {*} type - optional
15
   * @return {integer}
16
   */
17
  add (obj, type) {
18
    let ref = obj[this.intRefProp]
19
    if (ref === undefined) {
20
      ref = this._map.push({obj, type}) - 1
21
      obj[this.intRefProp] = ref
22
    }
23
    return ref
24
  }
25
26
  /**
27
   * gets a POJO given a refernce as an int
28
   * @param {integer} ref
29
   * @param {Object} type - optional
30
   * @return {*}
31
   */
32
  get (ref, typeCheck) {
33
    const {obj, type} = this._map[ref]
34
    if (obj === undefined || (typeCheck && type !== typeCheck)) {
35
      throw new Error('invalid referance')
36
    }
37
    return obj
38
  }
39
40
  /**
41
   * deletes an object given a referance as an int
42
   * @param {integer}
43
   * @return {boolean} whether or not the object was deleted
44
   */
45
  delete (ref) {
46
    delete this._map[ref][this.intRefProp]
47
    delete this._map[ref]
48
  }
49
50
  /**
51
   * clears the referance map of a objects
52
   */
53
  clear () {
54
    this.intRefProp = Symbol('int')
55
    this._map = []
56
  }
57
58
  /**
59
   * returns the number of items in the refernace map
60
   * @return {integer}
61
   */
62
  get size () {
63
    return this._map.length
64
  }
65
66
  /**
67
   * tests wether a given referance is valid or not
68
   * @return {boolean}
69
   */
70
  has (ref) {
71
    const obj = this._map[ref]
72
    return obj !== undefined
73
  }
74
}
75