src/optic_array.js

  1. import { isEmpty, isUndefined, reduce, reduceRight } from 'underscore';
  2. import Optic from './optic.js';
  3. import { isLens, lensCap } from './utils.js';
  5. /**
  6.  * @extends Optic
  7.  */
  8. class OpticArray extends Optic {
  9.   /**
  10.    * @summary Aggregation of multiple lens applied in series
  11.    *
  12.    * @description
  13.    * Construct this using {@link module:natural-lenses#fuse}.
  14.    */
  15.   constructor(lenses) {
  16.     super();
  17.     this.lenses = lenses;
  18.   }
  20.   /**
  21.    * @inheritdoc
  22.    */
  23.   present(subject) {
  24.     if (this.lenses.length === 0) return true;
  25.     const throughLenses = this.lenses.slice(), finalLens = throughLenses.pop();
  26.     const rval = reduce(
  27.       throughLenses,
  28.       (subject, lens) => lens.get(subject),
  29.       subject
  30.     );
  31.     return finalLens.present(rval);
  32.   }
  34.   /**
  35.    * @inheritdoc
  36.    */
  37.   get(subject, ...tail) {
  38.     const subjResult = reduce(
  39.       this.lenses,
  40.       (subject, lens) => lens.get(subject),
  41.       subject
  42.     );
  43.     if (tail.length > 0) {
  44.       return isLens(subjResult) ? subjResult.get(...tail) : undefined
  45.     }
  46.     return subjResult;
  47.   }
  49.   /**
  50.    * @inheritdoc
  51.    */
  52.   get_maybe(subject, ...tail) {
  53.     const stepSubject = get_maybe_internal.call(this, {just: subject});
  54.     const subjResult = stepSubject.just;
  55.     if (tail.length > 0) {
  56.       return isLens(subjResult) ? subjResult.get_maybe(...tail) : {};
  57.     }
  58.     return stepSubject;
  59.   }
  61.   /**
  62.    * @inheritdoc
  63.    */
  64.   xformInClone_maybe(subject, fn) {
  65.     var i;
  66.     const lensSubjects = new Array(this.lenses.length);
  67.     lensSubjects[0] = {just: subject};
  68.     
  69.     const leadingLensCount = this.lenses.length - 1;
  70.     for (i = 0; i < leadingLensCount; i++) {
  71.       const l = this.lenses[i];
  72.       lensSubjects[i + 1] = l.get_maybe(lensSubjects[i].just);
  73.       if (!('just' in lensSubjects[i + 1])) {
  74.         break;
  75.       }
  76.     }
  77.     
  78.     const xformResults = new Array(this.lenses.length);
  79.     i = this.lenses.length - 1;
  80.     const xformInput_maybe = (lensSubjects[i] || {});
  81.     xformResults[i] = this.lenses[i].xformInClone_maybe(xformInput_maybe.just, fn);
  82.     if ('just' in xformInput_maybe) {
  83.       if (xformResults[i] === xformInput_maybe.just) {
  84.         return subject;
  85.       }
  86.     }
  87.     for (i = leadingLensCount - 1; i >= 0; i--) {
  88.       let lensSubject = lensSubjects[i] || {};
  89.       xformResults[i] = this.lenses[i].setInClone(lensSubject.just, xformResults[i + 1]);
  90.     }
  91.     return xformResults[0];
  92.   }
  93. }
  95. export default OpticArray;
  97. /**
  98.  * @private
  99.  * @this OpticArray
  100.  * @param {Maybe.<*>} subject_maybe
  101.  * @returns {Maybe.<*>}
  102.  */
  103. function get_maybe_internal(subject_maybe) {
  104.   let stepSubject = subject_maybe;
  105.   for (let i = 0; i < this.lenses.length; i++) {
  106.     const lens = this.lenses[i];
  107.     stepSubject = lens.get_maybe(stepSubject.just);
  108.     if (isEmpty(stepSubject.just)) {
  109.       return {};
  110.     }
  111.   }
  112.   return stepSubject;
  113. }