src/optic_array.js

  1. import Optic from './optic.js';
  2. import { isLens, lensCap } from './utils.js';
  4. /**
  5.  * @extends Optic
  6.  */
  7. class OpticArray extends Optic {
  8.   /**
  9.    * @summary Aggregation of multiple lens applied in series
  10.    *
  11.    * @description
  12.    * Construct this using {@link module:natural-lenses#fuse}.
  13.    */
  14.   constructor(lenses) {
  15.     super();
  16.     this.lenses = lenses;
  17.   }
  19.   /**
  20.    * @inheritdoc
  21.    */
  22.   present(subject) {
  23.     if (this.lenses.length === 0) return true;
  24.     const throughLenses = this.lenses.slice(), finalLens = throughLenses.pop();
  25.     const rval = throughLenses.reduce(
  26.       (subject, lens) => lens.get(subject),
  27.       subject
  28.     );
  29.     return finalLens.present(rval);
  30.   }
  32.   /**
  33.    * @inheritdoc
  34.    */
  35.   get(subject, ...tail) {
  36.     const subjResult = Array.prototype.reduce.call(
  37.       this.lenses,
  38.       (subject, lens) => lens.get(subject),
  39.       subject
  40.     );
  41.     if (tail.length > 0) {
  42.       return isLens(subjResult) ? subjResult.get(...tail) : undefined
  43.     }
  44.     return subjResult;
  45.   }
  47.   /**
  48.    * @inheritdoc
  49.    */
  50.   get_maybe(subject, ...tail) {
  51.     const stepSubject = get_maybe_internal.call(this, {just: subject});
  52.     const subjResult = stepSubject.just;
  53.     if (tail.length > 0) {
  54.       return isLens(subjResult) ? subjResult.get_maybe(...tail) : {};
  55.     }
  56.     return stepSubject;
  57.   }
  59.   /**
  60.    * @inheritdoc
  61.    */
  62.   xformInClone_maybe(subject, fn) {
  63.     var i;
  64.     const lensSubjects = new Array(this.lenses.length);
  65.     lensSubjects[0] = {just: subject};
  66.     
  67.     const leadingLensCount = this.lenses.length - 1;
  68.     for (i = 0; i < leadingLensCount; i++) {
  69.       const l = this.lenses[i];
  70.       lensSubjects[i + 1] = l.get_maybe(lensSubjects[i].just);
  71.       if (!('just' in lensSubjects[i + 1])) {
  72.         break;
  73.       }
  74.     }
  75.     
  76.     const xformResults = new Array(this.lenses.length);
  77.     i = this.lenses.length - 1;
  78.     const xformInput_maybe = (lensSubjects[i] || {});
  79.     xformResults[i] = this.lenses[i].xformInClone_maybe(xformInput_maybe.just, fn);
  80.     if ('just' in xformInput_maybe) {
  81.       if (xformResults[i] === xformInput_maybe.just) {
  82.         return subject;
  83.       }
  84.     }
  85.     for (i = leadingLensCount - 1; i >= 0; i--) {
  86.       let lensSubject = lensSubjects[i] || {};
  87.       xformResults[i] = this.lenses[i].setInClone(lensSubject.just, xformResults[i + 1]);
  88.     }
  89.     return xformResults[0];
  90.   }
  91. }
  93. export default OpticArray;
  95. /**
  96.  * @private
  97.  * @this OpticArray
  98.  * @param {Maybe.<*>} subject_maybe
  99.  * @returns {Maybe.<*>}
  100.  */
  101. function get_maybe_internal(subject_maybe) {
  102.   let stepSubject = subject_maybe;
  103.   for (let i = 0; i < this.lenses.length; i++) {
  104.     const lens = this.lenses[i];
  105.     stepSubject = lens.get_maybe(stepSubject.just);
  106.     if (!('just' in stepSubject)) {
  107.       return {};
  108.     }
  109.   }
  110.   return stepSubject;
  111. }