scontainers/dist/decorators/map_key.js

A container/collection/iterator library for JavaScript, comfortable to use, performant and versatile.

"use strict";

function _implSymbol(target, sym, value) {
  Object.defineProperty(target, sym, {
    value,
    configurable: true
  });
  return target[sym];
}

function _getSymbol(targetSymName, ...traitSets) {
  let symbol;
  traitSets.forEach(traitSet => {
    const sym = traitSet[targetSymName];

    if (typeof sym === 'symbol') {
      if (!!symbol && symbol !== sym) {
        throw new Error(`Symbol ${targetSymName} offered by multiple trait sets.`);
      }

      symbol = sym;
    }
  });

  if (!symbol) {
    throw new Error(`No trait set is providing symbol ${targetSymName}.`);
  }

  return symbol;
}

function _testTraitSet(traitSet) {
  if (!traitSet || typeof traitSet === 'boolean' || typeof traitSet === 'number' || typeof traitSet === 'string') {
    throw new Error(`${traitSet} cannot be used as a trait set.`);
  }
}

const {
  traits,
  id
} = require('../utils.js');

_testTraitSet(traits.utils);

_testTraitSet(traits.scontainers);

_testTraitSet(traits.semantics);

const _describeScontainer = _getSymbol("describeScontainer", traits.utils, traits.scontainers, traits.semantics);

const _implCoreTraits = _getSymbol("implCoreTraits", traits.utils, traits.scontainers, traits.semantics);

const _reverse = _getSymbol("reverse", traits.utils, traits.scontainers, traits.semantics);

const _mapKey = _getSymbol("mapKey", traits.utils, traits.scontainers, traits.semantics);

module.exports = function (ParentCollection) {
  return function () {
    class MapKey {
      static get name() {
        return `${ParentCollection.name}::MapKey`;
      }

      constructor(coll, mapKeyFn) {
        this.wrapped = coll;
        this.mapKeyFn = mapKeyFn;
      }

      toString() {
        return `${this.wrapped}.mapKey(${this.mapFn.name || 'ƒ'})`;
      }

    }

    const parentProto = ParentCollection.prototype;

    MapKey[_describeScontainer]({
      InnerCollection: ParentCollection,
      innerCollectionKey: id`wrapped`,
      argKeys: [id`mapKeyFn`],
      standardIteration: true,
      transformStream: true
    });

    MapKey[_implCoreTraits]({
      stage(kvn) {
        kvn.key = this.mapKeyFn(kvn.value, kvn.key, kvn.n);
        return kvn;
      },

      nToParentN(n) {
        return n;
      },

      reverse() {
        if (parentProto[_reverse]) {
          return this.wrapped[_reverse]()[_mapKey](this.mapKeyFn);
        }
      }

    });

    return MapKey;
  };
};