scontainers/dist/decorators/entries.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,
  KVIt,
  Done
} = require('../utils.js');

_testTraitSet(traits.utils);

_testTraitSet(traits.scontainers);

_testTraitSet(traits.semantics);

const _kvIterator = _getSymbol("kvIterator", traits.utils, traits.scontainers, traits.semantics);

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

const _implTraits = _getSymbol("implTraits", traits.utils, traits.scontainers, traits.semantics);

const _implCoreGenerators = _getSymbol("implCoreGenerators", traits.utils, traits.scontainers, traits.semantics);

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

module.exports = function (ParentCollection) {
  if (!ParentCollection.prototype[_kvIterator]) {
    return;
  }

  return function () {
    class Entries {
      static get name() {
        return `${ParentCollection.name}::Entries`;
      }

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

      toString() {
        return `${this.wrapped}.entries()`;
      }

    }

    Entries.Iterator = class {
      constructor(it) {
        this.it = it;
      }

      next() {
        const next = this.it.next();

        if (!next) {
          return new Done();
        }

        const {
          key,
          value
        } = next;
        return new KVIt(key, value);
      }

    };

    Entries[_describeScontainer]({
      InnerCollection: ParentCollection,
      innerCollectionKey: id`wrapped`,
      argKeys: [],
      mappingOnly: true
    });

    traits.scontainers[_implTraits](Entries.prototype, {
      iterator() {
        return new Entries.Iterator(this.wrapped[_kvIterator]());
      }

    });

    Entries[_implCoreGenerators]({
      stage(kvn) {
        return kvn;
      },

      indexToParentIndex(index) {
        return index;
      }

    });

    Entries[_implCoreTraits]({
      stage(kvn) {
        return kvn;
      },

      indexToParentIndex(index) {
        return index;
      }

    });

    return Entries;
  };
};