iter-tools-es/internal/parts-iterator.js

The iterable toolbox

const {
  split
} = require('./symbols.js');

const {
  IterableIterator
} = require('./iterable-iterator.js');

const {
  Peekerator
} = require('./peekerator.js');

class PartIterator extends IterableIterator {
  constructor(partsIterator) {
    super();
    this.partsIterator = partsIterator;
    this.inactive = false;
    this.done = false;
  }

  assertActive() {
    if (this.inactive && !this.done) {
      throw new Error('Cannot take from this split part. It is no longer the active part.');
    }
  }

  next() {
    const {
      spliterator
    } = this.partsIterator;
    const {
      current
    } = spliterator;
    this.assertActive();

    if (this.done || current.done || current.value === split) {
      this.done = true;
      this.partsIterator.maybeReturnSource();
      return {
        value: undefined,
        done: true
      };
    } else {
      spliterator.advance();
      return current;
    }
  }

  return() {
    this.done = true;
    this.partsIterator.maybeReturnSource();
    return {
      value: undefined,
      done: true
    };
  }

  throw() {
    return this.return();
  }

}

exports.PartIterator = PartIterator;

class PartsIterator extends IterableIterator {
  constructor(source, strategy, options) {
    super();
    this.source = source;
    this.strategy = strategy;
    this.options = options;
    this.initialized = false;
    this.returned = false;
    this.spliterator = null;
    this.currentPart = null;
    this.splitStep = null;
  }

  init() {
    this.initialized = true;
    const {
      source,
      strategy,
      options
    } = this;
    this.spliterator = Peekerator.from(strategy(split, options, source));
  }

  maybeReturnSource() {
    if (this.spliterator && this.returned && this.currentPart.done) {
      this.spliterator.return();
    }
  }

  next() {
    if (!this.initialized) this.init();
    const {
      spliterator
    } = this;

    if (spliterator.done) {
      return {
        value: undefined,
        done: true
      };
    }

    if (this.currentPart !== null) {
      if (spliterator.value !== split || spliterator.current === this.splitStep) {
        this.currentPart.inactive = true;

        while (!spliterator.done && spliterator.value !== split) {
          spliterator.advance();
        }
      }

      spliterator.advance();
    }

    this.splitStep = spliterator.current;
    this.currentPart = new PartIterator(this);
    return {
      value: this.currentPart,
      done: false
    };
  }

  return(value) {
    this.returned = true;
    this.maybeReturnSource();
    return {
      value,
      done: true
    };
  }

  throw() {
    return this.return();
  }

}

exports.PartsIterator = PartsIterator;