@v4fire/core/lib/core/iter/combinators/index.js

V4Fire core library

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.sequence = sequence;
function sequence(...iterables) {
  let cursor = 0,
    iter;
  const isAsync = Object.isAsyncIterable(iterables[cursor]);
  if (isAsync) {
    return {
      [Symbol.asyncIterator]() {
        return this;
      },
      async next() {
        if (cursor >= iterables.length) {
          return Promise.resolve({
            value: undefined,
            done: true
          });
        }
        if (!Object.isTruly(iter)) {
          iter = getIter(iterables[cursor]);
        }
        let res;
        while ((res = await iter.next(), res.done) && ++cursor < iterables.length) {
          iter = getIter(iterables[cursor]);
        }
        return res;
        function getIter(obj) {
          let i;
          if (Object.isAsyncIterable(obj)) {
            i = obj[Symbol.asyncIterator]();
          } else {
            i = obj[Symbol.iterator]();
          }
          return Object.cast(i);
        }
      }
    };
  }
  return {
    [Symbol.iterator]() {
      return this;
    },
    next() {
      if (cursor >= iterables.length) {
        return {
          value: undefined,
          done: true
        };
      }
      if (!Object.isTruly(iter)) {
        iter = iterables[cursor][Symbol.iterator]();
      }
      let res;
      while ((res = iter.next(), res.done) && ++cursor < iterables.length) {
        iter = iterables[cursor][Symbol.iterator]();
      }
      return res;
    }
  };
}