DavidBM/iterated-pipes

exports.NO_ITERABLE_ERROR = 'first argument must be an iterable item or a generator';
exports.NO_FUNCTION_CALLBACK = 'second argument must be a function';
exports.MAX_ITERATION_NOT_NUMBER = 'max iterations must be a number';

exports.isPromise = (item) => item && typeof item.then === 'function';

exports.getIterator = function getIterator(iterable) {

    if(!iterable){
        throw new TypeError(exports.NO_ITERABLE_ERROR);
    }

    if(iterable[Symbol.iterator]) {
        //It comes from Symbol.iterator, is safe to assume that is a function that returns the iteraror
        //Funny fact, we can't store the result of iterable[Symbol.iterator] in a variable and execute later because it throws an error. Not sure why.
        return iterable[Symbol.iterator]();
    }

    //if iterable[Symbol.iterator] doesn't exit, assume a generator and try to execute to get the iterator.
    //But if is not a function, return an error
    if(typeof iterable !== 'function') {
        throw new TypeError(exports.NO_ITERABLE_ERROR);
    }

    //Get the iterator from the generator
    var iterator = iterable();

    //If not iterator, error
    if(!iterator || typeof iterator.next !== 'function'){
        throw new TypeError(exports.NO_ITERABLE_ERROR);
    }

    return iterator;
};

exports.wrapIteratorForAddIndex = function wrapIteratorForAddIndex(iterator) {
    var index = 0;

    return {
        next: () => {
            var item = iterator.next();
            item.index = index;
            index++;
            return item;
        }
    };
};