require_relative '../../spec_helper'

describe "Enumerator.product" do
  it "returns a Cartesian product of enumerators" do
    enum = Enumerator.product(1..2, ["A", "B"])
    enum.to_a.should == [[1, "A"], [1, "B"], [2, "A"], [2, "B"]]
  end

  it "accepts a list of enumerators of any length" do
    enum = Enumerator.product(1..2)
    enum.to_a.should == [[1], [2]]

    enum = Enumerator.product(1..2, ["A"])
    enum.to_a.should == [[1, "A"], [2, "A"]]

    enum = Enumerator.product(1..2, ["A"], ["B"])
    enum.to_a.should == [[1, "A", "B"], [2, "A", "B"]]

    enum = Enumerator.product(2..3, ["A"], ["B"], ["C"])
    enum.to_a.should == [[2, "A", "B", "C"], [3, "A", "B", "C"]]
  end

  it "returns an enumerator with an empty array when no arguments passed" do
    enum = Enumerator.product
    enum.to_a.should == [[]]
  end

  it "returns an instance of Enumerator::Product" do
    enum = Enumerator.product
    enum.class.should == Enumerator::Product
  end

  it "accepts infinite enumerators and returns infinite enumerator" do
    enum = Enumerator.product(1.., ["A", "B"])
    enum.take(5).should == [[1, "A"], [1, "B"], [2, "A"], [2, "B"], [3, "A"]]
    enum.size.should == Float::INFINITY
  end

  it "accepts a block" do
    elems = []
    enum = Enumerator.product(1..2, ["X", "Y"]) { elems << _1 }

    elems.should == [[1, "X"], [1, "Y"], [2, "X"], [2, "Y"]]
  end

  it "returns nil when a block passed" do
    Enumerator.product(1..2) {}.should == nil
  end

  # https://bugs.ruby-lang.org/issues/19829
  it "reject keyword arguments" do
    -> {
      Enumerator.product(1..3, foo: 1, bar: 2)
    }.should.raise(ArgumentError, "unknown keywords: :foo, :bar")
  end

  it "calls only #each_entry method on arguments" do
    object = Object.new
    def object.each_entry
      yield 1
      yield 2
    end

    enum = Enumerator.product(object, ["A", "B"])
    enum.to_a.should == [[1, "A"], [1, "B"], [2, "A"], [2, "B"]]
  end

  it "raises NoMethodError when argument doesn't respond to #each_entry" do
    -> {
      Enumerator.product(Object.new).to_a
    }.should.raise(NoMethodError, /undefined method [`']each_entry' for/)
  end

  it "calls #each_entry lazily" do
    Enumerator.product(Object.new).should.is_a?(Enumerator)
  end

  it "iterates through consuming enumerator elements only once" do
    a = [1, 2, 3]
    i = 0

    enum = Enumerator.new do |y|
      while i < a.size
        y << a[i]
        i += 1
      end
    end

    Enumerator.product(['a', 'b'], enum).to_a.should == [["a", 1], ["a", 2], ["a", 3]]
  end
end
