require File.expand_path('../../../spec_helper', __FILE__)
require File.expand_path('../fixtures/classes', __FILE__)

describe "Enumerable#max_by" do
  it "returns an enumerator if no block" do
    EnumerableSpecs::Numerous.new(42).max_by.should be_an_instance_of(enumerator_class)
  end

  it "returns nil if #each yields no objects" do
    EnumerableSpecs::Empty.new.max_by {|o| o.nonesuch }.should == nil
  end

  it "returns the object for whom the value returned by block is the largest" do
    EnumerableSpecs::Numerous.new(*%w[1 2 3]).max_by {|obj| obj.to_i }.should == '3'
    EnumerableSpecs::Numerous.new(*%w[three five]).max_by {|obj| obj.length }.should == 'three'
  end

  it "returns the object that appears first in #each in case of a tie" do
    a, b, c = '1', '2', '2'
    EnumerableSpecs::Numerous.new(a, b, c).max_by {|obj| obj.to_i }.should equal(b)
  end

  it "uses max.<=>(current) to determine order" do
    a, b, c = (1..3).map{|n| EnumerableSpecs::ReverseComparable.new(n)}

    # Just using self here to avoid additional complexity
    EnumerableSpecs::Numerous.new(a, b, c).max_by {|obj| obj }.should == a
  end

  it "is able to return the maximum for enums that contain nils" do
    enum = EnumerableSpecs::Numerous.new(nil, nil, true)
    enum.max_by {|o| o.nil? ? 0 : 1 }.should == true
    enum.max_by {|o| o.nil? ? 1 : 0 }.should == nil
  end

  it "gathers whole arrays as elements when each yields multiple" do
    multi = EnumerableSpecs::YieldsMulti.new
    multi.max_by {|e| e.size}.should == [6, 7, 8, 9]
  end
end
