enum_with_timeout.rb

module Enumerable
  class MaximumRuntimeExceeded < StandardError; end
  class ManuallyInterrupted < StandardError; end

  def with_timeout(timeout)
    return to_enum(:with_timeout, timeout) unless block_given?
    max_time = Time.now + timeout
    each do |elem|
      raise MaximumRuntimeExceeded if Time.now > max_time
      raise ManuallyInterrupted if Enumerable.interrupt_enumerables?
      yield elem
    end
  end

  def self.interrupt_enumerables?
    @interrupt_enumerables
  end

  def self.interrupt_enumerables!
    @interrupt_enumerables = true
  end

  def self.allow_enumerables!
    @interrupt_enumerables = false
  end
end

describe "Enumerable" do
  it "imposes a maximum runtime" do
    expect { [1, 2, 3, 4].each.with_timeout(0.1) {|v| sleep 1 } }.to raise_error(Enumerable::MaximumRuntimeExceeded)
  end

  it "can interrupt running loops" do
    expect { [1, 2].each.with_timeout(10) {|v| Enumerable.interrupt_enumerables! } }.to raise_error(Enumerable::ManuallyInterrupted)
    Enumerable.allow_enumerables!
  end

  it "doesn't change enumerable functionality" do
    expect( [1, 2, 3, 4].map.with_timeout(10) {|v| v * 2 }.to_a ).to eq([2, 4, 6, 8])
  end

  it "returns an enumerable if given without a block" do
    expect( [1, 2, 3, 4].map.with_timeout(10) ).to be_a Enumerable
  end

  it "is chainable with other enumerables" do
    expect([1, 2, 3, 4].map.with_timeout(10).with_index {|v, i| v + i }).to eq([1, 3, 5, 7])
  end

  it "works with loops" do
    expect {
      loop.with_timeout(0.1) do
        sleep 1
      end
    }.to raise_error Enumerable::MaximumRuntimeExceeded
  end
end