Add Flows#first and Flows#last

lib/rackstash/flows.rb

@@ -82,12 +82,50 @@ module Rackstash
       @flows.empty?
     end
 
+    # @overload first
+    #   @return [Flow, nil] the first flow. If the list is empty, `nil` is
+    #     returned.
+    #
+    # @overload first(n)
+    #   @param n [Integer] the number of flows to return
+    #   @return [Array<Flow>] the first `n` flows. If the list is empty, an
+    #     empty array is returned.
+    #
+    # @return [Flow, Array<Flow>, nil]
+    # @see #last #last for the opposite effect.
+    def first(n = UNDEFINED)
+      if UNDEFINED.equal? n
+        @flows.first
+      else
+        @flows.first(n)
+      end
+    end
+
     # @return [String] a string representation of `self`
     def inspect
       id_str = Object.instance_method(:to_s).bind(self).call[2..-2]
       "#<#{id_str} #{self}>"
     end
 
+    # @overload last
+    #   @return [Flow, nil] the last flow. If the list is empty, `nil` is
+    #     returned.
+    #
+    # @overload last(n)
+    #   @param n [Integer] the number of flows to return
+    #   @return [Array<Flow>] the last `n` flows. If the list is empty, an empty
+    #     array is returned.
+    #
+    # @return [Flow, Array<Flow>, nil]
+    # @see #first #first for the opposite effect.
+    def last(n = UNDEFINED)
+      if UNDEFINED.equal? n
+        @flows.last
+      else
+        @flows.last(n)
+      end
+    end
+
     # @return [Integer] the number of elements in `self`. May be zero.
     def length
       @flows.length

spec/rackstash/flows_spec.rb

@@ -161,6 +161,25 @@ describe Rackstash::Flows do
     end
   end
 
+  describe '#first' do
+    it 'gets the first flow' do
+      expect(flows.first).to be_nil
+
+      flows << a_flow
+      expect(flows.first).to equal flows[0]
+    end
+
+    it 'gets a number of flows' do
+      flow_list = [a_flow, a_flow, a_flow]
+      flow_list.each do |flow|
+        flows << flow
+      end
+
+      expect(flows.first(2)).to eql flow_list[0, 2]
+      expect(flows.first(4)).to eql flow_list
+    end
+  end
+
   describe '#inspect' do
     it 'formats the object' do
       expect(flows).to receive(:to_s).and_return('["<flow>"]')
@@ -170,6 +189,25 @@ describe Rackstash::Flows do
     end
   end
 
+  describe '#last' do
+    it 'gets the last flow' do
+      expect(flows.last).to be_nil
+
+      flows << a_flow
+      expect(flows.last).to equal flows[0]
+    end
+
+    it 'gets a number of flows' do
+      flow_list = [a_flow, a_flow, a_flow]
+      flow_list.each do |flow|
+        flows << flow
+      end
+
+      expect(flows.last(2)).to eql flow_list[1, 2]
+      expect(flows.last(4)).to eql flow_list
+    end
+  end
+
   describe '#length' do
     it 'returns the number of flows' do
       expect { flows << a_flow }