From 59eb99bcb849ad75f8715f5dbd56059943d66a69 Mon Sep 17 00:00:00 2001
From: Ian Katz <ikatz@drizly.com>
Date: Sat, 25 Jan 2020 00:09:29 -0500
Subject: [PATCH] Add each_line enumerator to IO class

---
 lib/piperator/io.rb       | 7 +++++++
 spec/piperator/io_spec.rb | 8 ++++++++
 2 files changed, 15 insertions(+)

diff --git a/lib/piperator/io.rb b/lib/piperator/io.rb
index abb8ff1..2bc0429 100644
--- a/lib/piperator/io.rb
+++ b/lib/piperator/io.rb
@@ -49,6 +49,13 @@ def gets(separator = $INPUT_RECORD_SEPARATOR, _limit = nil)
       read_with { @buffer.gets(separator) }
     end
 
+    # Returns an enumerator of lines in the stream, without reading the entire stream into memory
+    #
+    # @return [Enumerator]
+    def each_line
+      Enumerator.new { |y| loop { y << gets&.gsub(/#{$INPUT_RECORD_SEPARATOR}$/, '') } }.lazy.take_while(&:itself).each
+    end  
+
     # Flush internal buffer until the last unread byte
     def flush
       if @buffer.pos == @buffer_read_pos
diff --git a/spec/piperator/io_spec.rb b/spec/piperator/io_spec.rb
index 247a0dc..1770ffc 100644
--- a/spec/piperator/io_spec.rb
+++ b/spec/piperator/io_spec.rb
@@ -81,6 +81,14 @@
     end
   end
 
+  describe '#each_line' do
+    subject { Piperator::IO.new(["foo\n", "bar\n", "baz\nbmp"].each) }
+
+    it 'return enumerated lines' do
+      expect(subject.each_line.to_a).to eq(["foo", "bar", "baz", "bmp"])
+    end
+  end
+
   describe '#flush' do
     subject { Piperator::IO.new(['a' * 16 * KILOBYTE].each) }
     let(:flush_threshold) { Piperator::IO::FLUSH_THRESHOLD }