1 files changed, 121 insertions, 0 deletions
diff --git a/lib/gitlab/ci/trace/stream.rb b/lib/gitlab/ci/trace/stream.rb
new file mode 100644
index 00000000000..fa462cbe095
--- /dev/null
+++ b/lib/gitlab/ci/trace/stream.rb
@@ -0,0 +1,121 @@
+module Gitlab
+  module Ci
+    class Trace
+      # This was inspired from: http://stackoverflow.com/a/10219411/1520132
+      class Stream
+        BUFFER_SIZE = 4096
+        LIMIT_SIZE = 500.kilobytes
+
+        attr_reader :stream
+
+        delegate :close, :tell, :seek, :size, :path, :truncate, to: :stream, allow_nil: true
+
+        delegate :valid?, to: :stream, as: :present?, allow_nil: true
+
+        def initialize
+          @stream = yield
+          @stream&.binmode
+        end
+
+        def valid?
+          self.stream.present?
+        end
+
+        def file?
+          self.path.present?
+        end
+
+        def limit(last_bytes = LIMIT_SIZE)
+          if last_bytes < size
+            stream.seek(-last_bytes, IO::SEEK_END)
+            stream.readline
+          end
+        end
+
+        def append(data, offset)
+          stream.truncate(offset)
+          stream.seek(0, IO::SEEK_END)
+          stream.write(data)
+          stream.flush()
+        end
+
+        def set(data)
+          truncate(0)
+          stream.write(data)
+          stream.flush()
+        end
+
+        def raw(last_lines: nil)
+          return unless valid?
+
+          if last_lines.to_i > 0
+            read_last_lines(last_lines)
+          else
+            stream.read
+          end.force_encoding(Encoding.default_external)
+        end
+
+        def html_with_state(state = nil)
+          ::Ci::Ansi2html.convert(stream, state)
+        end
+
+        def html(last_lines: nil)
+          text = raw(last_lines: last_lines)
+          buffer = StringIO.new(text)
+          ::Ci::Ansi2html.convert(buffer).html
+        end
+
+        def extract_coverage(regex)
+          return unless valid?
+          return unless regex
+
+          regex = Regexp.new(regex)
+
+          match = ""
+
+          stream.each_line do |line|
+            matches = line.scan(regex)
+            next unless matches.is_a?(Array)
+            next if matches.empty?
+
+            match = matches.flatten.last
+            coverage = match.gsub(/\d+(\.\d+)?/).first
+            return coverage if coverage.present?
+          end
+
+          nil
+        rescue
+          # if bad regex or something goes wrong we dont want to interrupt transition
+          # so we just silentrly ignore error for now
+        end
+
+        private
+
+        def read_last_lines(last_lines)
+          chunks = []
+          pos = lines = 0
+          max = stream.size
+
+          # We want an extra line to make sure fist line has full contents
+          while lines <= last_lines && pos < max
+            pos += BUFFER_SIZE
+
+            buf =
+              if pos <= max
+                stream.seek(-pos, IO::SEEK_END)
+                stream.read(BUFFER_SIZE)
+              else # Reached the head, read only left
+                stream.seek(0)
+                stream.read(BUFFER_SIZE - (pos - max))
+              end
+
+            lines += buf.count("\n")
+            chunks.unshift(buf)
+          end
+
+          chunks.join.lines.last(last_lines).join
+        end
+      end
+    end
+  end
+end