diff -r cba9fb39bcdb -r a38e6916504c lib/ezmlm/list/thread.rb
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/ezmlm/list/thread.rb	Fri May 12 11:09:36 2017 -0700
@@ -0,0 +1,102 @@
+#!/usr/bin/ruby
+# vim: set nosta noet ts=4 sw=4:
+#
+# A collection of messages for a specific archive thread.
+#
+#    thread = Ezmlm::List::Thread.new( list, 'acgcbmbmeapgpfckcdol' )
+#    thread.subject         #=> "Help - navigate on interface?"
+#    thread.first.date.to_s #=> "2017-05-07T14:55:05-07:00"
+#
+#
+# == Version
+#
+#  $Id$
+#
+#---
+
+require 'pathname'
+require 'ezmlm' unless defined?( Ezmlm )
+
+
+### A collection of messages for a specific archive thread.
+###
+class Ezmlm::List::Thread
+	include Enumerable
+
+	### Instantiate a new thread of messages given
+	### a +list+ and a +thread_id+.
+	###
+	def initialize( list, thread_id )
+		raise ArgumentError, "Unknown list object." unless list.respond_to?( :listdir )
+		raise ArgumentError, "Malformed Thread ID." unless thread_id =~ /^\w{20}$/
+		raise "Thread indexing is not enabled." unless list.threaded?
+
+		@list     = list
+		@id       = thread_id
+		@subject  = nil
+		@messages = nil
+
+		self.load_thread
+	end
+
+
+	# The list object this message is stored in.
+	attr_reader :list
+
+	# The thread's identifier.
+	attr_reader :id
+
+	# The subject line of the thread.
+	attr_reader :subject
+
+	# An array of member messages.
+	attr_reader :messages
+
+	# An array of member authors.
+	attr_reader :authors
+
+
+	### Enumerable API:  Lazy load each message ID as a
+	### Ezmlm::List::Message, yielding it to the block.
+	###
+	def each
+		self.load_thread # refresh for any thread updates since object was created
+		self.messages.each do |id|
+			yield Ezmlm::List::Message.new( self.list, id )
+		end
+	end
+
+
+	#########
+	protected
+	#########
+
+	### Parse the subject index into an array of Messages.
+	###
+	def load_thread
+		@messages = []
+		@authors  = []
+		path = self.thread_path
+		raise "Unknown thread: %p" % [ self.id ] unless path.exist?
+
+		path.each_line.with_index do |line, i|
+			if i.zero?
+				@subject = line.match( /^\w+ (.+)/ )[1]
+			else
+				match = line.match( /^(\d+):\d+:(\w+) / ) or next
+				self.messages << match[1].to_i
+				self.authors  << match[2]
+			end
+		end
+	end
+
+
+	### Return the path on disk for the thread index.
+	###
+	def thread_path
+		prefix = self.id[ 0 ..  1 ]
+		hash   = self.id[ 2 .. -1 ]
+		return self.list.listdir + 'archive' + 'subjects' + prefix + hash
+	end
+
+end # class Ezmlm::List::Thread