require 'etc'

	# Quick address space detection, to (hopefully)

	# match the overflow size on this machine.

	#

	ADDRESS_SPACE = case [ 'i' ].pack( 'p' ).size

					when 4

						32

					when 8

						64

					end

	# Valid subdirectories/sections for subscriptions.

	SUBSCRIPTION_DIRS = %w[ deny mod digest allow ]

	###

		@name = self.read( 'outlocal' ) unless @name

		return @name

	###

		@host = self.read( 'outhost' ) unless @host

		return @host

	###

	### Return the email address of the list's owner.

	###

	def owner

		owner = self.read( 'owner' )

		return owner =~ /@/ ? owner : nil

	end

	### Return the number of messages in the list archive.

	###

		count = self.read( 'archnum' )

		return count ? Integer( count ) : 0

	end

	### Fetch a sorted Array of the email addresses for all of the list's

	### subscribers.

	###

	def subscribers

		return self.read_subscriber_dir

	end

	### Returns an Array of email addresses of people responsible for

	### moderating subscription of a closed list.

	###

	def moderators

		return self.read_subscriber_dir( 'mod' )

	end

	### Subscribe +addr+ to the list as a Moderator.

	###

	def add_moderator( *addr )

		return self.subscribe( *addr, section: 'mod' )

	end

	### Remove +addr+ from the list as a Moderator.

	###

	def remove_moderator( *addr )

		return self.unsubscribe( *addr, section: 'mod' )

	### Returns +true+ if +address+ is a subscriber to this list.

	###

	def include?( addr )

		addr.downcase!

		file = self.subscription_dir + self.hashchar( addr )

		return false unless file.exist?

		return file.read.scan( /T([^\0]+)\0/ ).flatten.include?( addr )

	end

	### Subscribe +addr+ to the list within +section+.

	###

	def subscribe( *addr, section: nil )

		addr.each do |address|

			next unless address.index( '@' )

			address.downcase!

			file = self.subscription_dir( section ) + self.hashchar( address )

			self.with_safety do

				if file.exist?

					addresses = file.read.scan( /T([^\0]+)\0/ ).flatten

					addresses << address

					file.open( 'w' ) do |f|

						f.print addresses.uniq.sort.map{|a| "T#{a}\0" }.join

					end

				else

					file.open( 'w' ) do |f|

						f.print "T%s\0" % [ address ]

					end

				end

			end

		end

	end

	### Unsubscribe +addr+ from the list within +section+.

	###

	def unsubscribe( *addr, section: nil )

		addr.each do |address|

			address.downcase!

			file = self.subscribers_dir( section ) + self.hashchar( address )

			self.with_safety do

				next unless file.exist?

				addresses = file.read.scan( /T([^\0]+)\0/ ).flatten

				addresses = addresses - [ address ]

				if addresses.empty?

					file.unlink

				else

					file.open( 'w' ) do |f|

						f.print addresses.uniq.sort.map{|a| "T#{a}\0" }.join

					end

				end

			end

		end

	end

=begin

	###

	###

	###

	###

	### Return a Mail::Message object loaded from the last post to the list. Returns

	###

				require 'pry'

				binding.pry

=end

	### Hash an email address, using the ezmlm algorithm for

	### fast user lookups.  Returns the hashed integer.

	###

	### Older ezmlm didn't lowercase addresses, anything within the last

	### decade did.  We're not going to worry about compatibility there.

	###

	### (See subhash.c in the ezmlm source.)

	###

	def subhash( addr )

		h = 5381

		over = 2 ** ADDRESS_SPACE

		addr = 'T' + addr

		addr.each_char do |c|

			h = ( h + ( h << 5 ) ) ^ c.ord

			h = h % over if h > over # emulate integer overflow

		end

		return h % 53

	end

	### Given an email address, return the ascii character.

	###

	def hashchar( addr )

		return ( self.subhash(addr) + 64 ).chr

	end

	### Just return the contents of the provided +file+, rooted

	### in the list directory.

	###

	def read( file )

		file = self.listdir + file unless file.is_a?( Pathname )

		return file.read.chomp

	rescue

		nil

	end

	### Return a Pathname to a subscription directory.

	###

	def subscription_dir( section=nil )

		section = nil if section && ! SUBSCRIPTION_DIRS.include?( section )

		if section

			return self.listdir + section + 'subscribers'

		else

			return self.listdir + 'subscribers'

		end

	end

	###

	def read_subscriber_dir( section=nil )

		directory = self.subscription_dir( section )

		return rval.flatten.sort

	end

	### Return a Pathname object for the list owner's home directory.

	###

	def homedir

		user = Etc.getpwuid( self.listdir.stat.uid )

		return Pathname( user.dir )

	end

	### Safely make modifications to a file within a list directory.

	###

	### Mail can come in at any time.  Make changes within a list

	### atomic -- if an incoming message hits when a sticky

	### is set, it is deferred to the Qmail queue.

	###

	###   - Set sticky bit on the list directory owner's homedir

	###   - Make changes with the block

	###   - Unset sticky (just back to what it was previously)

	###

	### All writes should be wrapped in this method.

	###

	def with_safety( &block )

		home = self.homedir

		mode = home.stat.mode

		home.chmod( mode | 01000 ) # enable sticky

		yield

	ensure

		home.chmod( mode )