lsyncd.lua

--~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- lsyncd.lua   Live (Mirror) Syncing Demon
--
-- This is the "runner" part of Lsyncd. It containts all its high-level logic.
-- It works closely together with the Lsyncd core in lsyncd.c. This means it
-- cannot be runned directly from the standard lua interpreter.
--
-- This code assumes your editor is at least 100 chars wide.
--
-- License: GPLv2 (see COPYING) or any later version
-- Authors: Axel Kittenberger <axkibe@gmail.com>
--
--~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

-- require('profiler')
-- profiler.start()

--
-- A security measurement.
-- The core will exit if version ids mismatch.
--
if lsyncd_version then

	-- ensures the runner is not being loaded twice
	lsyncd.log(
		'Error',
		'You cannot use the lsyncd runner as configuration file!'
	)

	lsyncd.terminate( -1 )
end

lsyncd_version = '2.1.5'

--
-- Hides the core interface from user scripts.
--
local _l = lsyncd
lsyncd = nil
local lsyncd = _l
_l = nil

--
-- Shortcuts (which user is supposed to be able to use them as well)
--
log       = lsyncd.log
terminate = lsyncd.terminate
now       = lsyncd.now
readdir   = lsyncd.readdir

--
-- Coping globals to ensure userscripts don't change this.
--
local log       = log
local terminate = terminate
local now       = now

--
-- Predeclarations
--
local Monitors

--
-- Global: total number of processess running
--
local processCount = 0

--
-- Settings specified by command line.
--
local clSettings = { }

--
-- Settings specified by config scripts.
--
local uSettings = { }

--
-- A copy of the settings function to see if the
-- user script replaced the settings() by a table
-- ( pre Lsyncd 2.1 style )
--
local settingsSafe

--============================================================================
-- Lsyncd Prototypes
--============================================================================

--
-- Array tables error if accessed with a non-number.
--
local Array = ( function( )

	-- Metatable
	local mt = { }

	-- on accessing a nil index.
	mt.__index = function( t, k )
		if type(k) ~= 'number' then
			error( 'Key "'..k..'" invalid for Array', 2 )
		end
		return rawget( t, k )
	end

	-- on assigning a new index.
	mt.__newindex = function( t, k, v )
		if type( k ) ~= 'number' then
			error( 'Key "'..k..'" invalid for Array', 2 )
		end
		rawset( t, k, v )
	end

	-- creates a new object
	local function new( )
		local o = { }
		setmetatable( o, mt )
		return o
	end

	--
	-- Public interface
	--
	return { new = new }

end )( )


--
-- Count array tables error if accessed with a non-number.
--
-- Additionally they maintain their length as 'size' attribute,
-- since Lua's # operator does not work on tables whose key values are not
-- strictly linear.
--
local CountArray = ( function( )

	--
	-- Metatable
	--
	local mt = { }

	--
	-- Key to native table
	--
	local k_nt = { }

	--
	-- On accessing a nil index.
	--
	mt.__index = function( t, k )
		if type( k ) ~= 'number' then
			error( 'Key "'..k..'" invalid for CountArray', 2 )
		end
		return t[ k_nt ][ k ]
	end

	--
	-- On assigning a new index.
	--
	mt.__newindex = function( t, k, v )

		if type(k) ~= 'number' then
			error( 'Key "'..k..'" invalid for CountArray', 2 )
		end

		-- value before
		local vb = t[ k_nt ][ k ]
		if v and not vb then
			t._size = t._size + 1
		elseif not v and vb then
			t._size = t._size - 1
		end
		t[ k_nt ][ k ] = v
	end

	--
	-- Walks through all entries in any order.
	--
	local function walk( self )
		return pairs( self[ k_nt ] )
	end

	--
	-- Returns the count
	--
	local function size( self )
		return self._size
	end

	--
	-- Creates a new count array
	--
	local function new( )

		-- k_nt is native table, private for this object.
		local o = {
			_size = 0,
			walk = walk,
			size = size,
			[k_nt] = { }
		}

		setmetatable(o, mt)
		return o
	end


	--
	-- Public interface
	--
	return { new = new }
end )( )

--
-- A queue is optimized for pushing on the right and poping on the left.
--
Queue = ( function( )

	--
	-- Creates a new queue.
	--
	local function new( )
		return {
			first = 1,
			last  = 0,
			size  = 0
		};
	end

	--
	-- Pushes a value on the queue.
	-- Returns the last value
	--
	local function push( list, value )

		if not value then
			error('Queue pushing nil value', 2)
		end

		local last = list.last + 1
		list.last = last
		list[ last ] = value
		list.size = list.size + 1
		return last
	end

	--
	-- Removes an item at pos from the Queue.
	--
	local function remove( list, pos )

		if list[ pos ] == nil then
			error('Removing nonexisting item in Queue', 2)
		end

		list[ pos ] = nil

		-- if removing first or last element,
		-- the queue limits are adjusted.
		if pos == list.first then

			local last = list.last

			while list[ pos ] == nil and pos <= list.last do
				pos = pos + 1
			end

			list.first = pos

		elseif pos == list.last then

			while list[ pos ] == nil and pos >= list.first do
				pos = pos - 1
			end

			list.last = pos

		end

		-- reset the indizies if the queue is empty
		if list.last < list.first then
			list.first = 1
			list.last  = 0
		end

		list.size = list.size - 1
	end

	--
	-- Queue iterator (stateless)
	--
	local function iter( list, pos )

		pos = pos + 1

		while list[ pos ] == nil and pos <= list.last do
			pos = pos + 1
		end

		if pos > list.last then
			return nil
		end

		return pos, list[ pos ]
	end

	--
	-- Reverse queue iterator (stateless)
	--
	local function iterReverse( list, pos )

		pos = pos - 1

		while list[pos] == nil and pos >= list.first do
			pos = pos - 1
		end

		if pos < list.first then
			return nil
		end

		return pos, list[ pos ]
	end

	--
	-- Iteraters through the queue
	-- returning all non-nil pos-value entries.
	--
	local function qpairs( list )
		return iter, list, list.first - 1
	end

	--
	-- Iteraters backwards through the queue
	-- returning all non-nil pos-value entries.
	--
	local function qpairsReverse( list )
		return iterReverse, list, list.last + 1
	end

	return {
		new = new,
		push = push,
		remove = remove,
		qpairs = qpairs,
		qpairsReverse = qpairsReverse
	}
end )( )

--
-- Locks globals,
-- No more globals can be created after this
--
local function lockGlobals( )

	local t = _G
	local mt = getmetatable( t ) or { }

	-- TODO try to remove the underscore exceptions
	mt.__index = function( t, k )
		if k ~= '_' and string.sub(k, 1, 2) ~= '__' then
			error( 'Access of non-existing global "'..k..'"', 2 )
		else
			rawget( t, k )
		end
	end

	mt.__newindex = function( t, k, v )
		if k ~= '_' and string.sub( k, 1, 2 ) ~= '__' then
			error('Lsyncd does not allow GLOBALS to be created on the fly. '..
			      'Declare "'..k..'" local or declare global on load.', 2)
		else
			rawset( t, k, v )
		end
	end

	setmetatable( t, mt )
end

--
-- Holds the information about a delayed event for one Sync.
--
local Delay = ( function( )

	--
	-- Creates a new delay.
	--
	-- Params see below.
	--
	local function new( etype, sync, alarm, path, path2 )

		local o = {
			--
			-- Type of event.
			-- Can be 'Create', 'Modify', 'Attrib', 'Delete' and 'Move'
			--
			etype = etype,

			--
			-- the Sync this delay belongs to
			--
			sync = sync,

			--
			-- Latest point in time this should be catered for.
			-- This value is in kernel ticks, return of the C's
			-- times(NULL) call.
			alarm = alarm,

			--
			-- Path and filename or dirname of the delay relative
			-- to the syncs root.
			--
			-- for the directories it contains a trailing slash
			--
			path = path,

			--
			-- Used only for Moves.
			-- Path and file/dirname of a move destination.
			--
			path2  = path2,

			--
			-- Status of the event. Valid stati are:
			--
			-- 'wait'    ... the event is ready to be handled.
			--
			-- 'active'  ... there is process running catering for this event.
			--
			-- 'blocked' ... this event waits for another to be handled first.
			--
			-- 'done'    ... event has been collected. This should never be
			--               visible as all references should be droped on
			--               collection, nevertheless the seperate status is
			--               used as insurrance everything is running correctly.
			status = 'wait',

			--
			-- Position in the queue
			--
			dpos = -1,
		}

		return o
	end


	--
	-- Public interface
	--
	return { new = new }

end )( )

--
-- Combines delays
--
local Combiner = ( function( )

	--
	-- The new delay is absorbed by an older one.
	--
	local function abso( d1, d2 )

		log(
			'Delay',
			d2.etype, ':',d2.path,
			' absorbed by ',
			d1.etype,':',d1.path
		)

		return 'absorb'

	end

	--
	-- The new delay replaces the old one if it's a file
	--
	local function refi( d1, d2 )

		-- but a directory blocks
		if d2.path:byte( -1 ) == 47 then

			log(
				'Delay',
				d2.etype,':',d2.path,
				' blocked by ',
				d1.etype,':',d1.path
			)

			return 'stack'

		end

		log(
			'Delay',
			d2.etype, ':', d2.path,
			' replaces ',
			d1.etype, ':', d1.path
		)

		return 'replace'

	end

	--
	-- The new delay replaces an older one.
	--
	local function repl( d1, d2 )

		log(
			'Delay',
			d2.etype, ':', d2.path,
			' replaces ',
			d1.etype, ':', d1.path
		)

		return 'replace'

	end

	--
	-- Two delays nullificate each other.
	--
	local function null( d1, d2 )

		log(
			'Delay',
			d2.etype,':',d2.path,
			' nullifies ',
			d1.etype,':',d1.path
		)

		return 'remove'

	end

	--
	-- Table on how to combine events that dont involve a move.
	--
	local combineNoMove = {

		Attrib = {
			Attrib = abso,
			Modify = repl,
			Create = repl,
			Delete = repl
		},

		Modify = {
			Attrib = abso,
			Modify = abso,
			Create = repl,
			Delete = repl
		},

		Create = {
			Attrib = abso,
			Modify = abso,
			Create = abso,
			Delete = repl
		},

		Delete = {
			Attrib = abso,
			Modify = abso,
			Create = refi,
			Delete = abso
		},
	}

	--
	-- Combines two delays
	--
	local function combine( d1, d2 )

		if d1.etype == 'Init' or d1.etype == 'Blanket' then

			-- everything is blocked by init or blanket delays.
			if d2.path2 then
				log(
					'Delay',
					d2.etype,':',d2.path,'->',d2.path2,
					' blocked by ',
					d1.etype,' event'
				)
			else
				log(
					'Delay',
					d2.etype,':',d2.path,
					' blocked by ',
					d1.etype,' event'
				)
			end

			return 'stack'
		end

		-- two normal events
		if d1.etype ~= 'Move' and d2.etype ~= 'Move' then

			if d1.path == d2.path then
				if d1.status == 'active' then
					return 'stack'
				end

				return combineNoMove[ d1.etype ][ d2.etype ]( d1, d2 )
			end

			-- if one is a parent directory of another, events are blocking
			if d1.path:byte(-1) == 47 and string.starts(d2.path, d1.path) or
			   d2.path:byte(-1) == 47 and string.starts(d1.path, d2.path)
			then
				return 'stack'
			end

			return nil

		end

		-- non-move event on a move.
		if d1.etype == 'Move' and d2.etype ~= 'Move' then
			-- if the from field could be damaged the events are stacked
			if d1.path == d2.path or
			   d2.path:byte(-1) == 47 and string.starts(d1.path, d2.path) or
			   d1.path:byte(-1) == 47 and string.starts(d2.path, d1.path)
			then
				log(
					'Delay',
					d2.etype, ':', d2.path,
					' blocked by ',
					'Move :', d1.path,'->', d1.path2
				)

				return 'stack'
			end

			--  the event does something with the move destination

			if d1.path2 == d2.path then

				if d2.etype == 'Delete' or d2.etype == 'Create' then

					if d1.status == 'active' then
						return 'stack'
					end

					log(
						'Delay',
						d2.etype, ':', d2.path,
						' turns ',
				        'Move :', d1.path, '->', d1.path2,
						' into ',
						'Delete:', d1.path
					)
					d1.etype = 'Delete'
					d1.path2 = nil

					return 'stack'
				end

				-- on 'Attrib' or 'Modify' simply stack on moves

				return 'stack'
			end

			if d2.path :byte(-1) == 47 and string.starts(d1.path2, d2.path) or
			   d1.path2:byte(-1) == 47 and string.starts(d2.path,  d1.path2)
			then
				log(
					'Delay'
					,d2.etype, ':', d2.path,
					' blocked by ',
					'Move:', d1.path, '->', d1.path2
				)

				return 'stack'
			end

			return nil
		end

		-- a move upon a non-move event
		if d1.etype ~= 'Move' and d2.etype == 'Move' then
			if d1.path == d2.path or d1.path == d2.path2 or
			   d1.path :byte(-1) == 47 and string.starts(d2.path,  d1.path) or
			   d1.path :byte(-1) == 47 and string.starts(d2.path2, d1.path) or
			   d2.path :byte(-1) == 47 and string.starts(d1.path,  d2.path) or
			   d2.path2:byte(-1) == 47 and string.starts(d1.path,  d2.path2)
			then
				log(
					'Delay',
					'Move:', d2.path, '->', d2.path2,
					' splits on ',
					d1.etype, ':', d1.path
				)
				return 'split'
			end

			return nil
		end

		--
		-- a move event upon a move event
		--
		if d1.etype == 'Move' and d2.etype == 'Move' then
			-- TODO combine moves,

			if d1.path  == d2.path or d1.path  == d2.path2 or
			   d1.path2 == d2.path or d2.path2 == d2.path or
			   d1.path :byte(-1) == 47 and string.starts(d2.path,  d1.path)  or
			   d1.path :byte(-1) == 47 and string.starts(d2.path2, d1.path)  or
			   d1.path2:byte(-1) == 47 and string.starts(d2.path,  d1.path2) or
			   d1.path2:byte(-1) == 47 and string.starts(d2.path2, d1.path2) or
			   d2.path :byte(-1) == 47 and string.starts(d1.path,  d2.path)  or
			   d2.path :byte(-1) == 47 and string.starts(d1.path2, d2.path)  or
			   d2.path2:byte(-1) == 47 and string.starts(d1.path,  d2.path2) or
			   d2.path2:byte(-1) == 47 and string.starts(d1.path2, d2.path2)
			then
				log(
					'Delay',
					'Move:', d2.path, '->', d1.path2,
					' splits on Move:',
					d1.path, '->', d1.path2
				)

				return 'split'
			end

			return nil
		end

		error( 'reached impossible state' )
	end


	--
	-- Public interface
	--
	return { combine = combine }

end )( )

--
-- Creates inlets for syncs: the user interface for events.
--
local InletFactory = ( function( )

	--
	-- Table to receive the delay of an event
	-- or the delay list of an event list.
	--
	-- Keys are events and values are delays.
	--
	local e2d = { }

	--
	-- Table to ensure the uniqueness of every event
	-- related to a delay.
	--
	-- Keys are delay and values are events.
	--
	local e2d2 = { }

	--
	-- Allows the garbage collector to remove not refrenced
	-- events.
	--
	setmetatable( e2d,  { __mode = 'k' } )
	setmetatable( e2d2, { __mode = 'v' } )

	--
	-- Removes the trailing slash from a path.
	--
	local function cutSlash( path )
		if string.byte(path, -1) == 47 then
			return string.sub(path, 1, -2)
		else
			return path
		end
	end

	--
	-- Gets the path of an event.
	--
	local function getPath( event )
		if event.move ~= 'To' then
			return e2d[ event ].path
		else
			return e2d[ event ].path2
		end
	end

	--
	-- Interface for user scripts to get event fields.
	--
	local eventFields = {

		--
		-- Returns a copy of the configuration as called by sync.
		-- But including all inherited data and default values.
		--
		-- TODO give user a readonly version.
		--
		config = function( event )
			return e2d[ event ].sync.config
		end,

		-----
		-- Returns the inlet belonging to an event.
		--
		inlet = function( event )
			return e2d[ event ].sync.inlet
		end,

		--
		-- Returns the type of the event.
		--
		-- Can be: 'Attrib', 'Create', 'Delete', 'Modify' or 'Move',
		--
		etype = function( event )
			return e2d[ event ].etype
		end,

		--
		-- Events are not lists.
		--
		isList = function( )
			return false
		end,

		--
		-- Returns the status of the event.
		--
		-- Can be:
		--    'wait', 'active', 'block'.
		--
		status = function( event )
			return e2d[ event ].status
		end,

		---
		-- Returns true if event relates to a directory
		--
		isdir = function( event )
			return lsyncd.realdir( getPath ( event ));
		end,

		--
		-- Returns the name of the file/dir.
		--
		-- Includes a trailing slash for dirs.
		--
		name = function( event )
			return string.match( getPath( event ), '[^/]+/?$' )
		end,

		--
		-- Returns the name of the file/dir
		-- excluding a trailing slash for dirs.
		--
		basename = function( event )
			return string.match( getPath( event ), '([^/]+)/?$')
		end,

		---
		-- Returns the file/dir relative to watch root
		-- including a trailing slash for dirs.
		--
		path = function( event )
			return getPath( event )
		end,

		--
		-- Returns the directory of the file/dir relative to watch root
		-- Always includes a trailing slash.
		--
		pathdir = function( event )
			return string.match( getPath( event ), '^(.*/)[^/]+/?' ) or ''
		end,

		--
		-- Returns the file/dir relativ to watch root
		-- excluding a trailing slash for dirs.
		--
		pathname = function( event )
			return cutSlash( getPath( event ) )
		end,

		---
		-- Returns the absolute path of the watch root.
		-- All symlinks are resolved.
		--
		source = function( event )
			return e2d[ event ].sync.source
		end,

		--
		-- Returns the absolute path of the file/dir
		-- including a trailing slash for dirs.
		--
		sourcePath = function( event )
			return e2d[ event ].sync.source .. getPath( event )
		end,

		--
		-- Returns the absolute dir of the file/dir
		-- including a trailing slash.
		--
		sourcePathdir = function( event )
			return e2d[event].sync.source ..
				( string.match( getPath( event ), '^(.*/)[^/]+/?' ) or '' )
		end,

		------
		-- Returns the absolute path of the file/dir
		-- excluding a trailing slash for dirs.
		--
		sourcePathname = function( event )
			return e2d[ event ].sync.source .. cutSlash( getPath( event ) )
		end,

		--
		-- Returns the configured target
		--
		target = function( event )
			return e2d[ event ].sync.config.target
		end,

		--
		-- Returns the relative dir/file appended to the target
		-- including a trailing slash for dirs.
		--
		targetPath = function( event )
			return e2d[ event ].sync.config.target .. getPath( event )
		end,

		--
		-- Returns the dir of the dir/file appended to the target
		-- including a trailing slash.
		--
		targetPathdir = function( event )
			return e2d[ event ].sync.config.target ..
				( string.match( getPath( event ), '^(.*/)[^/]+/?' ) or '' )
		end,

		--
		-- Returns the relative dir/file appended to the target
		-- excluding a trailing slash for dirs.
		--
		targetPathname = function( event )
			return e2d[ event ].sync.config.target ..
				cutSlash( getPath( event ) )
		end,
	}

	--
	-- Retrievs event fields for the user script.
	--
	local eventMeta = {

		__index = function( event, field )
			local f = eventFields[ field ]
			if not f then
				if field == 'move' then
					-- possibly undefined
					return nil
				end
				error( 'event does not have field "'..field..'"', 2 )
			end
			return f( event )
		end

	}

	--
	-- Interface for user scripts to get list fields.
	--
	local eventListFuncs = {

		--
		-- Returns a list of paths of all events in list.
		--
		-- @param elist -- handle returned by getevents()
		-- @param mutator -- if not nil called with (etype, path, path2)
		--                   returns one or two strings to add.
		--
		getPaths = function( elist, mutator )

			local dlist = e2d[elist]

			if not dlist then
				error( 'cannot find delay list from event list.' )
			end

			local result  = { }
			local resultn = 1

			for k, d in ipairs( dlist ) do

				local s1, s2

				if mutator then
					s1, s2 = mutator( d.etype, d.path, d.path2 )
				else
					s1, s2 = d.path, d.path2
				end

				result[ resultn ] = s1
				resultn = resultn + 1

				if s2 then
					result[ resultn ] = s2
					resultn = resultn + 1
				end
			end

			return result

		end
	}

	--
	-- Retrievs event list fields for the user script
	--
	local eventListMeta = {

		__index = function( elist, func )

			if func == 'isList' then
				return true
			end

			if func == 'config' then
				return e2d[ elist ].sync.config
			end

			local f = eventListFuncs[ func ]

			if not f then
				error(
					'event list does not have function "' .. func .. '"',
					2
				)
			end

			return function( ... )
				return f( elist, ... )
			end

		end

	}

	--
	-- Table of all inlets with their syncs.
	--
	local inlets = { }

	--
	-- Allows the garbage collector to remove entries.
	--
	setmetatable( inlets, { __mode = 'v' } )

	--
	-- Encapsulates a delay into an event for the user script.
	--
	local function d2e( delay )

		-- already created?
		local eu = e2d2[delay]

		if delay.etype ~= 'Move' then

			if eu then
				return eu
			end

			local event = { }
			setmetatable( event, eventMeta )
			e2d[ event ]  = delay
			e2d2[ delay ] = event

			return event

		else
			-- moves have 2 events - origin and destination
			if eu then
				return eu[1], eu[2]
			end

			local event  = { move = 'Fr' }
			local event2 = { move = 'To' }

			setmetatable( event,  eventMeta )
			setmetatable( event2, eventMeta )

			e2d[ event ]  = delay
			e2d[ event2 ] = delay

			e2d2[ delay ] = { event, event2 }

			-- move events have a field 'move'
			return event, event2

		end
	end

	--
	-- Encapsulates a delay list into an event list for the user script.
	--
	local function dl2el( dlist )

		local eu = e2d2[ dlist ]

		if eu then
			return eu
		end

		local elist = { }

		setmetatable( elist, eventListMeta )

		e2d [ elist ] = dlist
		e2d2[ dlist ] = elist

		return elist

	end

	--
	-- The functions the inlet provides.
	--
	local inletFuncs = {

		--
		-- Adds an exclude.
		--
		addExclude = function( sync, pattern )
			sync:addExclude( pattern )
		end,

		--
		-- Removes an exclude.
		--
		rmExclude = function( sync, pattern )
			sync:rmExclude( pattern )
		end,

		--
		-- Gets the list of excludes in their original rsynlike patterns form.
		--
		getExcludes = function( sync )

			-- creates a copy
			local e = { }
			local en = 1;

			for k, _ in pairs( sync.excludes.list ) do
				e[ en ] = k;
				en = en + 1;
			end

			return e;
		end,

		--
		-- Creates a blanketEvent that blocks everything
		-- and is blocked by everything.
		--
		createBlanketEvent = function( sync )
			return d2e( sync:addBlanketDelay( ) )
		end,

		--
		-- Discards a waiting event.
		--
		discardEvent = function( sync, event )
			local delay = e2d[ event ]
			if delay.status ~= 'wait' then
				log(
					'Error',
					'Ignored cancel of a non-waiting event of type ',
					event.etype
				)
				return
			end
			sync:removeDelay( delay )
		end,

		--
		-- Gets the next not blocked event from queue.
		--
		getEvent = function( sync )
			return d2e( sync:getNextDelay( now( ) ) )
		end,

		--
		-- Gets all events that are not blocked by active events.
		--
		-- @param if not nil a function to test each delay
		--
		getEvents = function( sync, test )
			local dlist = sync:getDelays( test )
			return dl2el( dlist )
		end,

		--
		-- Returns the configuration table specified by sync{}
		--
		getConfig = function( sync )
			-- TODO gives a readonly handler only.
			return sync.config
		end,
	}

	--
	-- Forwards access to inlet functions.
	--
	local inletMeta = {
		__index = function( inlet, func )
			local f = inletFuncs[ func ]
			if not f then
				error(
					'inlet does not have function "'..func..'"',
					2
				)
			end

			return function( ... )
				return f( inlets[ inlet ], ... )
			end
		end,
	}

	--
	-- Creates a new inlet for Sync.
	--
	local function newInlet( sync )

		-- Lsyncd runner controlled variables
		local inlet = { }

		-- sets use access methods
		setmetatable( inlet, inletMeta )
		inlets[ inlet ] = sync
		return inlet
	end

	--
	-- Returns the delay from a event.
	--
	local function getDelayOrList( event )
		return e2d[ event ]
	end

	--
	-- Returns the sync from an event or list
	--
	local function getSync( event )
		return e2d[ event ].sync
	end

	--
	-- Public interface.
	--
	return {
		getDelayOrList = getDelayOrList,
		d2e            = d2e,
		dl2el          = dl2el,
		getSync        = getSync,
		newInlet       = newInlet,
	}

end )( )


--
-- A set of exclude patterns
--
local Excludes = ( function( )

	--
	-- Turns a rsync like file pattern to a lua pattern.
	-- ( at best it can )
	--
	local function toLuaPattern( p )
		local o = p
		p = string.gsub( p, '%%', '%%%%'  )
		p = string.gsub( p, '%^', '%%^'   )
		p = string.gsub( p, '%$', '%%$'   )
		p = string.gsub( p, '%(', '%%('   )
		p = string.gsub( p, '%)', '%%)'   )
		p = string.gsub( p, '%.', '%%.'   )
		p = string.gsub( p, '%[', '%%['   )
		p = string.gsub( p, '%]', '%%]'   )
		p = string.gsub( p, '%+', '%%+'   )
		p = string.gsub( p, '%-', '%%-'   )
		p = string.gsub( p, '%?', '[^/]'  )
		p = string.gsub( p, '%*', '[^/]*' )
		-- this was a ** before
		p = string.gsub( p, '%[%^/%]%*%[%^/%]%*', '.*' )
		p = string.gsub( p, '^/', '^/'    )

		if p:sub( 1, 2 ) ~= '^/' then
			-- if does not begin with '^/'
			-- then all matches should begin with '/'.
			p = '/' .. p;
		end

		log(
			'Exclude',
			'toLuaPattern "',
			o, '" = "', p, '"'
		)

		return p
	end

	--
	-- Adds a pattern to exclude
	--
	local function add( self, pattern )

		if self.list[ pattern ] then
			-- already in the list
			return
		end

		local lp = toLuaPattern( pattern )
		self.list[ pattern ] = lp

	end

	--
	-- Removes a pattern to exclude.
	--
	local function remove( self, pattern )

		if not self.list[ pattern ] then
			-- already in the list?

			log(
				'Normal',
				'Removing not excluded exclude "' .. pattern .. '"'
			)

			return
		end

		self.list[pattern] = nil

	end


	-----
	-- Adds a list of patterns to exclude.
	--
	local function addList(self, plist)
		for _, v in ipairs(plist) do
			add(self, v)
		end
	end

	--
	-- Loads the excludes from a file
	--
	local function loadFile( self, file )

		f, err = io.open( file )

		if not f then
			log(
				'Error',
				'Cannot open exclude file "', file,'": ',
				err
			)

			terminate( -1 )
		end

	    for line in f:lines() do

			-- lsyncd 2.0 does not support includes

			if not string.match(line, '^%s*%+') and
					not string.match(line, '^%s*#') and
					not string.match(line, '^%s*$') then
				local p = string.match(
					line, '%s*-?%s*(.*)'
				)
				if p then
					add(self, p)
				end
			end
		end

		f:close( )
	end

	--
	-- Tests if 'path' is excluded.
	--
	local function test( self, path )

		for _, p in pairs( self.list ) do

			if p:byte( -1 ) == 36 then
				-- ends with $

				if path:match( p ) then
					return true
				end

			else

				-- ends either end with / or $
				if path:match(p .. '/') or path:match(p .. '$') then
					return true
				end

			end
		end

		return false

	end


	--
	-- Cretes a new exclude set
	--
	local function new( )

		return {
			list = { },

			-- functions
			add      = add,
			addList  = addList,
			loadFile = loadFile,
			remove   = remove,
			test     = test,
		}

	end

	--
	-- Public interface
	--
	return { new = new }

end )( )

--
-- Holds information about one observed directory including subdirs.
--
local Sync = ( function( )

	--
	-- Syncs that have no name specified by the user script
	-- get an incremental default name 'Sync[X]'
	--
	local nextDefaultName = 1

	--
	-- Adds an exclude.
	--
	local function addExclude( self, pattern )

		return self.excludes:add( pattern )

	end

	--
	-- Removes an exclude.
	--
	local function rmExclude( self, pattern )

		return self.excludes:remove( pattern )

	end

	--
	-- Removes a delay.
	--
	local function removeDelay( self, delay )

		if self.delays[ delay.dpos ] ~= delay then
			error( 'Queue is broken, delay not a dpos' )
		end

		Queue.remove( self.delays, delay.dpos )

		-- free all delays blocked by this one.
		if delay.blocks then

			for i, vd in pairs( delay.blocks ) do

				vd.status = 'wait'

			end

		end
	end

	--
	-- Returns true if this Sync concerns about 'path'
	--
	local function concerns( self, path )

		-- not concerned if watch rootdir doesnt match
		if not path:starts( self.source ) then

			return false

		end

		-- a sub dir and not concerned about subdirs
		if self.config.subdirs == false and

			path:sub( #self.source, -1 ):match( '[^/]+/?' )

		then

			return false

		end

		-- concerned if not excluded
		return not self.excludes:test( path:sub( #self.source ) )

	end

	--
	-- Collects a child process
	--
	local function collect( self, pid, exitcode )

		local delay = self.processes[ pid ]

		if not delay then
			-- not a child of this sync.
			return
		end

		if delay.status then

			log( 'Delay', 'collected an event' )

			if delay.status ~= 'active' then
				error('collecting a non-active process')
			end

			local rc = self.config.collect(
				InletFactory.d2e( delay ),
				exitcode
			)

			if rc == 'die' then
				log( 'Error', 'Critical exitcode.' );
				terminate( -1 )
			end

			if rc ~= 'again' then
				-- if its active again the collecter restarted the event
				removeDelay( self, delay )
				log(
					'Delay',
					'Finish of ',
					delay.etype,
					' on ',
					self.source,delay.path,
					' = ',
					exitcode
				)
			else
				-- sets the delay on wait again
				delay.status = 'wait'

				local alarm = self.config.delay

				-- delays at least 1 second
				if alarm < 1 then
					alarm = 1
				end

				delay.alarm = now( ) + alarm
			end
		else
			log(
				'Delay',
				'collected a list'
			)

			local rc = self.config.collect(
				InletFactory.dl2el( delay ),
				exitcode
			)

			if rc == 'die' then
				log( 'Error', 'Critical exitcode.' );
				terminate( -1 )
			end

			if rc == 'again' then

				-- sets the delay on wait again
				delay.status = 'wait'
				local alarm = self.config.delay
				-- delays at least 1 second
				if alarm < 1 then
					alarm = 1
				end

				alarm = now() + alarm

				for _, d in ipairs( delay ) do
					d.alarm = alarm
					d.status = 'wait'
				end
			end

			for _, d in ipairs( delay ) do
				if rc ~= 'again' then
					removeDelay( self, d )
				else
					d.status = 'wait'
				end
			end

			log( 'Delay','Finished list = ',exitcode )
		end

		self.processes[ pid ] = nil
	end

	--
	-- Stacks a newDelay on the oldDelay,
	-- the oldDelay blocks the new Delay.
	--
	-- A delay can block 'n' other delays,
	-- but is blocked at most by one, the latest delay.
	--
	local function stack( oldDelay, newDelay )

		newDelay.status = 'block'

		if not oldDelay.blocks then
			oldDelay.blocks = { }
		end

		table.insert( oldDelay.blocks, newDelay )

	end

	--
	-- Puts an action on the delay stack.
	--
	local function delay( self, etype, time, path, path2 )

		log(
			'Function',
			'delay( ',
				self.config.name, ', ',
				etype, ', ',
				path, ', ',
				path2,
			' )'
		)

		-- TODO
		local function recurse( )

			if etype == 'Create' and path:byte( -1 ) == 47 then

				local entries = lsyncd.readdir( self.source .. path )

				if entries then

					for dirname, isdir in pairs(entries) do

						local pd = path .. dirname

						if isdir then
							pd = pd..'/'
						end

						log(
							'Delay',
							'Create creates Create on ',
							pd
						)
						delay( self, 'Create', time, pd, nil )

					end

				end

			end

		end

		-- exclusion tests
		if not path2 then
			-- simple test for single path events
			if self.excludes:test(path) then
				log(
					'Exclude',
					'excluded ',
					etype,
					' on "',
					path,
					'"'
				)
				return
			end
		else
			-- for double paths (move) it might result into a split
			local ex1 = self.excludes:test( path  )
			local ex2 = self.excludes:test( path2 )

			if ex1 and ex2 then

				log(
					'Exclude',
					'excluded "',
					etype,
					' on "',
					path,
					'" -> "',
					path2,
					'"'
				)

				return

			elseif not ex1 and ex2 then

				-- splits the move if only partly excluded
				log(
					'Exclude',
					'excluded destination transformed ',
					etype,
					' to Delete ',
					path
				)

				delay(
					self,
					'Delete',
					time,
					path,
					nil
				)

				return

			elseif ex1 and not ex2 then
				-- splits the move if only partly excluded
				log(
					'Exclude',
					'excluded origin transformed ',
					etype,
					' to Create.',
					path2
				)

				delay(
					self,
					'Create',
					time,
					path2,
					nil
				)

				return
			end
		end

		if etype == 'Move' and not self.config.onMove then

			-- if there is no move action defined,
			-- split a move as delete/create
			-- layer 1 scripts which want moves events have to
			-- set onMove simply to 'true'
			log( 'Delay', 'splitting Move into Delete & Create' )
			delay( self, 'Delete', time, path,  nil )
			delay( self, 'Create', time, path2, nil )
			return

		end

		-- creates the new action
		local alarm
		if time and self.config.delay then
			alarm = time + self.config.delay
		else
			alarm = now( )
		end

		-- new delay
		local nd = Delay.new(
			etype,
			self,
			alarm,
			path,
			path2
		)

		if nd.etype == 'Init' or nd.etype == 'Blanket' then

			-- always stack init or blanket events on the last event
			log(
				'Delay',
				'Stacking ',
				nd.etype,
				' event.'
			)

			if self.delays.size > 0 then
				stack( self.delays[ self.delays.last ], nd )
			end

			nd.dpos = Queue.push( self.delays, nd )
			recurse( )

			return

		end

		-- detects blocks and combos by working from back until
		-- front through the fifo
		for il, od in Queue.qpairsReverse( self.delays ) do

			-- asks Combiner what to do
			local ac = Combiner.combine( od, nd )

			if ac then
				if ac == 'remove' then
					Queue.remove( self.delays, il )
				elseif ac == 'stack' then
					stack( od, nd )
					nd.dpos = Queue.push( self.delays, nd )
				elseif ac == 'absorb' then
					-- nada
				elseif ac == 'replace' then
					od.etype = nd.etype
					od.path  = nd.path
					od.path2 = nd.path2
				elseif ac == 'split' then
					delay( self, 'Delete', time, path,  nil )
					delay( self, 'Create', time, path2, nil )
				else
					error( 'unknown result of combine()' )
				end
				recurse( )
				return
			end

			il = il - 1
		end

		if nd.path2 then
			log( 'Delay','New ',nd.etype,':',nd.path,'->',nd.path2 )
		else
			log( 'Delay','New ',nd.etype,':',nd.path )
		end

		-- no block or combo
		nd.dpos = Queue.push( self.delays, nd )
		recurse( )
	end

	--
	-- Returns the soonest alarm for this Sync.
	--
	local function getAlarm( self )

		if self.processes:size( ) >= self.config.maxProcesses then
			return false
		end

		-- first checks if more processes could be spawned
		if self.processes:size( ) < self.config.maxProcesses then

			-- finds the nearest delay waiting to be spawned
			for _, d in Queue.qpairs( self.delays ) do
				if d.status == 'wait' then return d.alarm end
			end

		end

		-- nothing to spawn
		return false
	end

	--
	-- Gets all delays that are not blocked by active delays.
	--
	-- @param test   function to test each delay
	--
	local function getDelays( self, test )
		local dlist  = { sync = self}
		local dlistn = 1
		local blocks = { }

		--
		-- inheritly transfers all blocks from delay
		--
		local function getBlocks( delay )
			blocks[ delay ] = true
			if delay.blocks then
				for i, d in ipairs( delay.blocks ) do
					getBlocks( d )
				end
			end
		end

		for i, d in Queue.qpairs( self.delays ) do
			if d.status == 'active' or
				( test and not test( InletFactory.d2e( d ) ) )
			then
				getBlocks( d )
			elseif not blocks[ d ] then
				dlist[ dlistn ] = d
				dlistn = dlistn + 1
			end
		end

		return dlist
	end

	--
	-- Creates new actions
	--
	local function invokeActions( self, timestamp )

		log(
			'Function',
			'invokeActions( "',
				self.config.name, '", ',
				timestamp,
			' )'
		)

		if self.processes:size( ) >= self.config.maxProcesses then
			-- no new processes
			return
		end

		for _, d in Queue.qpairs( self.delays ) do

			-- if reached the global limit return
			if uSettings.maxProcesses and
				processCount >= uSettings.maxProcesses
			then
				log('Alarm', 'at global process limit.')
				return
			end

			if self.delays.size < self.config.maxDelays then
				-- time constrains are only concerned if not maxed
				-- the delay FIFO already.
				if d.alarm ~= true and timestamp < d.alarm then
					-- reached point in stack where delays are in future
					return
				end
			end

			if d.status == 'wait' then

				-- found a waiting delay
				if d.etype ~= 'Init' then
					self.config.action( self.inlet )
				else
					self.config.init( InletFactory.d2e( d ) )
				end

				if self.processes:size( ) >= self.config.maxProcesses then
					-- no further processes
					return
				end
			end
		end
	end

	--
	-- Gets the next event to be processed.
	--
	local function getNextDelay( self, timestamp )

		for i, d in Queue.qpairs( self.delays ) do

			if self.delays.size < self.config.maxDelays then
				-- time constrains are only concerned if not maxed
				-- the delay FIFO already.
				if d.alarm ~= true and timestamp < d.alarm then
					-- reached point in stack where delays are in future
					return nil
				end
			end

			if d.status == 'wait' then
				-- found a waiting delay
				return d
			end
		end

	end

	------
	-- Adds and returns a blanket delay thats blocks all.
	-- Used as custom marker.
	--
	local function addBlanketDelay( self )
		local newd = Delay.new( 'Blanket', self, true, '' )
		newd.dpos = Queue.push( self.delays, newd )
		return newd
	end

	--
	-- Adds and returns a blanket delay thats blocks all.
	-- Used as startup marker to call init asap.
	--
	local function addInitDelay( self )

		local newd = Delay.new( 'Init', self, true, '' )

		newd.dpos = Queue.push( self.delays, newd )

		return newd
	end

	--
	-- Writes a status report about delays in this sync.
	--
	local function statusReport( self, f )

		local spaces = '                    '

		f:write( self.config.name, ' source=', self.source, '\n' )
		f:write( 'There are ', self.delays.size, ' delays\n')

		for i, vd in Queue.qpairs( self.delays ) do
			local st = vd.status
			f:write( st, string.sub( spaces, 1, 7 - #st ) )
			f:write( vd.etype, ' ' )
			f:write( vd.path )

			if vd.path2 then
				f:write( ' -> ',vd.path2 )
			end

			f:write('\n')

		end

		f:write( 'Excluding:\n' )

		local nothing = true

		for t, p in pairs( self.excludes.list ) do
			nothing = false
			f:write( t,'\n' )
		end
		if nothing then
			f:write('  nothing.\n')
		end

		f:write( '\n' )
	end

	--
	-- Creates a new Sync
	--
	local function new( config )

		local s = {
			-- fields

			config = config,
			delays = Queue.new( ),
			source = config.source,
			processes = CountArray.new( ),
			excludes = Excludes.new( ),

			-- functions

			addBlanketDelay = addBlanketDelay,
			addExclude      = addExclude,
			addInitDelay    = addInitDelay,
			collect         = collect,
			concerns        = concerns,
			delay           = delay,
			getAlarm        = getAlarm,
			getDelays       = getDelays,
			getNextDelay    = getNextDelay,
			invokeActions   = invokeActions,
			removeDelay     = removeDelay,
			rmExclude       = rmExclude,
			statusReport    = statusReport,
		}

		s.inlet = InletFactory.newInlet( s )

		-- provides a default name if needed
		if not config.name then
			config.name = 'Sync' .. nextDefaultName
		end

		-- increments defaults if a config name was given or not
		-- so Sync{n} will be the n-th call to sync{}
		nextDefaultName = nextDefaultName + 1

		-- loads exclusions
		if config.exclude then

			local te = type( config.exclude )

			if te == 'table' then
				s.excludes:addList( config.exclude )
			elseif te == 'string' then
				s.excludes:add( config.exclude )
			else
				error( 'type for exclude must be table or string', 2 )
			end

		end

		if
			config.delay ~= nil and
			(
				type(config.delay) ~= 'number' or
				config.delay < 0
			)
		then
			error( 'delay must be a number and >= 0', 2 )
		end

		if config.excludeFrom then

			s.excludes:loadFile( config.excludeFrom )

		end

		return s
	end

	--
	-- Public interface
	--
	return {
		new = new
	}

end )( )


--
-- Syncs - a singleton
--
-- Syncs maintains all configured syncs.
--
local Syncs = ( function( )

	--
	-- the list of all syncs
	--
	local syncsList = Array.new( )

	--
	-- The round robin pointer. In case of global limited maxProcesses
	-- gives every sync equal chances to spawn the next process.
	--
	local round = 1

	--
	-- The cycle( ) sheduler goes into the next round of roundrobin.
	--
	local function nextRound( )

		round = round + 1;

		if round > #syncsList then
			round = 1
		end

		return round
	end

	--
	-- Returns the round
	--
	local function getRound( )
		return round
	end

	--
	-- Returns sync at listpos i
	--
	local function get( i )
		return syncsList[ i ];
	end

	--
	-- Helper function for inherit
	-- defined below
	--
	local inheritKV

	--
	-- Recurvely inherits a source table to a destionation table
	-- copying all keys from source.
	--
	-- table copy source ( cs )
	-- table copy destination ( cd )
	--
	-- All entries with integer keys are inherited as additional
	-- sources for non-verbatim tables
	--
	local function inherit( cd, cs )

		--
		-- First copies all entries with non-integer keys
		-- tables are merged, already present keys are not
		-- overwritten
		--
		-- For verbatim tables integer keys are treated like
		-- non integer keys
		--
		for k, v in pairs( cs ) do
			if
				(
					type( k ) ~= 'number' or
					cs._verbatim == true
				)
				and
				(
					type( cs._merge ) ~= 'table' or
					cs._merge[ k ] == true
				)
			then
				inheritKV( cd, k, v )
			end
		end

		--
		-- recursevely inherits all integer keyed tables
		-- ( for non-verbatim tables )
		--
		if cs._verbatim ~= true then

			local n = nil
			for k, v in ipairs( cs ) do
				n = k
				if type( v ) == 'table' then
					inherit( cd, v )
				else
					cd[ #cd + 1 ] = v
				end
			end

		end
	end

	--
	-- Helper to inherit. Inherits one key.
	--
	inheritKV = function( cd, k, v )

		-- don't merge inheritance controls
		if k == '_merge' or k == '_verbatim' then
			return
		end

		local dtype = type( cd [ k ] )

		if type( v ) == 'table' then

			if dtype == 'nil' then
				cd[ k ] = { }
				inherit( cd[ k ], v )
			elseif
				dtype == 'table' and
				v._merge ~= false
			then
				inherit( cd[ k ], v )
			end

		elseif dtype == 'nil' then
			cd[ k ] = v
		end

	end


	--
	-- Adds a new sync (directory-tree to observe).
	--
	local function add( config )

		-- workaround for backwards compatibility
		-- FIXME: remove when dropping that
		if settings ~= settingsSafe then
			log(
				'Warn',
				'settings = { ... } is deprecated.\n'..
				'      please use settings{ ... } (without the equal sign)'
			)

			for k, v in pairs( settings ) do
				uSettings[ k ] = v
			end

			settings = settingsSafe
		end

		-- Creates a new config table which inherits all keys/values
		-- from integer keyed tables
		local uconfig = config

		config = { }

		inherit( config, uconfig )

		--
		-- last and least defaults are inherited
		--
		inherit( config, default )

		local inheritSettings = {
			'delay',
			'maxDelays',
			'maxProcesses'
		}

		-- Lets settings override these values.
		for _, v in ipairs( inheritSettings ) do
			if uSettings[ v ] then
				config[ v ] = uSettings[ v ]
			end
		end

		-- Lets commandline override these values.
		for _, v in ipairs( inheritSettings ) do
			if clSettings[ v ] then
				config[ v ] = clSettings[ v ]
			end
		end

		--
		-- lets the userscript 'prepare' function
		-- check and complete the config
		--
		if type( config.prepare ) == 'function' then

			-- prepare is given a writeable copy of config
			config.prepare( config, 4 )

		end

		if not config[ 'source' ] then
			local info = debug.getinfo( 3, 'Sl' )
			log(
				'Error',
				info.short_src,':',
				info.currentline,': source missing from sync.'
			)
			terminate( -1 )
		end

		--
		-- absolute path of source
		--
		local realsrc = lsyncd.realdir( config.source )

		if not realsrc then
			log(
				'Error',
				'Cannot access source directory: ',
				config.source
			)
			terminate( -1 )
		end

		config._source = config.source
		config.source = realsrc

		if
			not config.action   and
			not config.onAttrib and
			not config.onCreate and
			not config.onModify and
			not config.onDelete and
			not config.onMove
		then
			local info = debug.getinfo( 3, 'Sl' )
			log(
				'Error',
				info.short_src, ':',
				info.currentline,
				': no actions specified.'
			)

			terminate( -1 )
		end

		-- the monitor to use
		config.monitor =
			uSettings.monitor or
			config.monitor or
			Monitors.default( )

		if
			config.monitor ~= 'inotify' and
			config.monitor ~= 'fsevents'
		then
			local info = debug.getinfo( 3, 'Sl' )

			log(
				'Error',
				info.short_src, ':',
				info.currentline,
				': event monitor "',
				config.monitor,
				'" unknown.'
			)

			terminate( -1 )
		end

		--- creates the new sync
		local s = Sync.new( config )

		table.insert( syncsList, s )

		return s
	end

	--
	-- Allows a for-loop to walk through all syncs.
	--
	local function iwalk( )
		return ipairs( syncsList )
	end

	--
	-- Returns the number of syncs.
	--
	local size = function( )
		return #syncsList
	end

	--
	-- Tests if any sync is interested in a path.
	--
	local function concerns( path )
		for _, s in ipairs( syncsList ) do
			if s:concerns( path ) then
				return true
			end
		end

		return false
	end

	--
	-- Public interface
	--
	return {
		add = add,
		get = get,
		getRound = getRound,
		concerns = concerns,
		iwalk = iwalk,
		nextRound = nextRound,
		size = size
	}
end )( )


--
-- Utility function,
-- Returns the relative part of absolute path if it
-- begins with root
--
local function splitPath( path, root )

	local rlen = #root
	local sp = string.sub( path, 1, rlen )

	if sp == root then
		return string.sub( path, rlen, -1 )
	else
		return nil
	end
end

--
-- Interface to inotify.
--
-- watches recursively subdirs and sends events.
--
-- All inotify specific implementation is enclosed here.
--
local Inotify = ( function( )

	--
	-- A list indexed by inotify watch descriptors yielding
	-- the directories absolute paths.
	--
	local wdpaths = CountArray.new( )

	--
	-- The same vice versa,
	-- all watch descriptors by their absolute paths.
	--
	local pathwds = { }

	--
	-- A list indexed by syncs containing yielding
	-- the root paths the syncs are interested in.
	--
	local syncRoots = { }

	--
	-- Stops watching a directory
	--
	-- path ... absolute path to unwatch
	-- core ... if false not actually send the unwatch to the kernel
	--          (used in moves which reuse the watch)
	--
	local function removeWatch( path, core )

		local wd = pathwds[ path ]

		if not wd then
			return
		end

		if core then
			lsyncd.inotify.rmwatch( wd )
		end

		wdpaths[ wd   ] = nil
		pathwds[ path ] = nil
	end


	--
	-- Adds watches for a directory (optionally) including all subdirectories.
	--
	-- @param path       absolute path of directory to observe
	-- @param recurse    true if recursing into subdirs
	--
	local function addWatch(path)

		log(
			'Function',
			'Inotify.addWatch( ',
				path,
			' )'
		)

		if not Syncs.concerns(path) then
			log('Inotify', 'not concerning "',path,'"')
			return
		end

		-- registers the watch
		local inotifyMode = ( uSettings and uSettings.inotifyMode ) or '';

		local wd = lsyncd.inotify.addwatch( path, inotifyMode) ;

		if wd < 0 then
			log( 'Inotify','Unable to add watch "', path, '"' )
			return
		end

		do
			-- If this watch descriptor is registered already
			-- the kernel reuses it since old dir is gone.
			local op = wdpaths[ wd ]
			if op and op ~= path then
				pathwds[ op ] = nil
			end
		end

		pathwds[ path ] = wd
		wdpaths[ wd   ] = path

		-- registers and adds watches for all subdirectories
		local entries = lsyncd.readdir( path )

		if not entries then
			return
		end

		for dirname, isdir in pairs( entries ) do


			isdir = lsyncd.isdir(path .. dirname)
			if isdir then
				addWatch( path .. dirname .. '/' )
			end
		end
	end

	--
	-- Adds a Sync to receive events.
	--
	-- sync:    Object to receive events
	-- rootdir: root dir to watch
	--
	local function addSync( sync, rootdir )
		if syncRoots[ sync ] then
			error( 'duplicate sync in Inotify.addSync()' )
		end
		syncRoots[ sync ] = rootdir
		addWatch( rootdir )
	end

	--
	-- Called when an event has occured.
	--
	local function event(
		etype,     -- 'Attrib', 'Modify', 'Create', 'Delete', 'Move'
		wd,        --  watch descriptor, matches lsyncd.inotifyadd()
		isdir,     --  true if filename is a directory
		time,      --  time of event
		filename,  --  string filename without path
		wd2,       --  watch descriptor for target if it's a Move
		filename2  --  string filename without path of Move target
	)
		-- looks up the watch descriptor id
		local path = wdpaths[ wd ]

		if path then
			path = path..filename
		end

		local path2 = wd2 and wdpaths[ wd2 ]

		if path2 and filename2 then
			path2 = path2..filename2
		end

		-- overwrite isdir --
		isdir = lsyncd.isdir(path);

		if isdir then
			filename = filename .. '/'
			path = path .. '/'

			if filename2 then
				filename2 = filename2 .. '/'
				path2 = path2 .. '/'
			end
		end

		if filename2 then
			log(
				'Inotify',
				'got event ',
				etype,
				' ',
				filename,
				'(', wd, ') to ',
				filename2,
				'(', wd2 ,')'
			)
		else
			log(
				'Inotify',
				'got event ',
				etype,
				' ',
				filename,
				'(', wd, ')'
			)
		end

		if not path and path2 and etype == 'Move' then
			log(
				'Inotify',
				'Move from deleted directory ',
				path2,
				' becomes Create.'
			)
			path  = path2
			path2 = nil
			etype = 'Create'
		end

		if not path then
			-- this is normal in case of deleted subdirs
			log(
				'Inotify',
				'event belongs to unknown watch descriptor.'
			)
			return
		end

		for sync, root in pairs( syncRoots ) do repeat

			local relative  = splitPath( path, root )
			local relative2 = nil

			if path2 then
				relative2 = splitPath( path2, root )
			end

			if not relative and not relative2 then
				-- sync is not interested in this dir
				break -- continue
			end

			-- makes a copy of etype to possibly change it
			local etyped = etype

			if etyped == 'Move' then
				if not relative2 then
					log(
						'Normal',
						'Transformed Move to Delete for ',
						sync.config.name
					)
					etyped = 'Delete'
				elseif not relative then
					relative = relative2
					relative2 = nil
					log(
						'Normal',
						'Transformed Move to Create for ',
						sync.config.name
					)
					etyped = 'Create'
				end
			end

			if isdir then
				if etyped == 'Create' then
					addWatch( path )
				elseif etyped == 'Delete' then
					removeWatch( path, true )
				elseif etyped == 'Move' then
					removeWatch( path, false )
					addWatch( path2 )
				end
			end

			sync:delay( etyped, time, relative, relative2 )

		until true end
	end

	--
	-- Writes a status report about inotify to a file descriptor
	--
	local function statusReport( f )

		f:write( 'Inotify watching ', wdpaths:size(), ' directories\n' )

		for wd, path in wdpaths:walk( ) do
			f:write( '  ', wd, ': ', path, '\n' )
		end
	end


	--
	-- Public interface.
	--
	return {
		addSync = addSync,
		event = event,
		statusReport = statusReport,
	}

end)( )

--
-- Interface to OSX /dev/fsevents
--
-- This watches all the filesystems at once,
-- but needs root access.
--
-- All fsevents specific implementation are enclosed here.
--
local Fsevents = ( function( )


	--
	-- A list indexed by syncs yielding
	-- the root path the sync is interested in.
	--
	local syncRoots = { }


	--
	-- Adds a Sync to receive events.
	--
	-- @param sync   Object to receive events
	-- @param dir    dir to watch
	--
	local function addSync( sync, dir )

		if syncRoots[ sync ] then
			error( 'duplicate sync in Fanotify.addSync()' )
		end

		syncRoots[ sync ] = dir

	end

	--
	-- Called when an event has occured.
	--
	local function event(
		etype,  --  'Attrib', 'Modify', 'Create', 'Delete', 'Move'
		isdir,  --  true if filename is a directory
		time,   --  time of event
		path,   --  path of file
		path2   --  path of target in case of 'Move'
	)
		if isdir then
			path = path .. '/'

			if path2 then
				path2 = path2 .. '/'
			end
		end

		log(
			'Fsevents',
			etype, ',',
			isdir, ',',
			time,  ',',
			path,  ',',
			path2
		)

		for _, sync in Syncs.iwalk() do repeat

			local root = sync.source

			-- TODO combine ifs
			if not path:starts( root ) then
				if not path2 or not path2:starts( root ) then
					break  -- continue
				end
			end

			local relative  = splitPath( path, root )

			local relative2
			if path2 then
				relative2 = splitPath( path2, root )
			end

			-- possibly change etype for this iteration only
			local etyped = etype
			if etyped == 'Move' then
				if not relative2 then
					log('Normal', 'Transformed Move to Delete for ', sync.config.name)
					etyped = 'Delete'
				elseif not relative then
					relative = relative2
					relative2 = nil
					log('Normal', 'Transformed Move to Create for ', sync.config.name)
					etyped = 'Create'
				end
			end

			sync:delay( etyped, time, relative, relative2 )

		until true end

	end


	--
	-- Writes a status report about fsevents to a filedescriptor.
	--
	local function statusReport( f )
		-- TODO
	end

	--
	-- Public interface
	--
	return {
		addSync      = addSync,
		event        = event,
		statusReport = statusReport
	}
end )( )


--
-- Holds information about the event monitor capabilities
-- of the core.
--
Monitors = ( function( )


	--
	-- The cores monitor list
	--
	local list = { }


	--
	-- The default event monitor.
	--
	local function default( )
		return list[ 1 ]
	end


	--
	-- Initializes with info received from core
	--
	local function initialize( clist )
		for k, v in ipairs( clist ) do
			list[ k ] = v
		end
	end


	--
	-- Public interface
	--
	return {
		default = default,
		list = list,
		initialize = initialize
	}

end)( )

--
-- Writes functions for the user for layer 3 configurations.
--
local functionWriter = ( function( )

	--
	-- All variables known to layer 3 configs.
	--
	transVars = {
		{ '%^pathname',          'event.pathname',        1 },
		{ '%^pathdir',           'event.pathdir',         1 },
		{ '%^path',              'event.path',            1 },
		{ '%^sourcePathname',    'event.sourcePathname',  1 },
		{ '%^sourcePathdir',     'event.sourcePathdir',   1 },
		{ '%^sourcePath',        'event.sourcePath',      1 },
		{ '%^source',            'event.source',          1 },
		{ '%^targetPathname',    'event.targetPathname',  1 },
		{ '%^targetPathdir',     'event.targetPathdir',   1 },
		{ '%^targetPath',        'event.targetPath',      1 },
		{ '%^target',            'event.target',          1 },
		{ '%^o%.pathname',       'event.pathname',        1 },
		{ '%^o%.path',           'event.path',            1 },
		{ '%^o%.sourcePathname', 'event.sourcePathname',  1 },
		{ '%^o%.sourcePathdir',  'event.sourcePathdir',   1 },
		{ '%^o%.sourcePath',     'event.sourcePath',      1 },
		{ '%^o%.targetPathname', 'event.targetPathname',  1 },
		{ '%^o%.targetPathdir',  'event.targetPathdir',   1 },
		{ '%^o%.targetPath',     'event.targetPath',      1 },
		{ '%^d%.pathname',       'event2.pathname',       2 },
		{ '%^d%.path',           'event2.path',           2 },
		{ '%^d%.sourcePathname', 'event2.sourcePathname', 2 },
		{ '%^d%.sourcePathdir',  'event2.sourcePathdir',  2 },
		{ '%^d%.sourcePath',     'event2.sourcePath',     2 },
		{ '%^d%.targetPathname', 'event2.targetPathname', 2 },
		{ '%^d%.targetPathdir',  'event2.targetPathdir',  2 },
		{ '%^d%.targetPath',     'event2.targetPath',     2 },
	}

	--
	-- Splits a user string into its arguments.
	-- Returns a table of arguments
	--
	local function splitStr(
		str -- a string where parameters are seperated by spaces.
	)
		local args = { }

		while str ~= '' do

			-- break where argument stops
			local bp = #str

			-- in a quote
			local inQuote = false

			-- tests characters to be space and not within quotes
			for i=1, #str do
				local c = string.sub( str, i, i )

				if c == '"' then
					inQuote = not inQuote
				elseif c == ' ' and not inQuote then
					bp = i - 1
					break
				end
			end

			local arg = string.sub( str, 1, bp )
			arg = string.gsub( arg, '"', '\\"' )
			table.insert( args, arg )
			str = string.sub( str, bp + 1, -1 )
			str = string.match( str, '^%s*(.-)%s*$' )

		end

		return args
	end


	--
	-- Translates a call to a binary to a lua function.
	-- TODO this has a little too blocking.
	--
	local function translateBinary( str )

		-- splits the string
		local args = splitStr( str )

		-- true if there is a second event
		local haveEvent2 = false

		for ia, iv in ipairs( args ) do

			-- a list of arguments this arg is being split into
			local a = { { true, iv } }

			-- goes through all translates
			for _, v in ipairs( transVars ) do
				local ai = 1
				while ai <= #a do
					if a[ ai ][ 1 ] then
						local pre, post =
							string.match( a[ ai ][ 2 ], '(.*)'..v[1]..'(.*)' )

						if pre then

							if v[3] > 1 then
								haveEvent2 = true
							end

							if pre ~= '' then
								table.insert( a, ai, { true, pre } )
								ai = ai + 1
							end

							a[ ai ] = { false, v[ 2 ] }

							if post ~= '' then
								table.insert( a, ai + 1, { true, post } )
							end
						end
					end
					ai = ai + 1
				end
			end

			-- concats the argument pieces into a string.
			local as = ''
			local first = true

			for _, v in ipairs( a ) do

				if not first then
					as = as..' .. '
				end

				if v[ 1 ] then
					as = as .. '"' .. v[ 2 ] .. '"'
				else
					as = as .. v[ 2 ]
				end

				first = false
			end

			args[ ia ] = as
		end

		local ft
		if not haveEvent2 then
			ft = 'function(event)\n'
		else
			ft = 'function(event, event2)\n'
		end

		ft = ft ..
			"    log('Normal', 'Event ', event.etype, \n" ..
			"        ' spawns action \"".. str.."\"')\n" ..
			"    spawn(event"

		for _, v in ipairs( args ) do
			ft = ft .. ',\n         ' .. v
		end

		ft = ft .. ')\nend'
		return ft

	end


	--
	-- Translates a call using a shell to a lua function
	--
	local function translateShell( str )

		local argn = 1
		local args = { }
		local cmd = str
		local lc = str

		-- true if there is a second event
		local haveEvent2 = false

		for _, v in ipairs( transVars ) do

			local occur = false

			cmd = string.gsub(
				cmd,
				v[ 1 ],
				function( )
					occur = true
					return '"$' .. argn .. '"'
				end
			)

			lc = string.gsub(
				lc,
				v[1],
				']]..' .. v[2] .. '..[['
			)

			if occur then
				argn = argn + 1
				table.insert( args, v[ 2 ] )

				if v[ 3 ] > 1 then
					haveEvent2 = true
				end
			end

		end

		local ft
		if not haveEvent2 then
			ft = 'function(event)\n'
		else
			ft = 'function(event, event2)\n'
		end

		-- TODO do array joining instead
		ft = ft..
			"    log('Normal', 'Event ',event.etype,\n"..
			"        [[ spawns shell \""..lc.."\"]])\n"..
			"    spawnShell(event, [["..cmd.."]]"

		for _, v in ipairs( args ) do
			ft = ft..',\n         '..v
		end

		ft = ft .. ')\nend'

		return ft

	end

	--
	-- Writes a lua function for a layer 3 user script.
	--
	local function translate( str )
		-- trim spaces
		str = string.match( str, '^%s*(.-)%s*$' )

		local ft
		if string.byte( str, 1, 1 ) == 47 then
			-- starts with /
			 ft = translateBinary( str )
		elseif string.byte( str, 1, 1 ) == 94 then
			-- starts with ^
			 ft = translateShell( str:sub( 2, -1 ) )
		else
			 ft = translateShell( str )
		end

		log(
			'FWrite',
			'translated "',
			str,
			'" to \n',
			ft
		)

		return ft
	end


	--
	-- Public interface.
	--
	return { translate = translate }


end )( )



--
-- Writes a status report file at most every [statusintervall] seconds.
--
local StatusFile = ( function( )


	--
	-- Timestamp when the status file has been written.
	--
	local lastWritten = false


	--
	-- Timestamp when a status file should be written.
	--
	local alarm = false


	--
	-- Returns the alarm when the status file should be written-
	--
	local function getAlarm()
		return alarm
	end


	--
	-- Called to check if to write a status file.
	--
	local function write( timestamp )

		log(
			'Function',
			'write( ',
				timestamp,
			' )'
		)

		--
		-- takes care not write too often
		--
		if uSettings.statusInterval > 0 then

			-- already waiting?
			if alarm and timestamp < alarm then
				log(
					'Statusfile',
					'waiting(',
					timestamp,
					' < ',
					alarm,
					')'
				)
				return
			end

			-- determines when a next write will be possible
			if not alarm then

				local nextWrite =
					lastWritten and timestamp +
					uSettings.statusInterval

				if nextWrite and timestamp < nextWrite then
					log(
						'Statusfile',
						'setting alarm: ',
						nextWrite
					)
					alarm = nextWrite

					return
				end
			end

			lastWritten = timestamp
			alarm = false
		end

		log( 'Statusfile', 'writing now' )

		local f, err = io.open( uSettings.statusFile, 'w' )

		if not f then
			log(
				'Error',
				'Cannot open status file "' ..
					uSettings.statusFile ..
					'" :' ..
					err
			)
			return
		end

		f:write( 'Lsyncd status report at ', os.date( ), '\n\n' )

		for i, s in Syncs.iwalk( ) do
			s:statusReport( f )
			f:write( '\n' )
		end

		Inotify.statusReport( f )
		f:close( )
	end


	--
	-- Public interface
	--
	return {
		write = write,
		getAlarm = getAlarm
	}

end )( )


--
-- Lets userscripts make their own alarms.
--
local UserAlarms = ( function( )

	local alarms = { }


	--
	-- Calls the user function at timestamp.
	--
	local function alarm( timestamp, func, extra )

		local idx
		for k, v in ipairs( alarms ) do
			if timestamp < v.timestamp then
				idx = k
				break
			end
		end

		local a = {
			timestamp = timestamp,
			func = func,
			extra = extra
		}

		if idx then
			table.insert( alarms, idx, a )
		else
			table.insert( alarms, a )
		end

	end


	--
	-- Retrieves the soonest alarm.
	--
	local function getAlarm( )

		if #alarms == 0 then
			return false
		else
			return alarms[1].timestamp
		end

	end


	--
	-- Calls user alarms.
	--
	local function invoke( timestamp )
		while
			#alarms > 0 and
			alarms[ 1 ].timestamp <= timestamp
		do
			alarms[ 1 ].func( alarms[ 1 ].timestamp, alarms[ 1 ].extra )
			table.remove( alarms, 1 )
		end
	end


	--
	-- Public interface
	--
	return {
		alarm    = alarm,
		getAlarm = getAlarm,
		invoke   = invoke
	}


end )( )

--============================================================================
-- Lsyncd runner's plugs. These functions are called from core.
--============================================================================

--
-- Current status of Lsyncd.
--
-- 'init'  ... on (re)init
-- 'run'   ... normal operation
-- 'fade'  ... waits for remaining processes
--
local lsyncdStatus = 'init'

--
-- The cores interface to the runner.
--
local runner = { }

--
-- Last time said to be waiting for more child processes
--
local lastReportedWaiting = false

--
-- Called from core whenever Lua code failed.
--
-- Logs a backtrace
--
function runner.callError( message )
	log('Error', 'in Lua: ', message )

	-- prints backtrace
	local level = 2
	while true do

		local info = debug.getinfo( level, 'Sl' )

		if not info then
			terminate( -1 )
		end

		log(
			'Error',
			'Backtrace ',
			level - 1, ' :',
			info.short_src, ':',
			info.currentline
		)

		level = level + 1
	end
end


--
-- Called from core whenever a child process has finished and
-- the zombie process was collected by core.
--
function runner.collectProcess( pid, exitcode )

	processCount = processCount - 1

	if processCount < 0 then
		error( 'negative number of processes!' )
	end

	for _, s in Syncs.iwalk() do
		if s:collect(pid, exitcode) then return end
	end

end

--
-- Called from core everytime a masterloop cycle runs through.
--
-- This happens in case of
--   * an expired alarm.
--   * a returned child process.
--   * received filesystem events.
--   * received a HUP, TERM or INT signal.
--
function runner.cycle(
	timestamp   -- the current kernel time (in jiffies)
)

	if lsyncdStatus == 'fade' then

		if processCount > 0 then

			if
				lastReportedWaiting == false or
				timestamp >= lastReportedWaiting + 60
			then
				lastReportedWaiting = timestamp

				log(
					'Normal',
					'waiting for ',
					processCount,
					' more child processes.'
				)
			end

			return true
		else

			return false
		end
	end

	if lsyncdStatus ~= 'run' then
		error( 'runner.cycle() called while not running!' )
	end

	--
	-- goes through all syncs and spawns more actions
	-- if possibly. But only let Syncs invoke actions if
	-- not at global limit
	--
	if
		not uSettings.maxProcesses or
		processCount < uSettings.maxProcesses
	then
		local start = Syncs.getRound( )

		local ir = start

		repeat

			local s = Syncs.get( ir )
			s:invokeActions( timestamp )
			ir = ir + 1

			if ir > Syncs.size( ) then

				ir = 1
			end
		until ir == start

		Syncs.nextRound( )
	end

	UserAlarms.invoke( timestamp )

	if uSettings.statusFile then
		StatusFile.write( timestamp )
	end

	return true
end

--
-- Called by core if '-help' or '--help' is in
-- the arguments.
--
function runner.help( )
	io.stdout:write(
[[

USAGE:
  runs a config file:
    lsyncd [OPTIONS] [CONFIG-FILE]

  default rsync behaviour:
    lsyncd [OPTIONS] -rsync [SOURCE] [TARGET]

  default rsync with mv's through ssh:
    lsyncd [OPTIONS] -rsyncssh [SOURCE] [HOST] [TARGETDIR]

  default local copying mechanisms (cp|mv|rm):
    lsyncd [OPTIONS] -direct [SOURCE] [TARGETDIR]

OPTIONS:
  -delay SECS         Overrides default delay times
  -help               Shows this
  -insist             Continues startup even if it cannot connect
  -log    all         Logs everything (debug)
  -log    scarce      Logs errors only
  -log    [Category]  Turns on logging for a debug category
  -logfile FILE       Writes log to FILE (DEFAULT: uses syslog)
  -nodaemon           Does not detach and logs to stdout/stderr
  -pidfile FILE       Writes Lsyncds PID into FILE
  -runner FILE        Loads Lsyncds lua part from FILE
  -version            Prints versions and exits

LICENSE:
  GPLv2 or any later version.

SEE:
  `man lsyncd` for further information.

]])

--
--  -monitor NAME       Uses operating systems event montior NAME
--                      (inotify/fanotify/fsevents)

	os.exit( -1 )
end


--
-- Called from core to parse the command line arguments
--
-- returns a string as user script to load.
--    or simply 'true' if running with rsync bevaiour
--
-- terminates on invalid arguments.
--
function runner.configure( args, monitors )

	Monitors.initialize( monitors )

	--
	-- a list of all valid options
	--
	-- first paramter is the number of parameters an option takes
	-- if < 0 the called function has to check the presence of
	-- optional arguments.
	--
	-- second paramter is the function to call
	--
	local options = {

		-- log is handled by core already.

		delay =
			{
				1,
				function( secs )
					clSettings.delay = secs + 0
				end
			},

		insist =
			{
				0,
				function( )
					clSettings.insist = true
				end
			},

		log =
			{
				1,
				nil
			},

		logfile =
			{
				1,
				function( file )
					clSettings.logfile = file
				end
			},

		monitor =
			{
				-1,
				function( monitor )
					if not monitor then
						io.stdout:write( 'This Lsyncd supports these monitors:\n' )
						for _, v in ipairs(Monitors.list) do
							io.stdout:write('   ',v,'\n')
						end

						io.stdout:write('\n')

						lsyncd.terminate(-1)
					else
						clSettings.monitor = monitor
					end
				end
			},

		nodaemon =
			{
				0,
				function( )
					clSettings.nodaemon = true
				end
			},

		pidfile =
			{
				1,
				function( file )
					clSettings.pidfile=file
				end
			},

		rsync    =
			{
				2,
				function( src, trg )
					clSettings.syncs = clSettings.syncs or { }
					table.insert(
						clSettings.syncs,
						{ 'rsync', src, trg }
					)
				end
			},

		rsyncssh =
			{
				3,
				function( src, host, tdir )
					clSettings.syncs = clSettings.syncs or { }
					table.insert(
						clSettings.syncs,
						{ 'rsyncssh', src, host, tdir }
					)
				end
			},

		direct =
			{
				2,
				function( src, trg )
					clSettings.syncs = clSettings.syncs or { }
					table.insert(
						clSettings.syncs,
						{ 'direct', src, trg }
					)
				end
			},

		version =
			{
				0,
				function( )
					io.stdout:write( 'Version: ', lsyncd_version, '\n' )
					os.exit( 0 )
				end
			}
	}

	-- non-opts is filled with all args that were no part dash options

	local nonopts = { }

	local i = 1
	while i <= #args do

		local a = args[ i ]

		if a:sub( 1, 1 ) ~= '-' then
			table.insert( nonopts, args[ i ] )
		else
			if a:sub( 1, 2 ) == '--' then
				a = a:sub( 3 )
			else
				a = a:sub( 2 )
			end

			local o = options[ a ]

			if not o then
				log(
					'Error',
					'unknown option command line option ',
					args[i]
				)
				os.exit( -1 )
			end

			if o[ 1 ] >= 0 and i + o[ 1 ] > #args then
				log( 'Error', a ,' needs ', o[ 1 ],' arguments' )
				os.exit( -1 )
			elseif o[1] < 0 then
				o[ 1 ] = -o[ 1 ]
			end

			if o[ 2 ] then
				if o[ 1 ] == 0 then
					o[ 2 ]( )
				elseif o[ 1 ] == 1 then
					o[ 2 ]( args[i + 1] )
				elseif o[ 1 ] == 2 then
					o[ 2 ]( args[i + 1], args[i + 2] )
				elseif o[ 1 ] == 3 then
					o[ 2 ]( args[i + 1], args[i + 2], args[i + 3] )
				end
			end
			i = i + o[1]
		end
		i = i + 1

	end

	if clSettings.syncs then

		if #nonopts ~= 0 then
			log(
				'Error',
				'There cannot be command line syncs and config file together.'
			)
			os.exit( -1 )
		end

	else

		if #nonopts == 0 then

			runner.help( args[ 0 ] )

		elseif #nonopts == 1 then

			return nonopts[ 1 ]

		else

			-- TODO make this possible
			log(
				'Error',
				'There can only be one config file in command line.'
			)
			os.exit( -1 )

		end

	end
end


--
-- Called from core on init or restart after user configuration.
--
-- firstTime:
--    true when Lsyncd startups the first time,
--    false on resets, due to HUP signal or monitor queue overflow.
--
function runner.initialize( firstTime )

	if settings ~= settingsSafe then
		log(
			'Warn',
			'settings = { ... } is deprecated.\n'..
			'      please use settings{ ... } (without the equal sign)'
		)

		for k, v in pairs( settings ) do
			uSettings[ k ] = v
		end

	end

	lastReportedWaiting = false

	--
	-- From this point on, no globals may be created anymore
	--
	lockGlobals( )

	--
	-- copies simple settings with numeric keys to 'key = true' settings.
	--
	-- FIXME this can be removed when
	-- Lsyncd 2.0.x backwards compatibility is dropped
	--
	for k, v in ipairs( uSettings ) do

		if uSettings[ v ] then
			log(
				'Error',
				'Double setting "' .. v.. '"'
			)
			os.exit( -1 )
		end

		uSettings[ v ]= true

	end

	--
	-- all command line settings overwrite config file settings
	--
	for k, v in pairs( clSettings ) do
		if k ~= 'syncs' then
			uSettings[ k ] = v
		end
	end

	--
	-- implicitly forces 'insist' on Lsyncd resets.
	--
	if not firstTime then
		uSettings.insist = true
	end

	--
	-- adds syncs specified by command line.
	--
	if clSettings.syncs then

		for _, s in ipairs( clSettings.syncs ) do

			if s[ 1 ] == 'rsync' then

				sync{
					default.rsync,
					source = s[ 2 ],
					target = s[ 3 ]
				}

			elseif s[ 1 ] == 'rsyncssh' then

				sync{
					default.rsyncssh,
					source = s[ 2 ],
					host   = s[ 3 ],
					targetdir=s[ 4 ]
				}

			elseif s[ 1 ] == 'direct' then
				sync{
					default.direct,
					source=s[ 2 ],
					target=s[ 3 ]
				}

			end

		end

	end

	if uSettings.nodaemon then
		lsyncd.configure( 'nodaemon' )
	end

	if uSettings.logfile then
		lsyncd.configure( 'logfile', uSettings.logfile )
	end

	if uSettings.logident then
		lsyncd.configure( 'logident', uSettings.logident )
	end

	if uSettings.logfacility then
		lsyncd.configure( 'logfacility', uSettings.logfacility )
	end

	if uSettings.pidfile then
		lsyncd.configure( 'pidfile', uSettings.pidfile )
	end

	--
	-- Transfers some defaults to uSettings
	--
	if uSettings.statusInterval == nil then
		uSettings.statusInterval = default.statusInterval
	end

	-- makes sure the user gave Lsyncd anything to do
	if Syncs.size() == 0 then

		log(
			'Error',
			'Nothing to watch!'
		)

		os.exit( -1 )
	end

	-- from now on use logging as configured instead of stdout/err.
	lsyncdStatus = 'run';

	lsyncd.configure( 'running' );

	local ufuncs = {
		'onAttrib',
		'onCreate',
		'onDelete',
		'onModify',
		'onMove',
		'onStartup',
	}

	-- translates layer 3 scripts
	for _, s in Syncs.iwalk() do

		-- checks if any user functions is a layer 3 string.
		local config = s.config

		for _, fn in ipairs(ufuncs) do

			if type(config[fn]) == 'string' then

				local ft = functionWriter.translate(config[fn])
				config[fn] = assert(loadstring('return '..ft))()

			end

		end
	end

	-- runs through the Syncs created by users
	for _, s in Syncs.iwalk( ) do

		if s.config.monitor == 'inotify' then

			Inotify.addSync( s, s.source )

		elseif s.config.monitor == 'fsevents' then

			Fsevents.addSync( s, s.source )

		else

			error(
				'sync ' ..
				s.config.name ..
				' has no known event monitor interface.'
			)

		end

		-- if the sync has an init function, the init delay
		-- is stacked which causes the init function to be called.
		if s.config.init then

			s:addInitDelay( )

		end
	end

end

--
-- Called by core to query the soonest alarm.
--
-- @return false ... no alarm, core can in untimed sleep, or
--         true  ... immediate action
--         times ... the alarm time (only read if number is 1)
--
function runner.getAlarm( )

	if lsyncdStatus ~= 'run' then
		return false
	end

	local alarm = false

	--
	-- Checks if 'a' is sooner than the 'alarm' up-value.
	--
	local function checkAlarm( a )

		if a == nil then
			error('got nil alarm')
		end

		if alarm == true or not a then
			-- 'alarm' is already immediate or
			-- a not a new alarm
			return
		end

		-- sets 'alarm' to a if a is sooner
		if not alarm or a < alarm then
			alarm = a
		end

	end

	--
	-- checks all syncs for their earliest alarm,
	-- but only if the global process limit is not yet reached.
	--
	if
		not uSettings.maxProcesses or
		processCount < uSettings.maxProcesses
	then
		for _, s in Syncs.iwalk( ) do
			checkAlarm( s:getAlarm ( ))
		end
	else
		log(
			'Alarm',
			'at global process limit.'
		)
	end

	-- checks if a statusfile write has been delayed
	checkAlarm( StatusFile.getAlarm( ) )

	-- checks for an userAlarm
	checkAlarm( UserAlarms.getAlarm( ) )

	log(
		'Alarm',
		'runner.getAlarm returns: ',
		alarm
	)

	return alarm

end


--
-- Called when an file system monitor events arrive
--
runner.inotifyEvent = Inotify.event
runner.fsEventsEvent = Fsevents.event

--
-- Collector for every child process that finished in startup phase
--
function runner.collector(
	pid,       -- pid of the child process
	exitcode   -- exitcode of the child process
)
	if exitcode ~= 0 then
		log('Error', 'Startup process',pid,' failed')
		terminate( -1 )
	end

	return 0
end

--
-- Called by core when an overflow happened.
--
function runner.overflow( )

	log(
		'Normal',
		'--- OVERFLOW in event queue ---'
	)

	lsyncdStatus = 'fade'

end

--
-- Called by core on a hup signal.
--
function runner.hup( )

	log(
		'Normal',
		'--- HUP signal, resetting ---'
	)

	lsyncdStatus = 'fade'

end

--
-- Called by core on a term signal.
--
function runner.term( sigcode )

	local sigtexts = {
		[ 2 ] =
			'INT',

		[ 15 ] =
			'TERM'
	};

	local sigtext = sigtexts[ sigcode ];

	if not sigtext then
		sigtext = 'UNKNOWN'
	end

	log(
		'Normal',
		'--- ', sigtext, ' signal, fading ---'
	)

	lsyncdStatus = 'fade'

end

--============================================================================
-- Lsyncd runner's user interface
--============================================================================

--
-- Main utility to create new observations.
--
-- Returns an Inlet to that sync.
--
function sync( opts )

	if lsyncdStatus ~= 'init' then
		error(
			'Sync can only be created during initialization.',
			2
		)
	end

	return Syncs.add( opts ).inlet

end


--
-- Spawns a new child process.
--
function spawn(
	agent,  -- the reason why a process is spawned.
	        -- a delay or delay list for a sync
	        -- it will mark the related files as blocked.
	binary, -- binary to call
	...     -- arguments
)
	if
		agent == nil or
		type( agent ) ~= 'table'
	then
		error(
			'spawning with an invalid agent',
			2
		)
	end

	if lsyncdStatus == 'fade' then
		log(
			'Normal',
			'ignored process spawning while fading'
		)
		return
	end

	if type( binary ) ~= 'string' then
		error(
			'calling spawn(agent, binary, ...): binary is not a string',
			2
		)
	end

	local dol = InletFactory.getDelayOrList( agent )

	if not dol then
		error(
			'spawning with an unknown agent',
			2
		)
	end

	--
	-- checks if a spawn is called on an already active event
	--
	if dol.status then

		-- is an event

		if dol.status ~= 'wait' then
			error('spawn() called on an non-waiting event', 2)
		end

	else
		-- is a list

		for _, d in ipairs(dol) do
			if d.status ~= 'wait' and d.status ~= 'block' then
				error('spawn() called on an non-waiting event list', 2)
			end
		end

	end

	--
	-- tries to spawn the process
	--
	local pid = lsyncd.exec( binary, ... )

	if pid and pid > 0 then

		processCount = processCount + 1
		if
			uSettings.maxProcesses and
			processCount > uSettings.maxProcesses
		then
			error( 'Spawned too much processes!' )
		end

		local sync = InletFactory.getSync( agent )

		-- delay or list
		if dol.status then

			-- is a delay
			dol.status = 'active'
			sync.processes[ pid ] = dol

		else

			-- is a list
			for _, d in ipairs( dol ) do
				d.status = 'active'
			end
			sync.processes[ pid ] = dol

		end

	end
end

--
-- Spawns a child process using the default shell.
--
function spawnShell(
	agent,     -- the delay(list) to spawn the command for
	command,   -- the shell command
	...        -- additonal arguments
)
	return spawn(
		agent,
		'/bin/sh',
		'-c',
		command,
		'/bin/sh',
		...
	)
end

-----
-- Observes a filedescriptor
--
function observefd(
	fd,     -- file descriptor
	ready,  -- called when fd is ready to be read
	writey  -- called when fd is ready to be written
)
	return lsyncd.observe_fd(
		fd,
		ready,
		writey
	)
end

--
-- Stops observeing a filedescriptor
--
function nonobservefd(
	fd      -- file descriptor
)
	return lsyncd.nonobserve_fd( fd )
end

--
-- Calls func at timestamp.
--
-- Use now() to receive current timestamp
-- add seconds with '+' to it
--
alarm = UserAlarms.alarm

--
-- Comfort routine also for user.
-- Returns true if 'String' starts with 'Start'
--
function string.starts( String, Start )

	return string.sub( String, 1, #Start )==Start

end

--
-- Comfort routine also for user.
-- Returns true if 'String' ends with 'End'
--
function string.ends( String, End )

	return End == '' or string.sub( String, -#End ) == End

end

--
-- The Lsyncd 2.1 settings call
--
function settings( a1 )
	-- if a1 is a string this is a get operation
	if type( a1 ) == 'string' then
		return uSettings[ a1 ]
	end

	-- if its a table it sets all the value of the bale
	for k, v in pairs( a1 ) do
		if type( k ) ~= 'number' then
			uSettings[ k ] = v
		else
			uSettings[ v ] = true
		end
	end
end
settingsSafe = settings

--
-- Returns the core the runners function interface.
--
return runner