--~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- 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.
--
-- 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
	-- checks if the runner is being loaded twice
	lsyncd.log('Error', 'You cannot use the lsyncd runner as configuration file!')
	lsyncd.terminate(-1) -- ERRNO
end
lsyncd_version = '2.0.7'

--
-- 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

--============================================================================
-- 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

	-- objects 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 let the move go first
				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

	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,

		-----
		-- Tells this isn't a list.
		--
		isList = function()
			return false
		end,

		-----
		-- Return 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 string.byte(getPath(event), -1) == 47
		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.
		-- Excludes a trailing slash for dirs.
		--
		basename = function(event)
			return string.match(getPath(event), '([^/]+)/?$')
		end,

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

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

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

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

		------
		-- Returns the target.
		-- Just for user comfort
		--
		-- (except here, the lsyncd.runner does not care event about the
		-- existance of 'target', this is up to the scripts.)
		--
		target = function(event)
			return e2d[event].sync.config.target
		end,

		------
		-- Returns the relative dir/file appended to the target.
		-- Includes 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.
		-- Includes 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.
		-- Excludes 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 event 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.
	-- TODO check memory use
	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)
		-- lua 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.
	-- this one is split, one for user one for runner.
	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.
	--
	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 -- does not begin with '^/'
			-- 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 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) -- ERRNO
		end
	    for line in f:lines() do
			-- lsyncd 2.0 does not support includes
			if 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 inclusively 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) --ERRNO
			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) --ERRNO
			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 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 nearest 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 settings.maxProcesses and processCount >= settings.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 default nevertheless to cause less confusion
		-- so name 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.excludeFrom then
			s.excludes:loadFile(config.excludeFrom)
		end

		return s
	end

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


-----
-- Syncs - a singleton
--
-- It maintains all configured directories to be synced.
--
local Syncs = (function()
	-----
	-- the list of all syncs
	--
	local list = 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 > #list 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 list[i];
	end

	-----
	-- Inheritly copies all non integer keys from
	-- copy source (cs) to copy destination (cd).
	--
	-- all entries with integer keys are treated as new sources to copy
	--
	local function inherit(cd, cs)
		-- first copies from source all
		-- non-defined non-integer keyed values
		for k, v in pairs(cs) do
			if type(k) ~= 'number' and cd[k] == nil then
				cd[k] = v
			end
		end
		-- first recurses into all integer keyed tables
		for i, v in ipairs(cs) do
			if type(v) == 'table' then
				inherit(cd, v)
			end
		end
	end

	-----
	-- Adds a new sync (directory-tree to observe).
	--
	local function add(config)
		-- Creates a new config table and inherit all keys/values
		-- from integer keyed tables
		local uconfig = config
		config = {}
		inherit(config, uconfig)

		-- Lets settings or commandline override delay values.
		if settings then
			config.delay = settings.delay or config.delay
		end

		-- at very first lets the userscript 'prepare' function
		-- fill out more values.
		if type(config.prepare) == 'function' then
			-- explicitly gives a writeable copy of config.
			config.prepare(config)
		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) -- ERRNO
		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) -- ERRNO
		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, use e.g. "config = default.rsync".')
			terminate(-1) -- ERRNO
		end

		-- loads a default value for an option if not existent
		if not settings then
			settings = {}
		end
		local defaultValues = {
			'action',
			'collect',
			'init',
			'maxDelays',
			'maxProcesses',
		}
		for _, dn in pairs(defaultValues) do
			if config[dn] == nil then
				config[dn] = settings[dn] or default[dn]
			end
		end

		-- the monitor to use
		config.monitor =
			settings.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) -- ERRNO
		end

		--- creates the new sync
		local s = Sync.new(config)
		table.insert(list, s)
		return s
	end

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

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

	------
	-- Tests if any sync is interested in a path.
	--
	local function concerns(path)
		for _, s in ipairs(list) 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 should be enclosed here.
--
local Inotify = (function()

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

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

	-----
	-- A list indexed by sync's containing the root path this
	-- sync is interested in.
	--
	local syncRoots = {}

	-----
	-- Stops watching a directory
	--
	-- @param path    absolute path to unwatch
	-- @param 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 = (settings and settings.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
			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.
	--
	-- 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
	--
	local function event(etype, wd, isdir, time, filename, wd2, filename2)
		if isdir then
			filename = filename..'/'
			if filename2 then filename2 = filename2..'/' end
		end

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

		-- 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

		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 inotifies to a filedescriptor
	--
	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, watches the whole filesystems
--
-- All fsevents specific implementation should be enclosed here.
--
local Fsevents = (function()

	-----
	-- A list indexed by sync's containing the root path this
	-- 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 any event has occured.
	--
	-- 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'
	--
	local function event(etype, isdir, time, path, path2)
		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
			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 inotifies 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 configuration.
--
local functionWriter = (function()

	-----
	-- all variables for layer 3
	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
	--
	-- @param a string where parameters are seperated by spaces.
	--
	-- @return a table of arguments
	--
	local function splitStr(str)
		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 much coding blocks.
	--
	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 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, ')')

		-- some logic to not write too often
		if settings.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 + settings.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(settings.statusFile, 'w')
		if not f then
			log('Error', 'Cannot open status file "'..settings.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 the userscript make its 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 nearest 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 plugs. These functions will be 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 = {}

-----
-- 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) -- ERRNO
		end
		log('Error', 'Backtrace ',level - 1,' :',info.short_src,':',info.currentline)
		level = level + 1
	end
end

-----
-- Called from code whenever a child process finished and
-- 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 or TERM signal.
--
-- @param timestamp   the current kernel time (in jiffies)
--
function runner.cycle(timestamp)
	-- goes through all syncs and spawns more actions
	-- if possible
	if lsyncdStatus == 'fade' then
		if processCount > 0 then
			log('Normal', 'waiting for ',processCount,' more child processes.')
			return true
		else
			return false
		end
	end
	if lsyncdStatus ~= 'run' then
		error('runner.cycle() called while not running!')
	end

	--- only let Syncs invoke actions if not on global limit
	if not settings.maxProcesses or processCount < settings.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 settings.statusFile then
		StatusFile.write(timestamp)
	end

	return true
end

-----
-- Called by core before anything is '-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) -- ERRNO
end


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

-----
-- 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 number of options
	--       if < 0 the function checks existance
	-- second paramter is function to call when in args
	--
	local options = {
		-- log is handled by core already.
		delay    =
			{1, function(secs)
				clSettings.delay = secs
			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); -- ERRNO
				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}
	}
	-- nonopts 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) -- ERRNO
			end
			if o[1] >= 0 and i + o[1] > #args then
				log('Error',a,' needs ',o[1],' arguments')
				os.exit(-1) -- ERRNO
			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 default syncs with a config file.')
			os.exit(-1) -- ERRNO
		end
	else
		if #nonopts == 0 then
			runner.help(args[0])
		elseif #nonopts == 1 then
			return nonopts[1]
		else
			log('Error', 'There can only be one config file in command line.')
			os.exit(-1) -- ERRNO
		end
	end
end


----
-- Called from core on init or restart after user configuration.
--
-- @firstTime true the first time Lsyncd startup, false on resets
-- due to HUP signal or monitor queue OVERFLOW.
--
function runner.initialize(firstTime)
	-- creates settings if user didnt
	settings = settings or {}

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

	-- copies simple settings with numeric keys to 'key=true' settings.
	for k, v in ipairs(settings) do
		if settings[v] then
			log('Error', 'Double setting "'..v..'"')
			os.exit(-1) -- ERRNO
		end
		settings[v]=true
	end

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

	-- implicitly force insist to be true on Lsyncd resets.
	if not firstTime then
		settings.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 settings.nodaemon then
		lsyncd.configure('nodaemon')
	end
	if settings.logfile then
		lsyncd.configure('logfile', settings.logfile)
	end
	if settings.logident then
		lsyncd.configure('logident', settings.logident)
	end
	if settings.logfacility then
		lsyncd.configure('logfacility', settings.logfacility)
	end
	if settings.pidfile then
		lsyncd.configure('pidfile', settings.pidfile)
	end

	-----
	-- transfers some defaults to settings
	if settings.statusInterval == nil then
		settings.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) -- ERRNO
	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, stacks an init delay
		-- that will cause the init function to be called.
		if s.config.init then
			s:addInitDelay()
		end
	end
end

----
-- Called by core to query 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 current nearest alarm or a is earlier
	--
	local function checkAlarm(a)
		if a == nil then
			error('got nil alarm')
		end
		if alarm == true or not a then
			-- already immediate or no new alarm
			return
		end
		-- returns the ealier time
		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 settings.maxProcesses or processCount < settings.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 inotify event arrived.
-- Simply forwards it directly to the object.
--
runner.inotifyEvent = Inotify.event
runner.fsEventsEvent = Fsevents.event

-----
-- Collector for every child process that finished in startup phase
--
-- Parameters are pid and exitcode of child process
--
-- Can return either a new pid if one other child process
-- has been spawned as replacement (e.g. retry) or 0 if
-- finished/ok.
--
function runner.collector(pid, exitcode)
	if exitcode ~= 0 then
		log('Error', 'Startup process',pid,' failed')
		terminate(-1) -- ERRNO
	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()
	log('Normal', '--- TERM signal, fading ---')
	lsyncdStatus = 'fade'
end

--============================================================================
-- Lsyncd 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.
--
-- @param agent   the reason why a process is spawned.
--                normally this is a delay/event of a sync.
--                it will mark the related files as blocked.
-- @param binary  binary to call
-- @param ...     arguments
--
function spawn(agent, binary, ...)
	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 spawn is called on already active event
	if dol.status then
		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

	local pid = lsyncd.exec(binary, ...)

	if pid and pid > 0 then
		processCount = processCount + 1
		if settings.maxProcesses and processCount > settings.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, command, ...)
	return spawn(agent, '/bin/sh', '-c', command, '/bin/sh', ...)
end

-----
-- Observes a filedescriptor
--
function observefd(fd, ready, writey)
	return lsyncd.observe_fd(fd, ready, writey)
end

-----
-- Nonobserves a filedescriptor
--
function nonobservefd(fd)
	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

-----
-- provides a default empty settings table.
--
settings = {}

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