FieldworkAIDriver.lua

--[[
This file is part of Courseplay (https://github.com/Courseplay/courseplay)
Copyright (C) 2018 Peter Vajko

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
]]

--[[
Fieldwork AI Driver

Can follow a fieldworking course, perform turn maneuvers, turn on/off and raise/lower implements,
add adjustment course if needed.
]]

---@class FieldworkAIDriver : AIDriver
FieldworkAIDriver = CpObject(AIDriver)

FieldworkAIDriver.myStates = {
	ON_FIELDWORK_COURSE = {},
	WORKING = {},
	ON_UNLOAD_OR_REFILL_COURSE = {},
	RETURNING_TO_FIRST_POINT = {},
	UNLOAD_OR_REFILL_ON_FIELD = {},
	WAITING_FOR_UNLOAD_OR_REFILL ={}, -- while on the field
	ON_CONNECTING_TRACK = {},
	WAITING_FOR_LOWER = {},
	WAITING_FOR_LOWER_DELAYED = {},
	WAITING_FOR_STOP = {},
	ON_UNLOAD_OR_REFILL_WITH_AUTODRIVE = {},
	TURNING = {},
}

-- Our class implementation does not call the constructor of base classes
-- through multiple level of inheritances therefore we must explicitly call
-- the base class ctr.
function FieldworkAIDriver:init(vehicle)
	courseplay.debugVehicle(11,vehicle,'FieldworkAIDriver:init()')
	AIDriver.init(self, vehicle)
	self:initStates(FieldworkAIDriver.myStates)
	-- waiting for tools to turn on, unfold and lower
	self.waitingForTools = true
	self.debugChannel = 14
	-- waypoint index on main (fieldwork) course where we aborted the work before going on
	-- an unload/refill course
	self.aiDriverData.continueFieldworkAtWaypoint = 1
	-- force stop for unload/refill, for example by a tractor, otherwise the same as stopping because full or empty
	self.heldForUnloadRefill = false
	self.heldForUnloadRefillTimestamp = 0
	-- stop and raise implements while refilling/unloading on field
	self.stopImplementsWhileUnloadOrRefillOnField = true
	-- duration of the last turn maneuver. This is a default value and the driver will measure
	-- the actual turn times. Used to calculate the remaining fieldwork time
	self.turnDurationMs = 20000
end

function FieldworkAIDriver:writeUpdateStream(streamId)
	AIDriver.writeUpdateStream(self,streamId)
end 

function FieldworkAIDriver:readUpdateStream(streamId)
	AIDriver.readUpdateStream(self,streamId)
end

function FieldworkAIDriver:setHudContent()
	AIDriver.setHudContent(self)
	courseplay.hud:setFieldWorkAIDriverContent(self.vehicle)
end

function FieldworkAIDriver.register()
	-- TODO: maybe just build a table with all specs we want to handle
	local strawHarvestBaleCollectSpec

	AIImplement.getCanImplementBeUsedForAI = Utils.overwrittenFunction(AIImplement.getCanImplementBeUsedForAI,
		function(self, superFunc)
			if self.customEnvironment ~= nil then
				strawHarvestBaleCollectSpec = _G[self.customEnvironment].StrawHarvestBaleCollect
			end
			-- if we have the Straw Harvest add on we want to handle the bale collector
			if SpecializationUtil.hasSpecialization(BaleLoader, self.specializations) then
				return true
			elseif SpecializationUtil.hasSpecialization(BaleWrapper, self.specializations) then
				return true
			elseif SpecializationUtil.hasSpecialization(Pickup, self.specializations) then
				return true
			elseif strawHarvestBaleCollectSpec and SpecializationUtil.hasSpecialization(strawHarvestBaleCollectSpec, self.specializations) then
				return true
			elseif superFunc ~= nil then
				return superFunc(self)
			end
		end)

	-- Make sure the Giants helper can't be hired for implements which have no Giants AI functionality
	AIVehicle.getCanStartAIVehicle = Utils.overwrittenFunction(AIVehicle.getCanStartAIVehicle,
		function(self, superFunc)
			if self.customEnvironment ~= nil then
				strawHarvestBaleCollectSpec = _G[self.customEnvironment].StrawHarvestBaleCollect
			end
			-- Only the courseplay helper can handle bale loaders.
			if FieldworkAIDriver.hasImplementWithSpecialization(self, BaleLoader) or
					FieldworkAIDriver.hasImplementWithSpecialization(self, BaleWrapper) or
					FieldworkAIDriver.hasImplementWithSpecialization(self, Pickup) then
				return false
			end
			if strawHarvestBaleCollectSpec and FieldworkAIDriver.hasImplementWithSpecialization(self, strawHarvestBaleCollectSpec) then
				return false
			end
			if superFunc ~= nil then
				return superFunc(self)
			end
		end)

	BaleLoaderAIDriver.register()

	Pickup.onAIImplementStartLine = Utils.overwrittenFunction(Pickup.onAIImplementStartLine,
		function(self, superFunc)
			if superFunc ~= nil then superFunc(self) end
			self:setPickupState(true)
		end)

	Pickup.onAIImplementEndLine = Utils.overwrittenFunction(Pickup.onAIImplementEndLine,
		function(self, superFunc)
			if superFunc ~= nil then superFunc(self) end
			self:setPickupState(false)
		end)

	-- TODO: move these to another dedicated class for implements?
	local PickupRegisterEventListeners = function(vehicleType)
		print('## Courseplay: Registering event listeners for loader wagons.')
		SpecializationUtil.registerEventListener(vehicleType, "onAIImplementStartLine", Pickup)
		SpecializationUtil.registerEventListener(vehicleType, "onAIImplementEndLine", Pickup)
	end

	print('## Courseplay: Appending event listener for loader wagons.')
	Pickup.registerEventListeners = Utils.appendedFunction(Pickup.registerEventListeners, PickupRegisterEventListeners)
end

function FieldworkAIDriver.hasImplementWithSpecialization(vehicle, specialization)
	return FieldworkAIDriver.getImplementWithSpecialization(vehicle, specialization) ~= nil
end

function FieldworkAIDriver.getImplementWithSpecialization(vehicle, specialization)
	local aiImplements = vehicle:getAttachedAIImplements()
	for _, implement in ipairs(aiImplements) do
		if SpecializationUtil.hasSpecialization(specialization, implement.object.specializations) then
			return implement.object
		end
	end
end

--- Start the course and turn on all implements when needed
--- @param startingPoint StartingPointSetting at which waypoint to start the course
function FieldworkAIDriver:start(startingPoint)
	self:debug('Starting in mode %d', self.mode)
	self.ppc:registerListeners(self, 'onWaypointPassed', 'onWaypointChange')
	self:setMarkers()
	self:beforeStart()
	-- time to lower all implements
	self:findLoweringDurationMs()
	-- always enable alignment with first waypoint, this is needed to properly start/continue fieldwork
	self.alignmentEnabled = self.vehicle.cp.alignment.enabled
	self.vehicle.cp.alignment.enabled = true
	-- stop at the last waypoint by default
	self.vehicle.cp.stopAtEnd = true
	-- any offset imposed by the driver itself (tight turns, end of course, etc.), additional to any
	-- tool offsets
	self.aiDriverOffsetX = 0
	self.aiDriverOffsetZ = 0

	self:setUpCourses()

	-- now that we have our unload/refill and fieldwork courses set up, see where to start
	local closestFieldworkIx, dClosestFieldwork, closestFieldworkIxRightDirection, dClosestFieldworkRightDirection =
	self.fieldworkCourse:getNearestWaypoints(AIDriverUtil.getDirectionNode(self.vehicle))

	-- default to math.huge in case there isn't an unload refill course to make sure it only the fieldwork Ix is used
	local closestUnloadRefillIx, dClosestUnloadRefill, closestUnloadRefillIxRightDirection, dClosestUnloadRefillRightDirection =
	0, math.huge, 0, math.huge

	if self.unloadRefillCourse then
		closestUnloadRefillIx, dClosestUnloadRefill, closestUnloadRefillIxRightDirection, dClosestUnloadRefillRightDirection =
		self.unloadRefillCourse:getNearestWaypoints(AIDriverUtil.getDirectionNode(self.vehicle))
	end

	local ix = self.course and self.course:getCurrentWaypointIx()
	local startWithFieldwork

	if startingPoint:is(StartingPointSetting.START_AT_NEAREST_POINT) then
		if dClosestFieldwork < dClosestUnloadRefill then
			ix = closestFieldworkIx
			startWithFieldwork = true
			self:debug('Starting at nearest waypoint %d on fieldwork course', ix)
		else
			ix = closestUnloadRefillIx
			startWithFieldwork = false
			self:debug('Starting at nearest waypoint %d on unload/refill course', ix)
		end
	end

	if startingPoint:is(StartingPointSetting.START_AT_NEXT_POINT) then
		if dClosestFieldworkRightDirection < dClosestUnloadRefillRightDirection then
			ix = closestFieldworkIxRightDirection
			startWithFieldwork = true
			self:debug('Starting at nearest waypoint %d (best direction) on fieldwork course', ix)
		else
			ix = closestUnloadRefillIxRightDirection
			startWithFieldwork = false
			self:debug('Starting at nearest waypoint %d (best direction) on unload/refill course', ix)
		end
	end
	if startingPoint:is(StartingPointSetting.START_AT_FIRST_POINT) then
		self:debug('Starting at first waypoint')
		ix = 1
		startWithFieldwork = true
	end

	if startingPoint:is(StartingPointSetting.START_AT_CURRENT_POINT) then
		-- use last fieldwork waypoint if we have the same fieldwork course as before
		if self.fieldworkCourseHash == self.aiDriverData.lastFieldworkCourseHash then
			self:debug('Starting at current waypoint %d', self.aiDriverData.lastFieldworkWaypointIx)
			ix = self.aiDriverData.lastFieldworkWaypointIx
		else
			self:debug('Current waypoint not found, starting at first')
			ix = 1
		end
		startWithFieldwork = true
	end

	self.waitingForTools = true
	self.ppc:setNormalLookaheadDistance()

	if startWithFieldwork then
		self:startFieldworkWithPathfinding(ix)
	else
		self:changeToUnloadOrRefill()
		self:startCourseWithAlignment(self.unloadRefillCourse, ix)
	end
end

function FieldworkAIDriver:startFieldworkWithAlignment(ix)
	if self:startCourseWithAlignment(self.fieldworkCourse, ix) then
		self.state = self.states.ON_FIELDWORK_COURSE
		self.fieldworkState = self.states.TEMPORARY
	else
		self:changeToFieldwork()
	end
end

function FieldworkAIDriver:startFieldworkWithPathfinding(ix)
	if self:startCourseWithPathfinding(self.fieldworkCourse, ix) then
		self.state = self.states.ON_FIELDWORK_COURSE
		self.fieldworkState = self.states.TEMPORARY
	else
		self:debug('No path to fieldwork start found.')
		self:changeToFieldwork()
	end
end

--- Start course with pathfinding
--- Will find a path on a field avoiding fruit as much as possible from the
--- current position to waypoint ix of course and start driving.
--- When waypoint ix of course reached, switch to the course and continue driving.
---
--- If no path found will use an alignment course to reach waypoint ix of course.
---@param course Course
---@param ix number
---@return boolean true when a pathfinding successfully started or an alignment course was added
function FieldworkAIDriver:startCourseWithPathfinding(course, ix)
	-- if the implement is in the front, generate a path so the implement will be at the goal
	local zOffset = self.frontMarkerDistance > 0 and - self.frontMarkerDistance or 0
	return AIDriver.startCourseWithPathfinding(self, course, ix, zOffset,0)
end

function FieldworkAIDriver:xonPathfindingDone(path)
	if path and #path > 2 then
		self:debug('(FieldworkAIDriver) Pathfinding finished with %d waypoints (%d ms)', #path, self.vehicle.timer - (self.pathfindingStartedAt or 0))
		local tempCourse = Course(self.vehicle, courseGenerator.pointsToXzInPlace(path), true)
		self:startCourse(tempCourse, 1, self.courseAfterPathfinding, self.waypointIxAfterPathfinding)
		return true
	else
		self:debug('(FieldworkAIDriver) Pathfinding was not able to find a path in %d ms', self.vehicle.timer - (self.pathfindingStartedAt or 0))
		self:startCourse(self.courseAfterPathfinding, self.waypointIxAfterPathfinding)
		return false
	end
end

function FieldworkAIDriver:stop(msgReference)
	self:stopWork()
	-- Issue with persisting fieldwork data in multiplayer, as the client doesn't maintain the fieldworkcourse (client never calls start)
	-- Persisted fieldwork data isn't needed by the client anyway, as its all handled by the server (also in start)
	if g_server ~= nil then
		-- persist last fieldwork waypoint data (for 'start at current waypoint')
		self.aiDriverData.lastFieldworkCourseHash = self.fieldworkCourse:getHash()
		self.aiDriverData.lastFieldworkWaypointIx = self.fieldworkCourse:getCurrentWaypointIx()
	end
	AIDriver.stop(self, msgReference)
	-- Restore alignment settings. TODO: remove this setting from the HUD and always enable it
	self.vehicle.cp.alignment.enabled = self.alignmentEnabled
end

function FieldworkAIDriver:drive(dt)
	-- TODO: this is also called in UnloadableFieldworkAIDriver
	courseplay:updateFillLevelsAndCapacities(self.vehicle)
	if self.state == self.states.ON_FIELDWORK_COURSE then
		if self:driveFieldwork(dt) then
			-- driveFieldwork is driving, no need for AIDriver
			return
		end
	elseif self.state == self.states.ON_UNLOAD_OR_REFILL_COURSE then
		if self:driveUnloadOrRefill(dt) then
			-- someone else is driving, no need to call AIDriver.drive()
			return
		end
	elseif self.state == self.states.RETURNING_TO_FIRST_POINT then
		self:setSpeed(self:getFieldSpeed())
	elseif self.state == self.states.ON_UNLOAD_OR_REFILL_WITH_AUTODRIVE then
		-- AutoDrive is driving, don't call AIDriver.drive()
		return
	end
	self:setRidgeMarkers()
	self:resetUnloadOrRefillHold()
	AIDriver.drive(self, dt)
	self:measureTurnTime()
end

-- Hold for unload (or refill) for example a combine can be asked by a an unloading tractor
-- to stop and wait. Must be called in every loop to keep waiting because it will automatically be
-- reset and the vehicle restarted. This way the users don't explicitly need to call resumeAfterUnloadOrRefill()
function FieldworkAIDriver:holdForUnloadOrRefill()
	self.heldForUnloadRefill = true
	self.heldForUnloadRefillTimestamp = g_updateLoopIndex
end

function FieldworkAIDriver:resumeAfterUnloadOrRefill()
	self.heldForUnloadRefill = false
end

function FieldworkAIDriver:resetUnloadOrRefillHold()
	if g_updateLoopIndex > self.heldForUnloadRefillTimestamp + 10 then
		self:resumeAfterUnloadOrRefill()
	end
end


--- Doing the fieldwork (headlands or up/down rows, including the turns)
---@return boolean true if driveFieldwork() is driving (no need to call ALDriver.drive())
function FieldworkAIDriver:driveFieldwork(dt)
	local iAmDriving = false
	self:updateFieldworkOffset()
	if self.fieldworkState == self.states.WAITING_FOR_LOWER_DELAYED then
		-- getCanAIVehicleContinueWork() seems to return false when the implement being lowered/raised (moving) but
		-- true otherwise. Due to some timing issues it may return true just after we started lowering it, so this
		-- here delays the check for another cycle.
		self.fieldworkState = self.states.WAITING_FOR_LOWER
	elseif self.fieldworkState == self.states.WAITING_FOR_LOWER then
		if self.vehicle:getCanAIVehicleContinueWork() then
			self:debug('all tools ready, start working')
			self.fieldworkState = self.states.WORKING
			self:setSpeed(self:getWorkSpeed())
		else
			self:debug('waiting for all tools to lower')
			self:setSpeed(0)
			self:checkFillLevels()
		end
	elseif self.fieldworkState == self.states.WORKING then
		self:setSpeed(self:getWorkSpeed())
		self:manageConvoy()
		self:checkWeather()
		self:checkFillLevels()
		self:checkFuelLevels()
	elseif self.fieldworkState == self.states.UNLOAD_OR_REFILL_ON_FIELD then
		self:driveFieldworkUnloadOrRefill()
	elseif self.fieldworkState == self.states.TEMPORARY then
		self:setSpeed(self:getFieldSpeed())
	elseif self.fieldworkState == self.states.ON_CONNECTING_TRACK then
		self:setSpeed(self:getFieldSpeed())
	elseif self.fieldworkState == self.states.TURNING and self.aiTurn then
		iAmDriving = self.aiTurn:drive(dt)
	end
	return iAmDriving
end

function FieldworkAIDriver:checkFillLevels()
	if not self:allFillLevelsOk() or self.heldForUnloadRefill then
		self:stopAndChangeToUnload()
	end
end

function FieldworkAIDriver:stopAndChangeToUnload()
	if self.unloadRefillCourse and not self.heldForUnloadRefill then
		self:rememberWaypointToContinueFieldwork()
		self:debug('at least one tool is empty/full, aborting work at waypoint %d.', self.aiDriverData.continueFieldworkAtWaypoint or -1)
		self:changeToUnloadOrRefill()
		self:startCourseWithPathfinding(self.unloadRefillCourse, 1)
	else
		if self.vehicle.cp.settings.autoDriveMode:useForUnloadOrRefill() then
			-- Switch to AutoDrive when enabled 
			self:rememberWaypointToContinueFieldwork()
			self:stopWork()
			self:foldImplements()
			self.state = self.states.ON_UNLOAD_OR_REFILL_WITH_AUTODRIVE
			self:debug('passing the control to AutoDrive to run the unload/refill course.')
			self.vehicle.spec_autodrive:StartDrivingWithPathFinder(self.vehicle, self.vehicle.ad.mapMarkerSelected, self.vehicle.ad.mapMarkerSelected_Unload, self, FieldworkAIDriver.onEndCourse, nil);
		else
			-- otherwise we'll 
			self:changeToFieldworkUnloadOrRefill()
		end;
	end
end

function FieldworkAIDriver:checkFuelLevels()
	if self.vehicle.getConsumerFillUnitIndex ~= nil then
		local dieselIndex = self.vehicle:getConsumerFillUnitIndex(FillType.DIESEL)
		local currentFuelPercentage = self.vehicle:getFillUnitFillLevelPercentage(dieselIndex) * 100;
		
		if currentFuelPercentage < 15 then
			self:stopAndRefuel()
		end;
	end
end

function FieldworkAIDriver:stopAndRefuel()
	if self.vehicle.cp.settings.autoDriveMode:useForUnloadOrRefill() then
		-- Switch to AutoDrive when enabled 
		self:rememberWaypointToContinueFieldwork()
		self:stopWork()
		self:foldImplements()
		self.state = self.states.ON_UNLOAD_OR_REFILL_WITH_AUTODRIVE
		self:debug('passing the control to AutoDrive to run the fuel refill course.')
		self.vehicle.spec_autodrive:StartDrivingWithPathFinder(self.vehicle, self.vehicle.ad.mapMarkerSelected, -2, self, FieldworkAIDriver.onEndCourse, nil);
	end
end

---@return boolean true if unload took over the driving
function FieldworkAIDriver:driveUnloadOrRefill()
	if self.course:isTemporary() then
		-- use the courseplay speed limit until we get to the actual unload course fields (on alignment/temporary)
		self:setSpeed(self.vehicle.cp.speeds.field)
	else
		-- just drive normally
		self:setSpeed(self:getRecordedSpeed())
	end
	-- except when in reversing, then always use reverse speed
	if self.ppc:isReversing() then
		self:setSpeed(self.vehicle.cp.speeds.reverse or self.vehicle.cp.speeds.crawl)
	end
	return false
end

--- Full during fieldwork
function FieldworkAIDriver:changeToFieldworkUnloadOrRefill()
	self.fieldworkState = self.states.UNLOAD_OR_REFILL_ON_FIELD
	if self.stopImplementsWhileUnloadOrRefillOnField then
		self.fieldworkUnloadOrRefillState = self.states.WAITING_FOR_STOP
	else
		self.fieldworkUnloadOrRefillState = self.states.WAITING_FOR_UNLOAD_OR_REFILL
	end
end

--- Stop for unload/refill while driving the fieldwork course
function FieldworkAIDriver:driveFieldworkUnloadOrRefill()
	-- don't move while empty
	self:setSpeed(0)
	if self.fieldworkUnloadOrRefillState == self.states.WAITING_FOR_STOP then
		-- wait until we stopped before raising the implements
		if self:isStopped() then
			self:debug('implements raised, stop')
			self:stopWork()
			self.fieldworkUnloadOrRefillState = self.states.WAITING_FOR_UNLOAD_OR_REFILL
		end
	elseif self.fieldworkUnloadOrRefillState == self.states.WAITING_FOR_UNLOAD_OR_REFILL then
		if self:allFillLevelsOk() and not self.heldForUnloadRefill then
			self:debug('unloaded, continue working')
			-- not full/empty anymore, maybe because Refilling to a trailer, go back to work
			self:clearInfoText(self:getFillLevelInfoText())
			self:changeToFieldwork()
		end
	end
end

function FieldworkAIDriver:changeToFieldwork()
	self:debug('change to fieldwork')
	self.state = self.states.ON_FIELDWORK_COURSE
	self.fieldworkState = self.states.WAITING_FOR_LOWER
	self:startWork()
	self:setDriveUnloadNow(false);
	self:refreshHUD();
end

function FieldworkAIDriver:changeToUnloadOrRefill()
	self:debug('changing to unload/refill course (%d waypoints)', self.unloadRefillCourse:getNumberOfWaypoints())
	self:stopWork()
	self:foldImplements()
	self:enableCollisionDetection()
	self.state = self.states.ON_UNLOAD_OR_REFILL_COURSE
end

function FieldworkAIDriver:onNextCourse()
	if self.state == self.states.ON_FIELDWORK_COURSE then
		if self.fieldworkState == self.states.TURNING then
			self:debug('onNextCourse: a turn course ended')
			-- a turn just ended, at this point all implements should already be lowered as the turn end course ended
			-- but just in case, lower them now
			self:lowerImplements()
			self.fieldworkState = self.states.WORKING
		else
			self:debug('onNextCourse: not a turn course ended')
			self:changeToFieldwork()
		end
	end
end

function FieldworkAIDriver:onEndCourse()
	if self.state == self.states.ON_UNLOAD_OR_REFILL_COURSE or
		self.state == self.states.ON_UNLOAD_OR_REFILL_WITH_AUTODRIVE then
		-- unload/refill course ended, return to fieldwork
		self:debug('AI driver in mode %d continue fieldwork at %d/%d waypoints', self:getMode(), self.aiDriverData.continueFieldworkAtWaypoint, self.fieldworkCourse:getNumberOfWaypoints())
		self:startFieldworkWithPathfinding(self.aiDriverData.continueFieldworkAtWaypoint)
	elseif self.state == self.states.RETURNING_TO_FIRST_POINT then
		AIDriver.onEndCourse(self)
	else
		self:debug('Fieldwork AI driver in mode %d ending fieldwork course', self:getMode())
		if self:shouldReturnToFirstPoint() then
			self:debug('Returning to first point')
			if self:driveToPointWithPathfinding(self.fieldworkCourse:getWaypoint(1)) then
				-- pathfinding was successful, drive back to first point
				self.state = self.states.RETURNING_TO_FIRST_POINT
				self:raiseImplements()
				self:foldImplements()
			else
				-- no path or too short, stop here.
				AIDriver.onEndCourse(self)
				-- (onEndCourse calls stopWork which raises the implements, fold must be called after that)
				-- TODO: add an option to enable fold implement on work end and make it part of stopWork()
				self:foldImplements()
			end
		else
			AIDriver.onEndCourse(self)
			self:foldImplements()
		end
	end
end

function FieldworkAIDriver:onWaypointPassed(ix)
	self:debug('onWaypointPassed %d', ix)
	if self.state == self.states.ON_FIELDWORK_COURSE then
		if self.fieldworkState == self.states.WORKING then
			-- check for transition to connecting track, make sure we've been on it for a few waypoints already
			-- to avoid raising the implements too soon, this can be a problem with long implements not yet reached
			-- the end of the headland track while the tractor is already on the connecting track
			if self.course:isOnConnectingTrack(ix) and self.course:isOnConnectingTrack(ix - 2) then
				-- reached a connecting track (done with the headland, move to the up/down row or vice versa),
				-- raise all implements while moving
				self:debug('on a connecting track now, raising implements.')
				self:raiseImplements()
				self.fieldworkState = self.states.ON_CONNECTING_TRACK
			end
		end
		if self.fieldworkState ~= self.states.TEMPORARY and self.course:isOnConnectingTrack(ix) then
			-- passed a connecting track waypoint
			-- check transition from connecting track to the up/down rows
			-- we are close to the end of the connecting track, transition back to the up/down rows with
			-- an alignment course
			local d, firstUpDownWpIx = self.course:getDistanceToFirstUpDownRowWaypoint(ix)
			self:debug('up/down rows start in %s meters.', tostring(d))
			if d < self.vehicle.cp.turnDiameter * 2 and firstUpDownWpIx then
				self:debug('End connecting track, start working on up/down rows (waypoint %d) with alignment course if needed.', firstUpDownWpIx)
				self:startFieldworkWithAlignment(firstUpDownWpIx)
			end
		end
	end
	--- Check if we are at the last waypoint and should we continue with first waypoint of the course
	-- or stop.
	if ix == self.course:getNumberOfWaypoints() then
		self:onLastWaypoint()
	end
end

function FieldworkAIDriver:onWaypointChange(ix)
	self:debug('onWaypointChange %d, connecting: %s, temp: %s',
		ix, tostring(self.course:isOnConnectingTrack(ix)), tostring(self.states == self.states.TEMPORARY))
	if self.state == self.states.ON_FIELDWORK_COURSE then
		self:updateRemainingTime(ix)
		self:calculateTightTurnOffset()
		self:debug('Tight turn offset = %.1f', self.tightTurnOffset)
		self.aiDriverOffsetZ = 0
		if self.fieldworkState == self.states.ON_CONNECTING_TRACK then
			if not self.course:isOnConnectingTrack(ix) then
				-- reached the end of the connecting track, back to work
				self:debug('connecting track ended, back to work, first lowering implements.')
				self:changeToFieldwork()
			end
		end
		if self.fieldworkState == self.states.TEMPORARY then
			-- band aid to make sure we have our implements lowered by the time we end the
			-- temporary course
			-- TODO: fix this and also PlowAIDriver:startWork()
			if ix == self.course:getNumberOfWaypoints() then
				self:debug('temporary (alignment) course is about to end, start work')
				self:startWork()
			end
		-- towards the end of the field course make sure the implement reaches the last waypoint
		-- TODO: this needs refactoring, for now don't do this for temporary courses like a turn as it messes up reversing
		elseif ix > self.course:getNumberOfWaypoints() - 3 and not self.course:isTemporary() then
			if self.frontMarkerDistance then
				self:debug('adding offset (%.1f front marker) to make sure we do not miss anything when the course ends', self.frontMarkerDistance)
				self.aiDriverOffsetZ = -self.frontMarkerDistance
			end
		end
		if self.fieldworkState ~= self.states.TURNING and self.course:isTurnStartAtIx(ix) then
			self:startTurn(ix)
		end
	end
	-- update the legacy waypoint counter on the HUD
	if self.state == self.states.ON_FIELDWORK_COURSE or self.states.ON_UNLOAD_OR_REFILL_COURSE then
		courseplay:setWaypointIndex(self.vehicle, self.ppc:getCurrentOriginalWaypointIx())
	end
end

function FieldworkAIDriver:onTowedImplementPassedWaypoint(ix)
	self:debug('Implement passsed waypoint %d', ix)
end

--- Should we return to the first point of the course after we are done?
function FieldworkAIDriver:shouldReturnToFirstPoint()
	-- TODO: implement and check setting in course or HUD
	if self.vehicle.cp.settings.returnToFirstPoint:is(true) then
		self:debug('Returning to first point.')
		return true
	else
		self:debug('Not returning to first point.')
		return false
	end
end

--- Pass on self.speed set elsewhere to the AIDriver.
function FieldworkAIDriver:getSpeed()
	local speed = AIDriver.getSpeed(self)
	-- as long as other CP components mess with the cruise control we need to reset this, for example after
	-- a turn
	self.vehicle:setCruiseControlMaxSpeed(speed)
	return speed
end

--- Start the actual work. Lower and turn on implements
function FieldworkAIDriver:startWork()
	self:debug('Starting work: turn on and lower implements.')
	-- send the event first and _then_ lower otherwise it sometimes does not turn it on
	self.vehicle:raiseAIEvent("onAIStart", "onAIImplementStart")
	self.vehicle:requestActionEventUpdate()
	self:startEngineIfNeeded()
	self:lowerImplements(self.vehicle)
end


--- Stop working. Raise and stop implements
function FieldworkAIDriver:stopWork()
	self:debug('Ending work: turn off and raise implements.')
	self:raiseImplements()
	self.vehicle:raiseAIEvent("onAIEnd", "onAIImplementEnd")
	self.vehicle:requestActionEventUpdate()
	self:clearRemainingTime()
end

--- Check if need to refill/unload anything
function FieldworkAIDriver:allFillLevelsOk()
	if not self.vehicle.cp.workTools then return false end
	-- what here comes is basically what Giants' getFillLevelInformation() does but this returns the real fillType,
	-- not the fillTypeToDisplay as this latter is different for each type of seed
	local fillLevelInfo = {}
	self:getAllFillLevels(self.vehicle, fillLevelInfo)
	return self:areFillLevelsOk(fillLevelInfo)
end

function FieldworkAIDriver:getAllFillLevels(object, fillLevelInfo)
	-- get own fill levels
	if object.getFillUnits then
		for _, fillUnit in pairs(object:getFillUnits()) do
			local fillType = self:getFillTypeFromFillUnit(fillUnit)
			local fillTypeName = g_fillTypeManager:getFillTypeNameByIndex(fillType)
			self:debugSparse('%s: Fill levels: %s: %.1f/%.1f', object:getName(), fillTypeName, fillUnit.fillLevel, fillUnit.capacity)
			if not fillLevelInfo[fillType] then fillLevelInfo[fillType] = {fillLevel=0, capacity=0} end
			fillLevelInfo[fillType].fillLevel = fillLevelInfo[fillType].fillLevel + fillUnit.fillLevel
			fillLevelInfo[fillType].capacity = fillLevelInfo[fillType].capacity + fillUnit.capacity
		end
	end
 	-- collect fill levels from all attached implements recursively
	for _,impl in pairs(object:getAttachedImplements()) do
		self:getAllFillLevels(impl.object, fillLevelInfo)
	end
end

function FieldworkAIDriver:getFillTypeFromFillUnit(fillUnit)
	local fillType = fillUnit.lastValidFillType or fillUnit.fillType
	-- TODO: do we need to check more supported fill types? This will probably cover 99.9% of the cases
	if fillType == FillType.UNKNOWN then
		-- just get the first valid supported fill type
		for ft, valid in pairs(fillUnit.supportedFillTypes) do
			if valid then return ft end
		end
	else
		return fillType
	end

end

-- is the fill level ok to continue?
function FieldworkAIDriver:areFillLevelsOk()
	-- implement specifics in the derived classes
	return true
end

--- Set up the main (fieldwork) course and the unload/refill course and initial state
-- Currently, the legacy CP code just dumps all loaded courses to vehicle.Waypoints so
-- now we have to figure out which of that is the actual fieldwork course and which is the
-- refill/unload part.
-- This should better be handled by the course management though and should be refactored.
function FieldworkAIDriver:setUpCourses()
	local nWaits = 0
	local endFieldCourseIx = 0
	for i, wp in ipairs(self.vehicle.Waypoints) do
		if wp.wait then
			nWaits = nWaits + 1
			-- the second wp with the wait attribute is the end of the field course (assuming
			-- the field course has been loaded first.
			if nWaits == 2 then
				endFieldCourseIx = i
				break
			end
		end
	end
	if #self.vehicle.Waypoints > endFieldCourseIx and endFieldCourseIx ~= 0 then
		self:debug('Course with %d waypoints set up, there seems to be an unload/refill course starting at waypoint %d',
			#self.vehicle.Waypoints, endFieldCourseIx + 1)
		---@type Course
		self.fieldworkCourse = Course(self.vehicle, self.vehicle.Waypoints, false, 1, endFieldCourseIx)
		---@type Course
		if #self.vehicle.Waypoints - endFieldCourseIx > 2 then
			self.unloadRefillCourse = Course(self.vehicle, self.vehicle.Waypoints, false, endFieldCourseIx + 1, #self.vehicle.Waypoints)
		else
			self:debug('Unload/refill course too short, ignoring')
		end
	else
		self:debug('Course with %d waypoints set up, there seems to be no unload/refill course', #self.vehicle.Waypoints)
		self.fieldworkCourse = Course(self.vehicle, self.vehicle.Waypoints, false, 1, #self.vehicle.Waypoints)
	end
	-- get a signature of the course now, before offsetting it so can compare for the convoy
	self.fieldworkCourseHash = self.fieldworkCourse:getHash()
	-- apply the current tool offset to the fieldwork part (multitool offset is added by calculateOffsetCourse when needed)
	self.fieldworkCourse:setOffset(self.vehicle.cp.toolOffsetX, self.vehicle.cp.toolOffsetZ)
	-- TODO: consolidate the working width calculation and usage, this is currently an ugly mess
	self.fieldworkCourse:setWorkWidth(self.vehicle.cp.courseWorkWidth or courseplay:getWorkWidth(self.vehicle))
	if self.vehicle.cp.multiTools > 1 then
		self:debug('Calculating offset course for position %d of %d', self.vehicle.cp.laneNumber, self.vehicle.cp.multiTools)
		self.fieldworkCourse = self.fieldworkCourse:calculateOffsetCourse(
				self.vehicle.cp.multiTools, self.vehicle.cp.laneNumber,  courseplay:getWorkWidth(self.vehicle),
				self.vehicle.cp.settings.symmetricLaneChange:is(true))
	end
end

function FieldworkAIDriver:setRidgeMarkers()
	-- no ridge markers with multitools to avoid collisions.
	if self.vehicle.cp.settings.ridgeMarkersAutomatic:is(false) or self.vehicle.cp.multiTools > 1 then return end
	local active = self.state == self.states.ON_FIELDWORK_COURSE and self.fieldworkState ~= self.states.TURNING
	for _, workTool in ipairs(self.vehicle.cp.workTools) do
		-- yes, another Giants typo. And not sure why implements with no ridge markers even have the spec_ridgeMarker
		if workTool.spec_ridgeMarker and workTool.spec_ridgeMarker.numRigdeMarkers > 0 then
			local state = active and self.course:getRidgeMarkerState(self.ppc:getCurrentWaypointIx()) or 0
			if workTool.spec_ridgeMarker.ridgeMarkerState ~= state then
				self:debug('Setting ridge markers to %d', state)
				workTool:setRidgeMarkerState(state)
			end
		end
	end
end

--- We already set the offsets on the course at start, this is to update those values
-- if the user changed them during the run or the AI driver wants to add an offset
function FieldworkAIDriver:updateFieldworkOffset()
	-- (as lua passes tables by reference, we can directly change self.fieldworkCourse even if we passed self.course
	-- to the PPC to drive)
	self.fieldworkCourse:setOffset(self.vehicle.cp.toolOffsetX + self.aiDriverOffsetX + (self.tightTurnOffset or 0),
		self.vehicle.cp.toolOffsetZ + self.aiDriverOffsetZ)
end

function FieldworkAIDriver:hasSameCourse(otherVehicle)
	if otherVehicle.cp.driver and otherVehicle.cp.driver.fieldworkCourseHash then
		return self.fieldworkCourseHash == otherVehicle.cp.driver.fieldworkCourseHash
	else
		return false
	end
end

function FieldworkAIDriver:getCurrentFieldworkWaypointIx()
	return self.fieldworkCourse:getCurrentWaypointIx()
end

--- When working in a group (convoy), do I have to hold so I don't get too close to the
-- other vehicles in front of me?
function FieldworkAIDriver:manageConvoy()
	if not self.vehicle.cp.convoyActive then return false end
	--get my position in convoy and look for the closest combine
	local position = 1
	local total = 1
	local closestDistance = math.huge
	for _, otherVehicle in pairs(CpManager.activeCoursePlayers) do
		if otherVehicle ~= self.vehicle and otherVehicle.cp.convoyActive and self:hasSameCourse(otherVehicle) then
			local myWpIndex = self:getCurrentFieldworkWaypointIx()
			local otherVehicleWpIndex = otherVehicle.cp.driver:getCurrentFieldworkWaypointIx()
			total = total + 1
			if myWpIndex < otherVehicleWpIndex then
				position = position + 1
				local distance = (otherVehicleWpIndex - myWpIndex) * courseGenerator.waypointDistance
				if distance < closestDistance then
					closestDistance = distance
				end
			end
		end
	end

	-- stop when I'm too close to the combine in front of me
	if position > 1 then
		if closestDistance < self.vehicle.cp.convoy.minDistance then
			self:debugSparse('too close (%.1f) to other vehicles in group, holding.', closestDistance)
			self:setSpeed(0)
			self:overrideAutoEngineStop()
		end
	else
		closestDistance = 0
	end

	-- TODO: check for change should be handled by setCpVar()
	if self.vehicle.cp.convoy.distance ~= closestDistance then
		self.vehicle:setCpVar('convoy.distance',closestDistance)
	end
	if self.vehicle.cp.convoy.number ~= position then
		self.vehicle:setCpVar('convoy.number',position)
	end
	if self.vehicle.cp.convoy.members ~= total then
		self.vehicle:setCpVar('convoy.members',total)
	end
end

-- Although raising the AI start/stop events supposed to fold/unfold the implements, it does not always happen.
-- So use these to explicitly do so
function FieldworkAIDriver:unfoldImplements()
	for _,workTool in pairs(self.vehicle.cp.workTools) do
		if courseplay:isFoldable(workTool) then
			local isFolding, isFolded, isUnfolded = courseplay:isFolding(workTool)
			if not isUnfolded and workTool:getIsFoldAllowed(workTool.cp.realUnfoldDirection) then
				self:debug('Unfolding %s', workTool:getName())
				workTool:setFoldDirection(workTool.cp.realUnfoldDirection)
			end
		end
	end
end

function FieldworkAIDriver:foldImplements()
	for _,workTool in pairs(self.vehicle.cp.workTools) do
		if courseplay:isFoldable(workTool) then
			local isFolding, isFolded, isUnfolded = courseplay:isFolding(workTool)
			if not isFolded and workTool:getIsFoldAllowed(-workTool.cp.realUnfoldDirection) then
				self:debug('Folding %s', workTool:getName())
				workTool:setFoldDirection(-workTool.cp.realUnfoldDirection)
			end
		end
	end
end

function FieldworkAIDriver:isAllUnfolded()
	for _,workTool in pairs(self.vehicle.cp.workTools) do
		if courseplay:isFoldable(workTool) then
			local isFolding, isFolded, isUnfolded = courseplay:isFolding(workTool)
			if not isUnfolded then return false end
		end
	end
	return true
end

function FieldworkAIDriver:clearRemainingTime()
	self.vehicle.cp.timeRemaining = nil
end

function FieldworkAIDriver:updateRemainingTime(ix)
	if self.state == self.states.ON_FIELDWORK_COURSE then
		local dist, turns = self.course:getRemainingDistanceAndTurnsFrom(ix)
		local turnTime = turns * self.turnDurationMs / 1000
		self.vehicle.cp.timeRemaining = math.max(0, dist / (self:getWorkSpeed() / 3.6) + turnTime)
		self:debug('Distance to go: %.1f; Turns left: %d; Time left: %ds', dist, turns, self.vehicle.cp.timeRemaining)
	else
		self:clearRemainingTime()
	end
end

function FieldworkAIDriver:measureTurnTime()
	local isTurning = self.state == self.states.ON_FIELDWORK_COURSE and self.fieldworkState == self.states.TURNING
	if self.wasTurning and not isTurning then
		-- end of turn
		if self.turnStartedAt then
			-- use sliding average to smooth jumps
			self.turnDurationMs = (self.turnDurationMs + self.vehicle.timer - self.turnStartedAt) / 2
			self.realTurnDurationMs = self.vehicle.timer - self.turnStartedAt
			self:debug('Measured turn duration is %.0f ms', self.turnDurationMs)
		end
	elseif not self.wasTurning and isTurning then
		-- start of turn
		self.turnStartedAt = self.vehicle.timer
	end
	self.wasTurning = isTurning
end

function FieldworkAIDriver:checkWeather()
	if self.vehicle.getIsThreshingAllowed and not self.vehicle:getIsThreshingAllowed() then
		self:debugSparse('No threshing in rain...')
		self:setSpeed(0)
		self:setInfoText('WEATHER')
	else
		self:clearInfoText('WEATHER')
	end
end

function FieldworkAIDriver:updateLights()
	if not self.vehicle.spec_lights then return end
	-- turn on beacon lights on unload/refill course when enabled
	if self.state == self.states.ON_UNLOAD_OR_REFILL_COURSE and self:areBeaconLightsEnabled() then
		self.vehicle:setBeaconLightsVisibility(true)
	else
		self:updateLightsOnField()
	end
end

function FieldworkAIDriver:updateLightsOnField()
	-- there are no beacons used on the field by default
	self.vehicle:setBeaconLightsVisibility(false)
end

function FieldworkAIDriver:startLoweringDurationTimer()
	-- then start but only after everything is unfolded as we don't want to include the
	-- unfold duration (since we don't fold at the end of the row).
	if self:isAllUnfolded() then
		self.startedLoweringAt = self.vehicle.timer
	end
end

function FieldworkAIDriver:calculateLoweringDuration()
	if self.startedLoweringAt then
		self.loweringDurationMs = self.vehicle.timer - self.startedLoweringAt
		self:debug('Measured implement lowering duration is %.0f ms', self.loweringDurationMs)
		self.startedLoweringAt = nil
	end
end

function FieldworkAIDriver:getLoweringDurationMs()
	return self.loweringDurationMs
end

function FieldworkAIDriver:calculateTightTurnOffset()
    self.tightTurnOffset = AIDriverUtil.calculateTightTurnOffset(self.vehicle, self.course, self.tightTurnOffset)
end

function FieldworkAIDriver:getFillLevelInfoText()
	return 'NEEDS_REFILLING'
end

function FieldworkAIDriver:lowerImplements()
	for _, implement in pairs(self.vehicle:getAttachedAIImplements()) do
		implement.object:aiImplementStartLine()
	end
	self.vehicle:raiseStateChange(Vehicle.STATE_CHANGE_AI_START_LINE)
	if FieldworkAIDriver.hasImplementWithSpecialization(self.vehicle, SowingMachine) or self.ppc:isReversing() then
		-- sowing machines want to stop while the implement is being lowered
		-- also, when reversing, we assume that we'll switch to forward, so stop while lowering, then start forward
		self.fieldworkState = self.states.WAITING_FOR_LOWER_DELAYED
	end
end

function FieldworkAIDriver:raiseImplements()
	for _, implement in pairs(self.vehicle:getAttachedAIImplements()) do
		implement.object:aiImplementEndLine()
	end
	self.vehicle:raiseStateChange(Vehicle.STATE_CHANGE_AI_END_LINE)
end

function FieldworkAIDriver:rememberWaypointToContinueFieldwork()
	local bestKnownCurrentWpIx = self.ppc:getLastPassedWaypointIx() or self.ppc:getCurrentWaypointIx()
	-- after we return from a refill/unload, continue a bit before the point where we left to
	-- make sure not leaving any unworked patches
	self.aiDriverData.continueFieldworkAtWaypoint = self.course:getPreviousWaypointIxWithinDistance(bestKnownCurrentWpIx, 10)
	if self.aiDriverData.continueFieldworkAtWaypoint then
		-- anything other than a turn start wp will work fine
		if self.course:isTurnStartAtIx(self.aiDriverData.continueFieldworkAtWaypoint) then
			self.aiDriverData.continueFieldworkAtWaypoint = self.aiDriverData.continueFieldworkAtWaypoint - 1
		end
	else
		self.aiDriverData.continueFieldworkAtWaypoint = bestKnownCurrentWpIx
	end
	self:debug('Will return to fieldwork at waypoint %d', self.aiDriverData.continueFieldworkAtWaypoint)
end


function FieldworkAIDriver:getCanShowDriveOnButton()
	return self.state == self.states.ON_FIELDWORK_COURSE 
end

function FieldworkAIDriver:getLoweringDurationMs()
	return self.loweringDurationMs
end

function FieldworkAIDriver:findLoweringDurationMs()
	local function getLoweringDurationMs(object)
		if object.spec_animatedVehicle then
			-- TODO: implement these in the specifications?
			return math.max(object.spec_animatedVehicle:getAnimationDuration('lowerAnimation'),
				object.spec_animatedVehicle:getAnimationDuration('rotatePickup'))
		else
			return 0
		end
	end

	self.loweringDurationMs = getLoweringDurationMs(self.vehicle)
	self:debug('Lowering duration: %d ms', self.loweringDurationMs)

	-- check all implements first
	local implements = self.vehicle:getAttachedImplements()
	for _, implement in ipairs(implements) do
		local implementLoweringDurationMs = getLoweringDurationMs(implement.object)
		self:debug('Lowering duration (%s): %d ms', implement.object:getName(), implementLoweringDurationMs)
		if implementLoweringDurationMs > self.loweringDurationMs then
			self.loweringDurationMs = implementLoweringDurationMs
		end
		local jointDescIndex = implement.jointDescIndex
		-- now check the attacher joints
		if self.vehicle.spec_attacherJoints and jointDescIndex then
			local ajs = self.vehicle.spec_attacherJoints:getAttacherJoints()
			local ajLoweringDurationMs = ajs[jointDescIndex] and ajs[jointDescIndex].moveDefaultTime or 0
			self:debug('Lowering duration (%s attacher joint): %d ms', implement.object:getName(), ajLoweringDurationMs)
			if ajLoweringDurationMs > self.loweringDurationMs then
				self.loweringDurationMs = ajLoweringDurationMs
			end
		end
	end
	if not self.loweringDurationMs or self.loweringDurationMs <= 1 then
		self.loweringDurationMs = 2000
		self:debug('No lowering duration found, setting to: %d ms', self.loweringDurationMs)
	end
	self:debug('Final lowering duration: %d ms', self.loweringDurationMs)
end

--- Never continue automatically at a wait point
function FieldworkAIDriver:isAutoContinueAtWaitPointEnabled()
	return false
end

-- instantiate generic turn course, derived classes may override
function FieldworkAIDriver:createTurnCourse()
	return CourseTurn(self.vehicle, self, self.turnContext, self.fieldworkCourse)
end

function FieldworkAIDriver:getTurnEndSideOffset()
	return 0
end

function FieldworkAIDriver:startTurn(ix)
	-- set a short lookahead distance for PPC to increase accuracy, especially after switching back from
	-- turn.lua. That often happens too early (when lowering the implement) when we still have a cross track error,
	-- this should help returning to the course faster.
	self.ppc:setShortLookaheadDistance()
	self:setMarkers()
	self.turnContext = TurnContext(self.course, ix, self.aiDriverData, self.vehicle.cp.workWidth, self.frontMarkerDistance,
			self:getTurnEndSideOffset())
	if self.vehicle.cp.settings.useAITurns:is(true) then
		if self:startAiTurn(ix) then
			return
		end
	end
	self.aiTurn = self:createTurnCourse()
	self.fieldworkState = self.states.TURNING
	self:debug('Generating turn course...')
end

--- Find the foremost and rearmost AI marker
function FieldworkAIDriver:setMarkers()
	local markers= {}
	local addMarkers = function(object, referenceNode)
		self:debug('Finding AI markers of %s', nameNum(object))
		local aiLeftMarker, aiRightMarker, aiBackMarker = self:getAIMarkers(object)
		if aiLeftMarker and aiBackMarker and aiRightMarker then
			local _, _, leftMarkerDistance = localToLocal(aiLeftMarker, referenceNode, 0, 0, 0)
			local _, _, rightMarkerDistance = localToLocal(aiRightMarker, referenceNode, 0, 0, 0)
			local _, _, backMarkerDistance = localToLocal(aiBackMarker, referenceNode, 0, 0, 0)
			table.insert(markers, leftMarkerDistance)
			table.insert(markers, rightMarkerDistance)
			table.insert(markers, backMarkerDistance)
			self:debug('%s: left = %.1f, right = %.1f, back = %.1f', nameNum(object), leftMarkerDistance, rightMarkerDistance, backMarkerDistance)
		end
	end

	local referenceNode = AIDriverUtil.getDirectionNode(self.vehicle)
	-- now go ahead and try to find the real markers
	-- work areas of the vehicle itself
	addMarkers(self.vehicle, referenceNode)
	-- and then the work areas of all the implements
	for _, implement in pairs( self:getAllAIImplements(self.vehicle)) do
		addMarkers(implement.object, referenceNode)
	end

	if #markers == 0 then
		-- make sure we always have a default front/back marker, placed on the direction node if nothing else found
		table.insert(markers, 0)
		table.insert(markers, 3)
	end
	-- now that we have all, find the foremost and the last
	self.frontMarkerDistance, self.backMarkerDistance = 0, 0
	local frontMarkerDistance, backMarkerDistance = -math.huge, math.huge
	for _, d in pairs(markers) do
		if d > frontMarkerDistance then
			frontMarkerDistance = d
		end
		if d < backMarkerDistance then
			backMarkerDistance = d
		end
	end
	-- set these up for turn.lua. TODO: pass in with the turn context and get rid of the aiFrontMarker and backMarkerOffset completely
	self.vehicle.cp.aiFrontMarker = frontMarkerDistance
	self.frontMarkerDistance = frontMarkerDistance
	self.vehicle.cp.backMarkerOffset = backMarkerDistance
	self.backMarkerDistance = backMarkerDistance
	self:debug('front marker: %.1f, back marker: %.1f', frontMarkerDistance, backMarkerDistance)
end

function FieldworkAIDriver:getAIMarkers(object, suppressLog)
	local aiLeftMarker, aiRightMarker, aiBackMarker
	if object.getAIMarkers then
		aiLeftMarker, aiRightMarker, aiBackMarker = object:getAIMarkers()
	end
	if not aiLeftMarker or not aiRightMarker or not aiLeftMarker then
		-- use the root node if there are no AI markers
		if not suppressLog then
			self:debug('%s has no AI markers, try work areas', nameNum(object))
		end
		aiLeftMarker, aiRightMarker, aiBackMarker = self:getAIMarkersFromWorkAreas(object)
		if not aiLeftMarker or not aiRightMarker or not aiLeftMarker then
			if not suppressLog then
				self:debug('%s has no work areas, giving up', nameNum(object))
			end
			return nil, nil, nil
		else
			return aiLeftMarker, aiRightMarker, aiBackMarker
		end
	else
		return aiLeftMarker, aiRightMarker, aiBackMarker
	end
end

--- When finishing a turn, is it time to lower all implements here?
-- TODO: remove the reversing parameter and use ppc to find out once not called from turn.lua
function FieldworkAIDriver:shouldLowerImplements(turnEndNode, reversing)
	-- see if the vehicle has AI markers -> has work areas (built-in implements like a mower or cotton harvester)
	local doLower, vehicleHasMarkers = self:shouldLowerThisImplement(self.vehicle, turnEndNode, reversing)
	if not vehicleHasMarkers and reversing then
		-- making sure the 'and' below will work if reversing and the vehicle has no markers
		doLower = true
	end
	-- and then check all implements
	for _, implement in ipairs(self:getAllAIImplements(self.vehicle)) do
		if reversing then
			-- when driving backward, all implements must reach the turn end node before lowering, hence the 'and'
			doLower = doLower and self:shouldLowerThisImplement(implement.object, turnEndNode, reversing)
		else
			-- when driving forward, if it is time to lower any implement, we'll lower all, hence the 'or'
			doLower = doLower or self:shouldLowerThisImplement(implement.object, turnEndNode, reversing)
		end
	end
	return doLower
end

---@param object table is a vehicle or implement object with AI markers (marking the working area of the implement)
---@param turnEndNode number node at the first waypoint of the row, pointing in the direction of travel. This is where
--- the implement should be in the working position after a turn
---@param reversing boolean are we reversing? When reversing towards the turn end point, we must lower the implements
--- when we are _behind_ the turn end node (dz < 0), otherwise once we reach it (dz > 0)
---@return boolean, boolean the second one is true when the first is valid
function FieldworkAIDriver:shouldLowerThisImplement(object, turnEndNode, reversing)
	local aiLeftMarker, aiRightMarker, aiBackMarker = self:getAIMarkers(object, true)
	if not aiLeftMarker then return false, false end
	local _, _, dzLeft = localToLocal(aiLeftMarker, turnEndNode, 0, 0, 0)
	local _, _, dzRight = localToLocal(aiRightMarker, turnEndNode, 0, 0, 0)
	local _, _, dzBack = localToLocal(aiBackMarker, turnEndNode, 0, 0, 0)
	local loweringDistance
	if FieldworkAIDriver.hasImplementWithSpecialization(self.vehicle, SowingMachine) then
		-- sowing machines are stopped while lowering, but leave a little reserve to allow for stopping
		-- TODO: rather slow down while approaching the lowering point
		loweringDistance = 0.5
	else
		-- others can be lowered without stopping so need to start lowering before we get to the turn end to be
		-- in the working position by the time we get to the first waypoint of the next row
		loweringDistance = self.vehicle.lastSpeed * self:getLoweringDurationMs() + 0.5 -- vehicle.lastSpeed is in meters per millisecond
	end
	local dzFront = (dzLeft + dzRight) / 2
	self:debug('%s: dzLeft = %.1f, dzRight = %.1f, dzFront = %.1f, dzBack = %.1f, loweringDistance = %.1f, reversing %s',
		nameNum(object), dzLeft, dzRight, dzFront, dzBack, loweringDistance, tostring(reversing))
	local dz = self.vehicle.cp.settings.implementLowerTime:is(ImplementRaiseLowerTimeSetting.EARLY) and dzFront or dzBack
	if reversing then
		return dz < 0 , true
	else
		-- dz will be negative as we are behind the target node
		return dz > - loweringDistance, true
	end
end

function FieldworkAIDriver:shouldRaiseImplements(turnStartNode)
	-- see if the vehicle has AI markers -> has work areas (built-in implements like a mower or cotton harvester)
	local doRaise = self:shouldRaiseThisImplement(self.vehicle, turnStartNode)
	-- and then check all implements
	for _, implement in ipairs(self:getAllAIImplements(self.vehicle)) do
		-- only when _all_ implements can be raised will we raise them all, hence the 'and'
		doRaise = doRaise and self:shouldRaiseThisImplement(implement.object, turnStartNode)
	end
	return doRaise
end

---@param turnStartNode node at the last waypoint of the row, pointing in the direction of travel. This is where
--- the implement should be raised when beginning a turn
function FieldworkAIDriver:shouldRaiseThisImplement(object, turnStartNode)
	local aiFrontMarker, _, aiBackMarker = self:getAIMarkers(object, true)
	-- if something (like a combine) does not have an AI marker it should not prevent from raising other implements
	-- like the header, which does have markers), therefore, return true here
	if not aiBackMarker or not aiFrontMarker then return true end
	local marker = self.vehicle.cp.settings.implementRaiseTime:is(ImplementRaiseLowerTimeSetting.EARLY) and aiFrontMarker or aiBackMarker
	-- turn start node in the back marker node's coordinate system
	local _, _, dz = localToLocal(marker, turnStartNode, 0, 0, 0)
	self:debugSparse('%s: shouldRaiseImplements: dz = %.1f', nameNum(object), dz)
	-- marker is just in front of the turn start node
	return dz > 0
end

--- Are all implements now aligned with the node? Can be used to find out if we are for instance aligned with the
--- turn end node direction in a question mark turn and can start reversing.
function FieldworkAIDriver:areAllImplementsAligned(node)
	-- see if the vehicle has AI markers -> has work areas (built-in implements like a mower or cotton harvester)
	local allAligned = self:isThisImplementAligned(self.vehicle, node)
	-- and then check all implements
	for _, implement in ipairs(self:getAllAIImplements(self.vehicle)) do
		-- _all_ implements must be aligned, hence the 'and'
		allAligned = allAligned and self:isThisImplementAligned(implement.object, node)
	end
	return allAligned
end

function FieldworkAIDriver:isThisImplementAligned(object, node)
	local aiFrontMarker, _, _ = self:getAIMarkers(object, true)
	if not aiFrontMarker then return true end
	return TurnContext.isSameDirection(aiFrontMarker, node, 2)
end

function FieldworkAIDriver:onDraw()

	if not courseplay.debugChannels[6] then return end

	local function showAIMarkersOfObject(object)
		if object.getAIMarkers then
			local aiLeftMarker, aiRightMarker, aiBackMarker = object:getAIMarkers()
			if aiLeftMarker then
				DebugUtil.drawDebugNode(aiLeftMarker, object:getName() .. ' AI Left')
			end
			if aiRightMarker then
				DebugUtil.drawDebugNode(aiRightMarker, object:getName() .. ' AI Right')
			end
			if aiBackMarker then
				DebugUtil.drawDebugNode(aiBackMarker, object:getName() .. ' AI Back')
			end
		end
		if object.getAISizeMarkers then
			local aiSizeLeftMarker, aiSizeRightMarker, aiSizeBackMarker = object:getAISizeMarkers()
			if aiSizeLeftMarker then
				DebugUtil.drawDebugNode(aiSizeLeftMarker, object:getName() .. ' AI Size Left')
			end
			if aiSizeRightMarker then
				DebugUtil.drawDebugNode(aiSizeRightMarker, object:getName() .. ' AI Size Right')
			end
			if aiSizeBackMarker then
				DebugUtil.drawDebugNode(aiSizeBackMarker, object:getName() .. ' AI Size Back')
			end
		end
		DebugUtil.drawDebugNode(object.cp.directionNode or object.rootNode, object:getName() .. ' root')
	end

	showAIMarkersOfObject(self.vehicle)
	-- draw the Giant's supplied AI markers for all implements
	local implements = self:getAllAIImplements(self.vehicle)
	if implements then
		for _, implement in ipairs(implements) do
			showAIMarkersOfObject(implement.object)
		end
	end

	if self.plowReferenceNode then
		DebugUtil.drawDebugNode(self.plowReferenceNode, 'Plow reference')
	end

	AIDriver.onDraw(self)
end

function FieldworkAIDriver:isValidWorkArea(area)
	return area.start and area.height and area.width and
		area.type ~= WorkAreaType.RIDGEMARKER and
		area.type ~= WorkAreaType.COMBINESWATH and
		area.type ~= WorkAreaType.COMBINECHOPPER
end

--- Calculate the front and back marker nodes of a work area
function FieldworkAIDriver:getAIMarkersFromWorkAreas(object)
	-- work areas are defined by three nodes: start, width and height. These nodes
	-- define a rectangular work area which you can make visible with the
	-- gsVehicleDebugAttributes console command and then pressing F5
	for _, area in courseplay:workAreaIterator(object) do
		if self:isValidWorkArea(area) then
			-- for now, just use the first valid work area we find
			self:debug('%s: Using %s work area markers as AIMarkers', nameNum(object), g_workAreaTypeManager.workAreaTypes[area.type].name)
			return area.start, area.width, area.height
		end
	end
end

function FieldworkAIDriver:getAllAIImplements(object, implements)
	if not implements then implements = {} end
	for _, implement in ipairs(object:getAttachedImplements()) do
		-- ignore everything which has no work area
		if self:isValidAIImplement(implement.object) then
			table.insert(implements, implement)
		end
		self:getAllAIImplements(implement.object, implements)
	end
	return implements
end

-- Is this and implement we should consider when deciding when to lift/raise implements at the end/start of a row?
function FieldworkAIDriver:isValidAIImplement(object)
	if courseplay:hasWorkAreas(object) then
		-- has work areas, good.
		return true
	else
		local aiLeftMarker, _, _ = self:getAIMarkers(object, true)
		if aiLeftMarker then
			-- has AI markers, good
			return true
		else
			-- no work areas, no AI markers, can't use.
			return false
		end
	end
end

function FieldworkAIDriver:startAiTurn(ix)
	self:debug('Starting an AI turn.')
	if AITurn.canMakeKTurn(self.vehicle, self.turnContext) then
		self:debug('Starting a K turn')
		---@type AITurn
		self.aiTurn = KTurn(self.vehicle, self, self.turnContext)
		self.fieldworkState = self.states.TURNING
		return true
	else
		self:debug('Can\'t make K turn, reverting to turn.lua')
		return false
	end
end

function FieldworkAIDriver:startFieldworkCourseWithTemporaryCourse(temporaryCourse, fieldworkIx)
	self:startCourse(temporaryCourse, 1, self.fieldworkCourse, fieldworkIx)
end

-- switch back to fieldwork after the turn ended.
function FieldworkAIDriver:resumeFieldworkAfterTurn(ix)
	self.ppc:setNormalLookaheadDistance()
	self.fieldworkState = self.states.WORKING
	self:lowerImplements()
	-- restore our own listeners for waypoint changes
	self.ppc:registerListeners(self, 'onWaypointPassed', 'onWaypointChange')
	self:startCourse( self.fieldworkCourse, self.fieldworkCourse:getNextFwdWaypointIxFromVehiclePosition(ix, AIDriverUtil.getDirectionNode(self.vehicle), 0))
end

--- Don't pay worker double when AutoDrive is driving
function FieldworkAIDriver:shouldPayWages()
	return self.state ~= self.states.ON_UNLOAD_OR_REFILL_WITH_AUTODRIVE
end

function FieldworkAIDriver:onBlocked()
	if self.state == self.states.ON_FIELDWORK_COURSE and self.fieldworkState == self.states.TURNING and self.aiTurn then
		self.aiTurn:onBlocked()
	end
end

function FieldworkAIDriver:setOffsetX()
	-- implement in derived classes if needed
end

function FieldworkAIDriver:setLightsMask(vehicle)
	vehicle:setLightsTypesMask(courseplay.lights.HEADLIGHT_FULL)
end