--TurtleSort 0.9
--by Shadow_8472
--This program intended for use on any kind of turtle.
--The basic operation:
--0 up to 15 comparison items go in slots 2-16, fill surplus slots (NBT is ignored)
--1 item arrives in slot 1
--2 turtle compares item to each other slot in inventory
--3 accept or reject item in slot 1
--4 operations stop if there are problems with outputting items
--5 in the event of a detected error, an error light can be lit (hook up to spawner lights to turn it off and manual kill on grinder line for updates in case of a fixed error)
--6 after fixing an error, update turtle to set it back in motion (a keystroke to the terminal works well)

--configuration variables
local upstream = "back"
local aDownstream = "bottom"
local rDownstream = "front"--set both downstream variables to the same side for just moving items
local errorLight = "left"--errorLight stores side rs lamp is on
local errorOnST = 15--strength of RS error to give
local errorOffST = 0--strength of RS for no error
local filterMin = 2--starting and end variables to sort from
local filterMax = 16

---------------------------------------------------------------------------
--evalItem0()--prototype code. depreciated to conform to updated standards among peer programs
--outputs matching filter item, or if 
--local function evalItem0()--this program may only use 1 here
--	if turtle.getItemCount(1) == 0 then--if no items
--		return 0--report no items
--	else--if item(s) present then
--		for n = filterMin, filterMax do--Compare up to 15 items (16-1 slots)
--			if turtle.getItemCount(n) == 0 then
--				--print("Slot "..n.." missing filter item.")
--			elseif turtle.getItemDetail(1)["name"] == turtle.getItemDetail(n)["name"] then
--				print("Match found in slot "..n..".")
--				return n--report matching slot
--			end
--		end
--		return 17-- range of n is < 17. Report no items match.
--	end
--end

--evalItem()
--outputs a string: "empty" "accept", or "reject".
local function evalItem(slot)--dummy int variable; this program may only use 1 here
	if turtle.getItemCount(1) == 0 then--if no items
		return "empty"--report no items
	else--if item(s) present then
		for n = filterMin, filterMax do--Compare up to 15 items (16-1 slots)
			if turtle.getItemCount(n) == 0 then
				--print("Slot "..n.." missing filter item.")
			elseif turtle.getItemDetail(1)["name"] == turtle.getItemDetail(n)["name"] then
				print("Match found in slot "..n..".")
				return "accept"--report matching slot
			end
		end
		return "reject"--report no items match.
	end
end

--ItemOut, (int, string)
--outputs: bool: success/failure of appropriate turtle.drop() variant
local function itemOut(slot, out1) --(int,string)
	--This function outputs item to either accept or reject paths.
	--Though not used now, this function facilitates dynamic item
	--accept/reject paths. I suppose, if more outputs were needed,
	--they could be added via the first if else statement.
	if out1 == "accept" then--sort between accept and reject mode.
		out = aDownstream
	elseif out1 == "reject" then
		out = rDownstream
	else
		print("Invalid term: "..out1)
		return false--this function designed for only "accept" or "reject"
	end
	
	local mx = 10--number of times to try to output before declaring a failure
	local rt = false--variable rt is the return value saved for console report
	turtle.select(slot)
	for n = 1, mx do--try a few times 
		if rs.getAnalogueInput(out) > 0 then
			--do nothing
		elseif out == "top" then--sort between each of the six faces of a turtle, rotate if need be
			rt = turtle.dropUp()
		elseif out == "front" then
			rt = turtle.drop()
		elseif out == "bottom" then
			rt = turtle.dropDown()
		elseif out == "left" then--elseif statements past here for forward compatibility
			turtle.turnLeft()
			rt = turtle.drop()
			turtle.turnRight()
		elseif out == "right" then
			turtle.turnRight()
			rt = turtle.drop()
			turtle.turnLeft()
		elseif out == "back" then
			turtle.turnLeft()
			turtle.turnLeft()
			rt = turtle.drop()
			turtle.turnLeft()
			turtle.turnLeft()
		else--else statement more for a debug POV.
			print("error: "..out.." is an invalid destination.")
			return false
		end
		
		--console report
		if rt then
			print("Item in slot "..slot.." "..out1.."ed.")
--			print(turtle.getItemCount(slot))
			break
		else--rt is false
			if n < mx then
				os.sleep(.1)
			else
				print("Item in slot "..slot.." could not be "..out1.."ed.")
				rs.setAnalogueOutput(upstream, 15)--call for help
			end
		end
	end
	return rt
end


--getState()
--returns string with curent state
local function getState()
	--possible states
		--passError --for when a rs signal of 15 is passed up from a turtle below
		--wait --slot1 empty, useful state for when changing filters.
		--filter --slot1 full
	local rs = bit32.bor(rs.getAnalogueInput(aDownstream), rs.getAnalogueInput(rDownstream))--get redstone downlines
	
	if rs == 15 then
		--error code incoming
		return "passError"
	elseif turtle.getItemCount(1) == 0 then
		--slot 1 empty
		return "wait"
	else
		return "eval"
	end
end

--main()
local event = false--boolean to flag an os.pullEvent() operation
local state = "start"
--local report = 0--old variable for use with old evalItem()
while true do
--	print(turtle.getItemCount(1).."X")
	state = getState()
--	print(turtle.getItemCount(1).."Y")
	turtle.select(1)--default
	print("Program state: "..state..".")--output state to console.
--	print(turtle.getItemCount(1).."Z")
	if state == "passError" then
		rs.setAnalogueOutput(upstream, 1)--closed for items
		rs.setAnalogueOutput(errorLight, errorOnST)--flag an error
		event = true
	elseif state == "wait" then
		rs.setAnalogueOutput(upstream, 0)--open for items
		rs.setAnalogueOutput(errorLight, errorOffST)--no error
		event = true
	elseif state == "eval" then--evalItem
		rs.setAnalogueOutput(upstream, 1)--closed for items
		rs.setAnalogueOutput(errorLight, errorOffST)--no error
--		if evalItem() < 17 then
--			--try to accept and report
--			event = not itemOut(1,"accept")
--		else
--			--try to reject and report
--			event = not itemOut(1,"reject")
--		end
		event = not itemOut(1, evalItem())
--		print(turtle.getItemCount(1).."A"..tostring(event))
		if event then--flag a problem with outputs
			rs.setAnalogueOutput(errorLight, errorOnST)
		end
--		print(turtle.getItemCount(1).."B"..tostring(event))
	else--invalid state
		rs.setAnalogueOutput(upstream, 15)
		print("State: "..state.. " not programmed into main loop.")
		event = true --wait for user
	end
--	print(turtle.getItemCount(1).."C"..tostring(event))
	if event then
--		print(turtle.getItemCount(1).."D")
--		print(evalItem())
		if evalItem() == "empty" or not itemOut(1, evalItem(1)) then--final check before an event
			os.sleep(.05)--this line due to a ComputerCraft glitched null event triggered when some states are triggered.
			os.pullEvent()
		end
	end
end