Shearman 2.1

-- Shearman 2.1
-- by MCKerrnel
--
-- A ComputerCraft program to shear
-- sheep.  This version includes
-- reloading shears when they break.

-- How much fuel it takes to
-- complete one cycle.
local fuelCycle = 54

function goForward(blocks)
	for count = 1, blocks, 1 do
		turtle.forward()
		turtle.suck()
	end
end

function turn(direction)
	if direction == "left" then
		turtle.turnLeft()
	else
		turtle.turnRight()
	end
end

-- A quick function to convert a decimal
-- value into an integer.  Dunno why
-- LUA has to be so difficult with this.
-- Should be a built-in function!
function toInt(decimalNum)
	local D2I = string.format("%i", decimalNum)
	return D2I
end

function shearCycle(direction, needShears)
	if direction == "left" then
		returndir = "right"
	else
		returndir = "left"
	end

	-- Chest to Start of Row
	turn(direction)
	goForward(3)
	turn(direction)

	-- Shear Row
	for count = 1, 8, 1 do
		needShears = shearPen(direction, needShears)
	end

	-- Return to Chest
	turtle.turnLeft()
	turtle.turnLeft()
	goForward(23)
	turn(returndir)
	goForward(3)
	turn(returndir)

	-- Unload
	if needShears then
		startSlot = 1
	else
		startSlot = 2
	end
	for slot = startSlot, 16, 1 do
		turtle.select(slot)
		turtle.drop()
	end

	turtle.turnLeft()
	turtle.turnLeft()

	return needShears
end

-- Shear the sheep in a 2x1 pen.
function shearPen(direction, needShears)
	turtle.select(1)
	for count = 1, 2, 1 do
		turtle.forward()
		turn(direction)

		-- If we still have shears
		-- then shear and reset
		-- the check status.
		-- If no shears, then
		-- don't try to shear.
		if needShears == false then
			turtle.place()
			needShears = needShearsCheck()
		end
		os.sleep(2)
		turtle.suck()
		if direction == "left" then
			turtle.turnRight()
		else
			turtle.turnLeft()
		end
	end
	turtle.forward()

	return needShears
end

-- Check to see if the shears
-- are broken.
function needShearsCheck()
	-- Check the # of items
	-- in the shears slot
	-- that are needed to
	-- complete a full stack.
	-- 0=Full stack
	-- 64=No item
	-- 1-63=Wool
	if turtle.getItemSpace(1) == 0 then
		return false
	else
		return true
	end
end

-- Check to see if we have
-- enough fuel for a cycle.
function needFuelCheck()
	if turtle.getFuelLevel() - fuelCycle < 0 then
		return true
	else
		return false
	end
end

-- Reload shears from the chest
-- below. If able to reload then
-- send back false to reset the
-- needShears variable, otherwise
-- return true for failure and
-- still needing shears.  The
-- turtle inventory should be empty
-- when it attempts to load items.
function reloadShears(needShears)
	if needShears then
		turtle.select(1)
		-- If we still need shears
		-- then alert console.
		if turtle.suckDown() == false then
			print "NO SHEARS: Reload the SHEARS chest."
		else
			needShears = false
		end
	end
	return needShears
end

function refuel(needFuel)
	-- Refuel.  This is a regular turtle
	-- so can only hold 20,000 units.
	if needFuel then
		turtle.select(2)

		-- Try to fill up, but if not enough to
		-- fill up, that's ok.
		while needFuel == true or turtle.getFuelLevel < 20000 do
			-- If there's nothing to grab, error out.
			if turtle.suckUp() == false then
				break
			end
			turtle.refuel()
			needFuel = needFuelCheck()
		end

		-- If we still need fuel
		-- then alert console.
		if needFuel then
			print "NO FUEL: Reload the FUEL chest."
		end
	end
	return needFuel
end

-- Not used in this version...wanted to
-- document it to have it for 3.0
function toTerm(column, row, text)
	-- Terminal size = 39 x 13
	setCursorPos(column, row)
	term.write(text)
end


-- MAINLINE
-- Check to see if we need shears.
local needShears = needShearsCheck()
local needFuel = needFuelCheck()

local fuelCycles = turtle.getFuelLevel() / fuelCycle
print("Enough fuel to shear ", toInt(fuelCycles), " rows.")

-- This is where it all happens.
while true do
	-- Reload shears, if needed.
	needShears = reloadShears(needShears)

	-- Refuel.
	needFuel = refuel(needFuel)

	-- Shear North Row
	print "CYCLE: North Row"
	if needShears == false and needFuel == false then
		needShears = shearCycle("left", needShears)
	end

	-- Reload shears, if needed.
	needShears = reloadShears(needShears)

	-- Shear South Row
	print "CYCLE: South Row"
	if needShears == false and needFuel == false then
		needShears = shearCycle("right", needShears)
	end

	-- Wait 2 minutes to allow
	-- sheep to regrow wool.
	print "CYCLE: Sleep 2 min"
	os.sleep(120)
end