Podman 1.0

-- Podman 1.0
-- by MCKerrnel
--
-- A ComputerCraft program to
-- operate a farm in a 15dia
-- pod/dome.  Turtle will
-- harvest and re-plant.

-- Size of farm grid that turtle
-- will traverse.  Middle position
-- is water.
local width = 9
local length = 9

-- Fuel needed to start a cycle.
local fuelCycle = 250

-- Harvests and replants the crop.
function harvestCrops(endCol)
	local colCount = 0
	while colCount < endCol do
		for rowCount = 1, length, 1 do
			turtle.select(1)

			-- Don't move forward if this is
			-- the first block in the row;
			-- we're already on it.
			if rowCount ~= 1 then
				turtle.forward()
			end

			-- Harvest the crop. If there
			-- is only one seed left in slot 1
			-- then do not plant it.
        		turtle.digDown()
			if turtle.getItemCount(1) > 1 then
				turtle.placeDown()
			end
		end
		colCount = colCount + 1

		-- Rotate around to start
		-- the new row.
		endColTurn(colCount)
		turtle.forward()
		endColTurn(colCount)
 	end
end

-- Determine which direction the
-- turtle should turn, based on
-- which row it just finished.
function endColTurn(column)
	-- Turtle will snake, so odd
	-- numbered columns turn left,
	-- even turn right.  Odd
	-- numbers will leave a
	-- remainder when divided by 2.
	local direction = column % 2

	if direction == 1 then
		turtle.turnLeft()
	else
		turtle.turnRight()
	end
end

-- Unloads the crops from the turtle
-- into the chest for crops.
function emptyHarvest()
        for slot = 2, 16, 1 do
                turtle.select(slot)
                turtle.drop()
        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 refuel(fuelCycles)
        -- Refuel.  We don't need a stupid
	-- amount of fuel, so cap it
	-- on refuel at 10k.
	local fuelMax = 10000

        if fuelCycles < 1 then
		-- Assume the turtle is facing
		-- forward and in-between the
		-- two chests.  Left chest is
		-- to dump harvest into, right
		-- is for fuel.
                turtle.turnRight()
                turtle.select(2)

                -- Try to fill up, but if not enough to
                -- fill up, that's ok.
                while fuelCycles < 1 or turtle.getFuelLevel() < fuelMax do
                        -- If there's nothing to grab, error out.
                        if turtle.suck() == false then
                                break
                        end
                        turtle.refuel()
                        fuelCycles = turtle.getFuelLevel() / fuelCycle
                end

                -- If we still need fuel
                -- then alert console.
                if fuelCycles < 1 then
                        print "NO FUEL: Reload the FUEL chest."
                end

		-- Restore original orientation.
                turtle.turnLeft()
        end
        return fuelCycles
end

-- Bring the turtle back at the end
-- of the harvest cycle, dumping off
-- the harvest and returning to
-- between the chests.  Assumption
-- here is that the full 9x9 grid has
-- been traveled. Function does not
-- account for custom number of
-- columns.
function turtleReturn()
	for count = 1, 8, 1 do
        	turtle.forward()
        end
        turtle.turnLeft()
	for count = 1, 5, 1 do
        	turtle.forward()
        end
        turtle.turnRight()
	turtle.forward()
	turtle.turnRight()
	turtle.down()
	emptyHarvest()
	turtle.turnRight()
end


-- MAINLINE
local fuelCycles = turtle.getFuelLevel() / fuelCycle
print("Enough fuel to harvest ", toInt(fuelCycles), " cycles.")

-- This is where it all happens.
while true do
	-- We must have at least 1 seed in slot 1
	-- so that the slot never is empty, otherwise
	-- the turtle might try planting harvest items.
	-- If we do not have a seed, then abort.
	if turtle.getItemCount(1) == 0 then
		print("There is no target seed in slot 1.")
		print("Need at least ONE seed of the crop.")
		break
	end

        -- Fuel Up
        fuelCycles = turtle.getFuelLevel() / fuelCycle
        if fuelCycles < 1 then
                fuelCycles = refuel(fuelCycles)
        end

	-- If we have enough fuel, let's harvest!
        if fuelCycles >= 1 then
                turtle.up()
		turtle.forward()
		turtle.turnRight()
		turtle.forward()
		turtle.forward()
		turtle.forward()
		turtle.forward()
		turtle.turnLeft()
                harvestCrops(width)

                -- Return to start
		turtleReturn()
        end

	-- To allow crops to grow to make
	-- harvesting worthwhile, we will
	-- wait 40 minutes.  60s * 40
	-- Can probably reduce this if
	-- using lilypad of fertility or
	-- something.
        sleep(2400)
end