Podman 1.1

-- Podman 1.1
-- by MCKerrnel
--
-- A ComputerCraft program to
-- operate a farm in a rectangular
-- area.  Turtle will harvest and
-- replant.
--
-- This version adapts start/return
-- movement to accomodate the
-- custom dimensions. Also
-- accommodates return if the
-- dimensions end the turtle
-- at farthest point out. Assumes
-- that the max dimension is 9x9.

-- Size of farm grid that turtle
-- will traverse.  Middle position
-- is water.
local width = 7
local length = 7

-- Fuel needed to start a cycle.
local fuelCycle = width * length + 20

-- 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(near)
	if near == false then
	        for count = 1, 9 - (5 - toInt(length/2)), 1 do
        	        turtle.forward()
	        end
	        turtle.turnLeft()
	        for count = 1, toInt(width/2) + 1, 1 do
	                turtle.forward()
	        end
	end
        turtle.turnRight()
        turtle.forward()
        turtle.turnRight()
        turtle.down()
        emptyHarvest()
        turtle.turnRight()

end


-- MAINLINE
local near = false
if length%2 == 0 then
	near = true
end

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()
		for count = 1, 5 - toInt(length/2), 1 do
	                turtle.forward()
		end
                turtle.turnRight()
		for count = 1, toInt(width/2), 1 do
	                turtle.forward()
		end
                turtle.turnLeft()
                harvestCrops(width)

                -- Return to start
                turtleReturn(near)
        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