farm.lua

farmLength = 19
farmWidth = 8

function fuel()
    if turtle.getFuelLevel() < 1 then
        turtle.select(1)
        turtle.refuel(1)
    end
end

function move(d, n)
    n = n or 1
    for i=1,n do
        fuel()
        d()
    end
end

function harvest()
    local success, data = turtle.inspectDown()
    if success then
        if data.state.age == 7 then
            turtle.digDown()
            turtle.select(2)
            if turtle.getItemCount() > 1 then
                turtle.placeDown()
            end
        end
    end
end

function harvestRow()
    harvest()
    for i=2, farmLength do
        move(turtle.forward)
        harvest()
    end
end

turnAround = {
    [0] = turtle.turnLeft,
    [1] = turtle.turnRight
}

function run()
    move(turtle.forward)
    for row=1, farmWidth do
        harvestRow()
        if row < farmWidth then
            turnAround[row % 2]()
            move(turtle.forward)
            turnAround[row % 2]()
        elseif row % 2 == 1 then
            turtle.turnRight()
            turtle.turnRight()
            move(turtle.forward,farmLength-1)
        end
    end
    turtle.turnRight()
    move(turtle.forward,farmWidth-1)
    turtle.turnRight()
    move(turtle.back)

    for i=3,16 do
        turtle.select(i)
        turtle.dropDown()
    end
end

local alarm = os.setAlarm(5)
while true do
    local evt, arg = os.pullEvent("alarm")
    if arg == alarm then
        run()
    end
end