TFarm

-- pastebin get 4SHjtFAU tfarm.lua
-- This turtle program harvests rows of crops with rows of water between them
-- Seeds go in the first slot and fuel goes in the last (16th) slot. Everything else gets dumped.
-- The turtle needs to be outside the end of the last crop row facing into the row and 1 block above crop height
-- To automate storage of crops and extra seeds place a chest under this position

-- Farm parameters
local rowLength = 20
local numRows = 16
local matureCropStage = 7 -- 7 will work for most crops
local turnRightFirst = true -- true if the first turn needed to face the next row is right
--Network parameters
local networkMessageKeyword = "harvest" -- if received over the network, this will trigger a harvest
local modemSide = "left" -- side the modem is on


-- Initialize
local turnRightNext = turnRightFirst
local currentSlot = 1
local onFirstRow = true;

function setActiveSlot(slotNumber)
    slotNumber = tonumber(slotNumber)
    if slotNumber ~= nil then
        currentSlot = slotNumber
        turtle.select(slotNumber)
    end
end

function harvest()
    local success, data = turtle.inspectDown()

    if success then
        if data.state.age == matureCropStage then -- 7 = fully grown
            setActiveSlot(1)
            turtle.digDown()
            turtle.placeDown()
        end
    end
end

function refuelFromLastSlot()
    setActiveSlot(16)
    turtle.refuel()
end

function forceMoveForward()
    while not turtle.forward() do
        print("Failed to move forward!")
        sleep(1)
    end
end

function forceTurn(goRight)
    if goRight == true then
        while not turtle.turnRight() do
            print("Failed to turn right!")
            sleep(1)
        end
    else
        while not turtle.turnLeft() do
            print("Failed to turn left!")
            sleep(1)
        end
    end
end

function forceDropDown()
    while not turtle.dropDown() do
        print("Failed to transfer items!")
        sleep(1)
    end
end

function returnHome()

    local distanceToHome = (numRows * 2) - 2

    forceMoveForward()
    forceTurn(true) -- TODO handle more cases

    for i=1, distanceToHome do
        forceMoveForward()
    end

    forceTurn(true)
end

function transferItems()
    for i=2, 15 do
        turtle.select(i)
        turtle.dropDown()
    end
end

function harvestField()
    print("Harvesting crops...")
    refuelFromLastSlot()
    forceMoveForward()

    for i=1, numRows do

        if onFirstRow == true then
            onFirstRow = false
        else
            -- Get to next row
            forceTurn(turnRightNext)
            forceMoveForward()
            forceMoveForward()
            forceTurn(turnRightNext)

            -- Zig zag efficiently through the crop rows
            turnRightNext = not turnRightNext
        end

        for j=2, rowLength do
            harvest()
            forceMoveForward()
        end

        harvest()

    end

    returnHome()
    transferItems()

    turnRightNext = turnRightFirst
    onFirstRow = true

end

-- Execution starts here --
print("Listening for messages...")
rednet.open(modemSide)
while true do
    id, msg = rednet.receive()
    if msg == networkMessageKeyword then
        rednet.close(modemSide)
        harvestField()
        print("Harvest finished. Listening...")
        rednet.open(modemSide)
    end
end