CC farming

fuelForCoal = 80
storageName = "storagedrawers:basicdrawers"
maxCoalLevel = 20
maxFuelLevel = 300
pickupSlot = 1
seedSlots = { 3, 4, 5 }
harvestSlots = { 6, 7, 8, 9, 10, 11, 12 }
coalSlot = 16
startingFuel = 0;

turnLeft = turtle.turnLeft
turnRight = turtle.turnRight
getFuel = turtle.getFuelLevel
digDown = turtle.digDown
inspect = turtle.inspect
inspectDown = turtle.inspectDown
count = turtle.getItemCount
move = turtle.forward

function select(x)
    turtle.select(x)
end

function transfer(x)
    turtle.transferTo(x)
end

function getCoal()
    select(coalSlot)
    local neededCoal = turtle.getItemSpace()
    turtle.suck(neededCoal)
end

function refuel()
    getCoal()
    local fuelLevel = getFuel()

    if fuelLevel >= maxFuelLevel then
        print("fuel is full")
        return true
    end

    local success, data = inspect();

    if not success then
        print("inspect not successful")
        return false
    end

    if data.name ~= storageName then
        print("not a drawer")
        return false
    end

    select(coalSlot)
    while fuelLevel < maxFuelLevel do
        turtle.refuel(1)
        fuelLevel = getFuel()
    end

    startingFuel = fuelLevel

    return true
end

function transferSeeds()
    select(1)
    local seedSlot = seedSlots[1]

    for i, v in ipairs(seedSlots) do
        select(v)
        local seedCount = count()
        if seedCount < 64 then
            seedSlot = v
            break
        end
    end

    select(1)
    transfer(seedSlot)
    select(seedSlot)
end

function transferHarvest()
    select(2)
    local harvestSlot = harvestSlots[1]

    for i, v in ipairs(harvestSlots) do
        select(v)
        local harvestCount = count()
        if harvestCount < 64 then
            harvestSlot = v
            break
        end
    end

    select(2)
    transfer(harvestSlot)
end

function plantSeed()
    for i, v in ipairs(seedSlots) do
        select(v)
        if count() > 0 then
            turtle.placeDown()
            return
        end
    end
end

function harvestCrop()
    local success, data = inspectDown();
    if not success then
        return
    end

    local age = data.state.age
    if age ~= 7 then
        return
    end

    select(1)
    digDown()

    transferSeeds()
    plantSeed()
    transferHarvest()
end

function dropOff(slots)
    for i, v in ipairs(slots) do
        select(v)
        if count() > 0 then
            turtle.drop()
        end
    end
end

function harvestField()
    refuel()
    turnLeft()

    for i = 1, 4 do
        for i = 1, 8 do
            harvestCrop()
            move()
        end

        turnLeft()
        harvestCrop()
        move()
        turnLeft()

        for i = 1, 8 do
            harvestCrop()
            move()
        end

        turnRight()
        harvestCrop()
        move()
        turnRight()
    end

    for i = 1, 8 do
        harvestCrop()
        move()
    end
    harvestCrop()

    turnRight()

    for i = 1, 8 do
        move()
    end

    turnRight()

    for i = 1, 6 do
        move()
    end

    turnLeft()
    dropOff(seedSlots)

    turnRight()
    move()
    turnLeft()
    dropOff(harvestSlots)

    turnRight()
    move()
    turnLeft()

    local fuelUsed = startingFuel - turtle.getFuelLevel()
    print("fuel used: " .. fuelUsed)
end

harvestField()