App

-- https://turtleappstore.com/u/BigMonValthor/a/farm_routine
-- Crop data
kSeedName = 'minecraft:wheat_seeds'
kCropName = 'minecraft:wheat'
kFullyGrownLevel = 7

-- States
kInitState = 0
kFarmRowState = 1
kSwitchRowState = 2
kMoveToChestsState = 3
kStoreState = 4
kReturnToRowState = 5
kShutdownState = 6

-- Directions
kNorth = 0
kEast = 1
kSouth = 2
kWest = 3
kNumDirections = 4

-- Farm params
kHeight = 10
kWidth = 11

-- Fuel params
kShutoffFuel = kWidth + kHeight
kMinFuel = kHeight * kWidth + kShutoffFuel * 2

state = kInitState
x = 0
y = 0
direction = kEast
destination_x = x
destination_y = y
saved_x = x
saved_y = y

local termination_requested = true
while not termination_requested do
    termination_requested = tick_state_machine()
end

function face_direction(desired_direction)
    while direction ~= desired_direction do
        turtle.turnRight()
        direction = (direction + 1) % kNumDirections
    end
end

function move_in_direction(desired_direction)
    face_direction(desired_direction)
    turtle.forward()
end

function move_to_destination()
    local at_destination = false
    if x < destination_x then
        move_in_direction(kEast)
        x = math.min(x + 1, kWidth - 1)
    elseif x > destination_x then
        move_in_direction(kWest)
        x = math.max(x - 1, 0)
    elseif y < destination_y then 
        move_in_direction(kSouth)
        y = math.min(y + 1, kHeight - 1)
    elseif y > destination_y then
        move_in_direction(kNorth)
        y = math.min(y - 1, 0)
    else
        at_destination = true
    end
    return at_destination
end
    
function tick_state_machine()
    local termination_requested = false

    if state == kInitState then
        -- Read from memory?
        -- Calibrate?

        if turtle.getFuelLevel() < kMinFuel then
            transition_to_state(kShutdownState)
        else
            transition_to_state(kFarmRowState)
        end

    elseif state == kFarmRowState then
        local success, data = turtle.inspectDown()
        local crop_fully_grown = (data ~= nil and block['name'] == kCropName and block['metadata'] == kFullyGrownLevel)

        local out_of_seeds = false
        if not success or crop_fully_grown then
            out_of_seeds = process_land()
        end

        local at_destination = move_to_destination()

        local cycle_complete = (y == kHeight - 1) and at_destination
        if cycle_complete then
            saved_x = 1
            saved_y = 0
        else
            saved_x = x
            saved_y = y
        end

        if turtle.getFuelLevel() < kShutoffFuel or out_of_seeds then
            transition_to_state(kShutdownState)
        elseif inventory_full() or cycle_complete then
            transition_to_state(kMoveToChestsState)
        elseif at_destination then
            transition_to_state(kSwitchRowState)
        end

    elseif state == kSwitchRowState then
        local at_destination = move_to_destination()

        if at_destination then
            transition_to_state(kFarmRowState)
        end

    elseif state == kMoveToChestsState then
        local at_destination = move_to_destination()

        if at_destination then
            move_in_direction(kSouth)
            turtle.down()
            transition_to_state(kFarmRowState)
        end

    elseif state == kStoreState then
        local all_chests_tested = false

        face_direction(kWest)
        while not all_chests_tested or transfer_all_crops() do
            face_direction(kSouth)
            all_chests_tested = turtle.detect()
            if not all_chests_tested then
                face_direction(kWest)
            end
        end
        turtle.up()

        if all_chests_tested then
            transition_to_state(kShutdownState)
        else
            transition_to_state(kReturnToRowState)
        end

    elseif state == kReturnToRowState then
        local at_destination = move_to_destination()

        if at_destination then
            transition_to_state(kFarmRowState)
        end

    else
        local at_destination = move_to_destination()

        if at_destination then
            termination_requested = true
        end

    end

    return termination_requested
end

function transition_to_state(new_state)
    if new_state == kFarmRowState then
        if y % 2 == 0 then
            destination_x = kWidth - 1
            destination_y = y
        else
            destination_x = 1
            destination_y = y
        end
    elseif new_state == kSwitchRowState then
        destination_x = x
        destination_y = y + 1
    elseif new_state == kReturnToRowState then
        destination_x = saved_x
        destination_y = saved_y
    else
        destination_x = 0
        destination_y = 0
    end

    state = new_state
end

function process_land()
    local out_of_seeds = true
    turtle.digDown()
    if select_item(kSeedName) then
        turtle.placeDown()
        out_of_seeds = false
    end
    return out_of_seeds
end

function select_item(name)
    -- check all inventory slots
    local item
    for slot = 1, 16 do
        item = turtle.getItemDetail(slot)
        if item ~= nil and item['name'] == name then
            turtle.select(slot)
            return true
        end
    end
    return false  -- couldn't find item
end

function transfer_all_crops()
    local item
    for slot = 1, 16 do
        item = turtle.getItemDetail(slot)
        if item ~= nil and item['name'] == kCropName then
            local success = turtle.drop()
            if not success then
                return false
            end
        end
    end
    return true
end

function inventory_full()
    local item
    for slot = 1, 16 do
        item = turtle.getItemDetail(slot)
        if item ~= nil and item['name'] == kCropName then
            local item_space = turtle.getItemSpace(slot)
            if item_space > 0 then
                return true
            end
        end
    end
    return false
end