Cane Harvester

local delay = 180
local price = 32

local activities = {
    CHEST_IDLE = 1,
    CHEST_OUT = 2,
    CHEST_IN = 3,
    TRANSIT_IN_HORIZONTAL = 4,
    TRANSIT_IN_VERTICAL = 5,
    TRANSIT_OUT = 6, -- entering the farming area
    TRANSIT_IN = 7, -- leaving the farming area
    NEXT_OUT_HORIZONTAL = 8,
    NEXT_OUT_VERTICAL = 9,
    NEXT_IN_HORIZONTAL = 10,
    CROP_OUT = 11, -- in the farming area, heading away from entry
    CROP_SWITCH = 12, -- in the farming area, heading toward entry
    CROP_IN = 13,
    TRANSIT_IN_SWITCH = 14
}

local directions = {
    OUT_TRANSIT = 0,
    OUT_CROP = 1,
    IN_TRANSIT = 2,
    IN_CROP = 3
}

local state
local function loadState()
    local h = fs.open("cane.state", "r")
    if h then
        state = textutils.unserialise(h.readAll())
        h.close()
    else
        state = {
            activity = activities.CHEST_IDLE,
            direction = directions.OUT_CROP,
            startFuel = turtle.getFuelLevel()
        }
    end
end

local function saveState()
    local h = fs.open("cane.state", "w")
    if h then
        h.write(textutils.serialise(state))
        h.close()
    end
end

local function turnTo(direction)
    local difference = direction - state.direction
    if math.abs(difference) >= 3 then
        difference = (difference - 2 * (difference / math.abs(difference))) * -1
    end
    if difference > 0 then
        for i = 1, difference do
            turtle.turnLeft()
            state.direction = (state.direction + 1) % 4
            saveState()
        end
    elseif difference < 0 then
        for i = 1, math.abs(difference) do
            turtle.turnRight()
            state.direction = (state.direction - 1) % 4
            saveState()
        end
    end
end

local function setActivity(activity)
    if not activity then error('act') end
    state.activity = activity
    saveState()
end

-- depart from the idle chest location
function chestOut()
    print("Starting harvest...")
    setActivity(activities.CHEST_OUT)
    turnTo(directions.OUT_TRANSIT)
    while true do
        local okay, block = turtle.inspectDown()
        if okay and block and block.name == "minecraft:planks" and block.state.variant == "birch" then
            break
        end
        if not turtle.forward() then
            error("WARNING! Failed to find tunnel start.")
        end
    end
    return nextHorizontalOut()
end

function enterCrop()
    setActivity(activities.TRANSIT_OUT)
    turnTo(directions.OUT_CROP)
    while true do
        local okay, block = turtle.inspect()
        if okay and block and block.name == "minecraft:reeds" then
            -- there are reeds in front of us, we're in a farming zone now
            return cropOut()
        else
            okay, block = turtle.inspectDown()
            if not okay or (okay and block and block.name == "minecraft:reeds") then
                -- there is no block or there are reeds below us, we're farming now
                return cropOut()
            end
        end
        if not turtle.forward() then
            error("WARNING! Failed to enter farming area.")
        end
    end
end

local function crop(isIn)
    local keepRunning = true
    while keepRunning do
        local okay, block = turtle.inspect()
        if okay and block then
            if block.name == "minecraft:reeds" then
                -- there are reeds in front of us
                turtle.dig()
            else
                -- there is another block, we need to stop
                keepRunning = false
            end
        end
        okay, block = turtle.inspectDown()
        if okay and block then
            if block.name == "minecraft:reeds" then
                -- there are reeds below us
                turtle.digDown()
            elseif isIn then
                -- there is another block, we must be in the exit
                keepRunning = false
            end
        end
        if keepRunning and not turtle.forward() then
            error("WARNING! Failed to move through the farm area (probably low fuel).")
        end
    end
end

function cropOut()
    setActivity(activities.CROP_OUT)
    turnTo(directions.OUT_CROP)
    crop()
    return cropSwitch()
end

function cropSwitch()
    setActivity(activities.CROP_SWITCH)
    turnTo(directions.OUT_TRANSIT)
    local okay, block = turtle.inspect()
    if okay and block then
        if block.name ~= "minecraft:reeds" then
            -- there is another block, we are in cropIn
            return cropIn()
        else
            turtle.dig()
        end
    end
    -- there is air in front of us, we can safely move forward
    turtle.forward()
    return cropIn()
end

function cropIn()
    setActivity(activities.CROP_IN)
    turnTo(directions.IN_CROP)
    crop(true)
    return exitSwitch()
end

function exitSwitch()
    setActivity(activities.TRANSIT_IN_SWITCH)
    turnTo(directions.IN_CROP)
    local okay, block = turtle.inspect()
    if not okay then
        -- we're already at the exit
        return exitCrop()
    end
    turnTo(directions.IN_TRANSIT)
    turtle.dig()
    turtle.forward()
    return exitCrop()
end

function exitCrop()
    setActivity(activities.TRANSIT_IN)
    turnTo(directions.IN_CROP)
    while true do
        local okay, block = turtle.inspect()
        if okay and block then
            -- this is the exit, we don't start any new tasks, simply let nextHorizontal takeover again
            return
        end
        if not turtle.forward() then
            error("WARNING! Failed to exit farming area.")
        end
    end
end

function nextHorizontalOut()
    state.nextHorizontal = "out"
    setActivity(activities.NEXT_OUT_HORIZONTAL)
    while true do
        turnTo(directions.OUT_CROP)
        local okay, block = turtle.inspect()
        if not okay then
            -- this is air and hence an entry, enter it
            enterCrop()
            setActivity(activities.NEXT_OUT_HORIZONTAL)
        end
        turnTo(directions.OUT_TRANSIT)
        -- there wasn't an entry or we've been through it, move along and try again
        local okay, block = turtle.inspect()
        if okay and block then
            -- there is a block in front of us, this is the last hoziontal, try going up
            return nextVerticalOut(false)
        end
        if not turtle.forward() then
            error("WARNING! Failed to move to next horizontal entry.")
        end
    end
end

function nextHorizontalIn()
    state.nextHorizontal = "in"
    setActivity(activities.NEXT_IN_HORIZONTAL)
    while true do
        turnTo(directions.OUT_CROP)
        local okay, block = turtle.inspect()
        if not okay then
            -- this is air and hence an entry, enter it
            enterCrop()
            setActivity(activities.NEXT_IN_HORIZONTAL)
        end
        turnTo(directions.IN_TRANSIT)
        -- there wasn't an entry, move along and try again
        local okay, block = turtle.inspect()
        if okay and block then
            -- there is a block in front of us, this is the last hoziontal, try going up
            return nextVerticalOut(true)
        end
        if not turtle.forward() then
            error("WARNING! Failed to move to next horizontal entry.")
        end
    end
end

function nextVerticalOut(horizontalOut)
    setActivity(activities.NEXT_OUT_VERTICAL)
    turnTo(directions.OUT_CROP)
    while true do
        local okay, block = turtle.inspectUp()
        if okay and block then
            -- there is a block in above us, this is the last vertical, go home
            return verticalIn()
        end
        if not turtle.up() then
            error("WARNING! Failed to move to next vertical entry.")
        end
        local okay, block = turtle.inspect()
        if not okay then
            -- this is air and hence an entry, do next horizonatal
            if horizontalOut then
                return nextHorizontalOut()
            else
                return nextHorizontalIn()
            end
        end
    end
end

function verticalIn()
    setActivity(activities.TRANSIT_IN_VERTICAL)
    turnTo(directions.IN_TRANSIT)
    while true do
        local okay, block = turtle.inspectDown()
        if okay and block then
            -- there is a block in below us, this is the last vertical, start horizontal
            return horizontalIn()
        end
        if not turtle.down() then
            error("WARNING! Failed to move to vertically home.")
        end
    end
end

function horizontalIn()
    setActivity(activities.TRANSIT_IN_HORIZONTAL)
    turnTo(directions.IN_TRANSIT)
    while true do
        local okay, block = turtle.inspectDown()
        if okay and block and block.name == "minecraft:planks" and block.state.variant == "birch" then
            -- the home plank is right below us, return to the chest
            return chestIn()
        end
        if not turtle.forward() then
            error("WARNING! Failed to move to horizontally home.")
        end
    end
end

function chestIn()
    -- at this point it is assumed that we are right above the plank block
    setActivity(activities.CHEST_IN)
    turnTo(directions.IN_TRANSIT)
    while true do
        local okay, block = turtle.inspectDown()
        if okay and block and block.name == "minecraft:wool" and block.state.color == "white" then
            break
        end
        if not turtle.forward() then
            error("WARNING! Failed to return to chest.")
        end
    end
    return chestIdle()
end

function chestIdle()
    setActivity(activities.CHEST_IDLE)
    turnTo(directions.OUT_CROP)
    local count = 0
    for i = 1, 16 do
        count = count + turtle.getItemCount(i)
        turtle.select(i)
        turtle.drop()
    end
    print("Harvested " .. count .. " cane.")
    print(string.format("Value: $%.2f", (count / 64) * price))
    print("Fuel consumption: " .. state.startFuel - turtle.getFuelLevel())
end

function resume()
    print("Resuming...")
    loadState()
    local funcs = {
        [activities.CHEST_IDLE] = chestIdle;
        [activities.CHEST_OUT] = chestOut;
        [activities.CHEST_IN] = chestIn;
        [activities.TRANSIT_IN_HORIZONTAL] = horizontalIn;
        [activities.TRANSIT_IN_VERTICAL] = verticalIn;
        [activities.TRANSIT_OUT] = enterCrop;
        [activities.TRANSIT_IN] = exitCrop;
        [activities.NEXT_OUT_HORIZONTAL] = nextHorizontalOut;
        [activities.NEXT_OUT_VERTICAL] = nextVerticalOut;
        [activities.NEXT_IN_HORIZONTAL] = nextHorizontalIn;
        [activities.CROP_OUT] = cropOut;
        [activities.CROP_SWITCH] = cropSwitch;
        [activities.CROP_IN] = cropIn;
        [activities.TRANSIT_IN_SWITCH] = exitSwitch;
    }
    funcs[state.activity]()
    if state.activity ~= activities.CHEST_IDLE then
        if state.nextHorizontal == "in" then
            return nextHorizontalIn()
        else
            return nextHorizontalOut()
        end
    end
end

resume()
while true do
    sleep(delay)
    print("Starting fresh...")
    state.startFuel = turtle.getFuelLevel()
    saveState()
    chestOut()
end