Turtle Tree Farm

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-- Computercraft Turtle Tree Farm
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-- Change the item IDs for the sapling, marker and storage block before use
-- Also can configure the minimum fuel level
--
-- Place at least 2 saplings in the first slot and
-- some of the desired fuel to use in the last slot
--
-- Build a ring of the marker block around the tree farm to keep
-- the turtle from flying away
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local sapling_name = "minecraft:spruce_sapling"
local marker_name = "minecraft:cobblestone_wall"
local storage_name = "minecraft:chest"
local min_fuel_level = 500

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-- Code
-- ONLY EDIT BEYOND THIS POINT IF YOU ARE CONFIDENT PROGRAMMER
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local sapling_slot = 1
local fuel_slot = 16

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local last_turn = 0


function isLeaf(blockName)
    return string.sub(blockName, -6, -1) == "leaves"
end

function isLog(blockName)
    return string.sub(blockName, -3, -1) == "log"
end

function findOperatingLevel()
    print("Trying to find the base level")
    turtle.select(sapling_slot)
    while true do
        local detected, data = turtle.inspectDown()
        if detected and (isLog(data.name) or isLeaf(data.name)) then
            print("Leaf or log is below. Going down.")
            turtle.digDown()
            turtle.down()
        elseif detected and turtle.compareDown() then
            print("Sapling is below. Must be there")
            break
        elseif detected and data.name == marker_name then
            print("Marker is below. Must be there")
            return
        elseif detected then
            print("Some sort of floor is below. Planting a sapling")
            turtle.up()
            if turtle.getItemCount() > 1 then
                turtle.placeDown()
            end
            break
        else
            print("Nothing below. Going down")
            turtle.down()
        end
    end
end

function findBoundary()
    print("Trying to find the boundary")
    findOperatingLevel()
    turtle.select(sapling_slot)
    while true do
        local detected, data = turtle.inspectDown()
        if detected and data.name == marker_name then
            break
        end
        if not turtle.forward() then
            turtle.dig()
            turtle.forward()
            turtle.digDown()
            while turtle.detectUp() do
                turtle.digUp()
                turtle.up()
            end
            while turtle.down() do
            end
            turtle.up()
            if turtle.getItemCount() > 1 then
                turtle.placeDown()
            end
        end
    end
end

function findStorage()
    print("Trying to find the chest")
    findBoundary()
    while true do
        local detected, data = turtle.inspect()
        if detected and data.name == storage_name then
            return
        else
            if not turtle.forward() then
                turtle.dig()
                turtle.forward()
            end
            local detected, data = turtle.inspectDown()
            if detected and data.name == marker_name then

            else
                turtle.back()
                turtle.turnLeft()
            end
        end
    end
end

function restockRefuel()
    print("Restock and Refuel")
    findStorage()
    turtle.select(sapling_slot)
    turtle.suck(turtle.getItemSpace())
    turtle.select(fuel_slot)
    turtle.suck(turtle.getItemSpace())
    for var=1,16 do
        turtle.select(var)
        if var == sapling_slot or var == fuel_slot then
        else
            if turtle.getItemCount(var) == 0 then
            elseif not turtle.drop() then
                print("The storage is full. Stopping...")
                error()
            end
        end
    end
    if turtle.getFuelLevel() < min_fuel_level then
        turtle.select(fuel_slot)
        turtle.refuel(turtle.getItemCount()-1)
    end

    turtle.back()
    turtle.turnLeft()
end

function chopTree()
    turtle.dig()
    turtle.forward()
    turtle.digDown()
    turtle.select(sapling_slot)
    turtle.placeDown()
    while turtle.detectUp() do
        turtle.digUp()
        turtle.up()
    end
    while turtle.down() do
        turtle.select(sapling_slot)
        local detected, data = turtle.inspectDown()
        if detected and (isLeaf(data.name) or isLog(data.name)) then
            turtle.digDown()
        elseif detected and turtle.compareDown() then
        else
            turtle.up()
            turtle.placeDown()
            break
        end
    end
end

while true do
    print("Loop")
    sleep(3)
    if turtle.getItemCount(sapling_slot) == 0 or turtle.getItemCount(fuel_slot) == 0 then
        print("Need fuel and saplings to work")
        sleep(10)
    end
    if turtle.getItemCount(sapling_slot) == 1 or turtle.getFuelLevel() < min_fuel_level then
        print(" Low on fuel" .. tostring(turtle.getFuelLevel()))
        restockRefuel()
    end

    if not turtle.forward() then
        local detected, data = turtle.inspect()
        if detected and isLeaf(data.name) then
            turtle.dig()
            turtle.forward()
        elseif detected and isLog(data.name) then
            chopTree()
        end
    end

    local detected, data = turtle.inspectDown()
    if detected and data.name == marker_name then
        print("On Marker")
        local turn_func = nil
        if last_turn == 0 then
            turn_func = turtle.turnLeft
            last_turn = 1
        else
            turn_func = turtle.turnRight
            last_turn = 0
        end
        print("Picked turning direction")
        while true do
            local downDetected, downData = turtle.inspectDown()
            if downDetected and downData.name == marker_name then
                turn_func()
                print("Turn")

                if not turtle.forward() then

                    local frontDetected, frontData = turtle.inspect()
                    if frontDetected and isLeaf(frontData.name) then
                        turtle.dig()
                        turtle.forward()
                        break
                    elseif frontDetected and isLog(frontData.name) then
                        chopTree()
                        break
                    end
                end
            else
                print("Marker not below. Resuming operation")
                break
            end
        end
    end
end