Lumberjack

print("Thanks for using Lumberjack v3, feel free to copy, distribute or edit this program. - Melodicolt")
direction = 0
function mainLoop()
    refuelTurtle()
    checkInventory()
    if turtle.detect() then
        process()
    end
    turtle.forward()
end
function refuelTurtle()
    if turtle.getFuelLevel() ~= "unlimited" and turtle.getFuelLevel() < 50 then
        local fuelCounter = 0
        for i = 1, 16 do
            if turtle.getItemCount(i) > 0 then
                local data = turtle.getItemDetail(i)
                if data.name == "minecraft:coal" then
                    turtle.select(i)
                    turtle.refuel()
                else
                    fuelCounter = fuelCounter + 1
                end
            end
        end
        if fuelCounter == 16 then
            print("I'm out of fuel.")
            fuelCounter = 0
        end
    end
end
function checkInventory()
    local emptyInvSlots = 0
    for i = 1, 16 do
        if turtle.getItemCount(i) == 0 then
            emptyInvSlots = emptyInvSlots + 1
        end
    end
    if emptyInvSlots == 0 then
        print("Inventory full.")
    else
        emptyInvSlots = 0
    end
end
function process()
    local success, data = turtle.inspect()
    if data.name == "minecraft:log" then
        local movesUp = 0
        turtle.dig()
        turtle.forward()
        turtle.digDown()
        while turtle.detectUp() do
            local success, data = turtle.inspectUp()
            if data.name == "minecraft:log" then
                turtle.digUp()
                turtle.up()
                movesUp = movesUp + 1
            else
                turtle.digUp()
            end
        end
        while movesUp ~= 0 do
            turtle.down()
            movesUp = movesUp - 1
        end
        local saplings = 0
        for i = 1, 16 do
            if turtle.getItemCount(i) > 0 then
                local data = turtle.getItemDetail(i)
                if data.name == "minecraft:sapling" then
                    turtle.select(i)
                    turtle.placeDown()
                    saplings = saplings + 1
                end
            end
        end
        if saplings == 0 then
            print("Out of saplings.")
        end
    elseif data.name == "minecraft:fence" then
        local success, data = turtle.inspectDown()
        if data.name == "IronChest:BlockIronChest" then
            for i = 1, 16 do
                if turtle.getItemCount(i) > 0 then
                    local data = turtle.getItemDetail(i)
                    if data.name == "minecraft:log" then
                        turtle.select(i)
                        turtle.dropDown()
                    end
                end
            end
        end
        if direction == 0 then
            turtle.turnRight()
            local success, data = turtle.inspect()
            if data.name == "minecraft:leaves" then
                turtle.dig()
            end
            if turtle.forward() then
                turtle.turnRight()
                direction = 1
            else
                turtle.turnLeft()
                turtle.turnLeft()
                if turtle.forward() then
                    turtle.turnLeft()
                end
            end
        elseif direction == 1 then
            turtle.turnLeft()
            local success, data = turtle.inspect()
            if data.name == "minecraft:leaves" then
                turtle.dig()
            end
            if turtle.forward() then
                turtle.turnLeft()
                direction = 0
            else
                turtle.turnRight()
                turtle.turnRight()
                if turtle.forward() then
                    turtle.turnRight()
                end
            end
        else
            print("Direction is messed up.")
        end
    else
        turtle.dig()
    end
end
while true do
    mainLoop()
end