harvestTree.lua

function ScanAndDig()
    if turtle.compareUp() == true then
        DigAndMove("up")
    else
        return false
    end
    return true
end

function DigAndScan( psDirection )
    local iSleep=0.5
    if psDirection=="up" then
        while turtle.detectUp() do
            if not turtle.digUp() then return false end
            sleep(iSleep)
        end
    elseif psDirection=="down" then
        while turtle.detectDown() do
            if not turtle.digDown() then return false end
            sleep(iSleep)
        end
    else
        while turtle.detect() do
            if not turtle.dig() then return false end
            sleep(iSleep)
        end
    end
    return true
end

function DigAndMove(psDirection)
    local bExit=false
    local iSleep=0.5
    while bExit==false do
        if not DigAndScan(psDirection) then
            return false
        end
        if psDirection=="up" then
            if not turtle.up() then
                turtle.attackUp()
                sleep(iSleep)
            else
                bExit=true
            end
        elseif psDirection=="down" then
            if not turtle.down() then
                turtle.attackDown()
                sleep(iSleep)
            else
                bExit=true
            end
        else
            if not turtle.forward() then
                turtle.attack()
                sleep(iSleep)
            else
                bExit=true
            end
        end
    end
    return true
end

if turtle.detect() == false and turtle.detectUp() == false then
    print("No tree detected")
    print("Place turtle under or against tree")
    return false
end

if turtle.getItemCount(1) > 0 then
    turtle.select(1)
    turtle.dropUp()
    for q=2,16 do
        turtle.select(q)
        if turtle.getItemCount(q) == 0 then
            turtle.suckUp()
            break
        end
    end
end

turtle.select(1)
local iLevel = 0
if turtle.detect() == true then
    DigAndMove("forward")
elseif turtle.detectUp() == true then
    DigAndMove("up")
    iLevel = iLevel + 1
end

while ScanAndDig() == true do
    iLevel = iLevel + 1
end

for q=(iLevel-1),0,-1 do
    DigAndMove("down")
end