Tree Farm

sel = 1;
turtle.select(sel);
select = function(n)
    sel = n;
    return turtle.select(n);
end
getSelected = function()
    return sel;
end

saplingSlot = 1
logSlot = 2
chestSlot = 3

function moveMethod(m)
    local r = function()
        local moved = m()
        if not moved then
            cantMove(m)
        end
        return moved
    end
    return r
end
function moveThenSuckMethod(m)
    local r = function()
        local moved = m()
        if not moved then
            cantMove(m)
        end
        turtle.suckDown()
        return moved
    end
    return r
end

up = moveMethod(turtle.up)
down = moveMethod(turtle.down)
forward = moveThenSuckMethod(turtle.forward)
back = moveMethod(turtle.back)

function clearChestSlot()
    if turtle.getItemCount(chestSlot) > 0 then
        select(chestSlot)
        for i=1,16 do
            if turtle.getItemCount(i) == 0 then
                if i ~= saplingSlot and i ~= logSlot and i ~= chestSlot then
                    turtle.transferTo(i)
                end
            else
                if i~= chestSlot and turtle.compareTo(i) and turtle.getItemSpace(i) > 0 then
                    turtle.transferTo(i)
                    clearChestSlot()
                end
            end
        end
    end
end

cantMove = function(move)
    if turtle.getFuelLevel() > 0 then
        select(logSlot)
        if turtle.compare() then
            turtle.dig()
            forward()
            turtle.digDown()
            if turtle.getItemCount(saplingSlot) > 0 then
                select(saplingSlot)
                turtle.placeDown()
                select(logSlot)
            end
            local n = 0
            local didCheck = false -- encountered a bug that stops the turtle short sometimes
            local keepChopping = turtle.compareUp()
            while keepChopping do
                turtle.digUp()
                up()
                select(saplingSlot)
                for i=1,4 do
                    turtle.dig()
                    turtle.turnRight()
                end
                n = n + 1
                select(logSlot)
                if turtle.compareUp() then
                    keepChopping = true
                    didCheck = false
                else
                    if didCheck then
                        keepChopping = false
                    else
                        didCheck = true
                    end
                    select(saplingSlot)
                end
            end
            while n > 0 do
                down()
                n = n - 1
            end
        else
            while not move() do
                sleep(1)
            end
        end
    else
        local dig, place, drop, suck = nil
        select(logSlot)
        if not turtle.detectUp() then
            dig = turtle.digUp
            place = turtle.placeUp
            drop = turtle.dropUp
            suck = turtle.suckUp
        else
            dig = turtle.dig
            place = turtle.place
            drop = turtle.drop
            suck = turtle.suck
        end
        dig()
        select(chestSlot)
        place()
        for i=1,16 do
            select(i)
            if i~=logSlot then
                drop()
            end
        end
        if turtle.getItemCount(logSlot) > 3 then
            turtle.craft(3)
            turtle.refuel()
        end
        select(1)
        while suck() do end
        clearChestSlot()
        select(chestSlot)
        dig()
        select(saplingSlot)
        suck()
        move()
    end
end

actions = {u=up,d=down,f=forward,b=back,tl=turtle.turnLeft,tr=turtle.turnRight}
function doInstructions(arr)
    for i,v in ipairs(arr) do
        if type(v) == 'function' then
            v()
        else
            local p = v:find(":")
            local a = {}
            if p == nil then
                a = {v, 1}
            else
                a = {v:sub(1, p-1), tonumber(v:sub(p+1))}
            end
            if actions[a[1]] ~= nil then
                for vari=1,a[2],1 do
                    actions[a[1]]()
                end
            end
        end
    end
end

function max(j, k)
    if j > k then
        return j
    else
        return k
    end
end

function dropOffItems()
    for i=1,16 do
        select(i)
        if i == logSlot then
            turtle.dropDown(max(turtle.getItemCount(logSlot) - 12, 0))
        elseif i ~= saplingSlot and i ~= chestSlot then
            turtle.dropDown()
        end
    end
end

inst = {'u', 'f', 'tr', 'f:15', 'tr', 'f:3', 'tr', 'f:12', 'tl', 'f:3', 'tl', 'f:12', 'tr', 'f:3', 'tr', 'f:12', 'tl', 'f:3', 'tl', 'f:12', 'tr', 'f:3', 'tr', 'f:15', 'tr', 'f:14', 'd', dropOffItems}
while true do
    select(logSlot)
    --[[while not turtle.compare() do
        sleep(5)
    end]]--
    doInstructions(inst)
    sleep(5)
    --doInstructions(inst)
end