stripmine

local x, z = 0, 0
local xdir, zdir = 0, 1

local collect
local refuel

local function select(c)
    turtle.select(c)
end

local function forward()
 refuel()
    while not turtle.forward() do
        if turtle.dig() then
            collect()
  else
   turtle.attack()
        end
    end
 x, z = x + xdir, z + zdir
 return true
end

local function turnLeft()
    turtle.turnLeft()
    xdir, zdir = -zdir, xdir
end

local function turnRight()
    turtle.turnRight()
    xdir, zdir = zdir, -xdir
end

local function goTo(xpos, zpos, xface, zface)
 turtle.up()
    if x < xpos then
        while xdir ~= 1 do
            turnRight()
        end
        while x < xpos do
            forward()
        end
    end
    if x > xpos then
        while xdir ~= -1 do
            turnRight()
        end
        while x > xpos do
            forward()
        end
    end
    if z > zpos then
        while zdir ~= -1 do
            turnRight()
        end
        while z > zpos do
            forward()
        end
    end
    if z < zpos then
        print("z is less than zero. Something is probably wrong!")
        while zdir ~= 1 do
            turnRight()
        end
        while z < zpos do
            forward()
        end
    end
    while xdir ~= xface or zdir ~= zface do
        turnRight()
    end
 turtle.down()
end

local function dumpResources()
    local prevx, prevz, prevxd, prevzd = x, z, xdir, zdir
    goTo(0, 0, 0, -1)
    for c=1, 16 do
        turtle.select(c)
        if turtle.getItemDetail() and turtle.getItemDetail().name == "minecraft:torch" or turtle.refuel(0) then
            print("useful item detected!")
        else
        turtle.drop()
        end
    end
    goTo(prevx, prevz, prevxd, prevzd)
end

function collect()
    for c=1, 16 do
        turtle.select(c)
        if turtle.getItemCount() == 0 then
    select(1)
             return
        end
    end
    dumpResources()
print("dumping resources")
end

local function dig()
    while turtle.detect() do
        if turtle.dig() then
            sleep(0.5f)
            collect()
        end
    end
end

local function digUp()
    while turtle.detectUp() do
        if turtle.digUp() then
            sleep(0.5f)
            collect()
        end
    end
end

local function fuelCheck()
    print ("Fuel level at "..turtle.getFuelLevel())
    if turtle.getFuelLevel() < 10 then
        print ("Out of fuel!")
        for n=1, 16 do
            turtle.select(n)
            if turtle.refuel() then
                turtle.select(1)
                return true
            end
        end
        return false
    end
    return true
end

function refuel()
    while not fuelCheck() do
        os.pullEvent("turtle_inventory")
    end
end

local function platform()
    for a=1, 16 do
        turtle.select(a)
        if turtle.getItemDetail() and turtle.getItemDetail().name == "minecraft:cobblestone" then
            turtle.placeDown()
            turtle.select(1)
            return
        end
    end
end

local function tunnel()
 local blockCount = 0
    for a=1, 32 do
        forward()
        platform()
        digUp()
        blockCount = blockCount + 1
        if blockCount == 8 then
            for a=1, 16 do
                turtle.select(a)
                if turtle.getItemDetail() and turtle.getItemDetail().name == "minecraft:torch" then
                    if turtle.getItemCount() > 1 then
                        blockCount = 0
                        turnLeft()
                        turnLeft()
                        turtle.place()
                        turnLeft()
                        turnLeft()
                        turtle.select(1)
                        break
                    end
                end
            end
        end
    end
end

local function returnTunnel()
    local blockCount = 0
    turtle.up()
    for a=1, 32 do
        while not forward() do
            dig()
        end
    end
    turtle.down()
end

for n=1, 16 do
    digUp()
    turnLeft()
    tunnel()
    turnRight()
    turnRight()
    returnTunnel()
    tunnel()
    turnRight()
    turnRight()
    returnTunnel()
    turnRight()
    forward()
    platform()
    digUp()
    if n > 1 then
      for p=1, 16 do
        turtle.select(p)
        if turtle.getItemDetail() and turtle.getItemDetail().name == "minecraft:torch" then
          turnLeft()
          turnLeft()
          turtle.place()
          turnLeft()
          turnLeft()
          turtle.select(1)
        end
      end
    end
    for a=1, 2 do
        forward()
        platform()
        digUp()
    end
end