Strip/Branch Tunnel Miner

print("Loading Robust Turtle API...")
local load = os.loadAPI("t")
if load then
  print("Robust Turtle API loaded.")
else
 print("Robust Turtle API not found in the root directory with filename t")
 print("Attempting to download as t from pastebin...")
 os.sleep(2)
 local response = http.get("http://pastebin.com/raw.php?i= e0UksEtT")
 if response then
    print("Great Success.")
    local data = response.readAll()
    response.close()
    local file = fs.open("t", "w")
    file.write(data)
    file.close()
    print("Downloaded as t")
    load = os.loadAPI("t")
    if load then
     print("Robust Turtle API installed & loaded.")
    end
 else
    print( "Download Failed. Please Install Manually." )
    return
 end
end


--Strip Mining/Branch Mining Turtle. Digs a staircase down a user specified depth,
--then digs pairs of tunnels one wide and 5 high.
--turtle places toches every 6 blocks and a floor when there isnt one.
--More efficient than quarrying or excavating with fall hazards


local torch, stone = {1,3},{4,5}

function stonedrop()
    for i=6,16 do --keeps two stacks of cobblestone
        turtle.select(i)
        if turtle.compareTo(stone[1]) then
            t.right()
            t.dig()
            turtle.drop()
            t.left()
        end
    end
end

function tunnel(dist)
    local breadcrumb=0
    --digs a 2 high one wide tunnel, placing down blocks
    --if there is no floor
    for i=1, dist do
     if t.forward() then
      breadcrumb = breadcrumb+1
     end
     t.digUp()
     if not turtle.detectDown() then
      t.placeDown(stone[1],stone[2])
     end
    end
    --prepare to dig top part of tunnel
    t.up(3)
    t.digUp()
    t.turnAround()
    local torchcount =5
    --digs a 3 high 1 wide tunnel on top resulting in a 5 high one wide tunnel.
    for i=1, breadcrumb do
     t.forward()
     t.digUp()
     t.digDown()
     torchcount = torchcount+1
     if torchcount == 6 then
      while not t.placeLeft(torch[1],torch[2]) do
        t.down()
       t.placeLeft(stone[1],stone[2])
       t.up()
      end--endwhile
      torchcount = 0
     end--end if
    end--end for
    t.down(3)
end-- function tunnel

function stairs(d)
 local torchcount =0
 for i=1, d do
  t.forward()
  t.digUp()
  t.down()
  if not turtle.detectDown() then
   t.placeDown(t.restack(stone[1],stone[2]))
  end
  torchcount = torchcount+1
  if torchcount == 6 then
   while not t.placeRight(t.restack(torch[1],torch[2])) do
    t.down()
    t.placeRight(t.restack(stone[1],stone[2]))
    t.up()
   end--endwhile
   torchcount = 0
  end--end if
 end--end while
end--end function stairs


term.clear()
term.setCursorPos(1,1)
print(tostring(os.getComputerLabel())..[=[ will dig a staircase and then dig branch tunnels to the left & right.
]=]..tostring(os.getComputerLabel())..[=[ will return to the bottom of the stairs after mining, not the top.]=])
print([=[Torches are placed on the right for finding your way back easily. If ]=]..os.getComputerLabel()..[=[ does not detect a floor, ]=]..tostring(os.getComputerLabel())..[=[ will place cobblestone.]=])
read()
term.clear()
term.setCursorPos(1,1)
print([==[If digging more than 15 blocks deep, ]==]..tostring(os.getComputerLabel())..[=[ will turn around and dig the branch mine under the staircase to avoid unloaded chunks.]=])
read()
term.clear()
term.setCursorPos(1,1)
print("Place torches in slots 1-3, cobblestone in slots 4&5 and spare fuel in slot 16.")
print("How deep should "..tostring(os.getComputerLabel()).." dig before digging the branch tunnels?")
local depth = term.readNum()
print("How long should each branch be?")
local length = term.readNum()--branch length
print("How many pairs of branches?")
local branch = term.readNum()--branch quantity
print(tostring(os.getComputerLabel()).."'s fuel level is "..turtle.getFuelLevel()..", ok?")
read()
local hall = 0
stairs(depth)

if depth > 15 then
    t.right()
    t.forward()
    t.digUp()
    t.right()
    for i=1,6 do
        if t.forward() then
         hall=hall+1
        end
        if i == 4 then
         while not t.placeRight(torch[1],torch[2]) do
            t.down()
            t.placeRight(stone[1],stone[2])
            t.up()
         end--endwhile
        end
        t.digUp()
        if not turtle.detectDown() then
            t.placeDown(stone[1],stone[2])
        end
    end
end

for i=1, branch do
    t.left()
    tunnel(length)
    tunnel(length)
    t.right()
    for i=1,3 do
     if i==2 then
      stonedrop()
     end
     if t.forward() then
      hall=hall+1
     end
     t.digUp()
     if not turtle.detectDown() then
      t.placeDown(stone[1],stone[2])
     end
    end
    print(i.." pairs of branches mined.")
end

t.back(hall)