local depth = 0
local length = 20
--                 pokehole length
local fuelNeeded = ((length/3)*20) + (length*2) + (depth*2)
local function checkFuel()
        while (turtle.getFuelLevel() < fuelNeeded) do
          turtle.select(1)
          if (turtle.getItemCount(1) == 0) then
        print("Not enough fuel.")
                return false
          end
          turtle.refuel(1)
        end
        return true
end
local function checkTorches()
        if (length / 10 > turtle.getItemCount(2)) then
          print("Not enough torchs.")
          return false
        end
        return true
end
local function checkLadders()
        if (turtle.getItemCount(3) < depth) then
          print("Not enough ladders.")
          return false
        end
        return true
end
local function placeTorch()
        turtle.select(2)
        turtle.placeDown()
end
local function dig()
        while (turtle.detect()) do
                turtle.dig()
                sleep(0.5)
        end
end
local function digPokeHoles()
        local i = 0
        turtle.turnRight()
        for i=0, 4 do
                dig()
                turtle.forward()
        end
        turtle.turnLeft()
        turtle.turnLeft()
        for i=0, 4 do
                turtle.forward()
        end
        for i=0, 4 do
                dig()
                turtle.forward()
        end
        turtle.turnRight()
        turtle.turnRight()
        for i=0, 4 do
                turtle.forward()
        end
        turtle.turnLeft()
end
local function digToDepth()
        local ladder = false
        if (depth > 1) then
                ladder = true
        end
        if (ladder) then
                turtle.turnRight()
                turtle.turnRight()
        end
        local i = 0
        while (i < depth) do
                turtle.digDown()
                turtle.down()
                if (ladder) then
                        turtle.dig()
                        turtle.select(3)
                        turtle.place()
                end
                i = i + 1
        end
        turtle.digDown()
        if (ladder) then
                turtle.down()
                turtle.dig()
                turtle.select(3)
                turtle.place()
                turtle.up()
                turtle.turnRight()
                turtle.turnRight()
        end
        placeTorch()
        digPokeHoles()
end
local function digTunnel()
        local i = 0
        local j = 0
        local k = 0
        while (i < length) do
                dig()
                turtle.forward()
                turtle.digDown()
                j = j + 1
                if (j == 10) then
                        placeTorch()
                        j = 0
                end
                k = k + 1
                if (k % 3 == 0) then
                        digPokeHoles()
                        k = 0
                end
                i = i + 1
        end
end
local function turnAround()
        turtle.turnRight()
        turtle.turnRight()
end
local function moveToTunnelStart()
        local i = 0
        for i=1,length do
          turtle.forward()
        end
end
local function moveToStartDepth()
        local i = 0
        for i=1,depth do
          turtle.up()
        end
end
local function placeSafetyBlock()
        turtle.select(4)
        turtle.placeDown()
        print("Complete.")
end

--If not enough fuel, torches or ladders don't do anything.
if checkFuel() and checkTorches() and checkLadders() then
        digToDepth()
        digTunnel()
        placeTorch()
        turnAround()
        moveToTunnelStart()
        turnAround()
        moveToStartDepth()
        placeSafetyBlock()
end