local tArgs = { ... }
if #tArgs ~= 1 then
    print( "Usage: tunnel <length>" )
    return
end

-- Mine in a quarry pattern until we hit something we can't dig
local length = tonumber( tArgs[1] )
if length < 1 then
    print( "Tunnel length must be positive" )
    return
end

local depth = 0
local collected = 0

local function collect()
    collected = collected + 1
    if math.fmod(collected, 25) == 0 then
        print( "Mined "..collected.." blocks." )
    end
end

local function tryDig()
    while turtle.dig() do
        collect()
        sleep(0.5)
        if not turtle.detect() then
            return true
        end
    end
    return not turtle.detect()
end

local function tryDigUp()
    while turtle.digUp() do
        collect()
        sleep(0.5)
        if not turtle.detectUp() then
            return true
        end
    end
    return not turtle.detectUp()
end

print( "Tunnelling..." )

for n=1,length do
    turtle.placeDown()
    tryDigUp()
    turtle.turnLeft()
    tryDig()
    turtle.up()
    tryDig()
    tryDigUp()
    turtle.up()
    tryDig()
    turtle.turnRight()
    turtle.turnRight()
    tryDig()
    turtle.down()
    tryDig()
    turtle.down()
    tryDig()
    turtle.turnLeft()

    if n<length then
        tryDig()
        if not turtle.forward() then
            print( "Aborting Tunnel." )
            break
        end
    else
        print( "Tunnel complete." )
    end

end

--[[
print( "Returning to start..." )

-- Return to where we started
turtle.turnLeft()
turtle.turnLeft()
while depth > 0 do
    if turtle.forward() then
        depth = depth - 1
    else
        turtle.dig()
    end
end
turtle.turnRight()
turtle.turnRight()
]]

print( "Tunnel complete." )
print( "Mined "..collected.." blocks total." )