ComputerCraft FastTunnel (modified default tunnel program)

local delay = 0.1

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.." items." )
    end
end

local function tryDig()
    while turtle.detect() do
        if turtle.dig() then
            collect()
            sleep( delay )
        else
            return false
        end
    end
    return true
end

local function tryDigUp()
    while turtle.detectUp() do
        if turtle.digUp() then
            collect()
            sleep( delay )
        else
            return false
        end
    end
    return true
end

local function tryDigDown()
    while turtle.detectDown() do
        if turtle.digDown() then
            collect()
            sleep( delay )
        else
            return false
        end
    end
    return true
end

local function refuel()
    local fuelLevel = turtle.getFuelLevel()
    if fuelLevel == "unlimited" or fuelLevel > 0 then
        return
    end

    local function tryRefuel()
        for n=1,16 do
            if turtle.getItemCount(n) > 0 then
                turtle.select(n)
                if turtle.refuel(1) then
                    turtle.select(1)
                    return true
                end
            end
        end
        turtle.select(1)
        return false
    end

    if not tryRefuel() then
        print( "Add more fuel to continue." )
        while not tryRefuel() do
            os.pullEvent( "turtle_inventory" )
        end
        print( "Resuming Tunnel." )
    end
end

local function tryUp()
    refuel()
    while not turtle.up() do
        if turtle.detectUp() then
            if not tryDigUp() then
                return false
            end
        elseif turtle.attackUp() then
            collect()
        else
            sleep( delay )
        end
    end
    return true
end

local function tryDown()
    refuel()
    while not turtle.down() do
        if turtle.detectDown() then
            if not tryDigDown() then
                return false
            end
        elseif turtle.attackDown() then
            collect()
        else
            sleep( delay )
        end
    end
    return true
end

local function tryForward()
    refuel()
    while not turtle.forward() do
        if turtle.detect() then
            if not tryDig() then
                return false
            end
        elseif turtle.attack() then
            collect()
        else
            sleep( delay )
        end
    end
    return true
end

print( "Tunnelling..." )

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

    if n<length then
        tryDig()
        if not tryForward() 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.." items total." )