TunnelExcavator

local length = 0

local currentFwd = 0
local stopReason = ""

function operationFinishMessage(reason)
    print("Operation has stopped.")
    os.sleep(1)
    print("Reason: ")
    os.sleep(2)
    print(reason)
end

function cls()
    term.clear()
    term.setCursorPos(1,1)
end

function craftDropOff()
    turtle.select(5)
    turtle.craft(turtle.getItemCount(5))
    --print("Crafted " .. tostring(turtle.getItemCount(5)) .. " " .. turtle.getItemDetail(5).name .. "(s).")
end

function move(direction)

    if direction == "forward" then
        return turtle.forward()
    elseif direction == "back" then
        return turtle.back()
    elseif direction == "up" then
        return turtle.up()
    elseif direction == "down" then
        return turtle.down()
    elseif direction == "left" then
        turtle.turnLeft()
        local success = turtle.forward()
        turtle.turnRight()
        return success
    elseif direction == "right" then
        turtle.turnRight()
        local success = turtle.forward()
        turtle.turnLeft()
        return success
    else
        print (direction .. " is not a valid direction!")
        return false
    end

end

function dig(direction)
    if direction == "forward" then
        return turtle.dig()
    elseif direction == "back" then
        turtle.turnRight()
        turtle.turnRight()
        local success = turtle.dig()
        turtle.turnRight()
        turtle.turnRight()
        return success
    elseif direction == "up" then
        return turtle.digUp()
    elseif direction == "down" then
        return turtle.digDown()
    elseif direction == "left" then
        turtle.turnLeft()
        local success = turtle.dig()
        turtle.turnRight()
        return success
    elseif direction == "right" then
        turtle.turnRight()
        local success = turtle.dig()
        turtle.turnLeft()
        return success
    else
        print (direction .. " is not a valid direction!")
        return false
    end
end

function excavate()
    cls()
    print("Starting excavation...")
    turtle.select(6)

    stopReason = "Movement blocked."
    while currentFwd <= length do

        dig("forward")
        if move("forward") == false then break end
        dig("right")
        dig("up")
        if move("up") == false then break end
        dig("right")
        dig("up")
        if move("up") == false then break end
        dig("right")

        if currentFwd % 2 == 0 then
            if move("down") == false then break end
            if move("down") == false then break end
        else
            if move("right") == false then break end
            if move("down") == false then break end
            turtle.turnLeft()
            turtle.select(1)
            turtle.place()
            turtle.select(6)
            turtle.turnRight()
            if move("down") == false then break end
            if move("left") == false then break end
        end

        dig("down")
        if move("down") == false then break end
        dig("down")

        turtle.select(5)
        if turtle.placeDown() == false then
            stopReason = "Can't place drop off point."
            if move("up") == false then break end
            break
        end
        turtle.select(6)
        if move("up") == false then break end
        --Places dropOffPoint

        currentFwd = currentFwd + 1
    end

    if currentFwd >= length then stopReason = "Finished operation." end
    if turtle.getFuelLevel() <= 0 then stopReason = "Ran out of fuel." end

    cls()
    operationFinishMessage(stopReason)
end

function startExcavation()
    print("Tunnel Excavation")
    print("")
    print("Please read instructions.")
    print("Press enter...")
    read()
    cls()

    print("How far would you like to")
    print("excavate?")
    length = tonumber(read())
    cls()

    turtle.select(2)
    turtle.refuel()
    turtle.select(1)
    --Refuel.

    print("Turtle now has: ")
    print(tostring(turtle.getFuelLevel()) .. " fuel.")
    print(tostring(turtle.getItemCount(1)) .. " torches.")
    os.sleep(2)
    cls()

    local craftInputSuccessful = false
    while craftInputSuccessful == false do
        print("Would you like to craft")
        print("drop off points?")
        print("(yes/no)")
        local craftInputReturn = read()

        if craftInputReturn == "yes" then
            craftInputSuccessful = true
            cls()
            print("Crafting drop off points...")
            craftDropOff()
        elseif craftInputReturn == "no" then
            craftInputSuccessful = true
        else
            print("Please input either yes or no.")
            os.sleep(1)
            cls()
        end
    end

    os.sleep(2)
    excavate()
end

startExcavation()