Turtle Stripmine

--What should this program accomplish?
--Create a 2x1 Tunnel with user given length
--Create roof against lava and depending on user input check also walls
--Place torches
--Automatically Refuel
--Broadcast status on rednet
--Automatically return to start location
--Sand / Gravel support

local DISTANCE_TO_MINE = 0
local SHOULD_CHECK_WALLS = false
local TORCH_SLOT = 1
local FUEL_SLOT = 2
local BLOCK_SLOT = 3
local USES_FUEL = (turtle.getFuelLevel() == "unlimited")
local DISTANCE_BETWEEN_TORCHES = 10
local REDNET_ACCESS = false
local MODEM_SIDE = ""
local MINING_START_TIME = 0
local MINING_FINISH_TIME = 0
local MINING_BLOCK_COUNT = 0

local function DigForward()
    if turtle.detect() then
        if turtle.dig() then
            MINING_BLOCK_COUNT = MINING_BLOCK_COUNT + 1
        end
    end
end

local function DigUp()
    if turtle.detectUp() then
        if turtle.digUp() then
            MINING_BLOCK_COUNT = MINING_BLOCK_COUNT + 1
        end
    end
end

local function DigDown()
    if turtle.detectDown() then
        if turtle.digDown() then
            MINING_BLOCK_COUNT = MINING_BLOCK_COUNT + 1
        end
    end
end

local function BroadcastMessage(text)
    if REDNET_ACCESS then
        rednet.broadcast(((os.getComputerLabel() or "nil") .. text), "miningturtle")
    end
end

--Returns true if a torch should be placed. False if not.
local function ShouldPlaceTorch(distance)
    if (distance % DISTANCE_BETWEEN_TORCHES == 0) then
        return not (turtle.detectDown())
    end
    return false
end

--Places a torch
local function PlaceTorch()
    turtle.select(TORCH_SLOT)
    if (turtle.getItemCount(TORCH_SLOT) > 0) then
        turtle.placeDown()
    end
end

--Checks if the turtle needs refuel
local function NeedsRefuel()
    if USES_FUEL then
        return false
    else
        return (turtle.getFuelLevel() < 100)
    end
end

--Refuels the turtle
local function Refuel()
    turtle.select(FUEL_SLOT)
    if (turtle.getItemCount(FUEL_SLOT) > 0) then
        turtle.refuel(1)
    else
        BroadcastMessage("nofuel")
    end
end

--Checks floor for existance.
local function ShouldPlaceFloor()
    return not (turtle.detectDown())
end

--Places a block down
local function PlaceFloor()
    turtle.select(BLOCK_SLOT)
    if (turtle.getItemCount(BLOCK_SLOT) > 0) then
        turtle.placeDown()
    end
end

--Checks the roof for existance.
local function ShouldPlaceRoof()
    return not (turtle.detectUp())
end

--Places a block up
local function PlaceRoof()
    turtle.select(BLOCK_SLOT)
    if (turtle.getItemCount(BLOCK_SLOT) > 0) then
        turtle.placeUp()
    end
end

--Checks walls left and right for existance. IF not, a block is placed.
local function CheckWalls()
    turtle.turnLeft()
    turtle.select(BLOCK_SLOT)
    if not (turtle.detect()) then
        turtle.place()
    end
    turtle.turnRight()
    turtle.turnRight()
    if not (turtle.detect()) then
        turtle.place()
    end
    turtle.turnLeft()
end

--Moves forward, mines forward and up.
local function MineForward(maxDistance)
    local currentDistance = 0
    repeat
        DigForward()
        DigUp()

        if ShouldPlaceFloor() then
            PlaceFloor()
        end

        if NeedsRefuel() then
            Refuel()
        end

        if turtle.forward() then
            currentDistance = currentDistance + 1
        end

        if SHOULD_CHECK_WALLS then
            CheckWalls()
        end

    until (currentDistance >= maxDistance)
end

--Turns the turtle 180° and makes it mine forward and move forward. Also moves the turtle up once at the beginning.
local function ReturnToStart(distanceToStart)
    DigUp()
    turtle.up()
    turtle.turnLeft()
    turtle.turnLeft()

    local distanceLeft = distanceToStart
    repeat
        DigForward()
        DigDown()

        if ShouldPlaceRoof() then
            PlaceRoof()
        end

        if ShouldPlaceTorch(distanceLeft) then
            PlaceTorch()
        end

        if SHOULD_CHECK_WALLS then
            CheckWalls()
        end

        if NeedsRefuel() then
            Refuel()
        end

        if turtle.forward() then
            distanceLeft = distanceLeft - 1
        end

    until (distanceLeft <= 0)

    turtle.turnLeft()
    turtle.turnLeft()
    DigDown()
    turtle.down()
end

--Tries to open a modem on all sides and checks if a modem is open then, therefor returning whether the turtle has a modem or not.
local function CheckIfModemExists()
    for n,m in ipairs(rs.getSides()) do
        if peripheral.isPresent(m) and peripheral.getType(m) == "modem" then
            rednet.open(m)
            MODEM_SIDE = m
            return true
        end
    end
    return false
end

--Converts a given user string (true/false OR y/n) to a boolean.
local function UserStringToBoolean(text)
    local input = string.lower(text)
    if (input == "true") then
        return true
    end
    if (input == "y") then
        return true
    end
    return false
end

--A delayed calls of CheckInventory()
local function DelayedRecheck(delay)
    local counter = 10
    repeat
        shell.run("clear")
        print("Please fill inventory with the required items.")
        print("Will recheck in " .. tostring(counter) .. " seconds.")
        sleep(1)
        counter = counter - 1
    until (counter == 0)
end

--Checks the inventory and the modem
local function CheckInventory()
    local torchCount = turtle.getItemCount(TORCH_SLOT)
    local fuelCount = turtle.getItemCount(FUEL_SLOT)
    local blockCount = turtle.getItemCount(BLOCK_SLOT)
    local invError = false

    if (torchCount == 0) then
        print("There are no torches in the inventory! (Slot 1)")
        invError = true
    end

    if (fuelCount == 0) then
        print("There is no fuel in the inventory! (Slot 2)")
        invError = true
    end

    if (blockCount == 0) then
        print("There are no blocks in the inventory! (Slot 3)")
        invError = true
    end

    REDNET_ACCESS = CheckIfModemExists()

    if not (REDNET_ACCESS) then
        print("There is no connected modem!")
        invError = true
    end

    if (invError) then
        print("Continue with current status? y/n")
        local input = io.read()
        local continue = UserStringToBoolean(input)
        if (not continue) then
            DelayedRecheck()
            CheckInventory()
            return nil
        end
    end
end

--Called upon program start
local function Startup()
    shell.run("clear")
    print("<== Stripmine Program ==>")
    print("Please enter tunnel length:")
    local input = io.read()
    DISTANCE_TO_MINE = tonumber(input)
    print("Should the turtle check the walls for holes? y/n")
    input = io.read()
    SHOULD_CHECK_WALLS = UserStringToBoolean(input)
    shell.run("clear")
    print("Tunnel length: " .. tostring(DISTANCE_TO_MINE))
    print("Check walls: " .. tostring(SHOULD_CHECK_WALLS))
    print("Continue with these settings? y/n")
    input = io.read()
    local continue = UserStringToBoolean(input)
    if (not continue) then
        Startup()
        return nil
    end

    CheckInventory()
    shell.run("clear")
    MINING_START_TIME = os.epoch("utc")
    BroadcastMessage("startmining")
    MineForward(DISTANCE_TO_MINE)
    ReturnToStart(DISTANCE_TO_MINE)
    MINING_FINISH_TIME = os.epoch("utc")
    local timeSpent = (MINING_FINISH_TIME - MINING_START_TIME) / 1000
    print("Time spent mining: " .. tostring(timeSpent) .. " seconds")
    print("Blocks mined: " .. tostring(MINING_BLOCK_COUNT))
    BroadcastMessage("endmining:" .. (tostring(timeSpent)) .. ":" .. (MINING_BLOCK_COUNT))
end

Startup()