recursive mining for computercraft turtles

--recursive digging
-- usage: recdig <mode> [list]

local sides = { "top", "front", "bottom", "left", "right", "back" }

local targs = { ... }

--local mode = "any"        -- dig any block detected
--local mode = "white"  -- takes a whitelist of blocks in form of inventory slots
--local mode = "black"  -- takes a blacklist of blocks in form of inventory slots
local mode = ""
local list = {}

function checkInput()
    local valid = true
    if #targs == 0 then
        valid = false
    end
    if #targs == 1 and targs[1] ~= "any" then
        valid = false
    end
    if #targs > 1 then
        if targs[1] ~= "white" and targs[1] ~= "black" then
            valid = false
        end
        for i = 2,#targs do
            if tonumber(targs[i]) < 1 or tonumber(targs[i]) > 16 then
                valid = false
            end
        end
    end
    if not valid then
        print("usage: recdig <mode> [list]")
        print("modes: any, white, black")
        print("list: list of slots used for black- or white-listing")
    end
    return valid
end

function turnAround()
    turtle.turnLeft()
    turtle.turnLeft()
end

function checkSides()
    sleep(0.25)
    for s = 1,#sides do
        print("checking "..sides[s])
        checkSide(sides[s])
    end
end

function wantThis(mode, side)       -- returns true or false depending on whether the block we're checking is one we want
    if mode == "any" then
        if side == "up" then
            return turtle.detectUp()
        elseif side == "down" then
            return turtle.detectDown()
        elseif side == "front" then
            return turtle.detect()
        end
    elseif mode == "white" then
        local ret = false
        for l = 1,#list do
            turtle.select(l)
            if side == "up" then
                if turtle.compareUp() then
                    ret = true
                end
            elseif side == "down" then
                if turtle.compareDown() then
                    ret = true
                end
            elseif side == "front" then
                if turtle.compare() then
                    ret = true
                end
            end
        end
        return ret
    elseif mode == "black" then
        local ret = true
        for l = 1,#list do
            turtle.select(l)
            if side == "up" then
                if turtle.compareUp() or not turtle.detectUp() then
                    ret = false
                end
            elseif side == "down" then
                if turtle.compareDown() or not turtle.detectDown() then
                    ret = false
                end
            elseif side == "front" then
                if turtle.compare() or not turtle.detect() then
                    ret = false
                end
            end
        end
        return ret
    end
end

function checkSide(side)
    if side == "top" then
        if wantThis(mode, "up") then
            print("block above detected")
            while not turtle.up() do
                if not turtle.digUp() then
                    turtle.attackUp()
                end
            end
            checkSides()
            while not turtle.down() do
                turtle.attackDown()
            end
        end
    elseif side == "front" then
        if wantThis(mode, "front") then
            print("blcok in front detected")
            while not turtle.forward() do
                if not turtle.dig() then
                    turtle.attack()
                end
            end
            checkSides()
            turnAround()
            while not turtle.forward() do
                turtle.attack()
            end
            turnAround()
        end
    elseif side == "bottom" then
        if wantThis(mode, "down") then
            print("block below detected")
            while not turtle.down() do
                if not turtle.digDown() then
                    turtle.attackDown()
                end
            end
            checkSides()
            while not turtle.up() do
                turtle.attackUp()
            end
        end
    elseif side == "left" then
        turtle.turnLeft()
        if wantThis(mode, "front") then
            print("block left detected")
            while not turtle.forward() do
                if not turtle.dig() then
                    turtle.attack()
                end
            end
            checkSides()
            turnAround()
            while not turtle.forward() do
                turtle.attack()
            end
            turnAround()
        end
        turtle.turnRight()
    elseif side == "right" then
        turtle.turnRight()
        if wantThis(mode, "front") then
            print("block right detected")
            while not turtle.forward() do
                if not turtle.dig() then
                    turtle.attack()
                end
            end
            checkSides()
            turnAround()
            while not turtle.forward() do
                turtle.attack()
            end
            turnAround()
        end
        turtle.turnLeft()
    elseif side == "back" then
        turnAround()
        if wantThis(mode, "front") then
            print("block behind detected")
            while not turtle.forward() do
                if not turtle.dig() then
                    turtle.attack()
                end
            end
            checkSides()
            turnAround()
            while not turtle.forward() do
                turtle.attack()
            end
            turnAround()
        end
        turnAround()
    end
end

if checkInput() then
    mode = targs[1]
    if #targs > 1 then
        for i = 2,#targs do
            list[i-1] = targs[i]
        end
    end
    if mode == "any" then
        print("Ready to start recursive mining in any-mode. I will mine all blocks I can reach until I run out of blocks or fuel.")
    elseif mode == "black" then
        print("Ready to start recursive mining in "..mode.."-list mode. I will mine all blocks not on the supplied list")
    elseif mode == "white" then
        print("Ready to start recursive mining in "..mode.."-list mode. I will mine all blocks on the supplied list")
    end
    print("ready to start? y/n")
    local yesno = read()
    if yesno ~= "y" then
        exit()
    else
        checkSides()
    end
end