MineDownCurrent

acceptableItems = {'minecraft:diamond','minecraft:coal','minecraft:iron_ore','minecraft:emerald','minecraft:gold_ore','draconicevolution:draconium_dust'}
acceptableItemsLength = 6
-- 1 breaks up, -1 breaks down
function destroy (direction)
    if direction == 1 then
        turtle.digUp()
        turtle.up()
    elseif direction == -1 then
        turtle.digDown()
        turtle.down()
    else
        error('invalid direction')
    end
    turtle.dig()
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.dig()
    turtle.turnLeft()
    turtle.turnLeft()
end

-- if coal slot (1) has more than one coal, use
function refuel ()
    if turtle.getItemCount(1) > 1 then
        temp = turtle.getSelectedSlot()
        turtle.select(1)
        turtle.refuel(turtle.getItemCount()-1)
        turtle.select(temp)
    end
end

-- remove all items not in list
function purge ()
    for i=2,16 do
        keep = false
        for j=1,acceptableItemsLength do
            if turtle.getItemDetail(i) == acceptableItems[j] then
                keep = true
            end
        end
        if not keep then
            turtle.select(i)
            turtle.drop(i)
        end
    end
end

-- returns true if every slot is completely full
function turtleInvFull ()
    fullCount = 0; -- # of slots full
    for i=2,16 do
        if turtle.getItemSpace(i) == 0 then
            fullCount = fullCount + 1;
        end
    end
    return fullCount == 15;
end


while (turtle.getFuelLevel() > 0) and not turtleInvFull() do
    -- mining down
    repeat
        success, data = turtle.inspectDown()
        destroy(-1)
        refuel()
        purge()
    until data.name == 'minecraft:bedrock'

    -- moves to new spot to mine up
    for i=1,3 do
        turtle.dig()
        turtle.forward()
    end

    -- end if turtle inv completely full
    if turtleInvFull() then
        break
    end

    -- mining up
    for i=2,70 do
        destroy(1)
        refuel()
        purge()
    end

    -- moves to new spot to mine down
    for i=1,3 do
        turtle.forward()
        turtle.dig()
    end
end