miner

function has_value (tab, val)
    for index, value in ipairs(tab) do
        if value == val then
            return true
        end
    end

    return false
end

function refuel()
    if turtle.getFuelLevel() < 10 then
        print("Refueling")
        turtle.select(1)
        turtle.refuel(1)
    end
end

retrace = {}
rares = {"minecraft:diamond_ore"}

print("Excavating ore vein")
while true do
    refuel()

    path_found = false

    a, b = turtle.inspect()
    if a then print("Forward found " .. b.name) end

    if a and has_value(rares, b.name) then
        print("Ore found forwards")
        turtle.dig()
        turtle.forward()
        table.insert(retrace, "back")
        path_found = true
    else
        a, b = turtle.inspectUp()
        if a then print("Up found " .. b.name) end

        if a and has_value(rares, b.name) then
            print("Ore found up")
            turtle.digUp()
            turtle.up()
            table.insert(retrace, "down")
            path_found = true
        else
            a, b = turtle.inspectDown()
            if a then print("Down found " .. b.name) end

            if a and has_value(rares, b.name) then
                print("Ore found down")
                turtle.digDown()
                turtle.down()
                table.insert(retrace, "up")
                path_found = true
            end
        end
    end
end

for i, command in ipairs(retrace) do
    print("Retracing, command: " .. command)
    refuel()
    if command == "up" then turtle.up() end
    if command == "down" then turtle.down() end
    if command == "left" then turtle.left() end
    if command == "right" then turtle.right() end
end