Add count_next function (#99)

lib/ring_logger.ex

@@ -104,6 +104,17 @@ defmodule RingLogger do
   @spec next([client_option]) :: :ok | {:error, term()}
   defdelegate next(opts \\ []), to: Autoclient
 
+  @doc """
+  Count the next messages in the log.
+
+  Options include:
+
+  * Options from `attach/1`
+  * `:pager` - a function for printing log messages to the console. Defaults to `IO.binwrite/2`.
+  """
+  @spec count_next([client_option]) :: non_neg_integer() | {:error, term()}
+  defdelegate count_next(opts \\ []), to: Autoclient
+
   @doc """
   Save the contents of the log to the specified path
 

lib/ring_logger/autoclient.ex

@@ -61,6 +61,15 @@ defmodule RingLogger.Autoclient do
          do: Client.next(pid, opts)
   end
 
+  @doc """
+  Print the log message count since the previous time this was called.
+  """
+  def count_next(opts \\ []) do
+    with :ok <- check_server_started(),
+         pid <- maybe_create_client(opts),
+         do: Client.count_next(pid)
+  end
+
   @doc """
   Print the most recent log messages.
   """

lib/ring_logger/client.ex

@@ -117,6 +117,14 @@ defmodule RingLogger.Client do
     pager.(io, to_print)
   end
 
+  @doc """
+  Count the next set of the messages in the log.
+  """
+  @spec count_next(GenServer.server()) :: non_neg_integer() | {:error, term()}
+  def count_next(client_pid) do
+    GenServer.call(client_pid, :count_next)
+  end
+
   @doc """
   Reset the index into the log for `tail/1` to the oldest entry.
   """
@@ -226,6 +234,14 @@ defmodule RingLogger.Client do
     end
   end
 
+  def handle_call(:count_next, _from, state) do
+    count =
+      Server.get(state.index, 0)
+      |> Enum.count(&should_print?(&1, state))
+
+    {:reply, count, state}
+  end
+
   def handle_call({:tail, n}, _from, state) do
     to_return =
       Server.tail(n)