Add general prepare and commit functions

lib/two_phase_commit.ex

@@ -1,18 +1,40 @@
 defmodule TwoPhaseCommit do
-  @moduledoc """
-  Documentation for TwoPhaseCommit.
-  """
+  alias TwoPhaseCommit.Store
+  alias TwoPhaseCommit.Action
 
-  @doc """
-  Hello world.
+  @type store :: module()
+  @type action :: module()
+  @type ref :: any()
+  @type revision :: term()
+  @type state :: term()
+  @type transaction :: term()
+  @type transaction_ref :: term()
+  @type args :: any()
 
-  ## Examples
+  @type error_reason ::
+          {:conflict, revision()}
+          | {:pending, transaction_ref()}
+          | term()
 
-      iex> TwoPhaseCommit.hello
-      :world
+  @type on_error :: {:error, error_reason}
 
-  """
-  def hello do
-    :world
+  @spec prepare(action(), state(), args(), store(), ref(), revision()) ::
+          {:ok, transaction_ref()}
+          | on_error()
+  def prepare(action, state, args, store, ref, revision) do
+    with {:ok, transaction} <- action.prepare(state, args),
+         {:ok, transaction_ref} <- store.prepare(ref, revision, action, transaction) do
+      {:ok, transaction_ref}
+    end
+  end
+
+  @spec commit(action(), state(), transaction(), store(), ref(), transaction_ref()) ::
+          {:ok, state(), revision(), result :: any()}
+          | on_error()
+  def commit(action, state, transaction, store, ref, transaction_ref) do
+    with {:ok, new_state, result} <- action.commit(state, transaction),
+         {:ok, revison} <- store.commit(ref, transaction_ref, new_state) do
+      {:ok, new_state, revison, result}
+    end
   end
 end

test/two_phase_commit_test.exs

@@ -1,8 +1,3 @@
 defmodule TwoPhaseCommitTest do
   use ExUnit.Case
-  doctest TwoPhaseCommit
-
-  test "greets the world" do
-    assert TwoPhaseCommit.hello() == :world
-  end
 end