sort erlang/otp applications into an order suitable for starting while keeping dependencies satisfied

eapplication.erl

-module(eapplication).
-export([deps_order/1]).

deps_order(App) ->
    G = digraph:new(),
    add_app_and_deps(G, [App], []),
    L = lists:reverse(digraph_utils:topsort(G)),
    digraph:delete(G),
    L.

add_app_and_deps(_, [], _) -> ok;
add_app_and_deps(G, [App | Todo], Done) ->
    Deps = get_deps(App),
    lists:foreach(fun(Dep) ->
                          ensure_edge(G, App, Dep)
                  end, Deps),
    add_app_and_deps(G, Todo ++ (Deps -- Done), Done).

get_deps(App) ->
    application:load(App),
    {ok, Deps} = application_controller:get_key(App, applications),
    Deps.

ensure_edge(G, A, B) ->
    ensure_vertex(G, A),
    ensure_vertex(G, B),
    case digraph:get_short_path(G, A, B) of
        L when length(L) == 1 -> ok;
        _ -> digraph:add_edge(G, A, B)
    end.

ensure_vertex(G, A) ->
    case digraph:vertex(G, A) of
        false -> digraph:add_vertex(G, A);
        _ -> ok
    end.