[WIP] Automatically build plugins topology

test/unit/plugin/topology_builder_test.exs

@@ -0,0 +1,76 @@
+defmodule Plugin.Topology do
+  alias :digraph, as: Digraph
+  alias :digraph_utils, as: DigraphUtils
+
+  def sort(plugins) do
+    graph = Digraph.new()
+
+    Enum.each(plugins, fn {plugin, opts} ->
+      deps = Keyword.fetch!(opts, :deps)
+
+      Digraph.add_vertex(graph, plugin)
+
+      Enum.each(deps, fn dep ->
+        add_dependency(graph, plugin, dep)
+      end)
+    end)
+
+    case DigraphUtils.is_acyclic(graph) do
+      false ->
+        circular_path =
+          Enum.each(Digraph.vertices(graph), fn vertix ->
+            if vs = Digraph.get_short_cycle(graph, vertix), do: Enum.join(vs, " -> ")
+          end)
+
+        raise "Plugins dependencies are containing circular dependencies: #{circular_path}"
+      true ->
+        DigraphUtils.topsort(graph)
+    end
+  end
+
+  defp add_dependency(_graph, plugin, dep) when plugin == dep,
+    do: :ok
+  defp add_dependency(graph, plugin, dep) do
+    Digraph.add_vertex(graph, plugin)
+    Digraph.add_edge(graph, plugin, dep)
+  end
+end
+
+defmodule Annon.Plugin.TopologyBuilderTest do
+  @moduledoc false
+  use ExUnit.Case, async: true
+
+  test "builds ordered topology" do
+    assert [:plugin1, :plugin2, :plugin3, :plugin4] ==
+      [
+        {:plugin1, deps: [:plugin2]},
+        {:plugin2, deps: [:plugin3]},
+        {:plugin3, deps: [:plugin4]},
+        {:plugin4, deps: [:plugin6]},
+      ]
+      |> Plugin.Topology.sort()
+
+    assert [:plugin1, :plugin2, :plugin3, :plugin4] ==
+      [
+        {:plugin2, deps: [:plugin3]},
+        {:plugin1, deps: [:plugin3]},
+        {:plugin4, deps: [:plugin4]},
+        {:plugin3, deps: [:plugin4]},
+      ]
+      |> Plugin.Topology.sort()
+
+    assert [:plugin3, :plugin4, :plugin2, :plugin1] ==
+      [
+        {:plugin1, deps: [:plugin2, :plugin3]},
+        {:plugin2, deps: [:plugin1]},
+        {:plugin3, deps: [:plugin1]},
+        {:plugin4, deps: [:plugin2]},
+      ]
+      |> Plugin.Topology.sort()
+  end
+
+
+  def build_topology() do
+    Application.get_env(:annon_api, :plugins_deps) |> Plugin.Topology.sort()
+  end
+end