[#44] Introduce Primus/WS transfer configuration at run-time

README.md

@@ -58,6 +58,41 @@ If you want to run it on the local host then the procedure is as simple as: `_bu
 **Note:** executables must be built on the platform (OS and architecture) they are destined for under the project's current configuration.
 Other options are possible (see `https://hexdocs.pm/distillery/getting-started.html`).
 
+## Configuration
+
+Executables are built with a configuration as described above.
+However the Primus/WebSocket transfer is configurable at run-time through a JSON configuration.
+To configure this supply a path to a JSON file with the `transfer_config_overlay` key/value.
+The following is an extract from [config/test.exs](config/test.exs):
+
+```Elixir
+config :poa_agent,
+    transfer_config_overlay: "config/transfer_overlay.json"
+```
+
+A corresponding example is provided in `config/transfer_overlay.json`:
+
+```JSON
+{
+    "POAAgent":{
+        "transfers":[
+            {
+                "id":"node_integration",
+                "address":"ws://localhost:3000/api",
+                "identifier":"elixirNodeJSIntegration",
+                "name":"Elixir-NodeJS-Integration",
+                "secret":"Fr00b5",
+                "contact":"a@b.c"
+            }
+        ]
+    }
+}
+
+```
+
+The file can reside anywhere on the machine that the Elixir executable has access to.
+The key/value pairs in the JSON configuration will replace the defaults specified in the Elixir configuration (i.e. `config/{dev,test,prod}.exs`).
+
 ## Coverage
 
 To get an HTML coverage report on your own machine try `env MIX_ENV=test mix coveralls.html` then open `cover/excoveralls.html`.

config/test.exs

@@ -1,5 +1,8 @@
 use Mix.Config
 
+config :poa_agent,
+    transfer_config_overlay: "config/transfer_overlay.json"
+
 config :ethereumex,
     url: "http://localhost:8545"
 

config/transfer_overlay.json

@@ -0,0 +1,14 @@
+{
+    "POAAgent":{
+        "transfers":[
+            {
+                "id":"node_integration",
+                "address":"ws://localhost:3000/api",
+                "identifier":"elixirNodeJSIntegration",
+                "name":"Elixir-NodeJS-Integration",
+                "secret":"Fr00b5",
+                "contact":"a@b.c"
+            }
+        ]
+    }
+}

lib/poa_agent/configuration.ex

@@ -0,0 +1,50 @@
+defmodule POAAgent.Configuration do
+  @moduledoc false
+
+  def transfers do
+    elixir_config = Application.fetch_env!(:poa_agent, :transfers)
+    case Application.fetch_env(:poa_agent, :transfer_config_overlay) do
+      :error ->
+        elixir_config
+      {:ok, path} when is_binary(path) ->
+        path
+        |> File.read!()
+        |> Jason.decode!()
+        |> transfers(elixir_config)
+    end
+  end
+
+  def transfers(_, []) do
+    []
+  end
+
+  def transfers(overlay, default) do
+    overlay
+    |> Kernel.get_in(["POAAgent", "transfers"])
+    |> Kernel.hd()
+    |> merge_overlay_into_config(default)
+  end
+
+  defp merge_overlay_into_config(overlay, [{id, module_name, default}]) do
+    keys = [
+      "address",
+      "identifier",
+      "name",
+      "secret",
+      "contact"
+    ]
+    POAAgent.Plugins.Transfers.WebSocket.Primus = module_name
+    ^id = String.to_existing_atom(Map.fetch!(overlay, "id"))
+    restricted = Map.take(overlay, keys)
+    want = to_keyword(restricted)
+    final = Keyword.merge(default, want)
+    [{id, module_name, final}]
+  end
+
+  defp to_keyword(x) do
+    f = fn {k, v} ->
+      {String.to_existing_atom(k), v}
+    end
+    Enum.into(x, [], f)
+  end
+end

lib/poa_agent/plugins/transfers/supervisor.ex

@@ -9,7 +9,7 @@ defmodule POAAgent.Plugins.Transfers.Supervisor do
     import Supervisor.Spec
 
     # create the children from the config file
-    transfers = Application.get_env(:poa_agent, :transfers)
+    transfers = POAAgent.Configuration.transfers()
 
     children = for {name, module, args} <- transfers do
       worker(module, [%{name: name, args: args}])
@@ -18,5 +18,4 @@ defmodule POAAgent.Plugins.Transfers.Supervisor do
     opts = [strategy: :one_for_one]
     supervise(children, opts)
   end
-
-end
+end

test/poa_agent/configuration_test.exs

@@ -0,0 +1,41 @@
+defmodule POAAgent.ConfigurationTest do
+  use ExUnit.Case
+
+  test "transfer configuration overlay and default merge" do
+    default = [
+      {:node_integration, POAAgent.Plugins.Transfers.WebSocket.Primus, [
+          address: "ws://localhost:3000/api",
+          identifier: "elixirNodeJSIntegration",
+          name: "Elixir-NodeJS-Integration",
+          secret: "",
+          contact: "mymail@mail.com"
+        ]
+      }
+    ]
+    overlay = %{"POAAgent" =>
+                 %{"transfers" =>
+                    [
+                      %{"address" => "ws://localhost:3000/api",
+                        "contact" => "a@b.c",
+                        "id" => "node_integration",
+                        "identifier" => "elixirNodeJSIntegration",
+                        "name" => "Elixir-NodeJS-Integration",
+                        "secret" => "Fr00b5"
+                       }
+                    ]
+                  }
+               }
+
+    assert POAAgent.Configuration.transfers(overlay, default) == [
+      {:node_integration, POAAgent.Plugins.Transfers.WebSocket.Primus,
+       [address: "ws://localhost:3000/api",
+        contact: "a@b.c",
+        identifier: "elixirNodeJSIntegration",
+        name: "Elixir-NodeJS-Integration",
+        secret: "Fr00b5"
+       ]
+      }
+    ]
+    assert POAAgent.Configuration.transfers(overlay, []) == []
+  end
+end