Moved poller and listener into lib, setup test

lib/exw3.ex

@@ -462,4 +462,74 @@ defmodule ExW3 do
       {:reply, {:ok, {receipt, formatted_logs}}, state}
     end
   end
+
+  defmodule Poller do
+    use GenServer
+
+    def start_link do
+      GenServer.start_link(__MODULE__, [], name: EventPoller)
+    end
+
+    def subscribe(event) do
+      GenServer.cast(EventPoller, {:subscribe, event})
+    end
+
+    @impl true
+    def init(state) do
+      schedule_work() # Schedule work to be performed on start
+      {:ok, state}
+    end
+
+    @impl true
+    def handle_cast({:subscribe, event}, state) do
+      {:noreply, [event | state]}
+    end
+
+    @impl true
+    def handle_info(:work, state) do
+      # Do the desired work here
+      Enum.each state, fn event ->
+	send EventListener, {:event, event, "Hello, World"}
+      end
+      
+      schedule_work() # Reschedule once more
+      {:noreply, state}
+    end
+
+    defp schedule_work() do
+      Process.send_after(self(), :work, 1000) # In 1 sec
+    end
+  end
+  
+  defmodule Listener do
+    def start_link do
+      Poller.start_link()
+      {:ok, pid} = Task.start_link(fn -> loop(%{}) end)
+      Process.register(pid, EventListener)
+      :ok
+    end
+
+    def subscribe(event, pid) do
+      Poller.subscribe(event)
+      send EventListener, {:subscribe, event, pid}
+    end
+
+    def listen(callback) do
+      receive do
+	{:event, result} -> apply callback, [result]
+      end
+      listen(callback)
+    end
+    
+    defp loop(map) do
+      receive do
+	{:subscribe, event, pid} ->
+	  loop(Map.put(map, event, pid))
+	{:event, event, data} ->
+	  send Map.get(map, event), {:event, {event, data}}
+	  loop(map)
+      end
+    end
+  end
+
 end

test/exw3_test.exs

@@ -133,6 +133,39 @@ defmodule EXW3Test do
     assert data == "Hello, World!"
   end
 
+  test "starts a Contract GenServer and uses the event listener", context do
+    ExW3.Contract.start_link(EventTester, abi: context[:event_tester_abi])
+
+    {:ok, address} =
+      ExW3.Contract.deploy(
+        EventTester,
+        bin: ExW3.load_bin("test/examples/build/EventTester.bin"),
+        options: %{
+          gas: 300_000,
+          from: Enum.at(context[:accounts], 0)
+        }
+      )
+
+    ExW3.Contract.at(EventTester, address)
+
+    {:ok, tx_hash} =
+      ExW3.Contract.send(
+	EventTester,
+	:simple,
+	["Hello, World!"],
+	%{from: Enum.at(context[:accounts], 0)}
+      )
+    
+    ExW3.Listener.start_link()
+
+    ExW3.Listener.subscribe("Hello", self())
+
+    receive do
+      {:event, {"Frank", data}} -> IO.inspect data
+    after 3_000 -> raise "Never received event"
+    end
+  end
+
   test "starts a Contract GenServer for Complex contract", context do
     ExW3.Contract.start_link(Complex, abi: context[:complex_abi])
 
@@ -217,4 +250,3 @@ defmodule EXW3Test do
     assert ExW3.is_valid_checksum_address("0x2f015c60e0be116b1f0cd534704db9c92118fb6a") == false
   end
 end
-