Add solution for exercise 1 from chapter 17

Author: Bernard Pietraga

chapter_17/sequence/lib/sequence/application.ex

@@ -11,7 +11,7 @@ defmodule Sequence.Application do
     # Define workers and child supervisors to be supervised
     children = [
       # Starts a worker by calling: Sequence.Worker.start_link(arg1, arg2, arg3)
-      # worker(Sequence.Worker, [arg1, arg2, arg3]),
+      worker(Sequence.Server, [123]),
     ]
 
     # See http://elixir-lang.org/docs/stable/elixir/Supervisor.html

chapter_17/sequence/lib/sequence/server.ex

@@ -0,0 +1,34 @@
+defmodule Sequence.Server do
+  use GenServer
+
+  def start_link(stack), do:
+    GenServer.start_link(__MODULE__, stack, name: __MODULE__)
+
+  def pop, do:
+    GenServer.call(__MODULE__, :pop)
+
+  def push(element), do:
+    GenServer.cast(__MODULE__, {:push, element})
+
+  def exit, do:
+    GenServer.cast(__MODULE__, {:push, :exit})
+
+  def handle_call({:set_stack, stack}, _from, _stack), do:
+    {:reply, stack, stack}
+
+  def handle_call(:pop, _from, []), do:
+    {:reply, [], []}
+  def handle_call(:pop, _from, [head | tail]), do:
+    {:reply, head, tail}
+
+  def handle_cast({:push, :exit}, list), do:
+    {:stop, :shutdown, list}
+
+  def handle_cast({:push, element}, list), do:
+    {:noreply, [element | list]}
+
+  def terminate(reason, status) do
+    IO.puts "Server shutdown, reason: #{reason}, current_status: #{status}"
+    :ok
+  end
+end

chapter_17/sequence/test/sequence_server_test.exs

@@ -0,0 +1,32 @@
+defmodule SequenceServerTest do
+  use ExUnit.Case, async: true
+  doctest Sequence
+
+  test "pop removes first element (not like normal pop)" do
+    {:ok, pid} = GenServer.start_link(Sequence.Server, [5, "cat", 9])
+    expected = GenServer.call(pid, :pop)
+    second_expected = GenServer.call(pid, :pop)
+    third_expected = GenServer.call(pid, :pop)
+    fourth_expected = GenServer.call(pid, :pop)
+
+    assert expected        == 5
+    assert second_expected == "cat"
+    assert third_expected  == 9
+    assert fourth_expected == []
+  end
+
+
+  test "push add element to array" do
+    {:ok, pid} = GenServer.start_link(Sequence.Server, [1, 2, 3])
+    GenServer.cast(pid, {:push, "mayoness"})
+    expected = GenServer.call(pid, :pop)
+
+    assert expected == "mayoness"
+  end
+
+  test "set_stack does its job" do
+    {:ok, pid} = GenServer.start_link(Sequence.Server, [1, 2, 3])
+    expected = GenServer.call(pid, {:set_stack, ["a", "b", "c"]})
+    assert expected == ["a", "b", "c"]
+  end
+end