Implement core denizen interface

lib/hostas/denizen.ex

@@ -27,6 +27,49 @@ defmodule Hostas.Denizen do
     %{password_hash: hash} = Bcrypt.add_hash(password)
     change(changeset, password: hash)
   end
-
   defp hash_password(changeset), do: changeset
+
+  @doc """
+  Returns an Ecto query searching for a denizen by the given ID
+  """
+  defp query_by_id(id) do
+    from d in Denizen, where: d.id == ^id
+  end
+
+  @doc """
+  Creates a denizen. Returns the result of the Ecto.Repo insertion
+  """
+  def create(denizen) do
+    Repo.insert(changeset(%Denizen{}, denizen))
+  end
+
+  @doc """
+  Returns a denizen
+  """
+  def get(id) do
+    case query_by_id(id) |> Repo.one do
+      nil -> {:error, :not_found}
+      struct -> {:ok, struct}
+    end
+  end
+
+  @doc """
+  Removes a denizen from the community. Does nothing if the denizen doesn't
+  exist
+  """
+  def delete(id) do
+    id
+    |> query_by_id
+    |> Repo.delete_all
+
+    :ok
+  end
+
+  @doc """
+  Modifies all the denizen's fields except `:id`, replacing them with the
+  corresponding values in the map
+  """
+  def update(%{"id" => id} = update_map) do
+    Repo.update(changeset(get(id), update_map))
+  end
 end