authentication with persistence working

lib/myapp/data/user.ex

@@ -0,0 +1,81 @@
+defmodule MyApp.Data.User do
+  use Ecto.Schema
+  import Ecto.Query
+  import Ecto.Changeset
+  alias MyApp.Repo
+  alias MyApp.Data
+
+  @derive {Poison.Encoder, except: [:__meta__]}
+  schema "user" do
+    field :battle_net_id, :integer
+    field :battletag, :string
+    timestamps()
+  end
+
+  def changeset(user, params \\ %{}) do
+    user
+    |> cast(params, [:battle_net_id, :battletag])
+    |> validate_required([:battle_net_id, :battletag])
+    |> unique_constraint(:battle_net_id)
+  end
+
+  @spec get_user(integer) :: nil | map
+  defp get_user(battle_net_id) do
+    query = from u in "user",
+      where: u.battle_net_id == ^battle_net_id,
+      select: [:id, :battle_net_id, :battletag]
+    Repo.one(query)
+  end
+
+  # insert user info in database - if not exists - update battletag if it has changed
+  @spec upsert_user(%{"battle_net_id": integer, "battletag": String.t} | tuple) :: {:ok, map} | {:error, any}
+  def upsert_user(params) when is_map(params) do
+    # check for current user in database
+    case get_user(Map.get(params, "battle_net_id")) do  
+      nil -> insert_user(params)
+      user ->
+        # update user if battletag has changed
+        if Map.get(user, :battletag) != Map.get(params, "battletag") do
+          update_battletag(user, params)
+        else
+          {:ok, user}
+        end
+    end
+    |> add_access_token(Map.get(params, "access_token"))
+  end
+  def upsert_user({:ok, params}), do: upsert_user(params)
+  def upsert_user({:error, error}), do: {:error, error}
+
+  # need to add token back to map because we don't store it in the database
+  defp add_access_token({:error, error}, _), do: {:error, error}
+  defp add_access_token({:ok, user}, access_token) do
+    {:ok, Map.merge(user, %{access_token: access_token})}
+  end
+
+  defp insert_user(params) do
+    cs = changeset(%Data.User{}, params)
+    cs
+    |> Repo.insert
+    |> process_insert_or_update
+  end
+
+  # it's possible for a user's battle tag to change - if so update it
+  defp update_battletag(user, params) do
+    cs = Data.User.changeset(Map.merge(%Data.User{}, user), %{battletag: Map.get(params, "battletag")})
+    cs
+    |> Repo.update
+    |> process_insert_or_update
+  end
+
+  defp process_insert_or_update({:error, changeset}), do: {:error, map_changeset(changeset)}
+  defp process_insert_or_update({:ok, user}) do
+    {:ok, Map.take(user, [:id, :battle_net_id, :battletag])} # only grab the fields we need
+  end
+
+  defp map_changeset(changeset) do
+    Enum.map(changeset.errors, fn {key, val} ->
+      %{key => elem(val, 0)}
+    end)
+  end
+
+end