defp deps do
  [
    {:arc_ecto, "~> 0.5.0"}
  ]
end

defp application do
  [applications: [:arc_ecto]]
end

defmodule MyApp.Avatar do
  use Arc.Definition
  use Arc.Ecto.Definition

  # ...
end

create table :users do
  add :avatar, :string
end

defmodule MyApp.User do
  use MyApp.Web, :model
  use Arc.Ecto.Schema

  schema "users" do
    field :name,   :string
    field :avatar, MyApp.Avatar.Type
  end

  @doc """
  Creates a changeset based on the `data` and `params`.

  If no params are provided, an invalid changeset is returned
  with no validation performed.
  """
  def changeset(user, params \\ :invalid) do
    user
    |> cast(params, [:name])
    |> cast_attachments(params, [:avatar])
    |> validate_required([:name, :avatar])
  end
end

  @doc """
  Given params of:

  %{
    "id" => 1,
    "user" => %{
      "avatar" => %Plug.Upload{
                    content_type: "image/png",
                    filename: "selfie.png",
                    path: "/var/folders/q0/dg42x390000gp/T//plug-1434/multipart-765369-5"}
    }
  }

  """
  def update(conn, %{"id" => id, "user" => user_params}) do
    user = Repo.get(User, id)
    changeset = User.changeset(user, user_params)

    if changeset.valid? do
      Repo.update(changeset)

      conn
      |> put_flash(:info, "User updated successfully.")
      |> redirect(to: user_path(conn, :index))
    else
      render conn, "edit.html", user: user, changeset: changeset
    end
  end

  user = Repo.get(User, 1)

  # To receive a single rendition:
  MyApp.Avatar.url({user.avatar, user}, :thumb)
    #=> "https://bucket.s3.amazonaws.com/uploads/avatars/1/thumb.png?v=63601457477"

  # To receive all renditions:
  MyApp.Avatar.urls({user.avatar, user})
    #=> %{original: "https://.../original.png?v=1234", thumb: "https://.../thumb.png?v=1234"}

  # To receive a signed url:
  MyApp.Avatar.url({user.avatar, user}, signed: true)
  MyApp.Avatar.url({user.avatar, user}, :thumb, signed: true)