Add global config via repo

Author: ftes

lib/dx.ex

@@ -12,6 +12,8 @@ defmodule Dx do
   The corresponding `get!/3`, `load!/3` and `put!/3` functions return `result`
   directly, or otherwise raise an exception.
 
+  If you want to apply default options to all functions, `use` `Dx.Repo`.
+
   Arguments:
   - **subjects** can either be an individual subject (with the given predicates defined on it), or a list of subjects.
     Passing an individual subject will return the predicates for the subject, passing a list will return a list of them.

lib/dx/repo.ex

@@ -0,0 +1,141 @@
+defmodule Dx.Repo do
+  @moduledoc """
+  Defines a repository with default options, similar to `Ecto.Repo`.
+
+  When used, the repository expects the `:otp_app` as option.
+  The `:otp_app` should point to an OTP application that has
+  the repository configuration. For example, the repository:
+
+      defmodule Repo do
+        use Dx.Repo,
+          otp_app: :my_app,
+          loader: Dx.Loaders.Dataloader,
+          loader_options: [telemetry_options: [dx: true]]
+      end
+
+  Could be configured with:
+
+      config :my_app, Repo,
+        loader_options: [timeout: 20_000]
+
+  See `Dx` for further options. The options are deep-merged,
+  with the following order of precedence:
+
+  1. Options passed to boundary functions, such as `Dx.get/3`
+  2. Options returned by `Dx.Repo.default_options/1` callback
+  3. Options from config
+  4. Options from `use Dx.Repo, ...`.
+  """
+
+  @doc false
+  defmacro __using__(opts) do
+    quote bind_quoted: [opts: opts] do
+      @behaviour Dx.Repo
+      @otp_app Keyword.fetch!(opts, :otp_app)
+      @opts opts
+
+      def default_options(_operation), do: []
+      defoverridable default_options: 1
+
+      @compile {:inline, prepare_opts: 2}
+      defp prepare_opts(operation_name, opts) do
+        config = Application.get_env(otp_app, __MODULE__, [])
+
+        @opts
+        |> Dx.Util.Keyword.deep_merge(config)
+        |> Dx.Util.Keyword.deep_merge(default_options(operation_name))
+        |> Dx.Util.Keyword.deep_merge(opts)
+      end
+
+      def get(records, predicates, opts \\ []) do
+        Dx.get(records, predicates, prepare_opts(opts, :get))
+      end
+
+      def get!(records, predicates, opts \\ []) do
+        Dx.get!(records, predicates, prepare_opts(opts, :get))
+      end
+
+      def load(records, predicates, opts \\ []) do
+        Dx.load(records, predicates, prepare_opts(opts, :load))
+      end
+
+      def load!(records, predicates, opts \\ []) do
+        Dx.load!(records, predicates, prepare_opts(opts, :load))
+      end
+
+      def put(records, predicates, opts \\ []) do
+        Dx.put(records, predicates, prepare_opts(opts, :put))
+      end
+
+      def put!(records, predicates, opts \\ []) do
+        Dx.put!(records, predicates, prepare_opts(opts, :put))
+      end
+
+      def filter(records, condition, opts \\ []) when is_list(records) do
+        Dx.filter(records, condition, prepare_opts(opts, :filter))
+      end
+
+      def reject(records, condition, opts \\ []) when is_list(records) do
+        Dx.reject(records, condition, prepare_opts(opts, :reject))
+      end
+
+      def query_all(queryable, condition, opts \\ []) do
+        Dx.query_all(queryable, condition, prepare_opts(opts, :query_all))
+      end
+
+      def query_one(queryable, condition, opts \\ []) do
+        Dx.query_one(queryable, condition, prepare_opts(opts, :query_one))
+      end
+    end
+  end
+
+  ## User callbacks
+
+  @doc """
+  A user customizable callback invoked to retrieve default options
+  for operations.
+  This can be used to provide default values per operation that
+  have higher precedence than the values given on configuration.
+  """
+  @doc group: "User callbacks"
+  @callback default_options(operation) :: Keyword.t()
+            when operation: :get | :load | :put | :filter | :reject | :query_one | :query_all
+
+  ## Query API
+
+  @type record :: any()
+  @type predicate :: any()
+  @type condition :: any()
+  @type queryable :: any()
+  @type opts :: Keyword.t()
+
+  @doc group: "Query API"
+  @callback get([record], [predicate], opts) :: any()
+
+  @doc group: "Query API"
+  @callback get!([record], [predicate], opts) :: any()
+
+  @doc group: "Query API"
+  @callback load([record], [predicate], opts) :: any()
+
+  @doc group: "Query API"
+  @callback load!([record], [predicate], opts) :: any()
+
+  @doc group: "Query API"
+  @callback put([record], [predicate], opts) :: any()
+
+  @doc group: "Query API"
+  @callback put!([record], [predicate], opts) :: any()
+
+  @doc group: "Query API"
+  @callback filter([record], condition, opts) :: any()
+
+  @doc group: "Query API"
+  @callback reject([record], condition, opts) :: any()
+
+  @doc group: "Query API"
+  @callback query_all(queryable, condition, opts) :: any()
+
+  @doc group: "Query API"
+  @callback query_one(queryable, condition, opts) :: any()
+end

lib/dx/util/keyword.ex

@@ -0,0 +1,18 @@
+defmodule Dx.Util.Keyword do
+  def deep_merge(left, right) do
+    Keyword.merge(left, right, &deep_resolve/3)
+  end
+
+  # Key exists in both lists, and both values are lists as well.
+  # These can be merged recursively.
+  defp deep_resolve(_key, left = [{_, _} | _], right = [{_, _} | _]) do
+    deep_merge(left, right)
+  end
+
+  # Key exists in both maps, but at least one of the values is
+  # NOT a list. We fall back to standard merge behavior, preferring
+  # the value on the right.
+  defp deep_resolve(_key, _left, right) do
+    right
+  end
+end