improvement: Add custom pagination start() callback for initial page request (#8)

.gitignore

@@ -27,3 +27,6 @@ ash_json_api_wrapper-*.tar
 
 # OS X folder metadata
 .DS_Store
+
+# VSCode settings
+.vscode/*

.vscode/settings.json

@@ -1,2 +0,0 @@
-{
-}

lib/data_layer/data_layer.ex

@@ -617,20 +617,27 @@ defmodule AshJsonApiWrapper.DataLayer do
             Logger.warning(
               "ash_json_api_wrapper does not support limits with offsets yet, and so they will both be applied after."
             )
-
-            query
-          else
-            case endpoint.limit_with do
-              {:param, param} ->
-                %{
-                  query
-                  | query_params: Map.put(query.query_params || %{}, param, query.limit)
-                }
-
-              _ ->
-                query
-            end
           end
+
+          case endpoint.limit_with do
+            {:param, param} ->
+              %{
+                query
+                | query_params: Map.put(query.query_params || %{}, param, query.limit)
+              }
+
+            _ ->
+              query
+          end
+        else
+          query
+        end
+
+      query =
+        if endpoint.paginator do
+          %{paginator: {module, opts}} = endpoint
+          {:ok, instructions} = module.start(opts)
+          apply_instructions(query, instructions)
         else
           query
         end

lib/paginator/continuation_property.ex

@@ -2,6 +2,10 @@ defmodule AshJsonApiWrapper.Paginator.ContinuationProperty do
   @moduledoc "A paginator that uses a continuation property to paginate"
   use AshJsonApiWrapper.Paginator
 
+  def start(_opts) do
+    {:ok, %{}}
+  end
+
   def continue(_response, [], _), do: :halt
 
   def continue(response, _entities, opts) do

lib/paginator/paginator.ex

@@ -11,6 +11,9 @@ defmodule AshJsonApiWrapper.Paginator do
     end
   end
 
+  @callback start(opts :: Keyword.t()) ::
+              {:ok, %{optional(:params) => map, optional(:headers) => map}}
+
   @callback continue(
               response :: term,
               entities :: [Ash.Resource.record()],

mix.exs

@@ -145,7 +145,8 @@ defmodule AshJsonApiWrapper.MixProject do
       {:git_ops, "~> 2.5", only: :dev},
       {:excoveralls, "~> 0.13.0", only: [:dev, :test]},
       {:mix_test_watch, "~> 1.0", only: :dev, runtime: false},
-      {:parse_trans, "3.3.0", only: [:dev, :test], override: true}
+      {:parse_trans, "3.3.0", only: [:dev, :test], override: true},
+      {:mox, "~> 1.0", only: :test}
     ]
   end
 

mix.lock

@@ -29,6 +29,7 @@
   "mime": {:hex, :mime, "2.0.5", "dc34c8efd439abe6ae0343edbb8556f4d63f178594894720607772a041b04b02", [:mix], [], "hexpm", "da0d64a365c45bc9935cc5c8a7fc5e49a0e0f9932a761c55d6c52b142780a05c"},
   "mimerl": {:hex, :mimerl, "1.2.0", "67e2d3f571088d5cfd3e550c383094b47159f3eee8ffa08e64106cdf5e981be3", [:rebar3], [], "hexpm", "f278585650aa581986264638ebf698f8bb19df297f66ad91b18910dfc6e19323"},
   "mix_test_watch": {:hex, :mix_test_watch, "1.1.1", "eee6fc570d77ad6851c7bc08de420a47fd1e449ef5ccfa6a77ef68b72e7e51ad", [:mix], [{:file_system, "~> 0.2.1 or ~> 0.3", [hex: :file_system, repo: "hexpm", optional: false]}], "hexpm", "f82262b54dee533467021723892e15c3267349849f1f737526523ecba4e6baae"},
+  "mox": {:hex, :mox, "1.1.0", "0f5e399649ce9ab7602f72e718305c0f9cdc351190f72844599545e4996af73c", [:mix], [], "hexpm", "d44474c50be02d5b72131070281a5d3895c0e7a95c780e90bc0cfe712f633a13"},
   "nimble_options": {:hex, :nimble_options, "1.0.2", "92098a74df0072ff37d0c12ace58574d26880e522c22801437151a159392270e", [:mix], [], "hexpm", "fd12a8db2021036ce12a309f26f564ec367373265b53e25403f0ee697380f1b8"},
   "nimble_parsec": {:hex, :nimble_parsec, "1.3.1", "2c54013ecf170e249e9291ed0a62e5832f70a476c61da16f6aac6dca0189f2af", [:mix], [], "hexpm", "2682e3c0b2eb58d90c6375fc0cc30bc7be06f365bf72608804fb9cffa5e1b167"},
   "parse_trans": {:hex, :parse_trans, "3.3.0", "09765507a3c7590a784615cfd421d101aec25098d50b89d7aa1d66646bc571c1", [:rebar3], [], "hexpm", "17ef63abde837ad30680ea7f857dd9e7ced9476cdd7b0394432af4bfc241b960"},

test/custom_pagination_test.exs

@@ -1,14 +1,36 @@
 defmodule AshJsonApiWrapper.CustomPagination.Test do
   use ExUnit.Case
   require Ash.Query
+  import Mox
   @moduletag :custom_pagination
 
+  # Make sure mocks are verified when the test exits
+  setup :verify_on_exit!
+
+  defmodule TestingTesla do
+    use Tesla
+
+    adapter(AshJsonApiWrapper.MockAdapter)
+    # plug(Tesla.Middleware.Logger)
+
+    plug(Tesla.Middleware.Retry,
+      delay: 2000,
+      max_retries: 5,
+      max_delay: 4_000,
+      should_retry: fn
+        {:ok, %{status: status}} when status in [429] -> true
+        {:ok, _} -> false
+        {:error, _} -> true
+      end
+    )
+  end
+
   # ── Custom paginator ──
 
   defmodule CustomPaginator do
     use AshJsonApiWrapper.Paginator
 
-    def cursor do
+    defp cursor do
       case :ets.whereis(:cursor) do
         :undefined ->
           :ets.new(:cursor, [:set, :protected, :named_table])
@@ -22,22 +44,27 @@ defmodule AshJsonApiWrapper.CustomPagination.Test do
       end
     end
 
-    def increment_cursor do
+    defp increment_cursor do
       :ets.insert(:cursor, {self(), cursor() + 1})
     end
 
-    def reset_cursor do
+    defp reset_cursor do
+      cursor()
       :ets.insert(:cursor, {self(), 1})
     end
 
-    def continue(_response, [], _) do
+    def start(_opts) do
       reset_cursor()
+      {:ok, %{params: %{"p" => 1}}}
+    end
+
+    def continue(_response, [], _) do
       :halt
     end
 
     def continue(_response, _entities, _opts) do
       increment_cursor()
-      {:ok, %{params: %{:p => cursor()}}}
+      {:ok, %{params: %{"p" => cursor()}}}
     end
   end
 
@@ -49,7 +76,7 @@ defmodule AshJsonApiWrapper.CustomPagination.Test do
       validate_api_inclusion?: false
 
     json_api_wrapper do
-      tesla(Tesla)
+      tesla(TestingTesla)
 
       endpoints do
         base("https://65383945a543859d1bb1528e.mockapi.io/api/v1")
@@ -99,13 +126,50 @@ defmodule AshJsonApiWrapper.CustomPagination.Test do
     Application.put_env(:ash, :validate_api_resource_inclusion?, false)
     Application.put_env(:ash, :validate_api_config_inclusion?, false)
 
+    AshJsonApiWrapper.MockAdapter
+    |> expect(:call, 4, fn env, _options ->
+      case env.query do
+        %{"l" => 3, "p" => 2} ->
+          {:ok, %Tesla.Env{env | status: 200, body: "[]"}}
+
+        %{"l" => 3, "p" => 1} ->
+          {:ok,
+           %Tesla.Env{
+             env
+             | status: 200,
+               body: """
+               [
+                {"name": "Kendra Ernser", "id":"1"},
+                {"name": "Max Hartman", "id":"2"},
+                {"name": "John Benton", "id":"3"}
+               ]
+               """
+           }}
+
+        query ->
+          {:ok,
+           %Tesla.Env{
+             env
+             | status: 500,
+               body: "Unexpected parameters: #{query |> Kernel.inspect()}"
+           }}
+      end
+    end)
+
     users =
       Users
       |> Ash.Query.for_read(:list_users)
-      |> Api.read!(page: [limit: 99])
+      # |> Ash.Query.limit(2)
+      |> Api.read!(page: [limit: 2, offset: 0])
 
-    user_count = users.results |> Enum.count()
+    users2 =
+      Users
+      |> Ash.Query.for_read(:list_users)
+      |> Api.read!(page: [limit: 2, offset: 1])
 
-    assert(user_count == 99)
+    users_count = users.results |> Enum.count()
+    users2_count = users2.results |> Enum.count()
+
+    assert(users_count == users2_count)
   end
 end

test/test_helper.exs

@@ -1,2 +1,3 @@
 ExUnit.start()
+Mox.defmock(AshJsonApiWrapper.MockAdapter, for: Tesla.Adapter)
 ExUnit.configure(exclude: [:hackernews])