Exemples d'usage de Stream.resource/3 et Stream.unfold pour pagin…

…er des ressources (#3486)

* Implement initial script with pagination

* Use pattern matching on anonymous functions

* Update pagination_example.exs

* Apply formatting

---------

Co-authored-by: Antoine Augusti <[email protected]>

scripts/pagination_example.exs

@@ -0,0 +1,101 @@
+Mix.install([
+  {:req, "~> 0.3.0"},
+  {:dotenvy, "~> 0.8.0"}
+])
+
+defmodule EnvConfig do
+  def read!() do
+    env_file = Path.join(__ENV__.file, "../../.env") |> Path.expand()
+    Dotenvy.source!(env_file)
+  end
+end
+
+# A simple example of HTTP pagination of an API, using tools provided by Elixir.
+# We build "streams" which are lazy-evaluated enumerables.
+defmodule NotionClient do
+  def http_options(notion_secret) do
+    [auth: {:bearer, notion_secret}, headers: [{"Notion-Version", "2022-06-28"}]]
+  end
+
+  def build_base_url(table_id), do: "https://api.notion.com/v1/databases/#{table_id}/query"
+
+  # an example of creating a stream (lazy-evaluted) based on HTTP pagination via `Stream.resource/3`
+  # https://hexdocs.pm/elixir/Stream.html#resource/3
+  def database_items_via_stream_resource(table_id, notion_secret) do
+    base_url = build_base_url(table_id)
+
+    # function called by `Stream.resource`, until it returns {:halt, ...}
+    next_fn = fn
+      :done ->
+        {:halt, nil}
+
+      {url, start_cursor} ->
+        # https://developers.notion.com/reference/pagination
+        json = %{page_size: 100}
+        json = if start_cursor, do: Map.put(json, :start_cursor, start_cursor), else: json
+        options = http_options(notion_secret) |> Keyword.put(:json, json)
+
+        %{status: 200, body: body} = Req.post!(url, options)
+        acc = if cursor = body["next_cursor"], do: {url, cursor}, else: :done
+        {body["results"], acc}
+    end
+
+    Stream.resource(
+      # initially, start_cursor is not available
+      fn -> {base_url, nil} end,
+      next_fn,
+      fn _ -> nil end
+    )
+  end
+
+  # Since we have a simple case, we can even just use `Stream.unfold`
+  # https://hexdocs.pm/elixir/Stream.html#unfold/2
+  def database_items_via_stream_unfold(table_id, notion_secret) do
+    base_url = build_base_url(table_id)
+
+    req = fn
+      nil ->
+        nil
+
+      {url, start_cursor} ->
+        # https://developers.notion.com/reference/pagination
+        json = %{page_size: 100}
+        json = if start_cursor, do: Map.put(json, :start_cursor, start_cursor), else: json
+        options = http_options(notion_secret) |> Keyword.put(:json, json)
+        %{status: 200, body: body} = Req.post!(url, options)
+        acc = if c = body["next_cursor"], do: {url, c}, else: nil
+        {body["results"], acc}
+    end
+
+    Stream.unfold({base_url, nil}, req)
+    # https://hexdocs.pm/elixir/Stream.html#flat_map/2 is needed
+    |> Stream.flat_map(fn x -> x end)
+  end
+end
+
+defmodule Mapper do
+  def run(stream) do
+    stream
+    |> Stream.map(fn x -> x["properties"]["Nom"]["title"] |> List.first() |> Map.fetch!("plain_text") end)
+    |> Stream.with_index()
+    |> Stream.each(&IO.inspect(&1, IEx.inspect_opts()))
+    |> Stream.run()
+  end
+end
+
+%{
+  "NOTION_SECRET" => notion_secret,
+  "NOTION_ORGANIZATIONS_TABLE_ID" => notion_org_table_id
+} = EnvConfig.read!()
+
+IO.puts("========= database_items_via_stream_resource =========")
+
+NotionClient.database_items_via_stream_resource(notion_org_table_id, notion_secret)
+|> Stream.take(3)
+|> Mapper.run()
+
+IO.puts("========= database_items_via_stream_unfold =========")
+
+NotionClient.database_items_via_stream_unfold(notion_org_table_id, notion_secret)
+|> Stream.take(2)
+|> Mapper.run()