From 2aead9edafb1645420a1bb899ee85fd556922d78 Mon Sep 17 00:00:00 2001
From: Cristen Jones <cjones3@mbta.com>
Date: Tue, 17 Oct 2023 14:18:16 -0400
Subject: [PATCH] feat(Algolia.Api): cache requests

---
 apps/algolia/lib/algolia/api.ex         | 18 +++++++++++++++---
 apps/algolia/lib/algolia/application.ex |  3 +--
 apps/algolia/mix.exs                    |  3 ++-
 apps/algolia/test/api_test.exs          |  6 ++++--
 4 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/apps/algolia/lib/algolia/api.ex b/apps/algolia/lib/algolia/api.ex
index fbb548d87a..c9a3b41d0e 100644
--- a/apps/algolia/lib/algolia/api.ex
+++ b/apps/algolia/lib/algolia/api.ex
@@ -4,6 +4,7 @@ defmodule Algolia.Api do
   """
   alias Algolia.Config
   require Logger
+  use RepoCache, ttl: :timer.hours(12)
 
   defstruct [:host, :index, :action, :body]
 
@@ -39,9 +40,20 @@ defmodule Algolia.Api do
       |> hackney_opts()
       |> Keyword.put(:pool, @http_pool)
 
-    opts
-    |> generate_url(config)
-    |> HTTPoison.post(body, headers(config), hackney: hackney)
+    send_post_request = fn {body, config} ->
+      opts
+      |> generate_url(config)
+      |> HTTPoison.post(body, headers(config), hackney: hackney)
+    end
+
+    # If we're making a query for results using the same request body AND same
+    # %Algolia.Config{}, cache the response instead of making extra calls to the
+    # Algolia REST API
+    if action == "queries" do
+      cache({body, config}, send_post_request)
+    else
+      send_post_request.({body, config})
+    end
   end
 
   @spec generate_url(t, Config.t()) :: String.t()
diff --git a/apps/algolia/lib/algolia/application.ex b/apps/algolia/lib/algolia/application.ex
index 81e3d094d4..9f23886108 100644
--- a/apps/algolia/lib/algolia/application.ex
+++ b/apps/algolia/lib/algolia/application.ex
@@ -8,8 +8,7 @@ defmodule Algolia.Application do
   def start(_type, _args) do
     # List all child processes to be supervised
     children = [
-      # Starts a worker by calling: Algolia.Worker.start_link(arg)
-      # {Algolia.Worker, arg},
+      Algolia.Api
     ]
 
     # See https://hexdocs.pm/elixir/Supervisor.html
diff --git a/apps/algolia/mix.exs b/apps/algolia/mix.exs
index 5feb42c9fc..abb5a2bd89 100644
--- a/apps/algolia/mix.exs
+++ b/apps/algolia/mix.exs
@@ -35,7 +35,8 @@ defmodule Algolia.Mixfile do
       {:util, in_umbrella: true},
       {:httpoison, "~> 1.5"},
       {:plug, "~> 1.14.2"},
-      {:bypass, "~> 1.0", only: :test}
+      {:bypass, "~> 1.0", only: :test},
+      {:repo_cache, in_umbrella: true}
     ]
   end
 end
diff --git a/apps/algolia/test/api_test.exs b/apps/algolia/test/api_test.exs
index 5249d1dbdb..4075c9e4c1 100644
--- a/apps/algolia/test/api_test.exs
+++ b/apps/algolia/test/api_test.exs
@@ -5,10 +5,10 @@ defmodule Algolia.ApiTest do
   @success_response ~s({"message" : "success"})
 
   describe "post" do
-    test "sends a post request to /1/indexes/$INDEX/$ACTION" do
+    test "sends a post request once to /1/indexes/$INDEX/$ACTION" do
       bypass = Bypass.open()
 
-      Bypass.expect(bypass, "POST", "/1/indexes/*/queries", fn conn ->
+      Bypass.expect_once(bypass, "POST", "/1/indexes/*/queries", fn conn ->
         {:ok, body, conn} = Plug.Conn.read_body(conn)
 
         case Poison.decode(body) do
@@ -29,6 +29,8 @@ defmodule Algolia.ApiTest do
 
       assert {:ok, %HTTPoison.Response{status_code: 200, body: body}} = Algolia.Api.post(opts)
       assert body == @success_response
+      # Can be called again with result from cache instead of hitting the API endpoint
+      assert {:ok, %HTTPoison.Response{status_code: 200, body: ^body}} = Algolia.Api.post(opts)
     end
 
     test "logs a warning if config keys are missing" do