Merge pull request #436 from MareStare/feat/server-side-suggestions-api-v2

[Part 1] Add server-side suggestions API v2

lib/philomena_web/controllers/autocomplete/tag_controller.ex

@@ -5,13 +5,100 @@ defmodule PhilomenaWeb.Autocomplete.TagController do
   alias Philomena.Tags.Tag
   import Ecto.Query
 
-  def show(conn, params) do
+  def show(conn, %{"vsn" => "2"} = params), do: show_v2(conn, params)
+  def show(conn, params), do: show_v1(conn, params)
+
+  # Returns a list of tag suggestions for an incomplete term. Does a prefix search
+  # on the canonical tag names and their aliases.
+  #
+  # See the docs on `show_v1` for the explanation on the breaking change we made
+  # in the `v2` version.
+  defp show_v2(conn, params) do
+    with {:ok, term} <- extract_term(params),
+         {:ok, limit} <- extract_limit(params) do
+      suggestions = search(term, limit)
+      json(conn, %{suggestions: suggestions})
+    else
+      {:error, message} ->
+        conn
+        |> put_status(:unprocessable_entity)
+        |> json(%{error: message})
+    end
+  end
+
+  defp extract_term(%{"term" => term}) when is_binary(term) and byte_size(term) > 2 do
+    result =
+      term
+      |> String.downcase()
+      |> String.trim()
+
+    {:ok, result}
+  end
+
+  defp extract_term(%{"term" => _}),
+    do: {:error, "Term is too short, must be at least 3 characters"}
+
+  defp extract_term(_params), do: {:error, "Term is missing"}
+
+  defp extract_limit(params) do
+    limit =
+      params
+      |> Map.get("limit", "10")
+      |> Integer.parse()
+
+    case limit do
+      {limit, ""} when limit > 0 and limit <= 10 ->
+        {:ok, limit}
+
+      _ ->
+        {:error, "Limit must be an integer between 1 and 10"}
+    end
+  end
+
+  @spec search(String.t(), integer()) :: [map()]
+  defp search(term, limit) do
+    Tag
+    |> Search.search_definition(
+      %{
+        query: %{
+          bool: %{
+            should: [
+              %{prefix: %{name: term}},
+              %{prefix: %{name_in_namespace: term}}
+            ]
+          }
+        },
+        sort: %{images: :desc}
+      },
+      %{page_size: 10}
+    )
+    |> Search.search_records(preload(Tag, :aliased_tag))
+    |> Enum.map(
+      &%{
+        :alias => if(is_nil(&1.aliased_tag), do: nil, else: &1.name),
+        canonical: if(is_nil(&1.aliased_tag), do: &1.name, else: &1.aliased_tag.name),
+        images: if(is_nil(&1.aliased_tag), do: &1.images_count, else: &1.aliased_tag.images_count)
+      }
+    )
+    |> Enum.filter(&(&1.images > 0))
+    |> Enum.take(limit)
+  end
+
+  # Version 1 is kept for backwards compatibility with the older versions of
+  # the frontend application that may still be cached in user's browsers. Don't
+  # change this code! All the new development should be done in the `v2` version.
+  #
+  # The problem of `v1` was that it was doing the work of formatting the completion
+  # results on the backend, which was not ideal. So instead, the `v2` version
+  # was created to return the raw data in fully structured JSON format, which
+  # the frontend application can then format and style as needed.
+  defp show_v1(conn, params) do
     tags =
       case extract_term(params) do
-        nil ->
+        {:error, _} ->
           []
 
-        term ->
+        {:ok, term} ->
           Tag
           |> Search.search_definition(
             %{
@@ -39,12 +126,4 @@ defmodule PhilomenaWeb.Autocomplete.TagController do
     conn
     |> json(tags)
   end
-
-  defp extract_term(%{"term" => term}) when is_binary(term) and byte_size(term) > 2 do
-    term
-    |> String.downcase()
-    |> String.trim()
-  end
-
-  defp extract_term(_params), do: nil
 end