autocomplete: render html server-side.

Render the HTML for autocomplete results server-side instead of in
Javascript. This is cleaner than building HTML in Javascript, but it may
hurt caching because the HTTP responses are larger.

Fixes #4698: user autocomplete contains links to /posts

Also fixes a bug where tag counts in the autocomplete menu were different
from tag counts displayed elsewhere because of differences in rounding.

app/components/autocomplete_component.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class AutocompleteComponent < ApplicationComponent
+  attr_reader :autocomplete_service
+
+  delegate :humanized_number, to: :helpers
+  delegate :autocomplete_results, to: :autocomplete_service
+
+  def initialize(autocomplete_service:)
+    @autocomplete_service = autocomplete_service
+  end
+
+  def link_to_result(result, &block)
+    case result.type
+    when "user"
+      link_to user_path(result.id), class: "user-#{result.level}", "@click.prevent": "", &block
+    when "pool"
+      link_to pool_path(result.id), class: "pool-category-#{result.category}", "@click.prevent": "", &block
+    else
+      link_to posts_path(tags: result.value), class: "tag-type-#{result.category}", "@click.prevent": "", &block
+    end
+  end
+end

app/components/autocomplete_component/autocomplete_component.html.erb

@@ -0,0 +1,20 @@
+<ul>
+  <% autocomplete_results.each do |result| %>
+    <%= tag.li class: "ui-menu-item", "data-autocomplete-type": result.type, "data-autocomplete-antecedent": result.antecedent, "data-autocomplete-value": result.value, "data-autocomplete-category": result.category, "data-autocomplete-post-count": result.post_count do %>
+      <div class="ui-menu-item-wrapper" tabindex="-1">
+        <%= link_to_result result do %>
+          <% if result.antecedent.present? %>
+            <span class="autocomplete-antecedent"><%= result.antecedent.tr("_", " ") %></span>
+            <span class="autocomplete-arrow">→</span>
+          <% end %>
+
+          <%= result.label %>
+        <% end %>
+
+        <% if result.post_count %>
+          <%= tag.span humanized_number(result.post_count), class: "post-count", style: "float: right;" %>
+        <% end %>
+      </div>
+    <% end %>
+  <% end %>
+</ul>

app/controllers/autocomplete_controller.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 class AutocompleteController < ApplicationController
-  respond_to :xml, :json
+  respond_to :html, :xml, :json
 
   def index
     @query = params.dig(:search, :query)
@@ -14,6 +14,6 @@ class AutocompleteController < ApplicationController
     @public = @autocomplete.cache_publicly?
 
     expires_in @expires_in, public: @public unless response.cache_control.present?
-    respond_with(@results)
+    respond_with(@results, layout: false)
   end
 end

app/javascript/src/javascripts/autocomplete.js

@@ -1,5 +1,6 @@
 let Autocomplete = {};
 
+Autocomplete.VERSION = 1; // This should be bumped whenever the /autocomplete API changes in order to invalid client caches.
 Autocomplete.MAX_RESULTS = 10;
 
 Autocomplete.initialize_all = function() {
@@ -138,64 +139,28 @@ Autocomplete.on_tab = function(event) {
 };
 
 Autocomplete.render_item = function(list, item) {
-  var $link = $("<a/>");
+  item.html.data("ui-autocomplete-item", item);
-  $link.text(item.label);
+  return list.append(item.html);
-  $link.attr("href", "/posts?tags=" + encodeURIComponent(item.value));
-  $link.on("click.danbooru", function(e) {
-    e.preventDefault();
-  });
-
-  if (item.antecedent) {
-    var antecedent = item.antecedent.replace(/_/g, " ");
-    var arrow = $("<span/>").html(" &rarr; ").addClass("autocomplete-arrow");
-    var antecedent_element = $("<span/>").text(antecedent).addClass("autocomplete-antecedent");
-    $link.prepend([
-      antecedent_element,
-      arrow
-    ]);
-  }
-
-  if (item.post_count !== undefined) {
-    var count = item.post_count;
-
-    if (count >= 1000) {
-      count = Math.floor(count / 1000) + "k";
-    }
-
-    var $post_count = $("<span/>").addClass("post-count").css("float", "right").text(count);
-    $link.append($post_count);
-  }
-
-  if (/^tag/.test(item.type)) {
-    $link.addClass("tag-type-" + item.category);
-  } else if (item.type === "user") {
-    var level_class = "user-" + item.level.toLowerCase();
-    $link.addClass(level_class);
-  } else if (item.type === "pool") {
-    $link.addClass("pool-category-" + item.category);
-  }
-
-  var $menu_item = $("<div/>").append($link);
-  var $list_item = $("<li/>").data("item.autocomplete", item).append($menu_item);
-
-  var data_attributes = ["type", "antecedent", "value", "category", "post_count"];
-  data_attributes.forEach(attr => {
-    $list_item.attr(`data-autocomplete-${attr.replace(/_/g, "-")}`, item[attr]);
-  });
-
-  return $list_item.appendTo(list);
 };
 
-Autocomplete.autocomplete_source = function(query, type) {
+Autocomplete.autocomplete_source = async function(query, type) {
   if (query === "") {
     return [];
   }
 
-  return $.getJSON("/autocomplete.json", {
+  let html = await $.get("/autocomplete", {
     "search[query]": query,
     "search[type]": type,
+    "version": Autocomplete.VERSION,
     "limit": Autocomplete.MAX_RESULTS
   });
+
+  let items = $(html).find("li").toArray().map(item => {
+    let $item = $(item);
+    return { value: $item.attr("data-autocomplete-value"), html: $item };
+  });
+
+  return items;
 }
 
 Autocomplete.tag_prefixes = function() {

app/logical/autocomplete_service.rb

@@ -48,6 +48,7 @@ class AutocompleteService
   # @return [Array<Hash>] the autocomplete results
   def autocomplete_results
     return [] if !enabled?
+    return autocomplete_opensearch(query) if type == :opensearch
 
     case type
     when :tag_query
@@ -68,11 +69,9 @@ class AutocompleteService
       autocomplete_favorite_group(query)
     when :saved_search_label
       autocomplete_saved_search_label(query)
-    when :opensearch
-      autocomplete_opensearch(query)
     else
       []
-    end
+    end.map { |result| OpenStruct.new(result) }
   end
 
   # Complete a tag search (a regular tag or a metatag)
@@ -238,7 +237,7 @@ class AutocompleteService
     pools = Pool.undeleted.name_matches(string).search(order: "post_count").limit(limit)
 
     pools.map do |pool|
-      { type: "pool", label: pool.pretty_name, value: pool.name, post_count: pool.post_count, category: pool.category }
+      { type: "pool", label: pool.pretty_name, value: pool.name, id: pool.id, post_count: pool.post_count, category: pool.category }
     end
   end
 
@@ -298,7 +297,7 @@ class AutocompleteService
     users = User.search(name_matches: string, current_user_first: true, order: "post_upload_count").limit(limit)
 
     users.map do |user|
-      { type: "user", label: user.pretty_name, value: user.name, level: user.level_string }
+      { type: "user", label: user.pretty_name, value: user.name, id: user.id, level: user.level_string.downcase }
     end
   end
 

app/views/autocomplete/index.html.erb

@@ -0,0 +1 @@
+<%= render AutocompleteComponent.new(autocomplete_service: @autocomplete) %>

test/functional/autocomplete_controller_test.rb

@@ -2,10 +2,10 @@ require "test_helper"
 
 class AutocompleteControllerTest < ActionDispatch::IntegrationTest
   def autocomplete(query, type)
-    get autocomplete_index_path(search: { query: query, type: type }), as: :json
+    get autocomplete_index_path(search: { query: query, type: type })
     assert_response :success
 
-    response.parsed_body.map { |result| result["value"] }
+    response.parsed_body.css("li").map { |html| html["data-autocomplete-value"] }
   end
 
   def assert_autocomplete_equals(expected_value, query, type)
@@ -35,6 +35,24 @@ class AutocompleteControllerTest < ActionDispatch::IntegrationTest
         assert_autocomplete_equals(["rating:sensitive"], "-rating:s", "tag_query")
       end
 
+      should "work for an aliased tag" do
+        create(:tag_alias, antecedent_name: "oc", consequent_name: "original")
+
+        assert_autocomplete_equals(["original"], "oc", "tag_query")
+      end
+
+      should "work for the user: metatag" do
+        create(:user, name: "foobar")
+
+        assert_autocomplete_equals(["user:foobar"], "user:foo", "tag_query")
+      end
+
+      should "work for the pool: metatag" do
+        as(create(:user)) { create(:pool, name: "foobar") }
+
+        assert_autocomplete_equals(["pool:foobar"], "pool:foo", "tag_query")
+      end
+
       should "work for a missing type" do
         get autocomplete_index_path(search: { query: "azur" }), as: :json
 
@@ -48,7 +66,7 @@ class AutocompleteControllerTest < ActionDispatch::IntegrationTest
       end
 
       should "not set session cookies when the response is publicly cached" do
-        get autocomplete_index_path(search: { query: "azur", type: "tag_query" }), as: :json
+        get autocomplete_index_path(search: { query: "azur", type: "tag_query" })
 
         assert_response :success
         assert_equal(true, response.cache_control[:public])