Fix #3214: Add autocomplete for saved searches.

* Autocomplete the `search:<label>` metatag.

* Make label autocompletion do a prefix match instead of a substring
  match. Example: `search:ar` matches `artists`, not `characters`. This
  is how tags and most other things are autocompleted.

app/assets/javascripts/autocomplete.js

@@ -93,7 +93,7 @@
     var prefixes = "-|~|general:|gen:|artist:|art:|copyright:|copy:|co:|character:|char:|ch:";
     var metatags = "order|-status|status|-rating|rating|-locked|locked|child|filetype|-filetype|" +
       "-user|user|-approver|approver|commenter|comm|noter|noteupdater|artcomm|-fav|fav|ordfav|" +
-      "sub|-pool|pool|ordpool|favgroup";
+      "sub|-pool|pool|ordpool|favgroup|-search|search";
 
     $fields_multiple.autocomplete({
       delay: 100,
@@ -183,6 +183,10 @@
         case "-favgroup":
           Danbooru.Autocomplete.favorite_group_source(term, resp, metatag);
           break;
+        case "search":
+        case "-search":
+          Danbooru.Autocomplete.saved_search_source(term, resp);
+          break;
         default:
           Danbooru.Autocomplete.normal_source(term, resp);
           break;
@@ -420,6 +424,17 @@
       }
     });
   }
+
+  Danbooru.Autocomplete.saved_search_source = function(term, resp) {
+    return Danbooru.SavedSearch.labels(term).success(function(labels) {
+      resp(labels.map(function(label) {
+        return {
+          label: label.replace(/_/g, " "),
+          value: "search:" + label,
+        };
+      }));
+    });
+  }
 })();
 
 $(document).ready(function() {

app/assets/javascripts/posts.js

@@ -550,21 +550,14 @@
     $("#saved_search_labels").autocomplete({
       minLength: 2,
       source: function(req, resp) {
-        $.ajax({
-          url: "/saved_searches/labels.json",
-          data: {
-            label: req.term
-          },
-          method: "get",
-          success: function(data) {
-            resp($.map(data, function(saved_search) {
-              return {
-                label: saved_search.replace(/_/g, " "),
-                value: saved_search
-              };
-            }));
-          }
-        })
+        Danbooru.SavedSearch.labels(req.term).success(function(labels) {
+          resp(labels.map(function(label) {
+            return {
+              label: label.replace(/_/g, " "),
+              value: label
+            };
+          }));
+        });
       }
     });
 

app/assets/javascripts/saved_searches.js

@@ -1,5 +1,16 @@
-$(document).ready(function() {
+Danbooru.SavedSearch = {};
+
+Danbooru.SavedSearch.initialize_all = function() {
   if ($("#c-saved-searches".length)) {
     Danbooru.sorttable($("#c-saved-searches table"));
   }
-});
+}
+
+Danbooru.SavedSearch.labels = function(term) {
+  return $.getJSON("/saved_searches/labels", {
+    "search[label]": term + "*",
+    "limit": 10
+  });
+}
+
+$(Danbooru.SavedSearch.initialize_all);