Add wikidata asynchronously based on wikipedia

ref #2680

index.html

@@ -43,6 +43,7 @@
         <script src='js/id/services/mapillary.js'></script>
         <script src='js/id/services/nominatim.js'></script>
         <script src='js/id/services/taginfo.js'></script>
+        <script src='js/id/services/wikidata.js'></script>
         <script src='js/id/services/wikipedia.js'></script>
 
         <script src='data/data_dev.js'></script>

js/id/services/wikidata.js

@@ -0,0 +1,22 @@
+iD.services.wikidata = function() {
+    var wiki = {},
+        endpoint = 'https://www.wikidata.org/w/api.php?';
+
+    // Given a Wikipedia language and article title, return an array of
+    // corresponding Wikidata entities.
+    wiki.itemsByTitle = function(lang, title, callback) {
+        lang = lang || 'en';
+        d3.jsonp(endpoint + iD.util.qsString({
+            action: 'wbgetentities',
+            format: 'json',
+            sites: lang.replace(/-/g, '_') + 'wiki',
+            titles: title,
+            languages: 'en', // shrink response by filtering to one language
+            callback: '{callback}'
+        }), function(data) {
+            callback(title, data.entities || {});
+        });
+    };
+
+    return wiki;
+};

js/id/ui/preset/wikipedia.js

@@ -1,6 +1,7 @@
 iD.ui.preset.wikipedia = function(field, context) {
     var dispatch = d3.dispatch('change'),
         wikipedia = iD.services.wikipedia(),
+        wikidata = iD.services.wikidata(),
         link, entity, lang, title;
 
     function i(selection) {
@@ -88,7 +89,8 @@ iD.ui.preset.wikipedia = function(field, context) {
         var value = title.value(),
             m = value.match(/https?:\/\/([-a-z]+)\.wikipedia\.org\/(?:wiki|\1-[-a-z]+)\/([^#]+)(?:#(.+))?/),
             l = m && _.find(iD.data.wikipedia, function(d) { return m[1] === d[2]; }),
-            anchor;
+            anchor,
+            syncTags = {};
 
         if (l) {
             // Normalize title http://www.mediawiki.org/wiki/API:Query#Title_normalization
@@ -107,9 +109,19 @@ iD.ui.preset.wikipedia = function(field, context) {
             title.value(value);
         }
 
-        var t = {};
-        t[field.key] = value ? language()[2] + ':' + value : undefined;
-        dispatch.change(t);
+        syncTags[field.key] = value ? language()[2] + ':' + value : undefined;
+        dispatch.change(syncTags);
+
+        if (value && language()[2]) {
+            wikidata.itemsByTitle(language()[2], value, function (title, entities) {
+                var qids = entities && Object.keys(entities),
+                    asyncTags = {};
+                asyncTags.wikidata = qids && _.find(qids, function (id) {
+                    return id.match(/^Q\d+$/);
+                });
+                dispatch.change(asyncTags);
+            });
+        }
     }
 
     i.tags = function(tags) {

test/index.html

@@ -48,6 +48,7 @@
     <script src='../js/id/services/mapillary.js'></script>
     <script src='../js/id/services/nominatim.js'></script>
     <script src='../js/id/services/taginfo.js'></script>
+    <script src='../js/id/services/wikidata.js'></script>
     <script src='../js/id/services/wikipedia.js'></script>
 
     <script src='../data/data_dev.js'></script>

test/spec/ui/preset/wikipedia.js

@@ -27,7 +27,9 @@ describe('iD.ui.preset.wikipedia', function() {
         happen.once(selection.selectAll('.wiki-lang').node(), {type: 'change'});
 
         wikipedia.on('change', function(tags) {
-            expect(tags).to.eql({wikipedia: 'de:Title'});
+            expect(tags).to.satisfy(function (tags) {
+                return tags.wikipedia === 'de:Title' || 'wikidata' in tags;
+            });
         });
 
         selection.selectAll('.wiki-title').value('Title');