Add direct linking feature flag

Add a feature flag for direct linking and
use the link provided by the API to a view of
the annotation in context when this flag is enabled.

h/static/scripts/directive/annotation.js

@@ -109,13 +109,22 @@ function updateDomainModel(domainModel, vm, permissions) {
 }
 
 /** Update the view model from the domain model changes. */
-function updateViewModel($scope, time, domainModel, vm, permissions) {
+function updateViewModel($scope, time, domainModel,
+                         vm, permissions) {
 
   vm.form = {
     text: domainModel.text,
     tags: viewModelTagsFromDomainModelTags(domainModel.tags),
   };
-  vm.annotationURI = new URL('/a/' + domainModel.id, vm.serviceUrl).href;
+
+  if (domainModel.links) {
+    vm.annotationURI = domainModel.links.incontext ||
+                       domainModel.links.html ||
+                       '';
+  } else {
+    vm.annotationURI = '';
+  }
+
   vm.isPrivate = permissions.isPrivate(
     domainModel.permissions, domainModel.user);
 

h/static/scripts/directive/test/annotation-test.js

@@ -347,7 +347,7 @@ describe('annotation', function() {
       };
 
       var fakeFeatures = {
-        flagEnabled: sandbox.stub().returns(true)
+        flagEnabled: sandbox.stub().returns(true),
       };
 
       fakeFlash = {
@@ -1496,5 +1496,32 @@ describe('annotation', function() {
                      'https://test.hypothes.is/stream?q=tag:atag');
       });
     });
+
+    describe('annotation metadata', function () {
+      function findLink(directive) {
+        var links = directive.element[0]
+          .querySelectorAll('header .annotation-link');
+        return links[links.length-1];
+      }
+
+      it('displays HTML links when in-context links are not available', function () {
+        var annotation = Object.assign({}, fixtures.defaultAnnotation(), {
+          links: {html: 'https://test.hypothes.is/a/deadbeef'},
+        });
+        var directive = createDirective(annotation);
+        assert.equal(findLink(directive).href, annotation.links.html);
+      });
+
+      it('displays in-context links when available', function () {
+        var annotation = Object.assign({}, fixtures.defaultAnnotation(), {
+          links: {
+            html: 'https://test.hypothes.is/a/deadbeef',
+            incontext: 'https://hpt.is/deadbeef'
+          },
+        });
+        var directive = createDirective(annotation);
+        assert.equal(findLink(directive).href, annotation.links.incontext);
+      });
+    });
   });
 });

h/static/scripts/test/annotation-fixtures.js

+'use strict';
+
 /**
  * Return a fake annotation with the basic properties filled in.
  */

h/templates/client/annotation.html

@@ -49,7 +49,7 @@
        target="_blank"
        title="{{vm.absoluteTimestamp}}"
        ng-if="!vm.editing() && vm.updated()"
-       ng-href="{{::vm.serviceUrl}}a/{{vm.id()}}"
+       ng-href="{{vm.annotationURI}}"
        >{{vm.relativeTimestamp}}</a>
   </header>