Improve global back button. Goes back to previous interface.

It’s not quite like the browser’s back button because it doesn’t
necessarily go back to the last URL; rather, it goes back to the last
interface. So if you go into a discussion, then go to a different
discussion via the side pane, the back button will still take you back
to the index (not the previous discussion).

framework/core/ember/app/components/application/back-button.js

@@ -10,21 +10,30 @@ export default Ember.Component.extend({
   active: Ember.computed.or('target.paneIsShowing', 'target.paneIsPinned'),
 
   mouseEnter: function() {
-    this.get('target').send('showPane');
+    var target = this.get('target');
+    if (target) {
+      target.send('showPane');
+    }
   },
 
   mouseLeave: function() {
-    this.get('target').send('hidePane');
+    var target = this.get('target');
+    if (target) {
+      target.send('hidePane');
+    }
   },
 
   actions: {
+    // WE HAVE TO GO BACK. WAAAAAALLLLLLTTTTT
     back: function() {
-      this.get('target').send('transitionFromBackButton');
-      this.set('target', null);
+      this.sendAction('goBack');
     },
 
     togglePinned: function() {
-      this.get('target').send('togglePinned');
+      var target = this.get('target');
+      if (target) {
+        target.send('togglePinned');
+      }
     },
 
     toggleDrawer: function() {

framework/core/ember/app/controllers/application.js

@@ -14,7 +14,41 @@ export default Ember.Controller.extend({
   searchQuery: '',
   searchActive: false,
 
+  history: null,
+
+  init: function() {
+    this._super();
+    this.set('history', []);
+    this.pushHistory('index', '/');
+  },
+
+  pushHistory: function(name, url) {
+    var url = url || this.get('target.url');
+    var last = this.get('history').get('lastObject');
+    if (last && last.name === name) {
+      last.url = url;
+    } else {
+      this.get('history').pushObject({name: name, url: url});
+    }
+  },
+
+  popHistory: function(name) {
+    var last = this.get('history').get('lastObject');
+    if (last && last.name === name) {
+      this.get('history').popObject();
+    }
+  },
+
+  canGoBack: Ember.computed('history.length', function() {
+    return this.get('history.length') > 1;
+  }),
+
   actions: {
+    goBack: function() {
+      this.get('history').popObject();
+      var history = this.get('history').get('lastObject');
+      this.transitionToRoute.call(this, history.url);
+    },
     search: function(query) {
       this.transitionToRoute('index', {queryParams: {searchQuery: query, sort: query ? 'relevance' : 'recent'}});
     },

framework/core/ember/app/controllers/index.js

@@ -32,10 +32,6 @@ export default Ember.Controller.extend(UseComposer, Paneable, {
   },
 
   actions: {
-    transitionFromBackButton: function() {
-      this.transitionToRoute('index');
-    },
-
     loadMore: function() {
       this.get('index').send('loadMore');
     },

framework/core/ember/app/mixins/pushes-history.js

@@ -0,0 +1,20 @@
+import Ember from 'ember';
+
+export default Ember.Mixin.create({
+  pushHistory: function() {
+    Ember.run.next(this, function() {
+      this.controllerFor('application').pushHistory(this.get('historyKey'), this.get('url'));
+    });
+  },
+
+  setupController: function(controller, model) {
+    this._super(controller, model);
+    this.pushHistory();
+  },
+
+  actions: {
+    queryParamsDidChange: function() {
+      this.pushHistory();
+    }
+  }
+})

framework/core/ember/app/routes/discussion.js

@@ -1,8 +1,11 @@
 import Ember from 'ember';
 
 import PostStream from 'flarum/models/post-stream';
+import PushesHistory from 'flarum/mixins/pushes-history';
+
+export default Ember.Route.extend(PushesHistory, {
+  historyKey: 'discussion',
 
-export default Ember.Route.extend({
   queryParams: {
     start: {replace: true}
   },
@@ -33,7 +36,7 @@ export default Ember.Route.extend({
   },
 
   setupController: function(controller, discussion) {
-    controller.set('model', discussion);
+    this._super(controller, discussion);
     this.controllerFor('index/index').set('lastDiscussion', discussion);
 
     // Set up the post stream object. It needs to know about the discussion
@@ -94,6 +97,8 @@ export default Ember.Route.extend({
 
   actions: {
     queryParamsDidChange: function(params) {
+      this._super(params);
+
       // If the ?start param has changed, we want to tell the view to
       // tell the streamContent component to jump to this start point.
       // We postpone running this code until the next run loop because

framework/core/ember/app/routes/index.js

@@ -0,0 +1,7 @@
+import Ember from 'ember';
+
+export default Ember.Route.extend({
+  deactivate: function() {
+    this.controllerFor('application').set('backButtonTarget', null);
+  }
+});

framework/core/ember/app/routes/index/index.js

@@ -1,8 +1,11 @@
 import Ember from 'ember';
 
 import AddCssClassToBody from 'flarum/mixins/add-css-class-to-body';
+import PushesHistory from 'flarum/mixins/pushes-history';
+
+export default Ember.Route.extend(AddCssClassToBody, PushesHistory, {
+  historyKey: 'index',
 
-export default Ember.Route.extend(AddCssClassToBody, {
   cachedModel: null,
 
   model: function() {
@@ -13,7 +16,7 @@ export default Ember.Route.extend(AddCssClassToBody, {
   },
 
   setupController: function(controller, model) {
-    controller.set('model', model);
+    this._super(controller, model);
 
     if (!model.get('length')) {
       controller.send('loadResults');

framework/core/ember/app/routes/user/activity.js

@@ -1,12 +1,17 @@
 import Ember from 'ember';
 
-export default Ember.Route.extend({
+import PushesHistory from 'flarum/mixins/pushes-history';
+
+export default Ember.Route.extend(PushesHistory, {
+  historyKey: 'user',
+
   model: function() {
     return Ember.RSVP.resolve(Ember.ArrayProxy.create());
   },
 
   setupController: function(controller, model) {
-    controller.set('model', model);
+    this._super(controller, model);
+
     controller.send('loadResults');
   }
 });

framework/core/ember/app/templates/application.hbs

@@ -1,10 +1,10 @@
 <div id="page" {{bind-attr class=":global-page backButtonTarget.paneIsPinned:with-pane"}}>
 
-  {{application/back-button target=backButtonTarget className="back-control" toggleDrawer="toggleDrawer"}}
+  {{application/back-button target=backButtonTarget className="back-control" toggleDrawer="toggleDrawer" goBack="goBack" canGoBack=canGoBack}}
 
   <div id="drawer" class="global-drawer">
     <header id="header" class="global-header">
-      {{application/back-button target=backButtonTarget}}
+      {{application/back-button target=backButtonTarget goBack="goBack" canGoBack=canGoBack}}
 
       <div class="container">
 

framework/core/ember/app/templates/components/application/back-button.hbs

@@ -1,4 +1,4 @@
-{{#if target}}
+{{#if canGoBack}}
   <div class="btn-group">
     <button class="btn btn-default btn-icon back" {{action "back"}}>{{fa-icon "chevron-left" class="icon-glyph"}}</button>
     {{#if target.paned}}