Feature/notifications (#87)

* #25: Implemented enough of the notification system to start writing drivers.

* #25: Implemented most of the Pony.fm notification driver's backend.

* #25: Abstracted the logic for building lists of notification recipients.

* #25: Implemented notification API endpoints for the SPA.

* Front end setup for notifications

* #25: Implemented notification API endpoints for the SPA.

README.md

@@ -25,6 +25,8 @@ For quick fixes, go ahead and submit a pull request!
 For larger features, it's best to open an issue before sinking a ton of work
 into building them, to coordinate with Pony.fm's maintainers.
 
+Developer documentation is available in the [`documentation` directory](documentation).
+
 **Protip:** Looking for a place to jump in and start coding? Try a
 [quickwin issue](https://github.com/Poniverse/Pony.fm/labels/quickwin%21) -
 these are smaller in scope and easier to tackle if you're unfamiliar with the codebase!

app/Commands/CreateCommentCommand.php

@@ -20,6 +20,7 @@
 
 namespace Poniverse\Ponyfm\Commands;
 
+use Notification;
 use Poniverse\Ponyfm\Models\Album;
 use Poniverse\Ponyfm\Models\Comment;
 use Poniverse\Ponyfm\Models\Playlist;
@@ -115,6 +116,8 @@ class CreateCommentCommand extends CommandBase
 
         $entity->comment_count = Comment::where($column, $this->_id)->count();
         $entity->save();
+        
+        Notification::newComment($comment);
 
         return CommandResponse::succeed(Comment::mapPublic($comment));
     }

app/Commands/CreatePlaylistCommand.php

@@ -20,6 +20,7 @@
 
 namespace Poniverse\Ponyfm\Commands;
 
+use Notification;
 use Poniverse\Ponyfm\Models\Playlist;
 use Illuminate\Support\Facades\Auth;
 use Illuminate\Support\Facades\Validator;
@@ -68,6 +69,8 @@ class CreatePlaylistCommand extends CommandBase
         $playlist->is_public = $this->_input['is_public'] == 'true';
 
         $playlist->save();
+        
+        Notification::publishedNewPlaylist($playlist);
 
         if ($this->_input['is_pinned'] == 'true') {
             $playlist->pin(Auth::user()->id);

app/Commands/EditTrackCommand.php

@@ -21,6 +21,7 @@
 namespace Poniverse\Ponyfm\Commands;
 
 use Gate;
+use Notification;
 use Poniverse\Ponyfm\Models\Album;
 use Poniverse\Ponyfm\Models\Image;
 use Poniverse\Ponyfm\Models\Track;
@@ -32,6 +33,10 @@ use DB;
 class EditTrackCommand extends CommandBase
 {
     private $_trackId;
+
+    /**
+     * @var Track
+     */
     private $_track;
     private $_input;
 
@@ -132,6 +137,8 @@ class EditTrackCommand extends CommandBase
 
             DB::table('tracks')->whereUserId($track->user_id)->update(['is_latest' => false]);
             $track->is_latest = true;
+            
+            Notification::publishedNewTrack($track);
         }
 
         if (isset($this->_input['cover_id'])) {
@@ -174,12 +181,13 @@ class EditTrackCommand extends CommandBase
         return CommandResponse::succeed(['real_cover_url' => $track->getCoverUrl(Image::NORMAL)]);
     }
 
-    private function removeTrackFromAlbum($track)
+    private function removeTrackFromAlbum(Track $track)
     {
         $album = $track->album;
         $index = 0;
 
         foreach ($album->tracks as $track) {
+            /** @var $track Track */
             if ($track->id == $this->_trackId) {
                 continue;
             }

app/Commands/ToggleFavouriteCommand.php

@@ -20,10 +20,14 @@
 
 namespace Poniverse\Ponyfm\Commands;
 
+use Notification;
+use Poniverse\Ponyfm\Contracts\Favouritable;
 use Poniverse\Ponyfm\Models\Favourite;
+use Poniverse\Ponyfm\Models\Playlist;
 use Poniverse\Ponyfm\Models\ResourceUser;
 use Illuminate\Support\Facades\Auth;
 use Illuminate\Support\Facades\DB;
+use Poniverse\Ponyfm\Models\Track;
 
 class ToggleFavouriteCommand extends CommandBase
 {
@@ -45,6 +49,20 @@ class ToggleFavouriteCommand extends CommandBase
 
         return $user != null;
     }
+    
+    private function getEntityBeingFavourited():Favouritable
+    {
+        switch ($this->_resourceType) {
+            case 'track':
+                return Track::find($this->_resourceId);
+            case 'album':
+                return Album::find($this->_resourceId);
+            case 'playlist':
+                return Playlist::find($this->_resourceId);
+            default:
+                throw new \InvalidArgumentException('Unknown resource type given!');
+        }
+    }
 
     /**
      * @throws \Exception
@@ -65,6 +83,8 @@ class ToggleFavouriteCommand extends CommandBase
             $fav->created_at = time();
             $fav->save();
             $isFavourited = true;
+            
+            Notification::newFavourite($this->getEntityBeingFavourited(), $fav->user);
         }
 
         $resourceUser = ResourceUser::get(Auth::user()->id, $this->_resourceType, $this->_resourceId);

app/Commands/ToggleFollowingCommand.php

@@ -22,7 +22,8 @@ namespace Poniverse\Ponyfm\Commands;
 
 use Poniverse\Ponyfm\Models\Follower;
 use Poniverse\Ponyfm\Models\ResourceUser;
-use Illuminate\Support\Facades\Auth;
+use Auth;
+use Notification;
 
 class ToggleFollowingCommand extends CommandBase
 {
@@ -64,6 +65,8 @@ class ToggleFollowingCommand extends CommandBase
             $follow->created_at = time();
             $follow->save();
             $isFollowed = true;
+            
+            Notification::newFollower($follow->artist, Auth::user());
         }
 
         $resourceUser = ResourceUser::get(Auth::user()->id, $this->_resourceType, $this->_resourceId);

app/Contracts/Commentable.php

@@ -0,0 +1,38 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Contracts;
+
+use Illuminate\Database\Eloquent\Relations\HasMany;
+
+/**
+ * This interface is used for type safety when referring to entities that
+ * are capable of accepting comments.
+ *
+ * @package Poniverse\Ponyfm\Contracts
+ */
+interface Commentable extends GeneratesNotifications {
+    /**
+     * This method returns an Eloquent relation to the entity's comments.
+     *
+     * @return HasMany
+     */
+    public function comments():HasMany;
+}

app/Contracts/Favouritable.php

@@ -0,0 +1,38 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Contracts;
+
+use Illuminate\Database\Eloquent\Relations\HasMany;
+
+/**
+ * This interface is used for type safety when referring to entities that
+ * are capable of being favourited.
+ *
+ * @package Poniverse\Ponyfm\Contracts
+ */
+interface Favouritable extends GeneratesNotifications {
+    /**
+     * This method returns an Eloquent relation to the entity's favourites.
+     *
+     * @return HasMany
+     */
+    public function favourites():HasMany;
+}

app/Contracts/GeneratesNotifications.php

@@ -0,0 +1,42 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Contracts;
+
+use Illuminate\Database\Eloquent\Relations\MorphMany;
+use Poniverse\Ponyfm\Models\User;
+
+/**
+ * This interface is used for type safety when referring to entities that can be
+ * the "target resource" of a notification (ie. what the notification is about).
+ *
+ * @package Poniverse\Ponyfm\Contracts
+ */
+interface GeneratesNotifications {
+    /**
+     * Returns a human-friendly string (lowercase & singular) representing this
+     * type of resource.
+     * 
+     * @return string
+     */
+    public function getResourceType():string;
+
+    public function activities():MorphMany;
+}

app/Contracts/NotificationHandler.php

@@ -0,0 +1,68 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Contracts;
+
+use Poniverse\Ponyfm\Models\Comment;
+use Poniverse\Ponyfm\Models\Playlist;
+use Poniverse\Ponyfm\Models\Track;
+use Poniverse\Ponyfm\Models\User;
+
+/**
+ * Interface NotificationHandler
+ * @package Poniverse\Ponyfm\Contracts
+ * 
+ * Each method in this interface represents a type of notification. To add a new
+ * type of notification, add a method for it to this interface and every class
+ * that implements it. Your IDE should be able to help with this.
+ */
+interface NotificationHandler {
+    /**
+     * @param Track $track
+     * @return void
+     */
+    public function publishedNewTrack(Track $track);
+
+    /**
+     * @param Playlist $playlist
+     * @return void
+     */
+    public function publishedNewPlaylist(Playlist $playlist);
+
+    /**
+     * @param User $userBeingFollowed
+     * @param User $follower
+     * @return void
+     */
+    public function newFollower(User $userBeingFollowed, User $follower);
+
+    /**
+     * @param Comment $comment
+     * @return void
+     */
+    public function newComment(Comment $comment);
+
+    /**
+     * @param Favouritable $entityBeingFavourited
+     * @param User $favouriter
+     * @return void
+     */
+    public function newFavourite(Favouritable $entityBeingFavourited, User $favouriter);
+}

app/Facades/Notification.php

@@ -0,0 +1,28 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Facades;
+use Illuminate\Support\Facades\Facade;
+
+class Notification extends Facade {
+    protected static function getFacadeAccessor() {
+        return 'notification';
+    }
+}

app/Http/Controllers/Api/Web/AccountController.php

@@ -20,10 +20,10 @@
 
 namespace Poniverse\Ponyfm\Http\Controllers\Api\Web;
 
+use Carbon\Carbon;
 use Poniverse\Ponyfm\Http\Controllers\ApiControllerBase;
 use Poniverse\Ponyfm\Commands\SaveAccountSettingsCommand;
 use Poniverse\Ponyfm\Models\User;
-use Cover;
 use Gate;
 use Illuminate\Support\Facades\Auth;
 use Illuminate\Support\Facades\Input;

app/Http/Controllers/Api/Web/NotificationsController.php

@@ -0,0 +1,63 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Http\Controllers\Api\Web;
+
+use Auth;
+use Carbon\Carbon;
+use Input;
+use Poniverse\Ponyfm\Http\Controllers\ApiControllerBase;
+use Poniverse\Ponyfm\Models\Notification;
+
+class NotificationsController extends ApiControllerBase
+{
+    /**
+     * Returns the logged-in user's last 20 notifications.
+     *
+     * @return array
+     */
+    public function getNotifications()
+    {
+        $notifications = Notification::forUser(Auth::user())
+            ->take(20)
+            ->get();
+
+
+        return ['notifications' => $notifications->toArray()];
+    }
+
+    /**
+     * This action returns the number of notifications that were updated.
+     * Any notifications that were specified that don't belong to the logged-in
+     * user are ignored.
+     *
+     * @return array
+     */
+    public function putMarkAsRead()
+    {
+        $notificationIds = Input::get('notification_ids');
+        $numberOfUpdatedRows = Auth::user()
+            ->notifications()
+            ->whereIn('id', $notificationIds)
+            ->update(['is_read' => true]);
+
+        return ['notifications_updated' => $numberOfUpdatedRows];
+    }
+}

app/Http/routes.php

@@ -134,6 +134,8 @@ Route::group(['prefix' => 'api/web'], function() {
 
     Route::group(['middleware' => 'auth'], function() {
         Route::get('/account/settings/{slug}', 'Api\Web\AccountController@getSettings');
+        Route::get('/notifications', 'Api\Web\NotificationsController@getNotifications');
+        Route::put('/notifications/mark-as-read', 'Api\Web\NotificationsController@putMarkAsRead');
 
         Route::get('/tracks/owned', 'Api\Web\TracksController@getOwned');
         Route::get('/tracks/edit/{id}', 'Api\Web\TracksController@getEdit');

app/Jobs/SendNotifications.php

@@ -0,0 +1,84 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Jobs;
+
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Queue\InteractsWithQueue;
+use Poniverse\Ponyfm\Jobs\Job;
+use Illuminate\Contracts\Bus\SelfHandling;
+use Poniverse\Ponyfm\Library\Notifications\Drivers\AbstractDriver;
+use Poniverse\Ponyfm\Library\Notifications\Drivers\PonyfmDriver;
+use Poniverse\Ponyfm\Models\User;
+use SerializesModels;
+
+class SendNotifications extends Job implements SelfHandling, ShouldQueue
+{
+    use InteractsWithQueue, SerializesModels;
+
+    protected $notificationType;
+    protected $notificationData;
+
+    /**
+     * Create a new job instance.
+     * @param string $notificationType
+     * @param array $notificationData
+     */
+    public function __construct(string $notificationType, array $notificationData)
+    {
+        $this->notificationType = $notificationType;
+        $this->notificationData = $notificationData;
+    }
+
+    /**
+     * Execute the job.
+     *
+     * @return void
+     */
+    public function handle()
+    {
+        $this->beforeHandle();
+        
+        // get list of users who are supposed to receive this notification
+        $recipients = [User::find(1)];
+
+        foreach ($recipients as $recipient) {
+            // get drivers that this notification should be delivered through
+            $drivers = $this->getDriversForNotification($recipient, $this->notificationType);
+
+            foreach ($drivers as $driver) {
+                /** @var $driver AbstractDriver */
+                call_user_func_array([$driver, $this->notificationType], $this->notificationData);
+            }
+        }
+    }
+
+    /**
+     * Returns the drivers with which the given user has subscribed to the given
+     * notification type.
+     *
+     * @param User $user
+     * @param string $notificationType
+     * @return AbstractDriver[]
+     */
+    private function getDriversForNotification(User $user, string $notificationType) {
+        return [new PonyfmDriver()];
+    }
+}

app/Library/Notifications/Drivers/AbstractDriver.php

@@ -0,0 +1,47 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Library\Notifications\Drivers;
+
+use ArrayAccess;
+use Poniverse\Ponyfm\Contracts\NotificationHandler;
+use Poniverse\Ponyfm\Library\Notifications\RecipientFinder;
+use Poniverse\Ponyfm\Models\User;
+
+abstract class AbstractDriver implements NotificationHandler {
+    private $recipientFinder;
+
+    public function __construct() {
+        $this->recipientFinder = new RecipientFinder(get_class($this));
+    }
+
+    /**
+     * Returns an array of users who are to receive the given notification type.
+     * This method is a wrapper around the {@link RecipientFinder} class, which
+     * does the actual processing for all the drivers.
+     *
+     * @param string $notificationType
+     * @param array $notificationData
+     * @return User[] collection of {@link User} objects
+     */
+    protected function getRecipients(string $notificationType, array $notificationData) {
+        return call_user_func_array([$this->recipientFinder, $notificationType], $notificationData);
+    }
+}

app/Library/Notifications/Drivers/PonyfmDriver.php

@@ -0,0 +1,123 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Library\Notifications\Drivers;
+
+
+use ArrayAccess;
+use Carbon\Carbon;
+use Poniverse\Ponyfm\Contracts\Favouritable;
+use Poniverse\Ponyfm\Models\Activity;
+use Poniverse\Ponyfm\Models\Comment;
+use Poniverse\Ponyfm\Models\Notification;
+use Poniverse\Ponyfm\Models\Playlist;
+use Poniverse\Ponyfm\Models\Track;
+use Poniverse\Ponyfm\Models\User;
+
+class PonyfmDriver extends AbstractDriver {
+    /**
+     * A helper method for bulk insertion of notification records.
+     *
+     * @param int $activityId
+     * @param User[] $recipients collection of {@link User} objects
+     */
+    private function insertNotifications(int $activityId, $recipients) {
+        $notifications = [];
+        foreach ($recipients as $recipient) {
+            $notifications[] = [
+                'activity_id'   => $activityId,
+                'user_id'       => $recipient->id
+            ];
+        }
+        Notification::insert($notifications);
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function publishedNewTrack(Track $track) {
+        $activity = Activity::create([
+            'created_at'    => Carbon::now(),
+            'user_id'       => $track->user_id,
+            'activity_type' => Activity::TYPE_PUBLISHED_TRACK,
+            'resource_type' => Track::class,
+            'resource_id'   => $track->id,
+        ]);
+
+        $this->insertNotifications($activity->id, $this->getRecipients(__FUNCTION__, func_get_args()));
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function publishedNewPlaylist(Playlist $playlist) {
+        $activity = Activity::create([
+            'created_at' => Carbon::now(),
+            'user_id' => $playlist->user_id,
+            'activity_type' => Activity::TYPE_PUBLISHED_PLAYLIST,
+            'resource_type' => Playlist::class,
+            'resource_id' => $playlist->id,
+        ]);
+
+        $this->insertNotifications($activity->id, $this->getRecipients(__FUNCTION__, func_get_args()));
+    }
+
+    public function newFollower(User $userBeingFollowed, User $follower) {
+        $activity = Activity::create([
+            'created_at' => Carbon::now(),
+            'user_id' => $follower->id,
+            'activity_type' => Activity::TYPE_NEW_FOLLOWER,
+            'resource_type' => User::class,
+            'resource_id' => $userBeingFollowed->id,
+        ]);
+
+        $this->insertNotifications($activity->id, $this->getRecipients(__FUNCTION__, func_get_args()));
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function newComment(Comment $comment) {
+        $activity = Activity::create([
+            'created_at' => Carbon::now(),
+            'user_id' => $comment->user_id,
+            'activity_type' => Activity::TYPE_NEW_COMMENT,
+            'resource_type' => Comment::class,
+            'resource_id' => $comment->id,
+        ]);
+
+        $this->insertNotifications($activity->id, $this->getRecipients(__FUNCTION__, func_get_args()));
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function newFavourite(Favouritable $entityBeingFavourited, User $favouriter) {
+        $activity = Activity::create([
+            'created_at' => Carbon::now(),
+            'user_id' => $favouriter->id,
+            'activity_type' => Activity::TYPE_CONTENT_FAVOURITED,
+            'resource_type' => get_class($entityBeingFavourited),
+            'resource_id' => $entityBeingFavourited->id,
+        ]);
+
+        $this->insertNotifications($activity->id, $this->getRecipients(__FUNCTION__, func_get_args()));
+    }
+}

app/Library/Notifications/NotificationManager.php

@@ -0,0 +1,83 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Library\Notifications;
+
+
+use Illuminate\Foundation\Bus\DispatchesJobs;
+use Poniverse\Ponyfm\Contracts\Favouritable;
+use Poniverse\Ponyfm\Contracts\NotificationHandler;
+use Poniverse\Ponyfm\Jobs\SendNotifications;
+use Poniverse\Ponyfm\Models\Comment;
+use Poniverse\Ponyfm\Models\Playlist;
+use Poniverse\Ponyfm\Models\Track;
+use Poniverse\Ponyfm\Models\User;
+
+/**
+ * Class NotificationManager
+ * @package Poniverse\Ponyfm\Library
+ *
+ * This class exists mostly to maintain type safety when sending notifications
+ * from around the Pony.fm codebase. There should be virtually zero logic here.
+ * All the heavy lifting happens asynchronously in the {@link SendNotifications}
+ * job and the notification drivers.
+ */
+class NotificationManager implements NotificationHandler {
+    use DispatchesJobs;
+
+    private function dispatchNotification(string $notificationType, array $notificationData) {
+        $this->dispatch( (new SendNotifications($notificationType, $notificationData))->onQueue('notifications') );
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function publishedNewTrack(Track $track) {
+        $this->dispatchNotification(__FUNCTION__, func_get_args());
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function publishedNewPlaylist(Playlist $playlist) {
+        $this->dispatchNotification(__FUNCTION__, func_get_args());
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function newFollower(User $userBeingFollowed, User $follower) {
+        $this->dispatchNotification(__FUNCTION__, func_get_args());
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function newComment(Comment $comment) {
+        $this->dispatchNotification(__FUNCTION__, func_get_args());
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function newFavourite(Favouritable $entityBeingFavourited, User $favouriter) {
+        $this->dispatchNotification(__FUNCTION__, func_get_args());
+    }
+}

app/Library/Notifications/RecipientFinder.php

@@ -0,0 +1,120 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Library\Notifications;
+
+
+use Illuminate\Foundation\Bus\DispatchesJobs;
+use Poniverse\Ponyfm\Contracts\Favouritable;
+use Poniverse\Ponyfm\Contracts\NotificationHandler;
+use Poniverse\Ponyfm\Jobs\SendNotifications;
+use Poniverse\Ponyfm\Library\Notifications\Drivers\PonyfmDriver;
+use Poniverse\Ponyfm\Models\Comment;
+use Poniverse\Ponyfm\Models\Playlist;
+use Poniverse\Ponyfm\Models\Track;
+use Poniverse\Ponyfm\Models\User;
+
+/**
+ * Class RecipientFinder
+ * @package Poniverse\Ponyfm\Library\Notifications
+ * 
+ * This class returns a list of users who are to receive a particular notification.
+ * It is instantiated on a per-driver basis.
+ */
+class RecipientFinder implements NotificationHandler {
+    /**
+     * @var string class name of a notification driver
+     */
+    private $notificationDriver;
+    
+    public function __construct(string $notificationDriver) {
+        $this->notificationDriver = $notificationDriver;
+    }
+
+    private function fail() {
+        throw new \InvalidArgumentException("Unknown notification driver given: {$this->notificationDriver}");
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function publishedNewTrack(Track $track) {
+        switch ($this->notificationDriver) {
+            case PonyfmDriver::class:
+                return $track->user->followers;
+            default:
+                return $this->fail();
+        }
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function publishedNewPlaylist(Playlist $playlist) {
+        switch ($this->notificationDriver) {
+            case PonyfmDriver::class:
+                return $playlist->user->followers;
+            default:
+                return $this->fail();
+        }
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function newFollower(User $userBeingFollowed, User $follower) {
+        switch ($this->notificationDriver) {
+            case PonyfmDriver::class:
+                return [$userBeingFollowed];
+            default:
+                return $this->fail();
+        }
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function newComment(Comment $comment) {
+        switch ($this->notificationDriver) {
+            case PonyfmDriver::class:
+                return
+                    $comment->user->id === $comment->resource->user->id
+                        ? []
+                        : [$comment->resource->user];
+            default:
+                return $this->fail();
+        }
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function newFavourite(Favouritable $entityBeingFavourited, User $favouriter) {
+        switch ($this->notificationDriver) {
+            case PonyfmDriver::class:
+                return
+                    $favouriter->id === $entityBeingFavourited->user->id
+                        ? []
+                        : [$entityBeingFavourited->user];
+            default:
+                return $this->fail();
+        }
+    }
+}

app/Models/Activity.php

@@ -0,0 +1,205 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Models;
+
+use Illuminate\Database\Eloquent\Model;
+
+/**
+ * Poniverse\Ponyfm\Models\Activity
+ *
+ * @property integer $id
+ * @property \Carbon\Carbon $created_at
+ * @property integer $user_id
+ * @property boolean $activity_type
+ * @property boolean $resource_type
+ * @property integer $resource_id
+ * @property-read \Illuminate\Database\Eloquent\Collection|\Poniverse\Ponyfm\Models\Notification[] $notifications
+ * @property-read \Poniverse\Ponyfm\Models\User $initiatingUser
+ * @property-read \Poniverse\Ponyfm\Models\Activity $resource
+ * @property-read mixed $url
+ * @property-read mixed $thumbnail_url
+ * @property-read mixed $text
+ */
+class Activity extends Model {
+    public $timestamps = false;
+    protected $dates = ['created_at'];
+    protected $fillable = ['created_at', 'user_id', 'activity_type', 'resource_type', 'resource_id'];
+    protected $appends = ['url', 'thumbnail_url', 'human_friendly_resource_type'];
+    protected $casts = [
+        'id'            => 'integer',
+        'created_at'    => 'datetime',
+        'user_id'       => 'integer',
+        'activity_type' => 'integer',
+        // resource_type has its own accessor and mutator
+        'resource_id'   => 'integer',
+    ];
+
+    const TYPE_NEWS = 1;
+    const TYPE_PUBLISHED_TRACK = 2;
+    const TYPE_PUBLISHED_ALBUM = 3;
+    const TYPE_PUBLISHED_PLAYLIST = 4;
+    const TYPE_NEW_FOLLOWER = 5;
+    const TYPE_NEW_COMMENT = 6;
+    const TYPE_CONTENT_FAVOURITED = 7;
+
+    /**
+     * These "target" constants are an implementation detail of this model and
+     * should not be used directly in other classes. They're used to efficiently
+     * store the type of resource this notification is about in the database.
+     *
+     * The "resource_type" attribute is transformed into a class name at runtime
+     * so that the use of an integer in the database to represent this info
+     * remains an implementation detail of this model. Outside of this class,
+     * the resource_type attribute should be treated as a fully-qualified class
+     * name.
+     */
+    const TARGET_USER = 1;
+    const TARGET_TRACK = 2;
+    const TARGET_ALBUM = 3;
+    const TARGET_PLAYLIST = 4;
+    const TARGET_COMMENT = 5;
+
+    public function initiatingUser() {
+        return $this->belongsTo(User::class, 'user_id', 'id');
+    }
+
+    public function notifications() {
+        return $this->hasMany(Notification::class, 'activity_id', 'id');
+    }
+    
+    public function notificationRecipients() {
+        return $this->hasManyThrough(User::class, Notification::class, 'activity_id', 'user_id', 'id');
+    }
+
+    public function resource() {
+        return $this->morphTo('resource', 'resource_type', 'resource_id');
+    }
+
+    public function getUrlAttribute() {
+        return $this->resource->url;
+    }
+    
+    public function getResourceTypeAttribute($value) {
+        switch ($value) {
+            case static::TARGET_USER:
+                return User::class;
+
+            case static::TARGET_TRACK:
+                return Track::class;
+
+            case static::TARGET_ALBUM:
+                return Album::class;
+
+            case static::TARGET_PLAYLIST:
+                return Playlist::class;
+
+            case static::TARGET_COMMENT:
+                return Comment::class;
+            
+            default:
+                // Null must be returned here for Eloquent's eager-loading
+                // of the polymorphic relation to work.
+                return NULL;
+                
+        }
+    }
+
+    public function setResourceTypeAttribute($value) {
+        switch ($value) {
+            case User::class:
+                $this->attributes['resource_type'] = static::TARGET_USER;
+                break;
+
+            case Track::class:
+                $this->attributes['resource_type'] = static::TARGET_TRACK;
+                break;
+
+            case Album::class:
+                $this->attributes['resource_type'] = static::TARGET_ALBUM;
+                break;
+
+            case Playlist::class:
+                $this->attributes['resource_type'] = static::TARGET_PLAYLIST;
+                break;
+
+            case Comment::class:
+                $this->attributes['resource_type'] = static::TARGET_COMMENT;
+                break;
+        }
+    }
+
+    public function getThumbnailUrlAttribute()
+    {
+        switch ($this->resource_type) {
+            case User::class:
+                return $this->resource->getAvatarUrl(Image::THUMBNAIL);
+
+            case Track::class:
+            case Album::class:
+            case Playlist::class:
+                return $this->resource->getCoverUrl(Image::THUMBNAIL);
+
+            case Comment::class:
+                return $this->resource->user->getAvatarUrl(Image::THUMBNAIL);
+
+            default:
+                throw new \Exception('This activity\'s resource is of an unknown type!');
+        }
+    }
+
+    /**
+     * @return string human-readable Markdown string describing this notification
+     * @throws \Exception
+     */
+    public function getTextAttribute()
+    {
+        switch ($this->activity_type) {
+            case static::TYPE_NEWS:
+                // not implemented yet
+                throw new \InvalidArgumentException('This type of activity has not been implemented yet!');
+
+            case static::TYPE_PUBLISHED_TRACK:
+                return "{$this->resource->user->display_name} published a new track, __{$this->resource->title}__!";
+
+            case static::TYPE_PUBLISHED_PLAYLIST:
+                return "{$this->resource->user->display_name} published a new playlist, __{$this->resource->title}__!";
+
+            case static::TYPE_NEW_FOLLOWER:
+                return "{$this->initiatingUser->display_name} is now following you!";
+
+            case static::TYPE_NEW_COMMENT:
+                // Is this a profile comment?
+                if ($this->resource_type === User::class) {
+                    return "{$this->initiatingUser->display_name} left a comment on your profile!";
+
+                // Must be a content comment.
+                } else {
+                    return "{$this->initiatingUser->display_name} left a comment on your {$this->resource->resource->getResourceType()}, __{$this->resource->resource->title}__!";
+                }
+            
+            case static::TYPE_CONTENT_FAVOURITED:
+                return "{$this->initiatingUser->display_name} favourited your {$this->resource->type}, __{$this->resource->title}__!";
+
+            default:
+                throw new \Exception('This activity\'s activity type is unknown!');
+        }
+    }
+}

app/Models/Album.php

@@ -23,10 +23,14 @@ namespace Poniverse\Ponyfm\Models;
 use Exception;
 use Helpers;
 use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\MorphMany;
 use Illuminate\Database\Eloquent\SoftDeletes;
 use Auth;
 use Gate;
 use Cache;
+use Poniverse\Ponyfm\Contracts\Commentable;
+use Poniverse\Ponyfm\Contracts\Favouritable;
 use Poniverse\Ponyfm\Contracts\Searchable;
 use Poniverse\Ponyfm\Exceptions\TrackFileNotFoundException;
 use Poniverse\Ponyfm\Traits\IndexedInElasticsearchTrait;
@@ -60,8 +64,9 @@ use Venturecraft\Revisionable\RevisionableTrait;
  * @property-read mixed $url
  * @property-read \Illuminate\Database\Eloquent\Collection|\Venturecraft\Revisionable\Revision[] $revisionHistory
  * @method static \Illuminate\Database\Query\Builder|\Poniverse\Ponyfm\Models\Album userDetails()
+ * @property-read \Illuminate\Database\Eloquent\Collection|\Poniverse\Ponyfm\Models\Activity[] $activities
  */
-class Album extends Model implements Searchable
+class Album extends Model implements Searchable, Commentable, Favouritable
 {
     use SoftDeletes, SlugTrait, TrackCollection, RevisionableTrait, IndexedInElasticsearchTrait;
 
@@ -101,7 +106,7 @@ class Album extends Model implements Searchable
         return $this->hasMany('Poniverse\Ponyfm\Models\ResourceUser');
     }
 
-    public function favourites()
+    public function favourites():HasMany
     {
         return $this->hasMany('Poniverse\Ponyfm\Models\Favourite');
     }
@@ -120,11 +125,15 @@ class Album extends Model implements Searchable
         return $this->hasManyThrough(TrackFile::class, Track::class, 'album_id', 'track_id');
     }
 
-    public function comments()
+    public function comments():HasMany
     {
         return $this->hasMany('Poniverse\Ponyfm\Models\Comment')->orderBy('created_at', 'desc');
     }
 
+    public function activities():MorphMany {
+        return $this->morphMany(Activity::class, 'resource');
+    }
+
     public static function mapPublicAlbumShow(Album $album)
     {
         $tracks = [];
@@ -429,4 +438,14 @@ class Album extends Model implements Searchable
     public function shouldBeIndexed():bool {
         return $this->track_count > 0 && !$this->trashed();
     }
+
+    /**
+     * Returns the corresponding resource type ID from the Activity class for
+     * this resource.
+     *
+     * @return string
+     */
+    public function getResourceType():string {
+        return 'album';
+    }
 }

app/Models/Comment.php

@@ -21,7 +21,10 @@
 namespace Poniverse\Ponyfm\Models;
 
 use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\MorphMany;
 use Illuminate\Database\Eloquent\SoftDeletes;
+use Poniverse\Ponyfm\Contracts\Commentable;
+use Poniverse\Ponyfm\Contracts\GeneratesNotifications;
 
 /**
  * Poniverse\Ponyfm\Models\Comment
@@ -42,7 +45,9 @@ use Illuminate\Database\Eloquent\SoftDeletes;
  * @property-read \Poniverse\Ponyfm\Models\Album $album
  * @property-read \Poniverse\Ponyfm\Models\Playlist $playlist
  * @property-read \Poniverse\Ponyfm\Models\User $profile
- * @property-read mixed $resource
+ * @property-read Commentable $resource
+ * @property-read \Illuminate\Database\Eloquent\Collection|\Poniverse\Ponyfm\Models\Activity[] $activities
+ * @property-read mixed $url
  */
 class Comment extends Model
 {
@@ -78,6 +83,16 @@ class Comment extends Model
         return $this->belongsTo('Poniverse\Ponyfm\Models\User', 'profile_id');
     }
 
+    public function activities():MorphMany
+    {
+        return $this->morphMany(Activity::class, 'resource');
+    }
+
+    public function getUrlAttribute()
+    {
+        return $this->resource->url;
+    }
+
     public static function mapPublic($comment)
     {
         return [
@@ -97,7 +112,7 @@ class Comment extends Model
         ];
     }
 
-    public function getResourceAttribute()
+    public function getResourceAttribute():Commentable
     {
         if ($this->track_id !== null) {
             return $this->track;

app/Models/Follower.php

@@ -21,6 +21,7 @@
 namespace Poniverse\Ponyfm\Models;
 
 use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
 
 /**
  * Poniverse\Ponyfm\Models\Follower
@@ -30,10 +31,21 @@ use Illuminate\Database\Eloquent\Model;
  * @property integer $artist_id
  * @property integer $playlist_id
  * @property string $created_at
+ * @property-read \Poniverse\Ponyfm\Models\User $follower
+ * @property-read \Poniverse\Ponyfm\Models\User $artist
  */
 class Follower extends Model
 {
     protected $table = 'followers';
 
     public $timestamps = false;
+
+
+    public function follower():BelongsTo {
+        return $this->belongsTo(User::class, 'user_id');
+    }
+
+    public function artist():BelongsTo {
+        return $this->belongsTo(User::class, 'artist_id');
+    }
 }

app/Models/Notification.php

@@ -0,0 +1,83 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Models;
+
+use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Database\Eloquent\Model;
+
+/**
+ * Poniverse\Ponyfm\Models\Notification
+ *
+ * @property integer $id
+ * @property integer $activity_id
+ * @property integer $user_id
+ * @property boolean $is_read
+ * @property-read \Poniverse\Ponyfm\Models\Activity $activity
+ * @property-read \Poniverse\Ponyfm\Models\User $recipient
+ * @method static \Illuminate\Database\Query\Builder|\Poniverse\Ponyfm\Models\Notification forUser($user)
+ */
+class Notification extends Model {
+    public $timestamps = false;
+    protected $fillable = ['activity_id', 'user_id'];
+    protected $casts = [
+        'id'            => 'integer',
+        'activity_id'   => 'integer',
+        'user_id'       => 'integer',
+        'is_read'       => 'boolean',
+    ];
+
+    public function activity() {
+        return $this->belongsTo(Activity::class, 'activity_id', 'id');
+    }
+    
+    public function recipient() {
+        return $this->belongsTo(User::class, 'user_id', 'id');
+    }
+
+    /**
+     * This scope grabs eager-loaded notifications for the given user.
+     *
+     * @param Builder $query
+     * @param User $user
+     * @return Builder
+     */
+    public function scopeForUser(Builder $query, User $user) {
+        return $query->with([
+            'activity',
+            'activity.initiatingUser',
+            'activity.resource',
+            'activity.resource.user',
+        ])
+         ->join('activities', 'notifications.activity_id', '=', 'activities.id')
+         ->where('notifications.user_id', $user->id)
+         ->orderBy('activities.created_at', 'DESC');
+    }
+
+    public function toArray() {
+        return [
+            'id'            => $this->id,
+            'date'          => $this->activity->created_at->toAtomString(),
+            'thumbnail_url' => $this->activity->thumbnail_url,
+            'text'          => $this->activity->text,
+            'url'           => $this->activity->url
+        ];
+    }
+}

app/Models/Playlist.php

@@ -22,10 +22,14 @@ namespace Poniverse\Ponyfm\Models;
 
 use Helpers;
 use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\MorphMany;
 use Illuminate\Database\Eloquent\SoftDeletes;
 use Illuminate\Foundation\Bus\DispatchesJobs;
 use Auth;
 use Cache;
+use Poniverse\Ponyfm\Contracts\Commentable;
+use Poniverse\Ponyfm\Contracts\Favouritable;
 use Poniverse\Ponyfm\Contracts\Searchable;
 use Poniverse\Ponyfm\Exceptions\TrackFileNotFoundException;
 use Poniverse\Ponyfm\Traits\IndexedInElasticsearchTrait;
@@ -59,8 +63,10 @@ use Venturecraft\Revisionable\RevisionableTrait;
  * @property-read mixed $url
  * @property-read \Illuminate\Database\Eloquent\Collection|\Venturecraft\Revisionable\Revision[] $revisionHistory
  * @method static \Illuminate\Database\Query\Builder|\Poniverse\Ponyfm\Models\Playlist userDetails()
+ * @property-read \Illuminate\Database\Eloquent\Collection|\Poniverse\Ponyfm\Models\Favourite[] $favourites
+ * @property-read \Illuminate\Database\Eloquent\Collection|\Poniverse\Ponyfm\Models\Activity[] $activities
  */
-class Playlist extends Model implements Searchable
+class Playlist extends Model implements Searchable, Commentable, Favouritable
 {
     use SoftDeletes, SlugTrait, TrackCollection, RevisionableTrait, IndexedInElasticsearchTrait;
 
@@ -212,7 +218,7 @@ class Playlist extends Model implements Searchable
         return $this->hasMany('Poniverse\Ponyfm\Models\ResourceUser');
     }
 
-    public function comments()
+    public function comments():HasMany
     {
         return $this->hasMany('Poniverse\Ponyfm\Models\Comment')->orderBy('created_at', 'desc');
     }
@@ -221,12 +227,20 @@ class Playlist extends Model implements Searchable
     {
         return $this->hasMany('Poniverse\Ponyfm\Models\PinnedPlaylist');
     }
+    
+    public function favourites():HasMany {
+        return $this->hasMany(Favourite::class);
+    }
 
     public function user()
     {
         return $this->belongsTo('Poniverse\Ponyfm\Models\User');
     }
 
+    public function activities():MorphMany {
+        return $this->morphMany(Activity::class, 'resource');
+    }
+
     public function hasPinFor($userId)
     {
         foreach ($this->pins as $pin) {
@@ -324,4 +338,11 @@ class Playlist extends Model implements Searchable
                $this->track_count > 0 &&
                !$this->trashed();
     }
+
+    /**
+     * @inheritdoc
+     */
+    public function getResourceType():string {
+        return 'playlist';
+    }
 }

app/Models/Track.php

@@ -25,6 +25,10 @@ use Cache;
 use Config;
 use DB;
 use Gate;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\MorphMany;
+use Poniverse\Ponyfm\Contracts\Commentable;
+use Poniverse\Ponyfm\Contracts\Favouritable;
 use Poniverse\Ponyfm\Contracts\Searchable;
 use Poniverse\Ponyfm\Exceptions\TrackFileNotFoundException;
 use Poniverse\Ponyfm\Traits\IndexedInElasticsearchTrait;
@@ -95,8 +99,10 @@ use Venturecraft\Revisionable\RevisionableTrait;
  * @method static \Illuminate\Database\Query\Builder|\Poniverse\Ponyfm\Models\Track explicitFilter()
  * @method static \Illuminate\Database\Query\Builder|\Poniverse\Ponyfm\Models\Track withComments()
  * @method static \Illuminate\Database\Query\Builder|\Poniverse\Ponyfm\Models\Track mlpma()
+ * @property-read \Illuminate\Database\Eloquent\Collection|\Poniverse\Ponyfm\Models\Activity[] $notifications
+ * @property-read \Illuminate\Database\Eloquent\Collection|\Poniverse\Ponyfm\Models\Activity[] $activities
  */
-class Track extends Model implements Searchable
+class Track extends Model implements Searchable, Commentable, Favouritable
 {
     use SoftDeletes, IndexedInElasticsearchTrait;
 
@@ -486,12 +492,12 @@ class Track extends Model implements Searchable
         return $this->belongsTo('Poniverse\Ponyfm\Models\TrackType', 'track_type_id');
     }
 
-    public function comments()
+    public function comments():HasMany
     {
         return $this->hasMany('Poniverse\Ponyfm\Models\Comment')->orderBy('created_at', 'desc');
     }
 
-    public function favourites()
+    public function favourites():HasMany
     {
         return $this->hasMany('Poniverse\Ponyfm\Models\Favourite');
     }
@@ -526,6 +532,15 @@ class Track extends Model implements Searchable
         return $this->hasMany('Poniverse\Ponyfm\Models\TrackFile');
     }
 
+    public function notifications()
+    {
+        return $this->morphMany(Activity::class, 'notification_type');
+    }
+
+    public function activities():MorphMany {
+        return $this->morphMany(Activity::class, 'resource');
+    }
+
     public function getYearAttribute()
     {
         return date('Y', strtotime($this->getReleaseDate()));
@@ -863,4 +878,8 @@ class Track extends Model implements Searchable
             'show_songs'    => $this->showSongs->pluck('title')
         ];
     }
+
+    public function getResourceType():string {
+        return 'track';
+    }
 }

app/Models/User.php

@@ -26,9 +26,12 @@ use Illuminate\Auth\Passwords\CanResetPassword;
 use Illuminate\Contracts\Auth\Authenticatable as AuthenticatableContract;
 use Illuminate\Contracts\Auth\CanResetPassword as CanResetPasswordContract;
 use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\MorphMany;
 use Illuminate\Foundation\Auth\Access\Authorizable;
 use Auth;
 use Illuminate\Support\Str;
+use Poniverse\Ponyfm\Contracts\Commentable;
 use Poniverse\Ponyfm\Contracts\Searchable;
 use Poniverse\Ponyfm\Traits\IndexedInElasticsearchTrait;
 use Venturecraft\Revisionable\RevisionableTrait;
@@ -63,8 +66,12 @@ use Venturecraft\Revisionable\RevisionableTrait;
  * @property-read mixed $message_url
  * @property-read \Illuminate\Database\Eloquent\Collection|\Venturecraft\Revisionable\Revision[] $revisionHistory
  * @method static \Illuminate\Database\Query\Builder|\Poniverse\Ponyfm\Models\User userDetails()
+ * @property-read \Illuminate\Database\Eloquent\Collection|\Poniverse\Ponyfm\Models\Notification[] $notifications
+ * @property-read \Illuminate\Database\Eloquent\Collection|\Poniverse\Ponyfm\Models\User[] $followers
+ * @property-read mixed $user
+ * @property-read \Illuminate\Database\Eloquent\Collection|\Poniverse\Ponyfm\Models\Activity[] $activities
  */
-class User extends Model implements AuthenticatableContract, CanResetPasswordContract, \Illuminate\Contracts\Auth\Access\Authorizable, Searchable
+class User extends Model implements AuthenticatableContract, CanResetPasswordContract, \Illuminate\Contracts\Auth\Access\Authorizable, Searchable, Commentable
 {
     use Authenticatable, CanResetPassword, Authorizable, RevisionableTrait, IndexedInElasticsearchTrait;
 
@@ -133,13 +140,18 @@ class User extends Model implements AuthenticatableContract, CanResetPasswordCon
     {
         return $this->hasMany('Poniverse\Ponyfm\Models\ResourceUser', 'artist_id');
     }
+    
+    public function followers()
+    {
+        return $this->belongsToMany(User::class, 'followers', 'artist_id', 'user_id');
+    }
 
     public function roles()
     {
         return $this->belongsToMany(Role::class, 'role_user');
     }
 
-    public function comments()
+    public function comments():HasMany
     {
         return $this->hasMany('Poniverse\Ponyfm\Models\Comment', 'profile_id')->orderBy('created_at', 'desc');
     }
@@ -148,6 +160,16 @@ class User extends Model implements AuthenticatableContract, CanResetPasswordCon
     {
         return $this->hasMany('Poniverse\Ponyfm\Models\Track', 'user_id');
     }
+    
+    public function notifications()
+    {
+        return $this->hasMany(Notification::class, 'user_id');
+    }
+
+    public function notificationActivities()
+    {
+        return $this->hasManyThrough(Activity::class, Notification::class, 'user_id', 'notification_id', 'id');
+    }
 
     public function getIsArchivedAttribute()
     {
@@ -235,6 +257,21 @@ class User extends Model implements AuthenticatableContract, CanResetPasswordCon
         return "remember_token";
     }
 
+    public function getUserAttribute():User {
+        return $this;
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function getResourceType():string {
+        return 'profile';
+    }
+
+    public function activities():MorphMany {
+        return $this->morphMany(Activity::class, 'resource');
+    }
+
     /**
      * Returns true if this user has the given role.
      *

app/Providers/AppServiceProvider.php

@@ -20,6 +20,7 @@
 
 namespace Poniverse\Ponyfm\Providers;
 
+use Illuminate\Database\Eloquent\Relations\Relation;
 use Illuminate\Foundation\Application;
 use Illuminate\Support\ServiceProvider;
 use PfmValidator;
@@ -58,5 +59,16 @@ class AppServiceProvider extends ServiceProvider
                 $app['config']->get('ponyfm.elasticsearch_index')
             );
         });
+
+        // NOTE: Use integer keys exclusively for Pony.fm's morphMap to avoid
+        //       any weirdness with merging array indices. $merge = false is
+        //       set below so that no morphMap array merging happens!
+        Relation::morphMap([
+            Poniverse\Ponyfm\Models\Activity::TARGET_TRACK => Poniverse\Ponyfm\Models\Track::class,
+            Poniverse\Ponyfm\Models\Activity::TARGET_ALBUM => Poniverse\Ponyfm\Models\Album::class,
+            Poniverse\Ponyfm\Models\Activity::TARGET_PLAYLIST => Poniverse\Ponyfm\Models\Playlist::class,
+            Poniverse\Ponyfm\Models\Activity::TARGET_USER => Poniverse\Ponyfm\Models\User::class,
+            Poniverse\Ponyfm\Models\Activity::TARGET_COMMENT => Poniverse\Ponyfm\Models\Comment::class,
+        ], false);
     }
 }

app/Providers/NotificationServiceProvider.php

@@ -0,0 +1,50 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+namespace Poniverse\Ponyfm\Providers;
+
+use Illuminate\Foundation\Application;
+use Illuminate\Support\ServiceProvider;
+use Poniverse\Ponyfm\Library\Notifications\NotificationManager;
+
+class NotificationServiceProvider extends ServiceProvider
+{
+    /**
+     * Bootstrap the application services.
+     *
+     * @return void
+     */
+    public function boot()
+    {
+        //
+    }
+
+    /**
+     * Register the application services.
+     *
+     * @return void
+     */
+    public function register()
+    {
+        $this->app->singleton('notification', function(Application $app){
+            return new NotificationManager();
+        });
+    }
+}

config/app.php

@@ -145,6 +145,7 @@ return [
         Poniverse\Ponyfm\Providers\EventServiceProvider::class,
         Poniverse\Ponyfm\Providers\RouteServiceProvider::class,
         Poniverse\Ponyfm\Providers\AuthServiceProvider::class,
+        Poniverse\Ponyfm\Providers\NotificationServiceProvider::class,
 
         Intouch\LaravelNewrelic\NewrelicServiceProvider::class,
         Barryvdh\LaravelIdeHelper\IdeHelperServiceProvider::class,
@@ -201,6 +202,7 @@ return [
 
         'Elasticsearch' => Cviebrock\LaravelElasticsearch\Facade::class,
         'Newrelic'  => Intouch\LaravelNewrelic\Facades\Newrelic::class,
+        'Notification'  => Poniverse\Ponyfm\Facades\Notification::class,
 
     ],
 

database/migrations/2016_04_06_152844_create_notifications_tables.php

@@ -0,0 +1,64 @@
+<?php
+
+/**
+ * Pony.fm - A community for pony fan music.
+ * Copyright (C) 2016 Peter Deltchev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Migrations\Migration;
+
+class CreateNotificationsTables extends Migration
+{
+    /**
+     * Run the migrations.
+     *
+     * @return void
+     */
+    public function up()
+    {
+        Schema::create('activities', function(Blueprint $table){
+            $table->bigIncrements('id');
+            $table->dateTime('created_at')->index();
+            $table->unsignedInteger('user_id'); // initiator of the action
+            $table->unsignedTinyInteger('activity_type');
+            $table->unsignedTinyInteger('resource_type');
+            $table->unsignedInteger('resource_id'); // ID of the entity this activity is about
+        });
+
+        Schema::create('notifications', function(Blueprint $table){
+            // Notifications are a pivot table between activities and users.
+            $table->bigIncrements('id');
+            $table->unsignedBigInteger('activity_id')->index();
+            $table->unsignedInteger('user_id')->index(); // recipient of the notification
+            $table->boolean('is_read')->default(false)->index();
+            
+            $table->foreign('activity_id')->references('id')->on('activities')->onDelete('cascade');
+            $table->foreign('user_id')->references('id')->on('users');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     *
+     * @return void
+     */
+    public function down()
+    {
+        Schema::drop('notifications');
+        Schema::drop('activities');
+    }
+}

documentation/notifications.md

@@ -0,0 +1,94 @@
+Developing notifications for Pony.fm
+====================================
+
+Pony.fm's notification system is designed around "drivers" for various
+notification delivery methods. The types of notification one can receive
+are defined in the
+[`NotificationHandler`](app/Contracts/NotificationHandler.php)
+interface, which is implemented by every class that needs to know about
+the various notification types.
+
+
+Sending a notification
+----------------------
+
+The `Notification` facade is used to send notifications as follows:
+
+```php
+use Notification;
+
+// Something happens, like a  newtrack getting published.
+$track = new Track();
+...
+
+// The "something" is done happening! Time to send a notification.
+Notification::publishedTrack($track);
+```
+
+This facade has a method for every notification type, drawn from the
+[`NotificationHandler`](../app/Contracts/NotificationHandler.php) interface.
+Each of these methods accepts the data needed to build a notification
+message and a list of the notification's recipients.
+
+
+Adding new notification types
+-----------------------------
+
+1. Add a method for the new notification type to the
+   [`NotificationHandler`](../app/Contracts/NotificationHandler.php)
+   interface.
+   
+2. Implement the new methods in every class that implements the
+   interface. Use your IDE to find these. An inexhaustive list:
+   
+   - [`NotificationManager`](../app/Library/Notifications/NotificationManager.php)
+   - [`RecipientFinder`](../app/Library/Notifications/RecipientFinder.php)
+   - [`PonyfmDriver`](../app/Library/Notifications/PonyfmDriver.php)
+
+3. Call the new method on the `Notification` facade from wherever the
+   new notification gets triggered.
+   
+4. Implement any necessary logic for the new notification type in the
+   [`Activity`](../app/Models/Activity.php) model.
+
+
+Adding new notification drivers
+-------------------------------
+
+1. Create a new class for the driver that implements the
+   [`NotificationHandler`](../app/Contracts/NotificationHandler.php)
+   interface.
+
+2. Make each method from the above interface send the corresponding type
+   of notification to everyone who is to receive it via that driver.
+   Implement UI and API integrations as needed.
+   
+3. Modify the
+   [`RecipientFinder`](../app/Library/Notifications/RecipientFinder.php)
+   class to build recipient lists for the new driver.
+   
+
+Architectural notes
+-------------------
+
+The notification system is designed around two ideas: being as type-safe
+as PHP allows it to be, and doing all the processing and sending of
+notifications asynchronously.
+
+To that end, the
+[`NotificationManager`](../app/Library/Notifications/NotificationManager.php)
+class is a thin wrapper around the `SendNotifications` job. The job
+calls the notification drivers asynchronously to actually send the
+notifications. This job should run on a dedicated queue in production.
+
+The [`NotificationHandler`](../app/Contracts/NotificationHandler.php)
+interface is key to maintaining type safety - it ensures that drivers
+and `NotificationManager` all support every type of notification. All
+classes that have logic specific to a notification type implement this
+interface to ensure that all notification types are handled.
+
+There's one exception to the use of `NotificationHandler` - the 
+[`Activity`](../app/Models/Activity.php) model. The logic for mapping the
+data we store about an activity in the database to a notification's API
+representation had to go somewhere, and using the `NotificationHandler`
+interface here would have made this logic a lot more obtuse.

resources/assets/scripts/app/app.coffee

@@ -285,6 +285,11 @@ ponyfm.config [
                 url: '/'
                 templateUrl: '/templates/dashboard/index.html'
                 controller: 'dashboard'
+
+            state.state 'notifications',
+                url: '/notifications'
+                templateUrl: '/templates/notifications/index.html'
+                controller: 'notifications'
         else
             state.state 'home',
                 url: '/'

resources/assets/scripts/app/controllers/notifications.coffee

@@ -0,0 +1,22 @@
+# Pony.fm - A community for pony fan music.
+# Copyright (C) 2016 Josef Citrine
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+module.exports = angular.module('ponyfm').controller "notifications", [
+    '$scope', 'notifications'
+    ($scope, notifications) ->
+        notifications.getNotifications().done (result) ->
+            console.log result
+]

resources/assets/scripts/app/services/notifications.coffee

@@ -0,0 +1,30 @@
+# Pony.fm - A community for pony fan music.
+# Copyright (C) 2016 Josef Citrine
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+module.exports = angular.module('ponyfm').factory('notifications', [
+    '$rootScope', '$http'
+    ($rootScope, $http) ->
+        self =
+            getNotifications: () ->
+                def = new $.Deferred()
+
+                $http.get('/api/web/account/notifications').success (response) ->
+                    def.resolve response
+
+                def.promise()
+
+        self
+])