migrating user preferences obviously works on empty table

framework/core/migrations/2018_01_30_222800_create_notification_preferences_table.php

@@ -0,0 +1,30 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Schema\Builder;
+
+return [
+    'up' => function (Builder $schema) {
+        $schema->create('notification_preferences', function (Blueprint $table) {
+            $table->integer('user_id')->unsigned();
+            $table->string('type');
+            $table->string('channel');
+            $table->boolean('enabled')->default(false);
+
+            $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
+        });
+    },
+
+    'down' => function (Builder $schema) {
+        $schema->drop('notification_preferences');
+    }
+];

framework/core/migrations/2018_01_30_222800_create_users_table_preferences_columns.php

@@ -0,0 +1,27 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Schema\Builder;
+
+return [
+    'up' => function (Builder $schema) {
+        $schema->table('users', function (Blueprint $table) {
+            $table->boolean('disclose_online')->default(false);
+        });
+    },
+
+    'down' => function (Builder $schema) {
+        $schema->table('users', function (Blueprint $table) {
+            $table->dropColumn('disclose_online');
+        });
+    }
+];

framework/core/migrations/2018_01_30_222801_migrate_users_table_preferences_columns.php

@@ -0,0 +1,51 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+use Illuminate\Database\Eloquent\Collection;
+use Illuminate\Database\Schema\Builder;
+use Illuminate\Support\Arr;
+
+return [
+    'up' => function (Builder $builder) {
+        $db = $builder->getConnection();
+
+        $db->table('users')
+            ->whereNotNull('preferences')
+            ->orderBy('id')
+            ->chunk(50, function (Collection $users) use ($db) {
+                $users->each(function ($user) use ($db) {
+                    collect(json_decode(Arr::get($user, 'preferences', '{}')))
+                        ->each(function ($value, $key) use ($user, $db) {
+                            if ($key === 'discloses_online') {
+                                $db->table('users')
+                                    ->where('id', $user['id'])
+                                    ->update(['discloses_online' => (bool) $value]);
+                            }
+                            if (preg_match('/^notify_(?<type>[^_]+)_(?<channel>.*)$/', $key, $matches)) {
+                                $db->table('notification_preferences')
+                                    ->insert([
+                                        'user_id' => $user['id'],
+                                        'type' => $matches['type'],
+                                        'channel' => $matches['channel'],
+                                        'enabled' => (bool) $value
+                                    ]);
+                            }
+                        });
+                });
+            });
+    },
+
+    'down' => function (Builder $builder) {
+        $db = $builder->getConnection();
+
+        $db->table('notification_preferences')->truncate();
+    }
+];