Laravel Eloquent 用户与朋友的关系

我对雄辩的关系感到困惑。我有两张桌子：

USERS:
id, name, pwd, etc...

FRIENDS:
id, user_id, friend_id

对于 FRIENDS 表，我有两个外键：

$t->foreign('user_id')
  ->references('id')
  ->on('users');

$t->foreign('friend_id')
  ->references('id')
  ->on('users');

在每个班级中我都有以下关系：

用户类别：

/**
 * A user can have many friends
 */
public function friends()
{
    return $this->hasMany(User::class, 'friend_id', 'id');
}

朋友班：

/**
 * A friend can belong to a user
 */
public function friend()
{
    return $this->belongsTo(User::class, 'id', 'user_id');
}

/**
 * A user friends are connected to
 */
public function user()
{
    return $this->belongsTo(User::class, 'id', 'friend_id');
}

我想结束

Auth::user()->friends()->get();

关系是否应该是hasManyThrough()？当 USERS 表通过 FRIENDS 表自引用时，如何实现此功能？

移民：

public function up()
{
    Schema::create('friend_user', function(Blueprint $table) {
        $table->increments('id');
        $table->integer('friend_id')->unsigned()->index();
        $table->integer('user_id')->unsigned()->index();
        $table->foreign('friend_id')->references('id')->on('users')->onDelete('cascade');
        $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
    });
}

用户模型：

public function friends()
{
    return $this->belongsToMany(User::class, 'friend_user', 'user_id', 'friend_id');
}

UPDATE

获取所有好友：

Auth::user()->friends (or Auth::user()->friends()->get())

添加朋友：

Auth::user()->friends()->attach([2,3,4]); // Add user_id 2, 3 and 4

删除好友：

Auth::user()->friends()->detach([2]); // Remove user_id = 2

同步好友：

Auth::user()->friends()->sync([7]); // Remove old and add user_id = 7