<?php
 
 namespace Illuminate\Contracts\Support;
 
 interface MessageBag extends Arrayable
 {
     /**
      * Get the keys present in the message bag.
      *
      * @return array
      */
     public function keys();
 
     /**
      * Add a message to the bag.
      *
      * @param  string  $key
      * @param  string  $message
      * @return $this
      */
     public function add($key, $message);
 
     /**
      * Merge a new array of messages into the bag.
      *
      * @param  \Illuminate\Contracts\Support\MessageProvider|array  $messages
      * @return $this
      */
     public function merge($messages);
 
     /**
      * Determine if messages exist for a given key.
      *
      * @param  string|array  $key
      * @return bool
      */
     public function has($key);
 
     /**
      * Get the first message from the bag for a given key.
      *
      * @param  string|null  $key
      * @param  string|null  $format
      * @return string
      */
     public function first($key = null, $format = null);
 
     /**
      * Get all of the messages from the bag for a given key.
      *
      * @param  string  $key
      * @param  string|null  $format
      * @return array
      */
     public function get($key, $format = null);
 
     /**
      * Get all of the messages for every key in the bag.
      *
      * @param  string|null  $format
      * @return array
      */
     public function all($format = null);
 
     /**
      * Get the raw messages in the container.
      *
      * @return array
      */
     public function getMessages();
 
     /**
      * Get the default message format.
      *
      * @return string
      */
     public function getFormat();
 
     /**
      * Set the default message format.
      *
      * @param  string  $format
      * @return $this
      */
     public function setFormat($format = ':message');
 
     /**
      * Determine if the message bag has any messages.
      *
      * @return bool
      */
     public function isEmpty();
 
     /**
      * Determine if the message bag has any messages.
      *
      * @return bool
      */
     public function isNotEmpty();
 
     /**
      * Get the number of messages in the container.
      *
      * @return int
      */
     public function count();
 }