<?php
/**
 * @link http://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

namespace yii\web;

use Yii;
use yii\base\Object;
use ArrayIterator;

/**
 * HeaderCollection is used by [[Response]] to maintain the currently registered HTTP headers.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
class HeaderCollection extends Object implements \IteratorAggregate, \ArrayAccess, \Countable
{
	/**
	 * @var array the headers in this collection (indexed by the header names)
	 */
	private $_headers = array();

	/**
	 * Returns an iterator for traversing the headers in the collection.
	 * This method is required by the SPL interface `IteratorAggregate`.
	 * It will be implicitly called when you use `foreach` to traverse the collection.
	 * @return ArrayIterator an iterator for traversing the headers in the collection.
	 */
	public function getIterator()
	{
		return new ArrayIterator($this->_headers);
	}

	/**
	 * Returns the number of headers in the collection.
	 * This method is required by the SPL `Countable` interface.
	 * It will be implicitly called when you use `count($collection)`.
	 * @return integer the number of headers in the collection.
	 */
	public function count()
	{
		return $this->getCount();
	}

	/**
	 * Returns the number of headers in the collection.
	 * @return integer the number of headers in the collection.
	 */
	public function getCount()
	{
		return count($this->_headers);
	}

	/**
	 * Returns the named header(s).
	 * @param string $name the name of the header to return
	 * @param mixed $default the value to return in case the named header does not exist
	 * @param boolean $first whether to only return the first header of the specified name.
	 * If false, all headers of the specified name will be returned.
	 * @return string|array the named header(s). If `$first` is true, a string will be returned;
	 * If `$first` is false, an array will be returned.
	 */
	public function get($name, $default = null, $first = true)
	{
		$name = strtolower($name);
		if (isset($this->_headers[$name])) {
			return $first ? reset($this->_headers[$name]) : $this->_headers[$name];
		} else {
			return $default;
		}
	}

	/**
	 * Adds a new header.
	 * If there is already a header with the same name, it will be replaced.
	 * @param string $name the name of the header
	 * @param string $value the value of the header
	 * @return HeaderCollection the collection object itself
	 */
	public function set($name, $value = '')
	{
		$name = strtolower($name);
		$this->_headers[$name] = (array)$value;
		return $this;
	}

	/**
	 * Adds a new header.
	 * If there is already a header with the same name, the new one will
	 * be appended to it instead of replacing it.
	 * @param string $name the name of the header
	 * @param string $value the value of the header
	 * @return HeaderCollection the collection object itself
	 */
	public function add($name, $value)
	{
		$name = strtolower($name);
		$this->_headers[$name][] = $value;
		return $this;
	}

	/**
	 * Sets a new header only if it does not exist yet.
	 * If there is already a header with the same name, the new one will be ignored.
	 * @param string $name the name of the header
	 * @param string $value the value of the header
	 * @return HeaderCollection the collection object itself
	 */
	public function setDefault($name, $value)
	{
		$name = strtolower($name);
		if (empty($this->_headers[$name])) {
			$this->_headers[$name][] = $value;
		}
		return $this;
	}

	/**
	 * Returns a value indicating whether the named header exists.
	 * @param string $name the name of the header
	 * @return boolean whether the named header exists
	 */
	public function has($name)
	{
		$name = strtolower($name);
		return isset($this->_headers[$name]);
	}

	/**
	 * Removes a header.
	 * @param string $name the name of the header to be removed.
	 * @return string the value of the removed header. Null is returned if the header does not exist.
	 */
	public function remove($name)
	{
		$name = strtolower($name);
		if (isset($this->_headers[$name])) {
			$value = $this->_headers[$name];
			unset($this->_headers[$name]);
			return $value;
		} else {
			return null;
		}
	}

	/**
	 * Removes all headers.
	 */
	public function removeAll()
	{
		$this->_headers = array();
	}

	/**
	 * Returns the collection as a PHP array.
	 * @return array the array representation of the collection.
	 * The array keys are header names, and the array values are the corresponding header values.
	 */
	public function toArray()
	{
		return $this->_headers;
	}

	/**
	 * Returns whether there is a header with the specified name.
	 * This method is required by the SPL interface `ArrayAccess`.
	 * It is implicitly called when you use something like `isset($collection[$name])`.
	 * @param string $name the header name
	 * @return boolean whether the named header exists
	 */
	public function offsetExists($name)
	{
		return $this->has($name);
	}

	/**
	 * Returns the header with the specified name.
	 * This method is required by the SPL interface `ArrayAccess`.
	 * It is implicitly called when you use something like `$header = $collection[$name];`.
	 * This is equivalent to [[get()]].
	 * @param string $name the header name
	 * @return string the header value with the specified name, null if the named header does not exist.
	 */
	public function offsetGet($name)
	{
		return $this->get($name);
	}

	/**
	 * Adds the header to the collection.
	 * This method is required by the SPL interface `ArrayAccess`.
	 * It is implicitly called when you use something like `$collection[$name] = $header;`.
	 * This is equivalent to [[add()]].
	 * @param string $name the header name
	 * @param string $value the header value to be added
	 */
	public function offsetSet($name, $value)
	{
		$this->set($name, $value);
	}

	/**
	 * Removes the named header.
	 * This method is required by the SPL interface `ArrayAccess`.
	 * It is implicitly called when you use something like `unset($collection[$name])`.
	 * This is equivalent to [[remove()]].
	 * @param string $name the header name
	 */
	public function offsetUnset($name)
	{
		$this->remove($name);
	}
}
