<?php

/**
 * @package KantPHP
 * @author  Zhenqiang Zhang <zhenqiang.zhang@hotmail.com>
 * @copyright (c) KantPHP Studio, All rights reserved.
 * @license http://www.opensource.org/licenses/BSD-3-Clause  The BSD 3-Clause License
 */
namespace Kant\Http;

/**
 * HeaderBag is a container for HTTP headers.
 */
class HeaderBag implements \IteratorAggregate, \Countable
{

    protected $headers = array();

    protected $cacheControl = array();

    /**
     * Constructor.
     *
     * @param array $headers
     *            An array of HTTP headers
     */
    public function __construct(array $headers = array())
    {
        foreach ($headers as $key => $values) {
            $this->set($key, $values);
        }
    }

    /**
     * Returns the headers as a string.
     *
     * @return string The headers
     */
    public function __toString()
    {
        if (!$this->headers) {
            return '';
        }
        
        $max = max(array_map('strlen', array_keys($this->headers))) + 1;
        $content = '';
        ksort($this->headers);
        foreach ($this->headers as $name => $values) {
            $name = implode('-', array_map('ucfirst', explode('-', $name)));
            foreach ($values as $value) {
                $content .= sprintf("%-{$max}s %s\r\n", $name . ':', $value);
            }
        }
        
        return $content;
    }

    /**
     * Returns the headers.
     *
     * @return array An array of headers
     */
    public function all()
    {
        return $this->headers;
    }

    /**
     * Returns the parameter keys.
     *
     * @return array An array of parameter keys
     */
    public function keys()
    {
        return array_keys($this->headers);
    }

    /**
     * Replaces the current HTTP headers by a new set.
     *
     * @param array $headers
     *            An array of HTTP headers
     */
    public function replace(array $headers = array())
    {
        $this->headers = array();
        $this->add($headers);
    }

    /**
     * Adds new headers the current HTTP headers set.
     *
     * @param array $headers
     *            An array of HTTP headers
     */
    public function add(array $headers)
    {
        foreach ($headers as $key => $values) {
            $this->set($key, $values);
        }
    }

    /**
     * Returns a header value by name.
     *
     * @param string $key
     *            The header name
     * @param mixed $default
     *            The default value
     * @param bool $first
     *            Whether to return the first value or all header values
     *            
     * @return string|array The first header value if $first is true, an array of values otherwise
     */
    public function get($key, $default = null, $first = true)
    {
        $key = str_replace('_', '-', strtolower($key));
        
        if (!array_key_exists($key, $this->headers)) {
            if (null === $default) {
                return $first ? null : array();
            }
            
            return $first ? $default : array(
                $default
            );
        }
        
        if ($first) {
            return count($this->headers[$key]) ? $this->headers[$key][0] : $default;
        }
        
        return $this->headers[$key];
    }

    /**
     * Sets a header by name.
     *
     * @param string $key
     *            The key
     * @param string|array $values
     *            The value or an array of values
     * @param bool $replace
     *            Whether to replace the actual value or not (true by default)
     */
    public function set($key, $values, $replace = true)
    {
        $key = str_replace('_', '-', strtolower($key));
        
        $values = array_values((array) $values);
        
        if (true === $replace || ! isset($this->headers[$key])) {
            $this->headers[$key] = $values;
        } else {
            $this->headers[$key] = array_merge($this->headers[$key], $values);
        }
        
        if ('cache-control' === $key) {
            $this->cacheControl = $this->parseCacheControl($values[0]);
        }
        return $this;
    }

    /**
     * Returns true if the HTTP header is defined.
     *
     * @param string $key
     *            The HTTP header
     *            
     * @return bool true if the parameter exists, false otherwise
     */
    public function has($key)
    {
        return array_key_exists(str_replace('_', '-', strtolower($key)), $this->headers);
    }

    /**
     * Returns true if the given HTTP header contains the given value.
     *
     * @param string $key
     *            The HTTP header name
     * @param string $value
     *            The HTTP value
     *            
     * @return bool true if the value is contained in the header, false otherwise
     */
    public function contains($key, $value)
    {
        return in_array($value, $this->get($key, null, false));
    }

    /**
     * Removes a header.
     *
     * @param string $key
     *            The HTTP header name
     */
    public function remove($key)
    {
        $key = str_replace('_', '-', strtolower($key));
        
        unset($this->headers[$key]);
        
        if ('cache-control' === $key) {
            $this->cacheControl = array();
        }
    }

    /**
     * Returns the HTTP header value converted to a date.
     *
     * @param string $key
     *            The parameter key
     * @param \DateTime $default
     *            The default value
     *            
     * @return null|\DateTime The parsed DateTime or the default value if the header does not exist
     *        
     * @throws \RuntimeException When the HTTP header is not parseable
     */
    public function getDate($key, \DateTime $default = null)
    {
        if (null === $value = $this->get($key)) {
            return $default;
        }
        
        if (false === $date = \DateTime::createFromFormat(DATE_RFC2822, $value)) {
            throw new \RuntimeException(sprintf('The %s HTTP header is not parseable (%s).', $key, $value));
        }
        
        return $date;
    }

    /**
     * Adds a custom Cache-Control directive.
     *
     * @param string $key
     *            The Cache-Control directive name
     * @param mixed $value
     *            The Cache-Control directive value
     */
    public function addCacheControlDirective($key, $value = true)
    {
        $this->cacheControl[$key] = $value;
        
        $this->set('Cache-Control', $this->getCacheControlHeader());
    }

    /**
     * Returns true if the Cache-Control directive is defined.
     *
     * @param string $key
     *            The Cache-Control directive
     *            
     * @return bool true if the directive exists, false otherwise
     */
    public function hasCacheControlDirective($key)
    {
        return array_key_exists($key, $this->cacheControl);
    }

    /**
     * Returns a Cache-Control directive value by name.
     *
     * @param string $key
     *            The directive name
     *            
     * @return mixed|null The directive value if defined, null otherwise
     */
    public function getCacheControlDirective($key)
    {
        return array_key_exists($key, $this->cacheControl) ? $this->cacheControl[$key] : null;
    }

    /**
     * Removes a Cache-Control directive.
     *
     * @param string $key
     *            The Cache-Control directive
     */
    public function removeCacheControlDirective($key)
    {
        unset($this->cacheControl[$key]);
        
        $this->set('Cache-Control', $this->getCacheControlHeader());
    }

    /**
     * Returns an iterator for headers.
     *
     * @return \ArrayIterator An \ArrayIterator instance
     */
    public function getIterator()
    {
        return new \ArrayIterator($this->headers);
    }

    /**
     * Returns the number of headers.
     *
     * @return int The number of headers
     */
    public function count()
    {
        return count($this->headers);
    }

    protected function getCacheControlHeader()
    {
        $parts = array();
        ksort($this->cacheControl);
        foreach ($this->cacheControl as $key => $value) {
            if (true === $value) {
                $parts[] = $key;
            } else {
                if (preg_match('#[^a-zA-Z0-9._-]#', $value)) {
                    $value = '"' . $value . '"';
                }
                
                $parts[] = "$key=$value";
            }
        }
        
        return implode(', ', $parts);
    }

    /**
     * Parses a Cache-Control HTTP header.
     *
     * @param string $header
     *            The value of the Cache-Control HTTP header
     *            
     * @return array An array representing the attribute values
     */
    protected function parseCacheControl($header)
    {
        $cacheControl = array();
        preg_match_all('#([a-zA-Z][a-zA-Z_-]*)\s*(?:=(?:"([^"]*)"|([^ \t",;]*)))?#', $header, $matches, PREG_SET_ORDER);
        foreach ($matches as $match) {
            $cacheControl[strtolower($match[1])] = isset($match[3]) ? $match[3] : (isset($match[2]) ? $match[2] : true);
        }
        
        return $cacheControl;
    }
}
