<?php

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

use Kant\Http\File\Exception\FileNotFoundException;
use Kant\Http\File\Exception\AccessDeniedException;

/**
 * A singleton mime type guesser.
 *
 * By default, all mime type guessers provided by the framework are installed
 * (if available on the current OS/PHP setup).
 *
 * You can register custom guessers by calling the register() method on the
 * singleton instance. Custom guessers are always called before any default ones.
 *
 * $guesser = MimeTypeGuesser::getInstance();
 * $guesser->register(new MyCustomMimeTypeGuesser());
 *
 * If you want to change the order of the default guessers, just re-register your
 * preferred one as a custom one. The last registered guesser is preferred over
 * previously registered ones.
 *
 * Re-registering a built-in guesser also allows you to configure it:
 *
 * $guesser = MimeTypeGuesser::getInstance();
 * $guesser->register(new FileinfoMimeTypeGuesser('/path/to/magic/file'));
 *
 * @author Bernhard Schussek <bschussek@gmail.com>
 */
class MimeTypeGuesser implements MimeTypeGuesserInterface
{

    /**
     * The singleton instance.
     *
     * @var MimeTypeGuesser
     */
    private static $instance = null;

    /**
     * All registered MimeTypeGuesserInterface instances.
     *
     * @var array
     */
    protected $guessers = array();

    /**
     * Returns the singleton instance.
     *
     * @return MimeTypeGuesser
     */
    public static function getInstance()
    {
        if (null === self::$instance) {
            self::$instance = new self();
        }
        
        return self::$instance;
    }

    /**
     * Resets the singleton instance.
     */
    public static function reset()
    {
        self::$instance = null;
    }

    /**
     * Registers all natively provided mime type guessers.
     */
    private function __construct()
    {
        if (FileBinaryMimeTypeGuesser::isSupported()) {
            $this->register(new FileBinaryMimeTypeGuesser());
        }
        
        if (FileinfoMimeTypeGuesser::isSupported()) {
            $this->register(new FileinfoMimeTypeGuesser());
        }
    }

    /**
     * Registers a new mime type guesser.
     *
     * When guessing, this guesser is preferred over previously registered ones.
     *
     * @param MimeTypeGuesserInterface $guesser            
     */
    public function register(MimeTypeGuesserInterface $guesser)
    {
        array_unshift($this->guessers, $guesser);
    }

    /**
     * Tries to guess the mime type of the given file.
     *
     * The file is passed to each registered mime type guesser in reverse order
     * of their registration (last registered is queried first). Once a guesser
     * returns a value that is not NULL, this method terminates and returns the
     * value.
     *
     * @param string $path
     *            The path to the file
     *            
     * @return string The mime type or NULL, if none could be guessed
     *        
     * @throws \LogicException
     * @throws FileNotFoundException
     * @throws AccessDeniedException
     */
    public function guess($path)
    {
        if (!is_file($path)) {
            throw new FileNotFoundException($path);
        }
        
        if (!is_readable($path)) {
            throw new AccessDeniedException($path);
        }
        
        if (!$this->guessers) {
            $msg = 'Unable to guess the mime type as no guessers are available';
            if (!FileinfoMimeTypeGuesser::isSupported()) {
                $msg .= ' (Did you enable the php_fileinfo extension?)';
            }
            throw new \LogicException($msg);
        }
        
        foreach ($this->guessers as $guesser) {
            if (null !== $mimeType = $guesser->guess($path)) {
                return $mimeType;
            }
        }
    }
}
