<?php

/**
 * @author http://php-fig.org/ <info@php-fig.org>
 * @site https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-4-autoloader-examples.md
 */
class Psr4AutoloaderClass {

  /**
   * An associative array where the key is a namespace prefix and the value
   * is an array of base directories for classes in that namespace.
   *
   * @var array
   */
  protected $prefixes = [];

  /**
   * Register loader with SPL autoloader stack.
   *
   * @return void
   */
  public function register() {
    spl_autoload_register(array($this, 'load_class'));
  }

  public function is_loaded(string $prefix): bool {
    $prefix = trim($prefix, '\\') . '\\';
    return (isset($this->prefixes[$prefix])) ? true : false;    
  }
  
  public function get_list(): array {
    return $this->prefixes;
  }
  
  /**
   * Adds a base directory for a namespace prefix.
   *
   * @param string $prefix The namespace prefix.
   * @param string $base_dir A base directory for class files in the
   * namespace.
   * @param bool $prepend If true, prepend the base directory to the stack
   * instead of appending it; this causes it to be searched first rather
   * than last.
   * @return void
   */
  public function add_namespace(string $prefix, string $base_dir, bool $prepend = false): void {
    $prefix = trim($prefix, '\\') . '\\';
    $base_dir = rtrim($base_dir, DIRECTORY_SEPARATOR) . '/';
    if (isset($this->prefixes[$prefix]) === false) {
      $this->prefixes[$prefix] = array();
    }
    if ($prepend) {
      array_unshift($this->prefixes[$prefix], $base_dir);
    } else {
      array_push($this->prefixes[$prefix], $base_dir);
    }
  }

  /**
   * Loads the class file for a given class name.
   *
   * @param string $class The fully-qualified class name.
   * @return mixed The mapped file name on success, or boolean false on
   * failure.
   */
  public function load_class(string $class) {
    /**
     * Semi-Fix for non-namespaced classes
     */
    if (! strrpos($class, '\\')) {
      return ($this->load_mapped_file($class . '\\', $class));
    }
    $prefix = $class;
    while (false !== $pos = strrpos($prefix, '\\')) {
      $prefix = substr($class, 0, $pos + 1);
      $relative_class = substr($class, $pos + 1);
      $mapped_file = $this->load_mapped_file($prefix, $relative_class);
      if ($mapped_file) {
        return $mapped_file;
      }
      $prefix = rtrim($prefix, '\\');
    }
    return false;
  }

  /**
   * Load the mapped file for a namespace prefix and relative class.
   *
   * @param string $prefix The namespace prefix.
   * @param string $relative_class The relative class name.
   * @return mixed Boolean false if no mapped file can be loaded, or the
   * name of the mapped file that was loaded.
   */
  protected function load_mapped_file(string $prefix, string $relative_class) {
    if (isset($this->prefixes[$prefix]) === false) {
      return false;
    }
    foreach ($this->prefixes[$prefix] as $base_dir) {
      $file = $base_dir
          . str_replace('\\', '/', $relative_class)
          . '.php';
      if ($this->require_file($file)) {
        return $file;
      }
    }
    return false;
  }

  /**
   * If a file exists, require it from the file system.
   *
   * @param string $file The file to require.
   * @return bool True if the file exists, false if not.
   */
  protected function require_file(string $file): bool {
    if (file_exists($file)) {
      require $file;
      return true;
    }
    return false;
  }

}