<?php

namespace Fgm\ComposerCheck;

/**
 * Class LoaderFactory builds Loader instances.
 */
class LoaderFactory {

  /**
   * The absolute path to the directory holding the composer.(json|lock) pair.
   *
   * @var string
   */
  protected $directory;

  /**
   * LoaderFactory constructor.
   *
   * @param string $directory
   *   The path of a directory holding a composer.(json|lock) file pair.
   */
  public function __construct(string $directory) {
    $validatedDirectory = self::validateDirectory($directory);
    if (empty($validatedDirectory)) {
      throw new \InvalidArgumentException("Unusable directory: $directory");
    }

    $this->directory = $validatedDirectory;
  }

  /**
   * Build the absolute path to the directory holding the file pair.
   *
   * @param string $directory
   *   A directory path to validate.
   *
   * @return false|string
   *   The absolute path to the directory, or FALSE if it does not contain
   *   a readable file pair.
   */
  public static function validateDirectory(string $directory) {
    $path = realpath($directory);
    // PHP is_dir() follows symlinks to report on the link target.
    if (empty($path) || !is_dir($path) || !is_readable($path)) {
      return FALSE;
    }

    foreach (['json', 'lock'] as $kind) {
      $filePath = realpath("${path}/composer.${kind}");
      if (empty($filePath) || !is_file($filePath) || !is_readable($filePath)) {
        return FALSE;
      }
    }

    return $path;
  }

  /**
   * The actual factory method.
   *
   * @param string $type
   *   The kind of loader to instantiate: "lock" or "requirements".
   *
   * @return \Fgm\ComposerCheck\LoaderInterface
   *   A loader instance.
   */
  public function createLoader(string $type) {
    $className = __NAMESPACE__ . '\\' . ucfirst($type) . 'Loader';
    if (!class_exists($className)) {
      throw new \InvalidArgumentException("Unknown loader type: $type.");
    }

    /** @var \Fgm\ComposerCheck\LoaderInterface $loader */
    $loader = new $className($this->directory);
    return $loader;
  }

}