<?php
/**
 * PSR-4 Autoloader
 *
 * Copied from http://www.php-fig.org/psr/psr-4/examples/
 *
 * @package   Lasso
 * @author    Josh Pollock <Josh@JoshPress.net>
 * @license   GPL-2.0+
 */

class lasso_autoloader {
	/**
	 * 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 = array();

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

	/**
	 * 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 $prepend If true, prepend the base directory to the stack
	 * instead of appending it; this causes it to be searched first rather
	 * than last.
	 * @return void
	 */
	public function addNamespace($prefix, $base_dir, $prepend = false) {
		// normalize namespace prefix
		$prefix = trim($prefix, '\\') . '\\';

		// normalize the base directory with a trailing separator
		$base_dir = rtrim($base_dir, DIRECTORY_SEPARATOR) . '/';

		// initialize the namespace prefix array
		if (isset($this->prefixes[$prefix]) === false) {
			$this->prefixes[$prefix] = array();
		}

		// retain the base directory for the namespace prefix
		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 $class The fully-qualified class name.
	 * @return mixed The mapped file name on success, or boolean false on
	 * failure.
	 */
	public function loadClass($class) {
		// the current namespace prefix
		$prefix = $class;

		// work backwards through the namespace names of the fully-qualified
		// class name to find a mapped file name
		while (false !== $pos = strrpos($prefix, '\\')) {

			// retain the trailing namespace separator in the prefix
			$prefix = substr($class, 0, $pos + 1);

			// the rest is the relative class name
			$relative_class = substr($class, $pos + 1);

			// try to load a mapped file for the prefix and relative class
			$mapped_file = $this->loadMappedFile($prefix, $relative_class);
			if ($mapped_file) {
				return $mapped_file;
			}

			// remove the trailing namespace separator for the next iteration
			// of strrpos()
			$prefix = rtrim($prefix, '\\');
		}

		// never found a mapped file
		return false;
	}

	/**
	 * Load the mapped file for a namespace prefix and relative class.
	 *
	 * @param string $prefix The namespace prefix.
	 * @param string $relative_class The relative class name.
	 * @return mixed Boolean false if no mapped file can be loaded, or the
	 * name of the mapped file that was loaded.
	 */
	protected function loadMappedFile($prefix, $relative_class) {
		// are there any base directories for this namespace prefix?
		if (isset($this->prefixes[$prefix]) === false) {
			return false;
		}

		// look through base directories for this namespace prefix
		foreach ($this->prefixes[$prefix] as $base_dir) {

			// replace the namespace prefix with the base directory,
			// replace namespace separators with directory separators
			// in the relative class name, append with .php
			$file = $base_dir
			        . str_replace('\\', '/', $relative_class)
			        . '.php';

			// if the mapped file exists, require it
			if ($this->requireFile($file)) {
				// yes, we're done
				return $file;
			}
		}

		// never found it
		return false;
	}

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

}
