<?php
/**
 * Autoloading for Advanced Permissions.
 *
 * @since   1.0
 * @package CosmicGiant\Advanced_Permissions
 */

namespace CosmicGiant\Advanced_Permissions;

/**
 * Autoload Advanced_Permissions class files.
 * Based on PHP-FIG PSR-4 example.
 *
 * @since     1.2
 * @package   CosmicGiant\Advanced_Permissions
 * @author    CosmicGiant
 * @copyright Copyright (c) 2020, CosmicGiant
 */
class 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.
	 *
	 * @since 1.2
	 * @var array
	 */
	protected $prefixes = [];

	/**
	 * Register loader with SPL autoloader stack.
	 *
	 * @sincw 2.4
	 */
	public function register() {

		spl_autoload_register( [ $this, 'load_class' ] );

	}

	/**
	 * Adds a base directory for a namespace prefix.
	 *
	 * @since 1.2
	 *
	 * @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.
	 */
	public function add_namespace( $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 ] = [];
		}

		// 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.
	 *
	 * @since 1.2
	 *
	 * @param string $class The fully-qualified class name.
	 *
	 * @return string|false The mapped file name on success, or boolean false on failure.
	 */
	public function load_class( $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->load_mapped_file( $prefix, $relative_class );
			if ( $mapped_file ) {
				return $mapped_file;
			}

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

		}

		return false;

	}

	/**
	 * Load the mapped file for a namespace prefix and relative class.
	 *
	 * @since 1.2
	 *
	 * @param string $prefix         The namespace prefix.
	 * @param string $relative_class The relative class name.
	 *
	 * @return false|string Boolean false if no mapped file can be loaded, or the name of the mapped file that was loaded.
	 */
	protected function load_mapped_file( $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 ) {

			// Prepare file name.
			$relative_path = str_replace( [ '\\', '_' ], [ '/', '-' ], $relative_class );
			$relative_path = strtolower( $relative_path );

			// Prepend file name with "class-".
			$file_parts    = explode( '/', $relative_path );
			$file_name     = array_pop( $file_parts );
			$file_parts[]  = 'class-' . $file_name;
			$relative_path = implode( '/', $file_parts );

			// Replace the namespace prefix with the base directory.
			$file = $base_dir . $relative_path . '.php';

			// If the mapped file exists, require it.
			if ( $this->require_file( $file ) ) {
				return $file;
			}

		}

		return false;

	}

	/**
	 * If a file exists, require it from the file system.
	 *
	 * @since 1.2
	 *
	 * @param string $file The file to require.
	 *
	 * @return bool True if the file exists, false if not.
	 */
	protected function require_file( $file ) {

		if ( file_exists( $file ) ) {
			require $file;
			return true;
		}

		return false;

	}

}

$autoloader = new Autoloader();
$autoloader->add_namespace( 'CosmicGiant\\Advanced_Permissions\\', dirname( __DIR__ ) . '/includes/' );
$autoloader->register();
