<?php
/**
 * Autoloader for chatway plugin
 *
 * @author  : Chatway
 * @license : GPLv3
 * */

namespace Chatway;
defined( 'ABSPATH' ) || exit;
/**
 * PSR4 Autoloader implementation that includes the optional
 * functionality of allowing multiple base directories for a single namespace
 * prefix.
 *
 * Sourced from @link http://www.php-fig.org/psr/psr-4/examples/
 *
 * Given a foo-bar package of classes in the file system at the following
 * paths ...
 *
 *     /path/to/packages/foo-bar/
 *         src/
 *             Baz.php             # Foo\Bar\Baz
 *             Qux/
 *                 Quux.php        # Foo\Bar\Qux\Quux
 *         tests/
 *             BazTest.php         # Foo\Bar\BazTest
 *             Qux/
 *                 QuuxTest.php    # Foo\Bar\Qux\QuuxTest
 *
 * ... add the path to the class files for the \Foo\Bar\ namespace prefix
 * as follows:
 *
 *      <?php
 *      // instantiate the loader
 *      $loader = new \Example\AutoLoaderClass;
 *
 *      // register the autoloader
 *      $loader->register();
 *
 *      // register the base directories for the namespace prefix
 *      $loader->add_namespace('Foo\Bar', '/path/to/packages/foo-bar/src');
 *      $loader->add_namespace('Foo\Bar', '/path/to/packages/foo-bar/tests');
 *
 * The following line would cause the autoloader to attempt to load the
 * \Foo\Bar\Qux\Quux class from /path/to/packages/foo-bar/src/Qux/Quux.php:
 *
 *      <?php
 *      new \Foo\Bar\Qux\Quux;
 *
 * The following line would cause the autoloader to attempt to load the
 * \Foo\Bar\Qux\QuuxTest class from /path/to/packages/foo-bar/tests/Qux/QuuxTest.php:
 *
 *      <?php
 *      new \Foo\Bar\Qux\QuuxTest;
 */
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.
     *
     * @var array
     */
    protected $prefixes = [];

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

    /**
     * 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( $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.
     *
     * @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( $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, '\\' );
        }

        // 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 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 ) {

            // 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->require_file( $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 require_file( $file ) {
        if ( file_exists( $file ) ) {
            require $file;

            return true;
        }

        return false;
    }
}