<?php

namespace Box\Spout\Autoloader;

/**
 * Class Psr4Autoloader
 * @see https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-4-autoloader-examples.md#class-example
 */
class Psr4Autoloader
{
    /**
     * 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([$this, 'loadClass']);
    }

    /**
     * Adds a base directory for a namespace prefix.
     *
     * @param string $prefix The namespace prefix.
     * @param string $baseDir 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, $baseDir, $prepend = false)
    {
        $prefix = \trim($prefix, '\\') . '\\';

        $baseDir = \rtrim($baseDir, DIRECTORY_SEPARATOR) . '/';

        if (isset($this->prefixes[$prefix]) === false) {
            $this->prefixes[$prefix] = [];
        }

        if ($prepend) {
            \array_unshift($this->prefixes[$prefix], $baseDir);
        } else {
            \array_push($this->prefixes[$prefix], $baseDir);
        }
    }

    /**
     * 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)
    {
        $prefix = $class;

        while (($pos = \strrpos($prefix, '\\')) !== false) {
            $prefix = \substr($class, 0, $pos + 1);

            $relativeClass = \substr($class, $pos + 1);

            $mappedFile = $this->loadMappedFile($prefix, $relativeClass);
            if ($mappedFile !== false) {
                return $mappedFile;
            }

            $prefix = \rtrim($prefix, '\\');
        }

        return false;
    }

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

        foreach ($this->prefixes[$prefix] as $baseDir) {
            $file = $baseDir
                  . \str_replace('\\', '/', $relativeClass)
                  . '.php';

            if ($this->requireFile($file)) {
                return $file;
            }
        }

        return false;
    }

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

            return true;
        }

        return false;
    }
}
