<?php
if (!defined('ABSPATH')) exit;

/**
 * Step registry. Singleton.
 *
 * discover() globs a directory for *.php files in sort order and requires each.
 * Each file MUST return a WPH_Step instance. The numeric filename prefix
 * (00, 10, 20...) controls the visual order.
 *
 * After discovery, the 'wph_steps' filter lets installation-specific code
 * remove/replace steps (return the array keyed by step id).
 */
final class WPH_Steps {

    private static ?WPH_Steps $instance = null;

    /** @var array<string,WPH_Step> */
    private array $steps = [];

    private bool $discovered = false;

    public static function instance(): WPH_Steps {
        return self::$instance ??= new self();
    }

    public function discover(string $dir): void {
        if ($this->discovered) return;
        $files = glob(rtrim($dir, '/') . '/*.php') ?: [];
        // Natural sort so 100-* comes after 20-* (not after 10-*).
        natsort($files);
        $files = array_values($files);
        foreach ($files as $file) {
            $obj = require $file;
            if ($obj instanceof WPH_Step) {
                $this->steps[$obj->id()] = $obj;
            }
        }
        /**
         * Filter the loaded steps. Return an array keyed by step id.
         * To drop a step on a particular install: unset($steps['backup']).
         */
        $this->steps = apply_filters('wph_steps', $this->steps);
        $this->discovered = true;
    }

    /** @return array<string,WPH_Step> */
    public function all(): array {
        return $this->steps;
    }

    public function get(string $id): ?WPH_Step {
        return $this->steps[$id] ?? null;
    }
}