<?php

namespace Alexr\Services\UrlShortener;

use Alexr\Models\UrlShortener;
use Exception;

class UrlShortenerService {

	/**
	 * Generate a short URL
	 *
	 * @param int $tenant_id Restaurant ID
	 * @param string $original_url
	 * @param int|null $expires_in_hours Optional expiration in hours
	 * @return string|null The short code or null if failed
	 */
	public function createShortUrl($tenant_id, $original_url, $expires_in_hours = null)
	{
		try {
			// Check if an identical URL already exists for this tenant
			$existing = UrlShortener::where('tenant_id', $tenant_id)
				->where('original_url', $original_url)
				->first();

			if ($existing && $existing->isValid()) {
				return $existing->short_code;
			}

			$short_code = $this->generateUniqueCode();

			$expires_at = null;
			if ($expires_in_hours) {
				$expires_at = date('Y-m-d H:i:s', strtotime("+{$expires_in_hours} hours"));
			}

			$shortener = new UrlShortener();
			$shortener->tenant_id = $tenant_id;
			$shortener->short_code = $short_code;
			$shortener->original_url = $original_url;
			$shortener->expires_at = $expires_at;
			$shortener->save();

			return $short_code;

		} catch (Exception $e) {
			error_log("UrlShortenerService::createShortUrl error: " . $e->getMessage());
			return null;
		}
	}

	/**
	 * Get original URL from short code and track visit
	 *
	 * @param string $short_code
	 * @return string|null Original URL or null if not found/expired
	 */
	public function getOriginalUrl($short_code)
	{
		try {
			$shortener = UrlShortener::where('short_code', $short_code)->first();

			if (!$shortener) {
				return null;
			}

			if ($shortener->isExpired()) {
				return null;
			}

			$shortener->incrementVisits();

			return $shortener->original_url;

		} catch (Exception $e) {
			error_log("UrlShortenerService::getOriginalUrl error: " . $e->getMessage());
			return null;
		}
	}

	/**
	 * Generate a unique short code
	 *
	 * @return string
	 */
	private function generateUniqueCode()
	{
		$chars = '23456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ';
		$code_length = 6;

		do {
			$short_code = '';
			for ($i = 0; $i < $code_length; $i++) {
				$short_code .= $chars[random_int(0, strlen($chars) - 1)];
			}
		} while (UrlShortener::where('short_code', $short_code)->exists());

		return $short_code;
	}

	/**
	 * Clean up expired URLs
	 *
	 * @return int Number of deleted records
	 */
	public function cleanupExpiredUrls()
	{
		try {
			return UrlShortener::where('expires_at', '<', date('Y-m-d H:i:s'))
				->whereNotNull('expires_at')
				->delete();
		} catch (Exception $e) {
			error_log("UrlShortenerService::cleanupExpiredUrls error: " . $e->getMessage());
			return 0;
		}
	}
}