<?php

namespace urlManipulator;

class UrlManipulator extends AbstractUrlManipulator
{
    private $paramsArray = ['param1', 'param2', 'param3', 'param4'];

    public function manipulateUrl($url): array
    {
        // Using Session to store the original URL and used parameters
        session_start();

        // Check if the original URL is stored in the session
        if (!isset($_SESSION['originalUrl'])) {
            // Store the original URL in the session
            $_SESSION['originalUrl'] = $url;
            // Initialize the used parameters array in the session
            $_SESSION['usedParams'] = [];
        }

        $originalUrl = $_SESSION['originalUrl'];
        $usedParams = $_SESSION['usedParams'];

        // Get a new parameter to add to the URL from the predefined array and existing parameters
        $newParam = $this->getNewParam($usedParams, $originalUrl);

        // If no new parameter is found, return an error
        if (!$newParam) {
            return ['error' => 'Unable to find a unique parameter to add', 'input' => $url];
        }

        $randomValue = $this->generateRandomValue();
        $modifiedUrl = $this->addParamToUrl($originalUrl, $newParam, $randomValue);

        // Store the used parameter in the session
        $usedParams[] = $newParam;
        $_SESSION['usedParams'] = $usedParams;

        return [
            'before' => $originalUrl,
            'after' => $modifiedUrl,
        ];
    }

    protected function addParamToUrl(string $url, string $param, string $value): string
    {
        $separator = (parse_url($url, PHP_URL_QUERY) == null) ? '?' : '&';

        if (strpos($url, $param . '=') !== false) {
            $modifiedUrl = preg_replace('/(' . $param . '=)[^&]+/', '$1' . urlencode($value), $url);
        } else {
            $modifiedUrl = $url . $separator . urlencode($param) . '=' . urlencode($value);
        }

        return $modifiedUrl;
    }

    protected function generateRandomValue(): string
    {
        return uniqid();
    }

    protected function getNewParam(array $usedParams, string $originalUrl)
    {
        $parsedUrl = parse_url($originalUrl);
        $existingParams = [];

        // Extract existing params from the original URL
        if (isset($parsedUrl['query'])) {
            parse_str($parsedUrl['query'], $existingParams);
        }

        // Find the first unused parameter from the predefined array and existing parameters
        foreach ($this->paramsArray as $param) {
            if (!in_array($param, $usedParams) && !array_key_exists($param, $existingParams)) {
                return $param;
            }
        }

        return null;
    }
}