<?php

namespace urlManipulator;

class UrlManipulator extends AbstractUrlManipulator
{
    private $paramsArray = ['param1', 'param2', 'param3', 'param4'];
    
    public function manipulateUrl($url): array
    {
        if (!filter_var($url, FILTER_VALIDATE_URL)) {
            return ['error' => 'Invalid URL', 'input' => $url];
        }

        $parsedUrl = parse_url($url);
        $existingParams = [];
        if (isset($parsedUrl['query'])) {
            parse_str($parsedUrl['query'], $existingParams);
        }


        if (empty($this->paramsArray)) {
            return ['error' => 'Params array is full', 'input' => $url];
        }

        $newParam = $this->getNewParam($existingParams);

        if (!$newParam) {
            return ['error' => 'Unable to find a unique parameter to add', 'input' => $url];
        }

        $randomValue = $this->generateRandomValue();

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

        return ['status' => 200, 'data' => $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 $existingParams): string | null
    {
      while (!empty($this->paramsArray)) {
          $newParam = array_pop($this->paramsArray);

          if (!array_key_exists($newParam, $existingParams)) {
              return $newParam;
          }
      }

      return null; 
    }

}