<?php

class OAuth2Handler
{
    private $clientId;
    private $clientSecret;
    private $tokenUrl;
    private $accessToken;
    private $tokenExpiry;
    private $grantType;

    public function __construct($clientId, $clientSecret, $tokenUrl, $grantType = 'client_credentials')
    {
        $this->clientId = $clientId;
        $this->clientSecret = $clientSecret;
        $this->tokenUrl = $tokenUrl;
        $this->grantType = $grantType;
        $this->accessToken = null;
        $this->tokenExpiry = 0;
    }

    public function getAccessToken()
    {
        if ($this->isTokenValid()) {
            return $this->accessToken;
        }

        return $this->requestNewToken();
    }

    private function isTokenValid()
    {
        return $this->accessToken && time() < $this->tokenExpiry;
    }

    private function requestNewToken()
    {
        $postData = [
            'grant_type' => $this->grantType,
            'client_id' => $this->clientId,
            'client_secret' => $this->clientSecret
        ];

        $ch = curl_init();
        
        curl_setopt_array($ch, [
            CURLOPT_URL => $this->tokenUrl,
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_POST => true,
            CURLOPT_POSTFIELDS => http_build_query($postData),
            CURLOPT_HTTPHEADER => [
                'Content-Type: application/x-www-form-urlencoded',
                'Accept: application/json'
            ],
            CURLOPT_SSL_VERIFYPEER => false,
            CURLOPT_TIMEOUT => 30
        ]);

        $response = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        $error = curl_error($ch);
        curl_close($ch);

        if ($error) {
            throw new Exception("OAuth2 cURL Error: " . $error);
        }

        if ($httpCode !== 200) {
            throw new Exception("OAuth2 Token Request Failed: HTTP {$httpCode} - " . $response);
        }

        $tokenData = json_decode($response, true);
        
        if (!$tokenData || !isset($tokenData['access_token'])) {
            throw new Exception("Invalid OAuth2 token response: " . $response);
        }

        $this->accessToken = $tokenData['access_token'];
        
        $expiresIn = $tokenData['expires_in'] ?? 3600;
        $this->tokenExpiry = time() + $expiresIn - 60; // 1 minute buffer

        return $this->accessToken;
    }

    public function getAuthHeader()
    {
        $token = $this->getAccessToken();
        return 'Bearer ' . $token;
    }

    public function refreshToken()
    {
        $this->accessToken = null;
        $this->tokenExpiry = 0;
        return $this->getAccessToken();
    }

    public function getTokenInfo()
    {
        return [
            'has_token' => !empty($this->accessToken),
            'expires_at' => date('Y-m-d H:i:s', $this->tokenExpiry),
            'expires_in' => max(0, $this->tokenExpiry - time()),
            'is_valid' => $this->isTokenValid()
        ];
    }
}

class CredentialsManager
{
    private $credsFile;
    private $credentials;

    public function __construct($credsFile = 'Creds.txt')
    {
        $this->credsFile = $credsFile;
        $this->loadCredentials();
    }

    private function loadCredentials()
    {
        if (!file_exists($this->credsFile)) {
            throw new Exception("Credentials file not found: " . $this->credsFile);
        }

        $content = file_get_contents($this->credsFile);
        $lines = explode("\n", trim($content));
        
        $this->credentials = [];
        
        foreach ($lines as $line) {
            $line = trim($line);
            if (empty($line)) continue;
            
            if (preg_match('/^Secret Key\s+(.+)$/i', $line, $matches)) {
                $this->credentials['client_secret'] = trim($matches[1]);
            } elseif (preg_match('/^Client ID\s+(.+)$/i', $line, $matches)) {
                $this->credentials['client_id'] = trim($matches[1]);
            } elseif (preg_match('/^([^:]+)[:=]\s*(.+)$/', $line, $matches)) {
                $key = strtolower(str_replace(' ', '_', trim($matches[1])));
                $this->credentials[$key] = trim($matches[2]);
            }
        }
    }

    public function get($key)
    {
        return $this->credentials[$key] ?? null;
    }

    public function getAll()
    {
        return $this->credentials;
    }

    public function has($key)
    {
        return isset($this->credentials[$key]);
    }
}