<?php

class PayPalClient
{
    private string $clientId;
    private string $clientSecret;
    private string $env; // sandbox|live
    private string $baseApi;

    public function __construct(array $config)
    {
        $this->clientId = $config['client_id'] ?? '';
        $this->clientSecret = $config['client_secret'] ?? '';
        $this->env = $config['env'] ?? 'sandbox';
        $this->baseApi = $this->env === 'live'
            ? 'https://api-m.paypal.com'
            : 'https://api-m.sandbox.paypal.com';

        if (!$this->clientId || !$this->clientSecret) {
            throw new RuntimeException('Missing PayPal client_id/client_secret in config.php');
        }
    }

    public function getAccessToken(): string
    {
        $url = $this->baseApi . '/v1/oauth2/token';
        $headers = [
            'Accept: application/json',
            'Accept-Language: en_US',
        ];
        $body = 'grant_type=client_credentials';

        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_HTTPHEADER => $headers,
            CURLOPT_POST => true,
            CURLOPT_POSTFIELDS => $body,
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_USERPWD => $this->clientId . ':' . $this->clientSecret,
        ]);
        $resp = curl_exec($ch);
        if ($resp === false) {
            throw new RuntimeException('OAuth token request failed: ' . curl_error($ch));
        }
        $code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);
        $data = json_decode($resp, true);
        if ($code < 200 || $code >= 300 || !isset($data['access_token'])) {
            throw new RuntimeException('OAuth token response error (' . $code . '): ' . $resp);
        }
        return $data['access_token'];
    }

    public function api(string $method, string $path, array $payload = null, array $headers = []): array
    {
        $url = $this->baseApi . $path;
        $accessToken = $this->getAccessToken();
        $defaultHeaders = [
            'Content-Type: application/json',
            'Authorization: Bearer ' . $accessToken,
        ];
        $allHeaders = array_merge($defaultHeaders, $headers);

        $ch = curl_init($url);
        $opts = [
            CURLOPT_HTTPHEADER => $allHeaders,
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_CUSTOMREQUEST => strtoupper($method),
        ];
        if ($payload !== null) {
            $opts[CURLOPT_POSTFIELDS] = json_encode($payload);
        }
        curl_setopt_array($ch, $opts);
        $resp = curl_exec($ch);
        if ($resp === false) {
            throw new RuntimeException('API request failed: ' . curl_error($ch));
        }
        $code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);
        $data = json_decode($resp, true);
        if ($data === null && $resp !== '' && $resp !== 'null') {
            // not JSON but body present
            $data = ['raw' => $resp];
        }
        return ['status' => $code, 'body' => $data];
    }

    public function getBaseApi(): string
    {
        return $this->baseApi;
    }
}