<?php

namespace App\Services\Fcm;

use Illuminate\Support\Facades\Http;
use Illuminate\Support\Facades\Log;
use Throwable;

class FcmService
{
    protected string $projectId;
    protected string $accessToken;

    public function __construct()
    {
        $this->projectId = config('fcm.project_id');
        $this->accessToken = $this->getAccessToken();
    }

    public function send(string $token, string $title, string $body, ?string $image = null): ?array
    {
        $url = "https://fcm.googleapis.com/v1/projects/{$this->projectId}/messages:send";

        $message = [
            'message' => [
                'token' => $token,
                'notification' => [
                    'title' => $title,
                    'body' => $body,
                    'image' => $image,
                ],
                'android' => [
                    'priority' => 'high',
                ],
                'apns' => [
                    'headers' => [
                        'apns-priority' => '10',
                    ],
                    'payload' => [
                        'aps' => [
                            'sound' => 'default',
                            'badge' => 1,
                        ],
                    ],
                ],
            ],
        ];

        try {
            $response = Http::withToken($this->accessToken)->post($url, $message);
            $result = $response->json();

            Log::channel('fcm')->info('FCM send', [
                'token' => substr($token, 0, 20) . '...',
                'title' => $title,
                'status' => $response->status(),
                'response' => $result,
            ]);

            if ($response->failed()) {
                Log::channel('fcm')->error('FCM send failed', [
                    'token' => substr($token, 0, 20) . '...',
                    'status' => $response->status(),
                    'error' => $result,
                ]);
            }

            return $result;
        } catch (Throwable $e) {
            Log::channel('fcm')->error('FCM exception', [
                'token' => substr($token, 0, 20) . '...',
                'message' => $e->getMessage(),
            ]);

            return null;
        }
    }

    protected function getAccessToken(): string
    {
        $clientEmail = config('fcm.client_email');
        $privateKey = config('fcm.private_key');

        $jwt = $this->createJwt($clientEmail, $privateKey);

        return $this->exchangeJwtForAccessToken($jwt);
    }

    protected function createJwt(string $clientEmail, string $privateKey): string
    {
        $header = json_encode(['alg' => 'RS256', 'typ' => 'JWT']);
        $now = time();

        $payload = json_encode([
            'iss' => $clientEmail,
            'sub' => $clientEmail,
            'aud' => 'https://oauth2.googleapis.com/token',
            'iat' => $now,
            'exp' => $now + 3600,
            'scope' => 'https://www.googleapis.com/auth/cloud-platform',
        ]);

        $base64Header = $this->base64UrlEncode($header);
        $base64Payload = $this->base64UrlEncode($payload);

        $signature = '';
        openssl_sign("{$base64Header}.{$base64Payload}", $signature, $privateKey, 'sha256');

        return "{$base64Header}.{$base64Payload}." . $this->base64UrlEncode($signature);
    }

    protected function exchangeJwtForAccessToken(string $jwt): string
    {
        $response = Http::asForm()->post('https://oauth2.googleapis.com/token', [
            'grant_type' => 'urn:ietf:params:oauth:grant-type:jwt-bearer',
            'assertion' => $jwt,
        ]);

        $data = $response->json();

        if (isset($data['access_token'])) {
            return $data['access_token'];
        }

        throw new \RuntimeException('FCM: Failed to obtain access token: ' . $response->body());
    }

    protected function base64UrlEncode(string $data): string
    {
        return str_replace(['+', '/', '='], ['-', '_', ''], base64_encode($data));
    }
}