<?php
/**
 * Firebase Notification Service (FCM HTTP v1)
 */

declare(strict_types=1);

namespace App\Services;

use App\Core\Database;
use App\Core\Security;

class NotificationService
{
    private string $projectId;
    private string $serviceAccountPath;

    public function __construct()
    {
        $this->projectId = env('FIREBASE_PROJECT_ID', '');
        $this->serviceAccountPath = env('FIREBASE_SERVICE_ACCOUNT_PATH', APP_PATH . '/config/firebase-service-account.json');
    }

    /**
     * Send a push notification to a specific user or device
     */
    public function sendNotification(string $userId, string $title, string $body, array $data = [], ?string $deviceId = null): bool
    {
        $db = Database::getInstance();
        
        // 1. Get push tokens for the user
        if ($deviceId) {
            $stmt = $db->prepare("SELECT push_token FROM user_devices WHERE user_id = ? AND device_fingerprint = ? AND push_token IS NOT NULL");
            $stmt->execute([$userId, $deviceId]);
        } else {
            $stmt = $db->prepare("SELECT push_token FROM user_devices WHERE user_id = ? AND push_token IS NOT NULL AND is_active = 1");
            $stmt->execute([$userId]);
        }

        $tokens = $stmt->fetchAll(\PDO::FETCH_COLUMN);

        if (empty($tokens)) {
            return false;
        }

        // 2. Save notification to database (Single direct insert)
        $stmt = $db->prepare("SELECT tenant_id FROM users WHERE id = ? LIMIT 1");
        $stmt->execute([$userId]);
        $tenantId = $stmt->fetchColumn();

        if ($tenantId) {
            $stmt = $db->prepare("INSERT INTO notifications (id, tenant_id, user_id, type, title, body, data, created_at) VALUES (UUID(), ?, ?, 'system', ?, ?, ?, NOW())");
            $stmt->execute([$tenantId, $userId, $title, $body, json_encode($data)]);
        }

        // 3. Send to each token
        $successCount = 0;
        foreach ($tokens as $token) {
            if ($this->dispatchToFcm($token, $title, $body, $data)) {
                $successCount++;
            }
        }

        return $successCount > 0;
    }

    /**
     * Dispatch notification to Firebase via HTTP v1 API
     */
    private function dispatchToFcm(string $token, string $title, string $body, array $data): bool
    {
        if (!file_exists($this->serviceAccountPath)) {
            error_log("[NotificationService] Firebase service account file missing: {$this->serviceAccountPath}");
            return false;
        }

        $accessToken = $this->getAccessToken();
        if (!$accessToken) return false;

        $url = "https://fcm.googleapis.com/v1/projects/{$this->projectId}/messages:send";

        $payload = [
            'message' => [
                'token' => $token,
                'notification' => [
                    'title' => $title,
                    'body' => $body,
                ],
                'data' => array_map('strval', $data), // FCM data values must be strings
                'android' => [
                    'priority' => 'high',
                    'notification' => [
                        'sound' => 'default',
                        'channel_id' => 'high_importance_channel'
                    ]
                ],
                'apns' => [
                    'payload' => [
                        'aps' => [
                            'sound' => 'default',
                        ],
                    ],
                ],
            ],
        ];

        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_HTTPHEADER, [
            'Authorization: Bearer ' . $accessToken,
            'Content-Type: application/json',
        ]);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($payload));

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

        if ($httpCode !== 200) {
            error_log("[NotificationService] FCM Send Error ($httpCode): " . $response);
            return false;
        }

        return true;
    }

    /**
     * Get OAuth2 Access Token for Firebase (Cache this in production!)
     * Note: This requires a JWT library or manual signing.
     * For simplicity, we assume the user might use a Google Auth library.
     * But since we avoid extra deps, I will provide a minimal implementation or suggestion.
     */
    private function getAccessToken(): ?string
    {
        // This is a complex part that usually requires 'google/auth' library.
        // For now, I will return null and tell the user they need to install google/auth via composer
        // OR I can write a minimal JWT signer for Google Auth if they don't want composer.
        error_log("[NotificationService] OAuth2 Token generation needs google/auth library.");
        return null; 
    }
}