require('dotenv').config();
const sql = require('mssql');
const AWS = require('aws-sdk');
const fs = require('fs');
const path = require('path');
const SambaClient = require('samba-client');

// AWS S3 Configuration
const s3 = new AWS.S3({
  accessKeyId: process.env.AWS_ACCESS_KEY_ID,
  secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY,
  region: process.env.AWS_REGION
});

// MSSQL Configuration
const config = {
  user: process.env.MSSQL_USER,
  password: process.env.MSSQL_PASSWORD,
  server: process.env.MSSQL_SERVER,
  port: parseInt(process.env.MSSQL_PORT) || 1433,
  database: process.env.MSSQL_DATABASE,
  options: {
    encrypt: true, // Use this if you're on Windows Azure
    trustServerCertificate: true // Change to true for local dev / self-signed certs
  }
};

// Backup file path
const backupFilePath = process.env.BACKUP_FILE_PATH;

// SMB Configuration
const smbConfig = {
  address: process.env.SMB_ADDRESS,
  username: process.env.SMB_USERNAME,
  password: process.env.SMB_PASSWORD,
  domain: process.env.SMB_DOMAIN || '', // optional
};

// Ensure download directory exists
const downloadFile = process.env.SMB_DOWNLOAD_FILE;
const localDownloadFile = process.env.SMB_LOCAL_DOWNLOAD_FILE;


// Admin Telegram Broadcast (env-configured)
const BASE_URL = process.env.BASE_URL;
const ADMIN_API_KEY = process.env.ADMIN_API_KEY;

async function sendTelegramBroadcast(target, message) {
  try {
    if (!BASE_URL || !ADMIN_API_KEY) {
      console.warn('Skipping admin broadcast: missing BASE_URL or ADMIN_API_KEY');
      return null;
    }
    const endpoint = `${BASE_URL.replace(/\/$/, '')}/api/admin/telegram/broadcast`;
    const res = await fetch(endpoint, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'X-API-Key': ADMIN_API_KEY,
      },
      body: JSON.stringify({ target, message }),
    });
    if (!res.ok) {
      const err = await res.json().catch(() => ({}));
      throw new Error(`Broadcast failed: ${res.status} ${res.statusText} ${err.error || ''}`);
    }
    return res.json();
  } catch (e) {
    console.error('Admin broadcast error:', e.message);
    return null;
  }
}

// Helper to format bytes to human-readable
function formatBytes(bytes) {
  if (bytes === 0 || bytes == null) return '0 B';
  const k = 1024;
  const sizes = ['B', 'KB', 'MB', 'GB', 'TB'];
  const i = Math.floor(Math.log(bytes) / Math.log(k));
  const val = bytes / Math.pow(k, i);
  return `${val.toFixed(val >= 100 ? 0 : val >= 10 ? 1 : 2)} ${sizes[i]}`;
}

// Query DB sizes (data + log) in bytes
async function getDbSizeBytes() {
  try {
    // Assumes active connection exists
    const dbName = process.env.MSSQL_DATABASE;
    const sizeQuery = `
      ;WITH s AS (
        SELECT
          type_desc,
          size_mb = SUM(size) * 8.0 / 1024.0
        FROM sys.master_files
        WHERE database_id = DB_ID(@db)
        GROUP BY type_desc
      )
      SELECT
        data_bytes = CAST(COALESCE((SELECT size_mb FROM s WHERE type_desc = 'ROWS'), 0) * 1024 * 1024 AS BIGINT),
        log_bytes  = CAST(COALESCE((SELECT size_mb FROM s WHERE type_desc = 'LOG'), 0) * 1024 * 1024 AS BIGINT);
    `;
    const request = new sql.Request();
    request.input('db', sql.NVarChar, dbName);
    const r = await request.query(sizeQuery);
    const row = r.recordset && r.recordset[0];
    return {
      dataBytes: row ? Number(row.data_bytes) : null,
      logBytes: row ? Number(row.log_bytes) : null,
    };
  } catch (e) {
    console.warn('Could not query DB size:', e.message);
    return { dataBytes: null, logBytes: null };
  }
}

// Function to create database backup
async function createDatabaseBackup() {
  try {
    console.log('Connecting to database...');
    await sql.connect(config);

    console.log('Creating database backup...');
    const backupQuery = `
      BACKUP DATABASE [${process.env.MSSQL_DATABASE}] 
      TO DISK = N'${backupFilePath}' 
      WITH NOFORMAT, NOINIT, NAME = N'${process.env.MSSQL_DATABASE}-Vollständig Datenbank Sichern', 
      SKIP, NOREWIND, NOUNLOAD, STATS = 10
    `;

    const result = await sql.query(backupQuery);
    console.log('Database backup created successfully');
    return backupFilePath;
  } catch (err) {
    console.error('Error creating database backup:', err);
    throw err;
  }
}

// Function to download backup file from SMB share
async function downloadBackupFile() {
  try {
    console.log('Downloading backup file from SMB share...');
    
    // Create SMB client
    const client = new SambaClient(smbConfig);
    
    // Download file from SMB share
    await client.getFile(downloadFile, localDownloadFile);
    
    console.log('Backup file downloaded successfully to:', localDownloadFile);
    return localDownloadFile;
  } catch (err) {
    console.error('Error downloading backup file from SMB share:', err);
    throw err;
  }
}

// Function to upload backup to S3
async function uploadBackupToS3(filePath) {
  try {
    console.log('Uploading backup to S3...');
    
    // Create a read stream for the file
    const fileStream = fs.createReadStream(filePath);
    
    // Handle stream errors
    fileStream.on('error', (err) => {
      console.error('File stream error:', err);
      throw err;
    });
    
    // Create S3 upload parameters using stream
    const params = {
      Bucket: process.env.S3_BUCKET_NAME,
      Key: `backups/${process.env.MSSQL_DATABASE}_${new Date().toISOString().replace(/[:.]/g, '-')}.bak`,
      Body: fileStream
    };
    
    // Upload file to S3 using stream
    const data = await s3.upload(params).promise();
    console.log('Backup uploaded successfully to S3:', data.Location);
    return data.Location;
  } catch (err) {
    console.error('Error uploading backup to S3:', err);
    throw err;
  }
}

// Function to run backup process
async function runBackupProcess() {
  try {
    console.log('Starting backup process at', new Date().toISOString());

    // Create database backup (opens connection)
    await createDatabaseBackup();

    // While connected, get DB size info
    const sizes = await getDbSizeBytes();

    // Close connection once done with SQL-related work
    await sql.close().catch(() => {});

    // Download backup file from SMB share
    const localBackupFile = await downloadBackupFile();

    // Upload backup to S3
    const s3Url = await uploadBackupToS3(localBackupFile);

    console.log('Backup process completed successfully at', new Date().toISOString());
    console.log('Backup available at:', s3Url);

    // Notify admins via Telegram broadcast with size
    const fileName = path.basename(localBackupFile || 'backup.bak');
    const when = new Date().toISOString();
    const sizeLine = sizes && (sizes.dataBytes != null || sizes.logBytes != null)
      ? `\nDB Size: ${sizes.dataBytes != null ? formatBytes(sizes.dataBytes) : '?'} (data), ${sizes.logBytes != null ? formatBytes(sizes.logBytes) : '?'} (log)`
      : '';
    const msg = `Backup completed ✅\nDB: ${process.env.MSSQL_DATABASE}\nFile: ${fileName}\nS3: ${s3Url}${sizeLine}\nTime: ${when}`;
    await sendTelegramBroadcast('admins', msg);
  } catch (err) {
    console.error('Backup process failed:', err);
    // Ensure connection closed on failure
    try { await sql.close(); } catch {}
    // Optional: notify error channel on failure (best-effort)
    const when = new Date().toISOString();
    const msg = `Backup failed 🔴\nDB: ${process.env.MSSQL_DATABASE}\nTime: ${when}\nError: ${err && err.message ? err.message : err}`;
    await sendTelegramBroadcast('errors', msg);
  }
}

// Run backup immediately when starting
runBackupProcess();

// Schedule backup to run every 24 hours (86400000 milliseconds)
// You can adjust this interval as needed
setInterval(runBackupProcess, 86400000);

console.log('Database backup service started. Running backups every 24 hours.');

// Startup health notification
(async () => {
  try {
    const when = new Date().toISOString();
    const host = require('os').hostname();
    const region = process.env.AWS_REGION || 'n/a';
    const bucket = process.env.S3_BUCKET_NAME || 'n/a';
    await sendTelegramBroadcast('admins', `Backup service started ✅\nDB: ${process.env.MSSQL_DATABASE}\nHost: ${host}\nAWS: ${region}/${bucket}\nTime: ${when}`);
  } catch (e) {
    console.warn('Startup broadcast failed:', e.message);
  }
})();