first commit

backend/src/utils/encryption.ts

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+import crypto from 'crypto';
+
+const ALGORITHM = 'aes-256-gcm';
+const IV_LENGTH = 16;
+const TAG_LENGTH = 16;
+
+function getEncryptionKey(): Buffer {
+  const key = process.env.ENCRYPTION_KEY;
+  if (!key) {
+    throw new Error('ENCRYPTION_KEY environment variable is not set');
+  }
+  // Convert hex string to buffer or hash if not correct length
+  if (key.length === 64) {
+    return Buffer.from(key, 'hex');
+  }
+  // Hash the key to get 32 bytes
+  return crypto.createHash('sha256').update(key).digest();
+}
+
+export function encrypt(text: string): string {
+  const key = getEncryptionKey();
+  const iv = crypto.randomBytes(IV_LENGTH);
+  const cipher = crypto.createCipheriv(ALGORITHM, key, iv);
+
+  let encrypted = cipher.update(text, 'utf8', 'hex');
+  encrypted += cipher.final('hex');
+
+  const authTag = cipher.getAuthTag();
+
+  // Format: iv:authTag:encryptedData (all in hex)
+  return `${iv.toString('hex')}:${authTag.toString('hex')}:${encrypted}`;
+}
+
+export function decrypt(encryptedText: string): string {
+  const key = getEncryptionKey();
+  const parts = encryptedText.split(':');
+
+  if (parts.length !== 3) {
+    throw new Error('Invalid encrypted text format');
+  }
+
+  const iv = Buffer.from(parts[0], 'hex');
+  const authTag = Buffer.from(parts[1], 'hex');
+  const encrypted = parts[2];
+
+  const decipher = crypto.createDecipheriv(ALGORITHM, key, iv);
+  decipher.setAuthTag(authTag);
+
+  let decrypted = decipher.update(encrypted, 'hex', 'utf8');
+  decrypted += decipher.final('utf8');
+
+  return decrypted;
+}

backend/src/utils/helpers.ts

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+export function generateCustomerNumber(): string {
+  const timestamp = Date.now().toString(36).toUpperCase();
+  const random = Math.random().toString(36).substring(2, 6).toUpperCase();
+  return `K${timestamp}${random}`;
+}
+
+export function generateContractNumber(type: string): string {
+  const prefix = type.substring(0, 3).toUpperCase();
+  const timestamp = Date.now().toString(36).toUpperCase();
+  const random = Math.random().toString(36).substring(2, 5).toUpperCase();
+  return `${prefix}-${timestamp}${random}`;
+}
+
+export function paginate(page: number = 1, limit: number = 20) {
+  const skip = (page - 1) * limit;
+  return { skip, take: limit };
+}
+
+export function buildPaginationResponse(
+  page: number,
+  limit: number,
+  total: number
+) {
+  return {
+    page,
+    limit,
+    total,
+    totalPages: Math.ceil(total / limit),
+  };
+}