/**
 * Input validators used by the UI to surface preview feedback before
 * the user hits the server. The Entropy Softworks application servers
 * enforce these same rules authoritatively (see `entropy-auth`'s
 * `password::policy` / `Validation`); these implementations are kept
 * deliberately strict to avoid false positives on the client.
 *
 * Email: a permissive `local@host.tld` shape — anything stricter risks
 * rejecting valid addresses, and the server validates anyway.
 *
 * Password: matches the default `entropy-auth` policy (≥8 chars, mixed
 * case, digit, symbol). Apps that opt their server into a different
 * policy can ignore the `valid` result and let the server be the source
 * of truth.
 *
 * Username: 3–30 chars, ASCII alnum + underscore.
 */

export interface PasswordValidation {
  valid: boolean;
  errors: string[];
}

export interface UsernameValidation {
  valid: boolean;
  error?: string;
}

const EMAIL = /^[^\s@]+@[^\s@]+\.[^\s@]{2,}$/;
const UPPER = /[A-Z]/;
const LOWER = /[a-z]/;
const DIGIT = /[0-9]/;
const SYMBOL = /[!@#$%^&*()_+\-=[\]{}|;:,.<>?]/;
const USERNAME = /^[a-zA-Z0-9_]+$/;

export function validateEmail(email: string): boolean {
  return EMAIL.test(email);
}

export function validatePassword(password: string): PasswordValidation {
  const errors: string[] = [];
  if (password.length < 8) {
    errors.push("Password must be at least 8 characters");
  }
  if (!UPPER.test(password)) {
    errors.push("Password must contain at least one uppercase letter");
  }
  if (!LOWER.test(password)) {
    errors.push("Password must contain at least one lowercase letter");
  }
  if (!DIGIT.test(password)) {
    errors.push("Password must contain at least one number");
  }
  if (!SYMBOL.test(password)) {
    errors.push("Password must contain at least one special character");
  }
  return { valid: errors.length === 0, errors };
}

export function validateUsername(username: string): UsernameValidation {
  if (username.length < 3 || username.length > 30) {
    return { valid: false, error: "Username must be between 3 and 30 characters" };
  }
  if (!USERNAME.test(username)) {
    return {
      valid: false,
      error: "Username can only contain letters, numbers, and underscores",
    };
  }
  return { valid: true };
}