import type { PasswordPolicy } from "./types";

export interface GeneratorOptions {
  length: number;
  includeUppercase: boolean;
  includeLowercase: boolean;
  includeNumbers: boolean;
  includeSymbols: boolean;
  /** Characters to exclude from every pool — honors site forbidden-char lists. */
  forbiddenChars?: string;
}

/**
 * Generate a cryptographically random password.
 */
export function generatePassword(options: Partial<GeneratorOptions> = {}): string {
  const {
    length = 20,
    includeUppercase = true,
    includeLowercase = true,
    includeNumbers = true,
    includeSymbols = true,
    forbiddenChars = "",
  } = options;

  const forbidden = new Set(forbiddenChars);
  const filter = (pool: string): string =>
    forbidden.size === 0
      ? pool
      : Array.from(pool).filter((c) => !forbidden.has(c)).join("");

  let chars = "";
  if (includeLowercase) chars += filter("abcdefghijklmnopqrstuvwxyz");
  if (includeUppercase) chars += filter("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
  if (includeNumbers) chars += filter("0123456789");
  if (includeSymbols) chars += filter("!@#$%^&*");

  if (chars.length === 0) chars = filter("abcdefghijklmnopqrstuvwxyz") || "abcdefghijklmnopqrstuvwxyz";

  const array = crypto.getRandomValues(new Uint32Array(length));
  let password = "";
  for (let i = 0; i < length; i++) {
    password += chars[array[i]! % chars.length];
  }
  return password;
}

/**
 * Generate a password that satisfies a detected site policy — clamps length
 * to maxLength, raises to minLength, honors forbidsSymbols, and excludes
 * forbiddenChars. Used by the inline popup when the user clicks "regen" on a
 * signup form with parseable requirements.
 */
export function generateSmartPassword(policy: PasswordPolicy = {}): string {
  const defaultLength = 20;
  let length = defaultLength;
  if (policy.minLength) length = Math.max(length, policy.minLength);
  if (policy.maxLength) length = Math.min(length, policy.maxLength);
  if (length < 8) length = 8;

  return generatePassword({
    length,
    includeSymbols: !policy.forbidsSymbols,
    forbiddenChars: policy.forbiddenChars,
  });
}