export const APP_LOCK_TIMEOUT_OPTIONS_MINUTES = [0, 1, 5, 15, 30, 60] as const;
export type AppLockTimeoutMinutes = typeof APP_LOCK_TIMEOUT_OPTIONS_MINUTES[number];

export interface AppLockPasswordVerifier {
  version: 1;
  algorithm: 'PBKDF2-SHA256';
  iterations: number;
  salt: string;
  hash: string;
}

export interface AppLockSettings {
  enabled: boolean;
  timeoutMinutes: AppLockTimeoutMinutes;
  systemUnlockEnabled: boolean;
  systemUnlockAutoPromptEnabled: boolean;
  passwordVerifier: AppLockPasswordVerifier | null;
}

export type AppLockSettingsChangeError =
  | 'empty-current'
  | 'empty-next'
  | 'incorrect';

export const DEFAULT_APP_LOCK_SETTINGS: AppLockSettings = {
  enabled: false,
  timeoutMinutes: 15,
  systemUnlockEnabled: false,
  systemUnlockAutoPromptEnabled: false,
  passwordVerifier: null,
};

const APP_LOCK_VERIFIER_VERSION = 1;
const APP_LOCK_ALGORITHM = 'PBKDF2-SHA256';
const APP_LOCK_SALT_BYTES = 16;
const APP_LOCK_HASH_BYTES = 32;

function base64ToBytes(value: string): Uint8Array | null {
  try {
    const binary = atob(value);
    const bytes = new Uint8Array(binary.length);
    for (let i = 0; i < binary.length; i += 1) {
      bytes[i] = binary.charCodeAt(i);
    }
    return bytes;
  } catch {
    return null;
  }
}

function isRecord(value: unknown): value is Record<string, unknown> {
  return Boolean(value && typeof value === 'object' && !Array.isArray(value));
}

export function normalizeAppLockTimeoutMinutes(input: unknown): AppLockTimeoutMinutes {
  const value = typeof input === 'string' && input.trim() !== '' ? Number(input) : input;
  return APP_LOCK_TIMEOUT_OPTIONS_MINUTES.includes(value as AppLockTimeoutMinutes)
    ? value as AppLockTimeoutMinutes
    : DEFAULT_APP_LOCK_SETTINGS.timeoutMinutes;
}

export function normalizeAppLockPasswordVerifier(input: unknown): AppLockPasswordVerifier | null {
  if (!isRecord(input)) return null;
  if (input.version !== APP_LOCK_VERIFIER_VERSION) return null;
  if (input.algorithm !== APP_LOCK_ALGORITHM) return null;
  if (typeof input.iterations !== 'number' || !Number.isInteger(input.iterations) || input.iterations < 100000) {
    return null;
  }
  if (typeof input.salt !== 'string' || base64ToBytes(input.salt)?.length !== APP_LOCK_SALT_BYTES) {
    return null;
  }
  if (typeof input.hash !== 'string' || base64ToBytes(input.hash)?.length !== APP_LOCK_HASH_BYTES) {
    return null;
  }

  return {
    version: APP_LOCK_VERIFIER_VERSION,
    algorithm: APP_LOCK_ALGORITHM,
    iterations: input.iterations,
    salt: input.salt,
    hash: input.hash,
  };
}

export function normalizeAppLockSettings(input: unknown): AppLockSettings {
  if (!isRecord(input)) return DEFAULT_APP_LOCK_SETTINGS;

  const timeoutMinutes = normalizeAppLockTimeoutMinutes(input.timeoutMinutes);
  const passwordVerifier = normalizeAppLockPasswordVerifier(input.passwordVerifier);
  const enabled = input.enabled === true && passwordVerifier !== null;
  const systemUnlockEnabled = input.systemUnlockEnabled === true && enabled;
  const systemUnlockAutoPromptEnabled = input.systemUnlockAutoPromptEnabled === true && systemUnlockEnabled;

  return {
    enabled,
    timeoutMinutes,
    systemUnlockEnabled,
    systemUnlockAutoPromptEnabled,
    passwordVerifier,
  };
}