/**
 * AES-256-GCM 加密存储 — 替代 XOR 加密
 * 依赖 @noble/ciphers + crypto-polyfill（wx.getRandomValuesSync）
 */
import Taro from '@tarojs/taro';
import { gcm } from '@noble/ciphers/aes.js';

const STORAGE_PREFIX = '_es_';
const AES_MARKER = 'aes:';
const NONCE_LENGTH = 12; // GCM 标准 nonce 长度

declare const wx: {
  getRandomValuesSync?: (params: { length: number }) => ArrayBuffer;
} | undefined;

function getEncryptionKey(): Uint8Array {
  const hex = process.env.TARO_APP_ENCRYPTION_KEY || '';
  if (hex && /^[0-9a-fA-F]{64}$/.test(hex)) {
    return new Uint8Array(hex.match(/.{2}/g)!.map((b) => parseInt(b, 16)));
  }
  // derive 32 bytes from passphrase
  const passphrase = process.env.TARO_APP_ENCRYPTION_KEY || 'hms-default-key';
  const bytes = new Uint8Array(32);
  for (let i = 0; i < 32; i++) {
    bytes[i] = passphrase.charCodeAt(i % passphrase.length) ^ ((i * 37) & 0xff);
  }
  return bytes;
}

function generateNonce(): Uint8Array {
  const nonce = new Uint8Array(NONCE_LENGTH);
  if (typeof globalThis.crypto?.getRandomValues === 'function') {
    globalThis.crypto.getRandomValues(nonce);
  } else if (typeof wx !== 'undefined' && typeof wx.getRandomValuesSync === 'function') {
    const buf = wx.getRandomValuesSync({ length: NONCE_LENGTH });
    const src = new Uint8Array(buf as ArrayBuffer);
    nonce.set(src);
  } else {
    for (let i = 0; i < NONCE_LENGTH; i++) {
      nonce[i] = (Math.random() * 256) | 0;
    }
  }
  return nonce;
}

function aesEncrypt(plaintext: string): string {
  const key = getEncryptionKey();
  const nonce = generateNonce();
  const cipher = gcm(key, nonce);
  const data = new TextEncoder().encode(plaintext);
  const ciphertext = cipher.encrypt(data);
  // nonce(12) + ciphertext 打包
  const combined = new Uint8Array(nonce.length + ciphertext.length);
  combined.set(nonce, 0);
  combined.set(ciphertext, nonce.length);
  return AES_MARKER + Taro.arrayBufferToBase64(combined.buffer as ArrayBuffer);
}

function aesDecrypt(encoded: string): string | null {
  try {
    const b64 = encoded.slice(AES_MARKER.length);
    const buf = Taro.base64ToArrayBuffer(b64);
    const combined = new Uint8Array(buf);
    if (combined.length < NONCE_LENGTH) return null;

    const nonce = combined.slice(0, NONCE_LENGTH);
    const ciphertext = combined.slice(NONCE_LENGTH);
    const key = getEncryptionKey();
    const cipher = gcm(key, nonce);
    const plaintext = cipher.decrypt(ciphertext);
    return new TextDecoder().decode(plaintext);
  } catch {
    return null;
  }
}

// XOR decryption for reading legacy data
function xorDecrypt(data: string, key: string): string {
  let result = '';
  for (let i = 0; i < data.length; i++) {
    result += String.fromCharCode(data.charCodeAt(i) ^ key.charCodeAt(i % key.length));
  }
  return result;
}

function fromBase64(b64: string): string {
  try {
    const buffer = Taro.base64ToArrayBuffer(b64);
    return new TextDecoder().decode(new Uint8Array(buffer));
  } catch {
    return '';
  }
}

const LEGACY_KEY = process.env.TARO_APP_ENCRYPTION_KEY || 'hms-default-key';

export function secureSet(key: string, value: string): void {
  if (!value) {
    Taro.removeStorageSync(STORAGE_PREFIX + key);
    return;
  }
  const encrypted = aesEncrypt(value);
  Taro.setStorageSync(STORAGE_PREFIX + key, encrypted);
}

export function secureGet(key: string): string {
  const prefixedKey = STORAGE_PREFIX + key;
  const raw = Taro.getStorageSync(prefixedKey);
  if (!raw || typeof raw !== 'string') {
    // fallback: 明文键（兼容 MCP 注入）
    const plain = Taro.getStorageSync(key);
    return plain && typeof plain === 'string' ? plain : '';
  }

  // AES 格式
  if (raw.startsWith(AES_MARKER)) {
    const decrypted = aesDecrypt(raw);
    if (decrypted !== null) return decrypted;
  }

  // XOR 格式（legacy）
  try {
    const decoded = fromBase64(raw);
    if (decoded) {
      return xorDecrypt(decoded, LEGACY_KEY);
    }
  } catch {
    // fallthrough
  }

  // 明文 fallback
  return raw;
}

export function secureRemove(key: string): void {
  Taro.removeStorageSync(STORAGE_PREFIX + key);
}

const MIGRATION_KEYS = [
  'access_token', 'refresh_token', 'token_expires_at',
  'user_data', 'user_roles', 'tenant_id', 'wechat_openid',
];

export function migrateLegacyStorage(): void {
  try {
    for (const key of MIGRATION_KEYS) {
      const prefixed = STORAGE_PREFIX + key;
      const already = Taro.getStorageSync(prefixed);
      if (already) {
        // re-encrypt with AES if not already
        if (typeof already === 'string' && !already.startsWith(AES_MARKER)) {
          const value = secureGet(key);
          if (value) secureSet(key, value);
        }
        continue;
      }

      const legacy = Taro.getStorageSync(key);
      if (!legacy || typeof legacy !== 'string') continue;

      secureSet(key, legacy);
      Taro.removeStorageSync(key);
    }
  } catch {
    // migration best-effort
  }
}