/**
 * Pinduoduo Extension Web Crypto Envelope Encryption Module
 * 基于浏览器原生 Web Crypto API 的端到端信封加密工具库（无任何第三方依赖）
 */

// 将 Base64 字符串转换为 ArrayBuffer
function base64ToArrayBuffer(base64) {
  const binaryString = atob(base64.replace(/\s+/g, ''))
  const len = binaryString.length
  const bytes = new Uint8Array(len)
  for (let i = 0; i < len; i++) {
    bytes[i] = binaryString.charCodeAt(i)
  }
  return bytes.buffer
}

// 将 ArrayBuffer / Uint8Array 转换为 Base64 字符串
function arrayBufferToBase64(buffer) {
  let binary = ''
  const bytes = new Uint8Array(buffer)
  const len = bytes.byteLength
  for (let i = 0; i < len; i++) {
    binary += String.fromCharCode(bytes[i])
  }
  return btoa(binary)
}

// 导入服务端 RSA-OAEP (SHA-256) 公钥 (SPKI 格式)
async function importRsaPublicKey(spkiBase64) {
  const cleanSpki = spkiBase64
    .replace(/-----BEGIN PUBLIC KEY-----/, '')
    .replace(/-----END PUBLIC KEY-----/, '')
    .replace(/\s+/g, '')

  const keyBuffer = base64ToArrayBuffer(cleanSpki)
  return await crypto.subtle.importKey(
    'spki',
    keyBuffer,
    {
      name: 'RSA-OAEP',
      hash: 'SHA-256',
    },
    false,
    ['encrypt'],
  )
}

// 计算文本 SHA-256 哈希（用于 Cookie 指纹比对）
async function computeSha256(text) {
  const encoder = new TextEncoder()
  const data = encoder.encode(text)
  const hashBuffer = await crypto.subtle.digest('SHA-256', data)
  const hashArray = Array.from(new Uint8Array(hashBuffer))
  return hashArray.map((b) => b.toString(16).padStart(2, '0')).join('')
}

/**
 * 执行混合信封加密
 * 1. 生成一次性 256 位 AES-GCM 密钥 + 12 字节 IV
 * 2. 用 AES-256-GCM 加密明文载荷，分离密文与 128 位认证标签 (Tag)
 * 3. 用服务端 RSA 公钥加密 AES 密钥
 * 4. 返回标准信封包 { key, iv, tag, cipher }
 */
async function encryptPayloadWithEnvelope(payload, serverPublicKeySpki) {
  const cryptoObj = self.crypto || window.crypto
  if (!cryptoObj || !cryptoObj.subtle) {
    throw new Error('当前浏览器环境不支持 Web Crypto API')
  }

  // 1. 生成一次性 AES-GCM 对称密钥
  const aesKey = await cryptoObj.subtle.generateKey(
    {
      name: 'AES-GCM',
      length: 256,
    },
    true,
    ['encrypt'],
  )

  // 2. 生成 12 字节加密 IV
  const iv = cryptoObj.getRandomValues(new Uint8Array(12))

  // 3. 使用 AES-256-GCM 加密明文 JSON
  const encoder = new TextEncoder()
  const plainBytes = encoder.encode(JSON.stringify(payload))
  const encryptedBuf = await cryptoObj.subtle.encrypt(
    {
      name: 'AES-GCM',
      iv,
      tagLength: 128,
    },
    aesKey,
    plainBytes,
  )

  // Web Crypto AES-GCM 的输出格式为: [密文 (前 N 字节)] + [认证标签 Tag (后 16 字节)]
  const totalLen = encryptedBuf.byteLength
  const cipherBytes = encryptedBuf.slice(0, totalLen - 16)
  const tagBytes = encryptedBuf.slice(totalLen - 16)

  // 4. 导出对称密钥原始字节 (32 字节)
  const rawAesKey = await cryptoObj.subtle.exportKey('raw', aesKey)

  // 5. 导入服务端 RSA 公钥并加密 AES 密钥
  const rsaKey = await importRsaPublicKey(serverPublicKeySpki)
  const encKeyBuf = await cryptoObj.subtle.encrypt(
    {
      name: 'RSA-OAEP',
    },
    rsaKey,
    rawAesKey,
  )

  return {
    key: arrayBufferToBase64(encKeyBuf),
    iv: arrayBufferToBase64(iv),
    tag: arrayBufferToBase64(tagBytes),
    cipher: arrayBufferToBase64(cipherBytes),
  }
}

// 导出全局函数供 background.js 与 popup.js 引用
if (typeof self !== 'undefined') {
  self.encryptPayloadWithEnvelope = encryptPayloadWithEnvelope
  self.computeSha256 = computeSha256
  self.importRsaPublicKey = importRsaPublicKey
}