import { PUBLIC_KEY_PEM } from './public';

function arrayBufferToBase64(buffer: ArrayBuffer) {
  let binary = '';
  const bytes = new Uint8Array(buffer);
  const len = bytes.byteLength;
  for (let i = 0; i < len; i++) {
    binary += String.fromCharCode(bytes[i]);
  }
  return window.btoa(binary);
}

function importPublicKeyFromString(pem: string) {
  const pemHeader = '-----BEGIN PUBLIC KEY-----';
  const pemFooter = '-----END PUBLIC KEY-----';
  const pemContents = pem
    .substring(pem.indexOf(pemHeader) + pemHeader.length, pem.indexOf(pemFooter))
    .replace(/\s+/g, '');

  const binaryDerString = window.atob(pemContents);
  const binaryDer = new Uint8Array(binaryDerString.length);
  for (let i = 0; i < binaryDerString.length; i++) {
    binaryDer[i] = binaryDerString.charCodeAt(i);
  }

  return binaryDer.buffer;
}

interface ReportBody {
  eventType: string;
  gameInfo: {
    gameId: string;
    sessionId: string;
  };
}

export async function generateEncryptedPayload(payload: ReportBody) {
  const crypto = window.crypto;
  const subtle = crypto.subtle;

  const keyBuffer = importPublicKeyFromString(PUBLIC_KEY_PEM);

  const publicKey = await subtle.importKey(
    'spki',
    keyBuffer,
    {
      name: 'RSA-OAEP',
      hash: 'SHA-1'
    },
    false,
    ['encrypt']
  );

  const aesKeyRaw = crypto.getRandomValues(new Uint8Array(32));
  const aesKeyObj = await subtle.importKey('raw', aesKeyRaw, 'AES-GCM', false, ['encrypt']);

  const encryptedAesKeyBuffer = await subtle.encrypt(
    {
      name: 'RSA-OAEP'
    },
    publicKey,
    aesKeyRaw
  );

  const k = arrayBufferToBase64(encryptedAesKeyBuffer);

  const timestamp = Date.now();
  const payloadJson = {
    timestamp,
    data: payload
  };

  const encoder = new TextEncoder();
  const payloadBytes = encoder.encode(JSON.stringify(payloadJson));

  const iv = crypto.getRandomValues(new Uint8Array(12));

  const ciphertextWithTagBuffer = await subtle.encrypt(
    {
      name: 'AES-GCM',
      iv: iv,
      tagLength: 128
    },
    aesKeyObj,
    payloadBytes
  );

  const ciphertextWithTag = new Uint8Array(ciphertextWithTagBuffer);
  const finalPayloadBuffer = new Uint8Array(iv.length + ciphertextWithTag.length);

  finalPayloadBuffer.set(iv, 0); // 先放 IV
  finalPayloadBuffer.set(ciphertextWithTag, iv.length); // 再放 Ciphertext + Tag

  const encryptedPayload = arrayBufferToBase64(finalPayloadBuffer.buffer);
  const data = {
    k: k,
    v: '1.0',
    payload: encryptedPayload
  };

  return data;
}