import { getPublicKey, getSharedSecret } from '@noble/secp256k1';
import { bytesToHex, hexToBytes } from '@noble/hashes/utils';

/**
 * Encrypt data with AES-GCM using a shared secret derived from ECDH.
 */
export async function encryptWithECDH(
  data: string,
  recipientPublicKey: string,
  senderPrivateKey: string,
): Promise<{
  encrypted: string;
  iv: string;
  publicKey: string;
}> {
  const recipientPubKey = hexToBytes(recipientPublicKey);
  const senderPrivKey = hexToBytes(senderPrivateKey);

  const sharedSecret = getSharedSecret(senderPrivKey, recipientPubKey, true);
  const keyMaterial = await crypto.subtle.importKey(
    'raw',
    sharedSecret.slice(0, 32) as BufferSource,
    { name: 'HKDF' },
    false,
    ['deriveBits', 'deriveKey'],
  );

  const derivedKey = await crypto.subtle.deriveKey(
    {
      name: 'HKDF',
      hash: 'SHA-256',
      salt: new Uint8Array(32),
      info: new Uint8Array(0),
    },
    keyMaterial,
    { name: 'AES-GCM', length: 256 },
    false,
    ['encrypt'],
  );

  const iv = crypto.getRandomValues(new Uint8Array(12));
  const encoder = new TextEncoder();
  const dataBytes = encoder.encode(data);

  const encrypted = await crypto.subtle.encrypt(
    {
      name: 'AES-GCM',
      iv,
    },
    derivedKey,
    dataBytes,
  );

  return {
    encrypted: bytesToHex(new Uint8Array(encrypted)),
    iv: bytesToHex(iv),
    publicKey: bytesToHex(getPublicKey(senderPrivKey, true)),
  };
}

/**
 * Decrypt data with AES-GCM using a shared secret derived from ECDH.
 */
export async function decryptWithECDH(
  encrypted: string,
  iv: string,
  senderPublicKey: string,
  recipientPrivateKey: string,
): Promise<string> {
  const senderPubKey = hexToBytes(senderPublicKey);
  const recipientPrivKey = hexToBytes(recipientPrivateKey);

  const sharedSecret = getSharedSecret(recipientPrivKey, senderPubKey, true);
  const keyMaterial = await crypto.subtle.importKey(
    'raw',
    sharedSecret.slice(0, 32) as BufferSource,
    { name: 'HKDF' },
    false,
    ['deriveBits', 'deriveKey'],
  );

  const derivedKey = await crypto.subtle.deriveKey(
    {
      name: 'HKDF',
      hash: 'SHA-256',
      salt: new Uint8Array(32),
      info: new Uint8Array(0),
    },
    keyMaterial,
    { name: 'AES-GCM', length: 256 },
    false,
    ['decrypt'],
  );

  const encryptedBytes = hexToBytes(encrypted);
  const ivBytes = hexToBytes(iv);

  const decrypted = await crypto.subtle.decrypt(
    {
      name: 'AES-GCM',
      iv: ivBytes as BufferSource,
    },
    derivedKey,
    encryptedBytes as BufferSource,
  );

  const decoder = new TextDecoder();
  return decoder.decode(decrypted);
}

/**
 * Encrypt data for "publish to all" scenario.
 * Uses a symmetric key that can be shared via ECDH with multiple recipients.
 */
export async function encryptForAll(
  data: string,
  encryptionKey: Uint8Array,
): Promise<{
  encrypted: string;
  iv: string;
}> {
  const key = await crypto.subtle.importKey(
    'raw',
    encryptionKey as BufferSource,
    { name: 'AES-GCM' },
    false,
    ['encrypt'],
  );

  const iv = crypto.getRandomValues(new Uint8Array(12));
  const encoder = new TextEncoder();
  const dataBytes = encoder.encode(data);

  const encrypted = await crypto.subtle.encrypt(
    {
      name: 'AES-GCM',
      iv: iv as BufferSource,
    },
    key,
    dataBytes,
  );

  return {
    encrypted: bytesToHex(new Uint8Array(encrypted)),
    iv: bytesToHex(iv),
  };
}

/**
 * Decrypt data encrypted with encryptForAll.
 */
export async function decryptForAll(
  encrypted: string,
  iv: string,
  encryptionKey: Uint8Array,
): Promise<string> {
  const key = await crypto.subtle.importKey(
    'raw',
    encryptionKey as BufferSource,
    { name: 'AES-GCM' },
    false,
    ['decrypt'],
  );

  const encryptedBytes = hexToBytes(encrypted);
  const ivBytes = hexToBytes(iv);

  const decrypted = await crypto.subtle.decrypt(
    {
      name: 'AES-GCM',
      iv: ivBytes as BufferSource,
    },
    key,
    encryptedBytes as BufferSource,
  );

  const decoder = new TextDecoder();
  return decoder.decode(decrypted);
}