import type { Account } from "@solana/spl-token";
import { TOKEN_PROGRAM_ID, unpackAccount } from "@solana/spl-token";
import type { Connection, PublicKey } from "@solana/web3.js";

/**
 * Get all token accounts by delegate.
 * @param connection - The connection to the Solana blockchain.
 * @param delegatePubkey - The public key of the delegate.
 * @returns The token accounts by delegate.
 */
export async function getTokenAccountsByDelegate({
  connection,
  delegate,
  mint,
}: {
  connection: Connection;
  delegate: PublicKey;
  mint: PublicKey;
}): Promise<Account[]> {
  // Each SPL token account is 165 bytes, with the delegate at offset 73
  const filters = [
    { dataSize: 165 },
    {
      memcmp: {
        offset: 76,
        bytes: delegate.toBase58(),
      },
    },
    {
      memcmp: {
        offset: 0,
        bytes: mint.toBase58(),
      },
    },
  ];

  const accounts = await connection.getProgramAccounts(TOKEN_PROGRAM_ID, {
    filters,
  });

  return accounts.map((account) =>
    unpackAccount(account.pubkey, account.account),
  );
}