standard ctv hash in typescript

ctvUtils.ts

import { Transaction } from '@scure/btc-signer';
import { Buffer } from 'buffer'; // You may need to import the appropriate library for Buffer
import { sha256 } from '@noble/hashes/sha256';


function ser_compact_size(l: number): Buffer {
  let r: Buffer = Buffer.from('');
  if (l < 253) {
    r = Buffer.from([l]);
  } else if (l < 0x10000) {
    r = Buffer.concat([Buffer.from([253]), Buffer.from([l & 0xff, (l >> 8) & 0xff])]);
  } else if (l < 0x100000000) {
    r = Buffer.concat([
      Buffer.from([254]),
      Buffer.from([l & 0xff, (l >> 8) & 0xff, (l >> 16) & 0xff, (l >> 24) & 0xff]),
    ]);
  } else {
    r = Buffer.concat([
      Buffer.from([255]),
      Buffer.from([l & 0xff, (l >> 8) & 0xff, (l >> 16) & 0xff, (l >> 24) & 0xff]),
      Buffer.from([l >> 32, (l >> 40) & 0xff, (l >> 48) & 0xff, (l >> 56) & 0xff]),
    ]);
  }
  return r;
}

function ser_string(s: Buffer): Buffer {
  const length = s.length;
  return Buffer.concat([ser_compact_size(length), s]);
}



function getStandardTemplateHash(transaction: Transaction, nIn: number): Buffer {
    let r: Buffer = Buffer.from('');

    r = Buffer.concat([r, Buffer.from(transaction.version.toString(), 'binary')]);
    r = Buffer.concat([r, Buffer.from(transaction.lockTime.toString(), 'binary')]);

    const inputs = transaction.inputsLength;
    for (let i = 0; i < inputs; i++) {
        const input = transaction.getInput(i);
        if (input.finalScriptSig) {
            r = Buffer.concat([r, Buffer.from(input.finalScriptSig)]);
        }
        r = Buffer.concat([r, Buffer.from(input.sequence!.toString(), 'binary')]);
    }

    r = Buffer.concat([r, ser_compact_size(inputs)]);

    const outputs = transaction.outputsLength;
    for (let i = 0; i < outputs; i++) {
        const output = transaction.getOutput(i);
        r = Buffer.concat([r, Buffer.from(output.amount!.toString(), 'binary')]);
        r = Buffer.concat([r, ser_string(Buffer.from(output.script!.toString(), 'binary'))]);
    }

    r = Buffer.concat([r, ser_compact_size(nIn.toString().length)]);
    r = Buffer.concat([r, Buffer.from(nIn.toString(), 'binary')]);


    return Buffer.from(sha256(Buffer.from(r)));

}