import { isDeepStrictEqual } from 'node:util';

const names = ['ledger.csv', 'exceptions.json', 'dispatch.json'];
const sameKeys = (value, keys) => value !== null && typeof value === 'object'
  && !Array.isArray(value) && isDeepStrictEqual(Object.keys(value).sort(), [...keys].sort());

// Accept CSV quoting and CRLF; compare records, not a preferred serialization.
export function parseCsv(input) {
  const rows = [];
  let row = [], field = '', quoted = false, closed = false;
  for (let i = 0; i < input.length; i++) {
    const char = input[i];
    if (quoted) {
      if (char === '"' && input[i + 1] === '"') { field += '"'; i++; }
      else if (char === '"') { quoted = false; closed = true; }
      else field += char;
    } else if (char === ',' || char === '\n' || char === '\r') {
      row.push(field); field = ''; closed = false;
      if (char !== ',') {
        rows.push(row); row = [];
        if (char === '\r' && input[i + 1] === '\n') i++;
      }
    } else if (char === '"' && field === '' && !closed) quoted = true;
    else if (char === '"' || closed) throw new Error('Malformed CSV quoting');
    else field += char;
  }
  if (quoted) throw new Error('Unterminated CSV quote');
  if (row.length || field || closed || input.endsWith(',')) { row.push(field); rows.push(row); }
  return rows;
}

const sortedExceptions = (value) => Array.isArray(value)
  ? [...value].sort((a, b) => JSON.stringify([a?.source, a?.recordId, a?.kind])
    .localeCompare(JSON.stringify([b?.source, b?.recordId, b?.kind]))) : null;

export function validateBundle(output, expected) {
  let value;
  try {
    if (typeof output !== 'string' || Buffer.byteLength(output) > 1_000_000)
      throw new Error('Output exceeds the bundle limit');
    value = JSON.parse(output);
    if (!sameKeys(value, names) || typeof value['ledger.csv'] !== 'string')
      throw new Error('Expected exactly the three named deliverables');
    const ledger = isDeepStrictEqual(parseCsv(value['ledger.csv']), parseCsv(expected['ledger.csv']));
    const exceptions = isDeepStrictEqual(sortedExceptions(value['exceptions.json']), sortedExceptions(expected['exceptions.json']));
    const dispatch = isDeepStrictEqual(value['dispatch.json'], expected['dispatch.json']);
    const passed = ledger && exceptions && dispatch;
    return { passed, reason: passed ? 'The independent reconciliation matches all three deliverables.'
      : `Independent reconciliation mismatch: ${[!ledger && 'ledger', !exceptions && 'exceptions', !dispatch && 'dispatch'].filter(Boolean).join(', ')}.`,
      metrics: { ledgerCorrect: Number(ledger), exceptionsCorrect: Number(exceptions), dispatchCorrect: Number(dispatch) },
      bundle: passed ? value : null };
  } catch {
    return { passed: false, reason: 'Response is not a valid bounded three-file reconciliation bundle.',
      metrics: { ledgerCorrect: 0, exceptionsCorrect: 0, dispatchCorrect: 0 }, bundle: null };
  }
}