// scripts/backfill-series-id.js
const { readFileSync, writeFileSync } = require('node:fs');
const { resolve } = require('node:path');
const { getCalendarEvents } = require('./lib/o365-calendar.js');

function upsertFrontmatterField(md, key, value) {
  const fmMatch = md.match(/^---\n([\s\S]*?)\n---/);
  if (!fmMatch) return md;
  const fm = fmMatch[1];
  const lineRegex = new RegExp(`^${key}:.*$`, 'm');
  let newFm;
  if (lineRegex.test(fm)) {
    newFm = fm.replace(lineRegex, `${key}: ${value}`);
  } else {
    newFm = `${fm}\n${key}: ${value}`;
  }
  return md.replace(/^---\n[\s\S]*?\n---/, `---\n${newFm}\n---`);
}

async function backfill(agendaPath, titleRegex, daysAhead = 30) {
  const events = await getCalendarEvents(daysAhead);
  const re = new RegExp(titleRegex, 'i');
  const match = events.find(e => re.test(e.title) && e.isRecurring);
  if (!match) {
    throw new Error(`no recurring event matching /${titleRegex}/ in next ${daysAhead} days`);
  }
  // Need raw seriesMasterId — re-fetch single event by id (parseEventToMeeting drops it)
  const { getEventById } = require('./lib/o365-calendar.js');
  const raw = await getEventById(match.id);
  const seriesId = raw.seriesMasterId;
  if (!seriesId) {
    throw new Error(`event ${match.id} has no seriesMasterId`);
  }
  const md = readFileSync(agendaPath, 'utf-8');
  const updated = upsertFrontmatterField(md, 'o365_series_id', seriesId);
  writeFileSync(agendaPath, updated, 'utf-8');
  return seriesId;
}

async function main() {
  const args = process.argv.slice(2);
  if (args.length < 2) {
    console.error('Usage: node backfill-series-id.js <agenda-path> <title-regex>');
    process.exit(2);
  }
  const [agendaPath, titleRegex] = args;
  const id = await backfill(resolve(agendaPath), titleRegex);
  console.log(`set o365_series_id=${id} in ${agendaPath}`);
}

if (require.main === module) {
  main().catch(e => { console.error(e.stack || e.message); process.exit(1); });
}

module.exports = { upsertFrontmatterField, backfill };