#!/usr/bin/env node
// backfill-toc.mjs — Fase 1b applier: insert a `## Innhold` TOC into EXISTING large
// reference files via transform.insertToc. Dry-run by default; --write applies in place.
//
// transform.mjs stays pure (it never writes — architecture invariant); THIS script is
// the operator-gate-side applier, the same seam commands/kb-update.md occupies when it
// writes a composed file after the gate clears. All the logic lives in the tested
// insertToc (no-op on small/already-TOC'd files, body byte-identical) — this is glue.
//
//   node scripts/kb-update/backfill-toc.mjs <file.md ...>           # dry-run (report)
//   node scripts/kb-update/backfill-toc.mjs --write <file.md ...>   # apply in place
//
// Per file: would/write (+N lines, M sections) | skip (small or already has TOC).
// A file whose content insertToc leaves unchanged is never rewritten (no churn).

import { readFileSync, writeFileSync } from 'node:fs';
import { insertToc, buildToc } from './lib/transform.mjs';

const argv = process.argv.slice(2);
const write = argv.includes('--write');
const files = argv.filter((a) => a !== '--write');

if (files.length === 0) {
  console.error('usage: backfill-toc.mjs [--write] <file.md ...>');
  process.exit(2);
}

let changed = 0;
let skipped = 0;
for (const path of files) {
  const before = readFileSync(path, 'utf8');
  const after = insertToc(before);
  if (after === before) {
    skipped++;
    console.log(`skip   ${path}  (small or already has TOC)`);
    continue;
  }
  const addedLines = after.split('\n').length - before.split('\n').length;
  const sections = (buildToc(before).match(/^- /gm) || []).length;
  changed++;
  if (write) {
    writeFileSync(path, after);
    console.log(`write  ${path}  (+${addedLines} lines, ${sections} sections)`);
  } else {
    console.log(`would  ${path}  (+${addedLines} lines, ${sections} sections)`);
  }
}

const verb = write ? 'wrote' : 'would change';
const hint = write ? '' : '  — re-run with --write to apply';
console.log(`\n${verb} ${changed}, skipped ${skipped}${hint}`);