#!/usr/bin/env node
/**
 * frontmatter-touch.js — Nomad Stop hook: keep the `updated` field of
 * charter-schema markdown files honest, without git.
 *
 * WHAT IT DOES
 * At session close-out, every `.md` under the team root whose ON-DISK reality
 * is newer than its DECLARED freshness gets its frontmatter `updated` field
 * refreshed:
 *
 *     file mtime's calendar date  >  frontmatter `updated`
 *     (or `created`, when no `updated` line exists yet)
 *         → set `updated: <mtime date>`
 *
 * WHY NOT `git status` (how the production original finds changed files)
 * The production deployment this ports from lives in a git repository, so
 * "what changed" is one `git status --porcelain` away. A Nomad team is
 * typically a zip-extracted plain folder — no `.git`, no installer-run
 * `git init` — so the discovery mechanism had to be rebuilt, not desensitized.
 * The mtime-vs-frontmatter reconciliation above was chosen over the closer
 * "files modified today" imitation because it is an ASYNC CATCH-UP: edits
 * made on a hookless harness yesterday (see the team charter's "no-hook
 * platforms reconcile on next start" compensation clause) are still caught
 * the next time ANY hook-bearing session closes — `git status` and
 * "today only" both miss that case. Trade-off accepted: mtime is a cruder
 * signal than a git diff (a content-identical rewrite still counts as
 * "changed"); the charter-schema gate below keeps the blast radius to files
 * that opted into this metadata contract.
 *
 * SAFETY RAILS (each one exists because of a concrete failure mode):
 *   1. Charter-schema gate — only files whose frontmatter carries all of
 *      `owner` + `created` + `status` are ever touched. SKILL.md-style files
 *      with their own metadata vocabulary are structurally invisible to this
 *      hook. Malformed date values (anything not YYYY-MM-DD) → skip, never
 *      "fix" (would rather leave a stale field than guess).
 *   2. mtime restore after write — rewriting the file would itself bump
 *      mtime, which next Stop would read as "changed again", re-dating
 *      `updated` to today forever. After a verified write, mtime is restored
 *      to its pre-write value, so the reconciliation converges.
 *   3. Per-run touch cap (default 100, env NOMAD_FMTOUCH_MAX_TOUCH) — a bulk
 *      copy/extraction done with a tool that does NOT preserve mtimes can
 *      make hundreds of files look freshly edited at once. The cap turns
 *      that into bounded work per close-out (progress resumes next Stop —
 *      converges, never deadlocks) instead of an IO storm inside a hook
 *      timeout window.
 *   4. Scan-baseline state file (OS temp dir, keyed by team root) — steady
 *      state, only files whose mtime moved since the last completed run get
 *      their content read at all; everything else is a bare stat() during
 *      the directory walk. Losing the state file (temp cleanup) just means
 *      one full re-read pass, which the idempotent rule then no-ops.
 *   5. Per-file lock + atomic write + read-back verify — same `<file>.lock`
 *      naming as append-log.js, so this hook and a concurrent append can
 *      never interleave a lost update on a shared file. Lock busy → skip,
 *      next Stop catches up (nothing here is worth blocking close-out for).
 *   6. Stop-hook iron rule — every failure path is silent-skip + local log
 *      line (OS temp dir, `nomad_fmtouch.log`); stdout stays empty (this is
 *      pure housekeeping, zero injection budget), close-out is NEVER blocked.
 *
 * ONE DELIBERATE DIVERGENCE from the production original: when a
 * charter-schema file has no `updated` line yet, this version INSERTS one
 * (right after `created`). The production deployment leaves missing fields
 * to its structure-sentinel to report — that sentinel is not part of this
 * portable package, and Nomad-scaffolded teams ship with `updated` absent
 * everywhere (it's optional in the charter), so "replace-only" would make
 * this hook a permanent no-op on exactly the teams it ships to.
 *
 * Usage: node frontmatter-touch.js [--platform claude|codex|cursor]
 *   stdin: hook input JSON (cwd / session_id). Not inside a Nomad team
 *   (no team-config.json up the tree) → exits silently.
 */
'use strict';
const fs = require('fs');
const path = require('path');
const os = require('os');
const crypto = require('crypto');
const emit = require('./lib/emit');
const cfg = require('./lib/config');
const fm = require('./lib/frontmatter');
const flock = require('./lib/file-lock');

const LOG_FILE = path.join(os.tmpdir(), 'nomad_fmtouch.log');
const STATE_FILE_PREFIX = 'nomad_fmtouch_state_';
const DATE_RE = /^\d{4}-\d{2}-\d{2}$/;
const DEFAULT_MAX_TOUCH_PER_RUN = 100;

function log(msg) {
  try {
    fs.appendFileSync(LOG_FILE, '[' + new Date().toISOString() + '] ' + msg + '\n', 'utf8');
  } catch (e) {
    /* logging must never hurt */
  }
}

/** Local-calendar date string (YYYY-MM-DD) for an epoch-ms timestamp. */
function dateStrFromMs(ms) {
  const d = new Date(ms);
  return d.getFullYear() + '-' + String(d.getMonth() + 1).padStart(2, '0') + '-' + String(d.getDate()).padStart(2, '0');
}

// ── exclusion rules (pure functions, exported for tests) ──────────────────
//
// Deliberately structural, never one deployment's folder names:
//   - dot-directories (.git/.claude/.codex/...) — tool internals
//   - node_modules — dependency trees are nobody's team documents
//   - 97/98/99-prefixed slots — the team-skeleton convention numbers its
//     inbox-misc / archive / recycle-bin slots 97/98/99 in BOTH the English
//     and native-language layouts, so the digits are the stable signal while
//     the human-readable part varies by language.
// Everything else is left to the charter-schema gate: a file that carries
// owner+created+status has opted into this metadata contract wherever it
// lives; one that doesn't is invisible regardless of directory.

function isExcludedDirName(name) {
  if (!name) return true;
  if (name.charAt(0) === '.') return true;
  if (name === 'node_modules') return true;
  if (/^9[789]([-_ ]|$)/.test(name)) return true;
  return false;
}

function isExcludedFileName(name) {
  if (!name) return true;
  if (name.charAt(0) === '~') return true;
  if (/\.bak(\.|_|$)/i.test(name)) return true;
  return false;
}

/**
 * Recursively collect candidate .md files under rootDir (exclusion-pruned).
 * Returns [{abs, mtimeMs}]. Symlinked directories are not followed
 * (readdirSync dirents report them as symlinks, not directories). Never throws.
 */
function collectMdFiles(rootDir) {
  const out = [];
  function walk(dir) {
    let entries;
    try {
      entries = fs.readdirSync(dir, { withFileTypes: true });
    } catch (e) {
      return;
    }
    for (const ent of entries) {
      if (ent.isDirectory()) {
        if (!isExcludedDirName(ent.name)) walk(path.join(dir, ent.name));
      } else if (ent.isFile()) {
        if (isExcludedFileName(ent.name)) continue;
        if (!/\.md$/i.test(ent.name)) continue;
        const abs = path.join(dir, ent.name);
        try {
          out.push({ abs, mtimeMs: fs.statSync(abs).mtimeMs });
        } catch (e) {
          /* raced deletion etc. — skip */
        }
      }
    }
  }
  walk(rootDir);
  return out;
}

// ── core decision (pure function, exported for tests) ─────────────────────

/**
 * Decide whether/how to refresh `updated` for one file's content.
 *
 * @param {string} content full file text
 * @param {string} fileDate the file's mtime as YYYY-MM-DD
 * @returns {null|{content:string, date:string, inserted:boolean}}
 *   null = leave the file alone (no frontmatter / broken block / not
 *   charter-schema / malformed dates / already up to date).
 */
function computeNext(content, fileDate) {
  if (!DATE_RE.test(fileDate)) return null;
  const parsed = fm.parse(content);
  if (!parsed || !parsed.complete) return null;

  const f = parsed.fields;
  // Charter-schema gate: owner + created + status must all be present (non-empty).
  if (!f.owner || !f.created || !f.status) return null;

  const hasUpdated = Object.prototype.hasOwnProperty.call(f, 'updated');
  let baseline;
  if (hasUpdated) {
    if (!DATE_RE.test(f.updated)) return null; // malformed — never "fix" by guessing
    baseline = f.updated;
  } else {
    if (!DATE_RE.test(f.created)) return null;
    baseline = f.created;
  }
  // YYYY-MM-DD strings compare correctly as strings.
  if (!(fileDate > baseline)) return null;

  // Surgical single-line edit: split preserving separators so the file's
  // newline style (and any mixed usage) survives byte-for-byte elsewhere.
  const body = parsed.hasBom ? content.slice(1) : content;
  const parts = body.split(/(\r\n|\r|\n)/); // [line0, sep0, line1, sep1, ...]
  const dominantSep = parts.length > 1 ? parts[1] : '\n';

  // blockLines index → physical logical-line index: block starts after the
  // opening fence (logical line 0), so blockLines[i] is logical line i+1.
  const targetKey = hasUpdated ? 'updated' : 'created';
  const blockIdx = parsed.lineIndexByKey[targetKey];
  if (blockIdx === undefined) return null; // defensive — fields came from these lines
  const logicalIdx = blockIdx + 1;
  const partsIdx = logicalIdx * 2;
  if (partsIdx >= parts.length) return null;

  if (hasUpdated) {
    parts[partsIdx] = 'updated: ' + fileDate;
  } else {
    // Insert a brand-new `updated` line right after the `created` line,
    // reusing that line's own separator so CRLF files stay CRLF.
    const sep = partsIdx + 1 < parts.length ? parts[partsIdx + 1] : dominantSep;
    parts.splice(partsIdx + 2, 0, 'updated: ' + fileDate, sep);
  }
  return {
    content: (parsed.hasBom ? '' : '') + parts.join(''),
    date: fileDate,
    inserted: !hasUpdated,
  };
}

// ── per-file processing ────────────────────────────────────────────────────

/**
 * Lock → re-read → re-decide → atomic write → verify → restore mtime.
 * @returns {'touched'|'skipped'|'locked'|'failed'}
 */
function touchFile(absPath) {
  const lockPath = absPath + '.lock';
  try {
    // Short retry only: lock busy means someone (e.g. append-log.js) is
    // writing right now — skip, next Stop catches up. Not worth waiting on.
    flock.acquireLockSync(lockPath, { retryMax: 3, retryIntervalMs: 500 });
  } catch (e) {
    return 'locked';
  }
  try {
    // Re-stat and re-read AFTER acquiring the lock — the pre-lock snapshot
    // may be stale by the time we hold exclusivity.
    const st = fs.statSync(absPath);
    const content = fs.readFileSync(absPath, 'utf8');
    const next = computeNext(content, dateStrFromMs(st.mtimeMs));
    if (next === null) return 'skipped';

    flock.atomicWriteSync(absPath, next.content);
    const verify = fs.readFileSync(absPath, 'utf8');
    if (verify.indexOf('updated: ' + next.date) === -1) {
      log('VERIFY-FAIL ' + absPath);
      return 'failed';
    }
    // Restore mtime so this write doesn't read as a fresh edit next run
    // (safety rail #2 in the header). utimesSync takes seconds.
    try {
      fs.utimesSync(absPath, st.atimeMs / 1000, st.mtimeMs / 1000);
    } catch (e) {
      // Non-fatal: worst case is one extra (idempotent, hence no-op) check
      // next run — computeNext will see updated == fileDate and skip.
      log('MTIME-RESTORE-FAIL ' + absPath + ' :: ' + e.message);
    }
    return 'touched';
  } catch (e) {
    log('ERR ' + absPath + ' :: ' + e.message);
    return 'failed';
  } finally {
    flock.releaseLock(lockPath);
  }
}

// ── scan-baseline state (perf only — correctness never depends on it) ─────

function stateFilePath(teamRoot) {
  const key = crypto.createHash('sha256').update(String(teamRoot).toLowerCase(), 'utf8').digest('hex').slice(0, 12);
  return path.join(os.tmpdir(), STATE_FILE_PREFIX + key + '.txt');
}

function readScanBaseline(teamRoot) {
  try {
    const raw = fs.readFileSync(stateFilePath(teamRoot), 'utf8');
    const ms = parseInt(raw, 10);
    return Number.isFinite(ms) && ms > 0 ? ms : 0;
  } catch (e) {
    return 0; // no/broken state = full pass (safe: rule is idempotent)
  }
}

function writeScanBaseline(teamRoot, ms) {
  try {
    fs.writeFileSync(stateFilePath(teamRoot), String(ms), 'utf8');
  } catch (e) {
    /* perf optimization only — losing it is harmless */
  }
}

function maxTouchPerRun() {
  const raw = parseInt(process.env.NOMAD_FMTOUCH_MAX_TOUCH || '', 10);
  return Number.isFinite(raw) && raw > 0 ? raw : DEFAULT_MAX_TOUCH_PER_RUN;
}

// ── main ───────────────────────────────────────────────────────────────────

async function main() {
  const platform = emit.getPlatform();
  try {
    const raw = await emit.readStdin();
    const sid = emit.extractSessionId(raw);
    if (sid && emit.isDuplicateInvocation('FmTouch', sid)) {
      process.exit(0);
      return;
    }

    const cwd = emit.resolveCwd(raw, platform);
    const teamRoot = cfg.resolveTeamRoot(cwd || process.cwd());
    if (!teamRoot) {
      process.exit(0); // not inside a Nomad team — none of our business
      return;
    }

    const baseline = readScanBaseline(teamRoot);
    const scanStartMs = Date.now();
    const files = collectMdFiles(teamRoot);
    // Only files whose mtime moved since the last COMPLETED run need their
    // content read; on a first run (baseline 0) that's everything.
    const candidates = files.filter((f) => f.mtimeMs > baseline);

    const cap = maxTouchPerRun();
    let touched = 0;
    let skipped = 0;
    let locked = 0;
    let failed = 0;
    let capped = 0;
    for (const f of candidates) {
      if (touched >= cap) {
        capped++;
        continue;
      }
      const r = touchFile(f.abs);
      if (r === 'touched') touched++;
      else if (r === 'locked') locked++;
      else if (r === 'failed') failed++;
      else skipped++;
    }

    // Advance the baseline only when this run actually processed everything —
    // capped/locked leftovers stay visible to the next run. Baseline is the
    // scan START time so edits landing mid-run are re-checked next time
    // (over-checking is a no-op; under-checking would be a miss).
    if (capped === 0 && locked === 0) writeScanBaseline(teamRoot, scanStartMs);

    // One line per run even when nothing happened — "did the host actually
    // invoke this hook" is the #1 debugging question, and a temp-dir log
    // line per close-out is cheap.
    log(
      'done root=' + teamRoot + ' scanned=' + files.length + ' candidates=' + candidates.length +
      ' touched=' + touched + ' skipped=' + skipped + ' locked=' + locked +
      ' failed=' + failed + ' capped=' + capped
    );
    // stdout stays empty by design: pure housekeeping, zero injection budget.
  } catch (e) {
    // Stop-hook iron rule: never block close-out. stderr trace only.
    try {
      process.stderr.write('[frontmatter-touch] non-fatal error, close-out not blocked: ' + ((e && e.stack) || e) + '\n');
    } catch (e2) {
      /* nothing left to do */
    }
  }
  process.exit(0);
}

if (require.main === module) {
  main();
}

module.exports = {
  dateStrFromMs,
  isExcludedDirName,
  isExcludedFileName,
  collectMdFiles,
  computeNext,
  touchFile,
  stateFilePath,
  readScanBaseline,
  writeScanBaseline,
  DATE_RE,
  DEFAULT_MAX_TOUCH_PER_RUN,
};