scripts/lib/emit.js

'use strict';
/**
 * emit.js — hook I/O wrapper shared by session-start.js / session-stop.js / precompact.js.
 *
 * Ported from a production hooks-core module, deployed at `91-team-tools/hooks-core/emit.js`, desensitized.
 * One deliberate simplification versus the production version: this port covers
 * `claude` and `codex` (byte-for-byte identical stdin/stdout schema for the three
 * hook events used here) plus a best-effort `cursor` branch, since those are the
 * two harnesses named in this batch's brief. The switch-per-event structure is
 * kept exactly as the production version so adding another harness later means
 * touching only this one file, never the three hook scripts.
 *
 * Output discipline: UTF-8, no BOM, one JSON object per line, trailing newline —
 * matches what a hook host reading stdout line-by-line expects.
 */

const SUPPORTED_PLATFORMS = ['claude', 'codex', 'cursor'];

function normalizePlatform(p) {
  p = String(p || '').trim().toLowerCase();
  return SUPPORTED_PLATFORMS.includes(p) ? p : 'claude';
}

/** Read `--platform <name>` or `--platform=<name>` from argv; default 'claude'. */
function getPlatform(argv) {
  argv = argv || process.argv.slice(2);
  const idx = argv.indexOf('--platform');
  if (idx >= 0 && argv[idx + 1]) return normalizePlatform(argv[idx + 1]);
  const eq = argv.find((a) => a.startsWith('--platform='));
  if (eq) return normalizePlatform(eq.split('=').slice(1).join('='));
  return 'claude';
}

/** SessionStart event: inject additional context. */
function buildSessionStartPayload(additionalContext, platform) {
  switch (normalizePlatform(platform)) {
    case 'cursor':
      // Cursor's `sessionStart` hook takes a top-level snake_case `additional_context`
      // field, no hookSpecificOutput wrapper. Best-effort — not independently
      // verified against a real Cursor install by this batch; see README.md.
      return { additional_context: additionalContext };
    case 'codex':
    case 'claude':
    default:
      return { hookSpecificOutput: { hookEventName: 'SessionStart', additionalContext: additionalContext } };
  }
}

/** Stop event: emitting nothing at all means "let the session end" — callers should not print when remind=false. */
function buildStopBlockPayload(reason, platform) {
  switch (normalizePlatform(platform)) {
    case 'cursor':
      // Cursor's `stop` hook has no decision:block mechanism, only an optional
      // `followup_message` (re-injected as a follow-up turn). Close enough in
      // effect to "the reminder text reaches the session" — not identical semantics.
      return { followup_message: reason };
    case 'codex':
    case 'claude':
    default:
      return { decision: 'block', reason: reason };
  }
}

/** PreCompact event: only the top-level systemMessage field is honored by claude/codex — no hookSpecificOutput here. */
function buildPreCompactPayload(systemMessage, platform) {
  switch (normalizePlatform(platform)) {
    case 'cursor':
      return { user_message: systemMessage };
    case 'codex':
    case 'claude':
    default:
      return { systemMessage: systemMessage };
  }
}

/** Serialize payload as single-line JSON to stdout, UTF-8 no BOM, trailing newline. */
function writeJson(payload) {
  process.stdout.write(JSON.stringify(payload) + '\n');
}

/**
 * Read all of stdin as a UTF-8 string (Promise). No timeout — a real hook host
 * closes stdin (EOF) after sending its payload; running this file directly in
 * an interactive terminal with no redirection will hang waiting for input,
 * which is expected (pipe in `echo ... |` or `printf '' |` for manual testing).
 */
function readStdin() {
  return new Promise((resolve) => {
    let data = '';
    try {
      process.stdin.setEncoding('utf8');
    } catch (e) {
      /* ignore */
    }
    process.stdin.on('data', (chunk) => {
      data += chunk;
    });
    process.stdin.on('end', () => resolve(data));
    process.stdin.on('error', () => resolve(data));
  });
}

/** Rough mojibake detector — looks for the Unicode replacement character U+FFFD. */
function looksMojibake(s) {
  return typeof s === 'string' && s.indexOf('�') !== -1;
}

/**
 * Unified cwd resolution, shared by session-start.js / session-stop.js.
 * Priority: ① stdin JSON's `cwd` field (not mojibake-damaged) → ② `process.cwd()`
 * (the hook subprocess's own working directory, set by the OS directly, not routed
 * through any text transcoding — usually equivalent to ① anyway) → ③ cursor-only
 * fallback to stdin's `workspace_roots[0]` (must be pure ASCII and undamaged —
 * non-ASCII workspace_roots are not trusted on Cursor, see production hooks-core's
 * documented finding of a UTF-8-decoded-as-GBK corruption case) → '' if nothing works.
 * @param {string} raw stdin raw text
 * @param {string} platform claude|codex|cursor
 * @param {Function} [pcwdFn] injectable process.cwd stand-in for tests
 */
function resolveCwd(raw, platform, pcwdFn) {
  pcwdFn = pcwdFn || process.cwd;
  let j = null;
  try {
    j = raw && raw.trim() ? JSON.parse(raw) : null;
  } catch (e) {
    j = null;
  }

  const stdinCwd = j && typeof j.cwd === 'string' ? j.cwd : '';
  if (stdinCwd && !looksMojibake(stdinCwd)) return stdinCwd;

  let pcwd = '';
  try {
    pcwd = pcwdFn() || '';
  } catch (e) {
    pcwd = '';
  }
  if (pcwd && !looksMojibake(pcwd)) return pcwd;

  if (normalizePlatform(platform) === 'cursor') {
    try {
      const root = j && Array.isArray(j.workspace_roots) ? j.workspace_roots[0] : '';
      if (root && /^[\x00-\x7F]+$/.test(root) && !looksMojibake(root)) {
        // Only rewrite a POSIX-style Windows drive path (/D:/foo -> D:\foo).
        // A genuine POSIX path (/home/user/...) has no drive-letter prefix and
        // must be returned untouched — unconditionally turning every '/' into
        // '\' (the previous behavior) would corrupt a real Mac/Linux path in
        // the low-probability case where a Cursor session on a POSIX host falls
        // through both earlier fallbacks to here. Gate the slash-flip on an
        // actual drive-letter match rather than doing it always.
        const winDrive = /^\/([A-Za-z]):/;
        if (winDrive.test(root)) return root.replace(winDrive, '$1:').replace(/\//g, '\\');
        return root;
      }
    } catch (e) {
      /* ignore */
    }
  }
  return '';
}

/** Safely extract session_id from raw stdin text. Never throws. */
function extractSessionId(raw) {
  try {
    if (!raw || !raw.trim()) return '';
    const j = JSON.parse(raw);
    return typeof j.session_id === 'string' ? j.session_id : '';
  } catch (e) {
    return '';
  }
}

/**
 * Double-fire dedup guard. Some harnesses (documented case: Claude Code's
 * project-level config lookup climbing to a repository root that also has its
 * own hooks config) can end up firing the same hook event twice for one
 * session. This gives callers a short-window idempotency check: same event +
 * same session_id within `windowMs` (default 5s) is treated as a duplicate.
 * No session_id means no dedup (would rather occasionally double-fire than
 * risk false-positively swallowing a legitimate single call).
 * @param {string} eventName e.g. 'SessionStart' | 'Stop' | 'PreCompact'
 * @param {string} sessionId
 * @param {{windowMs?: number}} [opts]
 * @returns {boolean} true = duplicate, caller should skip
 */
function isDuplicateInvocation(eventName, sessionId, opts) {
  if (!sessionId) return false;
  opts = opts || {};
  const windowMs = typeof opts.windowMs === 'number' ? opts.windowMs : 5000;
  const fs = require('fs');
  const os = require('os');
  const path = require('path');
  const key = String(eventName) + '_' + String(sessionId).replace(/[^A-Za-z0-9]/g, '');
  const markerFile = path.join(os.tmpdir(), 'nomad_dedupe_' + key + '.marker');
  const now = Date.now();
  try {
    fs.writeFileSync(markerFile, String(now), { flag: 'wx' });
    return false; // exclusive create succeeded — first arrival of this batch
  } catch (e) {
    if (e && e.code === 'EEXIST') {
      try {
        const raw = fs.readFileSync(markerFile, 'utf8');
        const ts = parseInt(raw, 10);
        if (Number.isFinite(ts) && now - ts < windowMs) return true; // within window = duplicate
        fs.writeFileSync(markerFile, String(now), 'utf8'); // stale marker — treat as new batch
        return false;
      } catch (e2) {
        return false; // read/overwrite failure — fail open
      }
    }
    return false; // any other write failure — fail open
  }
}

module.exports = {
  SUPPORTED_PLATFORMS,
  getPlatform,
  normalizePlatform,
  buildSessionStartPayload,
  buildStopBlockPayload,
  buildPreCompactPayload,
  writeJson,
  readStdin,
  looksMojibake,
  resolveCwd,
  extractSessionId,
  isDuplicateInvocation,
};