GitNexus/gitnexus-claude-plugin/hooks/gitnexus-hook.js

#!/usr/bin/env node
/**
 * GitNexus Claude Code Plugin Hook
 *
 * PreToolUse  — intercepts Grep/Glob/Bash searches and augments
 *               with graph context from the GitNexus index.
 * PostToolUse — detects stale index after git mutations and notifies
 *               the agent to reindex.
 *
 * NOTE: SessionStart hooks are broken on Windows (Claude Code bug #23576).
 * Session context is injected via CLAUDE.md / skills instead.
 */

const fs = require('fs');
const path = require('path');
const { spawnSync } = require('child_process');
const { acquireHookSlot } = require('./hook-lock.js');
const {
  hasGitNexusDbLockedByGitNexusServer,
  resolveUnixGuardTimeout,
} = require('./hook-db-lock-probe.cjs');
const { formatAnalyzeCommand } = require('./resolve-analyze-cmd.cjs');

/**
 * Read JSON input from stdin synchronously.
 */
function readInput() {
  try {
    const data = fs.readFileSync(0, 'utf-8');
    return JSON.parse(data);
  } catch {
    return {};
  }
}

/**
 * Find the .gitnexus directory by walking up from startDir.
 * Returns the path to .gitnexus/ or null if not found.
 */
function isGlobalRegistryDir(candidate) {
  if (
    fs.existsSync(path.join(candidate, 'gitnexus.json')) ||
    fs.existsSync(path.join(candidate, 'meta.json'))
  ) {
    return false;
  }
  return (
    fs.existsSync(path.join(candidate, 'registry.json')) ||
    fs.existsSync(path.join(candidate, 'repos'))
  );
}

/**
 * Read the index metadata file, preferring `gitnexus.json` (current format)
 * and falling back to the legacy `meta.json` mirror. Returns `null` if
 * neither exists or parses.
 */
function readIndexMeta(gitNexusDir) {
  try {
    return JSON.parse(fs.readFileSync(path.join(gitNexusDir, 'gitnexus.json'), 'utf-8'));
  } catch {
    try {
      return JSON.parse(fs.readFileSync(path.join(gitNexusDir, 'meta.json'), 'utf-8'));
    } catch {
      return null;
    }
  }
}

/**
 * Walk up from `startDir` looking for a non-registry `.gitnexus/` folder.
 * Returns the path to `.gitnexus/` or null if not found within 5 levels.
 */
function walkForGitNexusDir(startDir) {
  let dir = startDir;
  for (let i = 0; i < 5; i++) {
    const candidate = path.join(dir, '.gitnexus');
    if (fs.existsSync(candidate)) {
      if (!isGlobalRegistryDir(candidate)) return candidate;
    }
    const parent = path.dirname(dir);
    if (parent === dir) break;
    dir = parent;
  }
  return null;
}

/**
 * Resolve the canonical (main) worktree root for `cwd`, when `cwd` is inside
 * any git working tree — including a *linked* worktree created via
 * `git worktree add`. Linked worktrees never contain `.gitnexus/`, so the
 * upward walk from cwd alone misses the index. Returns null when `cwd` is
 * not inside a git repo or `git` is not available.
 *
 * Implementation: `git rev-parse --git-common-dir` resolves to the canonical
 * `.git/` directory (or `.git/worktrees/...` parent) that is shared across
 * all linked worktrees. The canonical repo root is its parent directory.
 */
function findCanonicalRepoRoot(cwd) {
  try {
    const result = spawnSync('git', ['rev-parse', '--path-format=absolute', '--git-common-dir'], {
      encoding: 'utf-8',
      timeout: 2000,
      cwd,
      stdio: ['pipe', 'pipe', 'pipe'],
      windowsHide: true,
    });
    if (result.error || result.status !== 0) return null;
    const commonDir = (result.stdout || '').trim();
    if (!commonDir || !path.isAbsolute(commonDir)) return null;
    return path.dirname(commonDir);
  } catch {
    return null;
  }
}

function findGitNexusDir(startDir) {
  const cwd = startDir || process.cwd();

  // Fast path: the cwd is inside the canonical repo (most common case).
  const fromCwd = walkForGitNexusDir(cwd);
  if (fromCwd) return fromCwd;

  // Fallback: cwd may be inside a linked git worktree whose `.gitnexus/`
  // only lives in the canonical repo root. Resolve the shared git dir
  // and retry from there.
  const canonicalRoot = findCanonicalRepoRoot(cwd);
  if (canonicalRoot && canonicalRoot !== cwd) {
    return walkForGitNexusDir(canonicalRoot);
  }
  return null;
}

function hasGitNexusServerOwner(gitNexusDir) {
  return hasGitNexusDbLockedByGitNexusServer(path.join(gitNexusDir, 'lbug'), process.pid);
}

/**
 * Whether opt-in diagnostics should be written to the hook's stderr. Strict
 * hook runners (e.g. Codex `PreToolUse`) validate hook output, so normal,
 * non-error skip paths must stay silent unless the operator explicitly asks
 * for diagnostics via GITNEXUS_DEBUG. See issue #1913.
 */
function isDebugEnabled() {
  return process.env.GITNEXUS_DEBUG === '1' || process.env.GITNEXUS_DEBUG === 'true';
}

function extractAugmentContext(stderr) {
  const output = (stderr || '').trim();
  const marker = output.indexOf('[GitNexus]');
  const debug = isDebugEnabled();
  if (debug && output.length > 0) {
    // Emit the FULL discarded prefix (everything before the marker, or all of
    // it when no marker is present) so suppressed diagnostics — LadybugDB lock
    // warnings, parser errors, etc. — remain recoverable on the hook's own
    // stderr. The untruncated payload lets operators see exactly what was
    // filtered out instead of a 180-char JSON-quoted preview.
    const discarded = marker === -1 ? output : output.slice(0, marker).trim();
    if (discarded.length > 0) {
      process.stderr.write(`[GitNexus hook] augment stderr discarded prefix:\n${discarded}\n`);
    }
  }
  return marker === -1 ? '' : output.slice(marker).trim();
}

/**
 * Extract search pattern from tool input.
 */
function extractPattern(toolName, toolInput) {
  if (toolName === 'Grep') {
    return toolInput.pattern || null;
  }

  if (toolName === 'Glob') {
    const raw = toolInput.pattern || '';
    const match = raw.match(/[*\/]([a-zA-Z][a-zA-Z0-9_-]{2,})/);
    return match ? match[1] : null;
  }

  if (toolName === 'Bash') {
    const cmd = toolInput.command || '';
    if (!/\brg\b|\bgrep\b/.test(cmd)) return null;

    const tokens = cmd.split(/\s+/);
    let foundCmd = false;
    let skipNext = false;
    const flagsWithValues = new Set([
      '-e',
      '-f',
      '-m',
      '-A',
      '-B',
      '-C',
      '-g',
      '--glob',
      '-t',
      '--type',
      '--include',
      '--exclude',
    ]);

    for (const token of tokens) {
      if (skipNext) {
        skipNext = false;
        continue;
      }
      if (!foundCmd) {
        if (/\brg$|\bgrep$/.test(token)) foundCmd = true;
        continue;
      }
      if (token.startsWith('-')) {
        if (flagsWithValues.has(token)) skipNext = true;
        continue;
      }
      const cleaned = token.replace(/['"]/g, '');
      return cleaned.length >= 3 ? cleaned : null;
    }
    return null;
  }

  return null;
}

// Debounce for the unguarded-CLI diagnostic below (#2163 follow-up review):
// at most one line per (short-lived) hook process, even if a future change
// runs the CLI more than once.
let unguardedCliWarned = false;

/**
 * Spawn a gitnexus CLI command synchronously.
 * Detects binary on PATH once, then runs exactly once.
 *
 * SECURITY: Never use shell: true with user-controlled arguments.
 * On Windows, invoke gitnexus.cmd directly (no shell needed).
 *
 * Unix orphan containment (#2163 follow-up): the augment CLI is the
 * longest-lived hook child (inner spawnSync timeout 7s locally, 12s via
 * npx), so on Unix every CLI-running branch gets the same SIGKILL-surviving
 * coreutils `timeout` wrapper as the probe's lsof/ps (the cheap which/where
 * PATH check stays unwrapped). The wrapper budget is ceil(inner/1000)+1
 * seconds — STRICTLY greater than the inner spawnSync timeout, so on the
 * supervised path Node's SIGTERM always fires first and the existing
 * error/status contract is untouched. Once the hook itself has been
 * SIGKILLed (exactly the orphan case the wrapper exists for), the guard
 * semantics differ per branch:
 *   - direct exec (GITNEXUS_HOOK_CLI_PATH / PATH-installed `gitnexus`; the
 *     CLI is the guard's CHILD): `-k 1` TERM-first — a SIGTERM-immune CLI
 *     can hold the guard ~1s past the inner timeout before the `-k` SIGKILL
 *     escalation reaps it.
 *   - npx (the CLI is a GRANDCHILD: guard → npx → CLI): `-s KILL` — the
 *     budget expiry SIGKILLs the whole process group outright. TERM-first
 *     would kill only the obedient npx parent, making `timeout` reap it and
 *     return before the `-k` escalation ever fires, stranding a
 *     SIGTERM-immune CLI grandchild unbounded (reproduced on coreutils
 *     9.x). `-k 1` is retained alongside `-s KILL` as a harmless belt: with
 *     `-s KILL` the `-k` escalation signal is also KILL. Two residual gaps
 *     on this branch, both bounded by "no worse than pre-fix" (where the
 *     grandchild received no signal at all): the group-wide SIGKILL is
 *     coreutils semantics — a busybox `timeout` passes the self-test (it
 *     has `-k` and propagates exit status) but signals only its direct
 *     child, so a busybox guard cannot reach the grandchild; and on the
 *     SUPERVISED path (hook alive, inner spawnSync timeout SIGTERMs the
 *     guard) coreutils forwards TERM rather than the `-s` signal, npx dies,
 *     and the guard exits before any KILL fires — so a SIGTERM-immune CLI
 *     grandchild still escapes in those two cases.
 * If the sibling probe predates the resolveUnixGuardTimeout export (version
 * skew), the adapter degrades to the unwrapped invocation instead of
 * throwing. Windows is deliberately NOT wrapped — there is no coreutils
 * timeout to resolve there and the resolver's self-test spawns /bin/sh — so
 * on win32 (the gitnexus.cmd / npx.cmd paths) and whenever the guard
 * resolves to null (e.g. macOS without Homebrew coreutils — reported once
 * under GITNEXUS_DEBUG) the argv stays byte-identical to the pre-wrap
 * invocation.
 */
function runGitNexusCli(args, cwd, timeout) {
  const isWin = process.platform === 'win32';
  // Version-skew guard (#2163 follow-up review): an older sibling probe
  // without the resolveUnixGuardTimeout export must degrade to the unwrapped
  // invocation — a TypeError here would be swallowed by the caller's catch
  // and silently kill the augment.
  const guard =
    isWin || typeof resolveUnixGuardTimeout !== 'function' ? null : resolveUnixGuardTimeout();
  if (!isWin && !guard && !unguardedCliWarned && isDebugEnabled()) {
    // Diagnose the "stays unwrapped" Unix paths once per hook process: no
    // usable coreutils timeout/gtimeout (e.g. macOS without Homebrew
    // coreutils), GITNEXUS_HOOK_TIMEOUT_PATH=disabled, or probe skew above.
    unguardedCliWarned = true;
    process.stderr.write(
      '[GitNexus hook] no usable timeout/gtimeout guard; augment CLI child runs unguarded\n',
    );
  }
  const hookCli = process.env.GITNEXUS_HOOK_CLI_PATH;
  if (hookCli !== undefined && String(hookCli).trim() && fs.existsSync(String(hookCli))) {
    const [cmd, cmdArgs] = guard
      ? [
          guard,
          [
            '-k',
            '1',
            String(Math.ceil(timeout / 1000) + 1),
            process.execPath,
            String(hookCli),
            ...args,
          ],
        ]
      : [process.execPath, [String(hookCli), ...args]];
    return spawnSync(cmd, cmdArgs, {
      encoding: 'utf-8',
      timeout,
      cwd,
      stdio: ['pipe', 'pipe', 'pipe'],
      windowsHide: true,
    });
  }

  // Detect whether 'gitnexus' is on PATH (cheap check, no execution)
  let useDirectBinary = false;
  try {
    const which = spawnSync(isWin ? 'where' : 'which', ['gitnexus'], {
      encoding: 'utf-8',
      timeout: 3000,
      stdio: ['pipe', 'pipe', 'pipe'],
      windowsHide: true,
    });
    useDirectBinary = which.status === 0;
  } catch {
    /* not on PATH */
  }

  if (useDirectBinary) {
    // A non-null guard implies non-Windows, so the wrapped arm can hardcode
    // plain `gitnexus` (the guard resolves it via PATH, like spawnSync does).
    const [cmd, cmdArgs] = guard
      ? [guard, ['-k', '1', String(Math.ceil(timeout / 1000) + 1), 'gitnexus', ...args]]
      : [isWin ? 'gitnexus.cmd' : 'gitnexus', args];
    return spawnSync(cmd, cmdArgs, {
      encoding: 'utf-8',
      timeout,
      cwd,
      stdio: ['pipe', 'pipe', 'pipe'],
      windowsHide: true,
    });
  }
  // npx fallback needs shell on Windows since npx is a .cmd script. The
  // wrapped arm leads with `-s KILL` (NOT TERM-first like the direct
  // branches above): the CLI here is a grandchild behind npx — see the
  // docblock.
  const [cmd, cmdArgs] = guard
    ? [
        guard,
        [
          '-s',
          'KILL',
          '-k',
          '1',
          String(Math.ceil((timeout + 5000) / 1000) + 1),
          'npx',
          '-y',
          'gitnexus',
          ...args,
        ],
      ]
    : [isWin ? 'npx.cmd' : 'npx', ['-y', 'gitnexus', ...args]];
  return spawnSync(cmd, cmdArgs, {
    encoding: 'utf-8',
    timeout: timeout + 5000,
    cwd,
    stdio: ['pipe', 'pipe', 'pipe'],
    windowsHide: true,
  });
}

/**
 * Emit a hook response with additional context for the agent.
 */
function sendHookResponse(hookEventName, message) {
  console.log(
    JSON.stringify({
      hookSpecificOutput: { hookEventName, additionalContext: message },
    }),
  );
}

/**
 * Fallback augmentation for the #2396 path: when a GitNexus process holds the
 * lbug DB write lock the CLI `augment` can't run, so point the agent at the MCP
 * `query` tool instead. Phrased conditionally ("if the MCP tools are live") so it
 * stays truthful on every owner path — a confirmed MCP owner, a `serve` owner, or
 * a fail-closed probe where no server is actually confirmed. `pattern` is embedded
 * verbatim; the caller (sendHookResponse) JSON-escapes it structurally.
 */
function buildMcpQueryHint(pattern) {
  return (
    `[GitNexus] Local augment is unavailable (the graph DB is held by another ` +
    `GitNexus process). If the GitNexus MCP tools are live in this session, call ` +
    `the GitNexus \`query\` MCP tool (e.g. mcp__gitnexus__query) with ` +
    `search_query "${pattern}".`
  );
}

/**
 * #2396 throttle: emit the MCP-query hint at most once per repo per window, so an
 * owner-locked session isn't nudged on every search. Window (ms) via
 * GITNEXUS_MCP_HINT_THROTTLE_MS (default 10min; 0/invalid disables). Best-effort —
 * any fs error falls back to emitting.
 * ponytail: per-repo mtime marker, shared across concurrent sessions on the same
 * repo; add per-session dedup only if that sharing becomes a problem.
 */
function shouldEmitMcpHint(gitNexusDir) {
  const raw = process.env.GITNEXUS_MCP_HINT_THROTTLE_MS;
  const windowMs = raw === undefined || raw === '' ? 600000 : Number(raw);
  if (!Number.isFinite(windowMs) || windowMs <= 0) return true;
  const marker = path.join(gitNexusDir, '.mcp-hint-shown');
  try {
    if (Date.now() - fs.statSync(marker).mtimeMs < windowMs) return false;
  } catch {
    /* marker missing/unreadable → emit */
  }
  try {
    fs.writeFileSync(marker, '');
  } catch {
    /* best-effort; still emit */
  }
  return true;
}

/**
 * PreToolUse handler — augment searches with graph context.
 */
function handlePreToolUse(input) {
  const cwd = input.cwd || process.cwd();
  if (!path.isAbsolute(cwd)) return;
  const gitNexusDir = findGitNexusDir(cwd);
  if (!gitNexusDir) return;

  const toolName = input.tool_name || '';
  const toolInput = input.tool_input || {};

  if (toolName !== 'Grep' && toolName !== 'Glob' && toolName !== 'Bash') return;

  const pattern = extractPattern(toolName, toolInput);
  if (!pattern || pattern.length < 3) return;

  // Acquire the per-repo slot BEFORE the DB-owner probe (#2163): the probe
  // itself spawns lsof/ps, so it must be bounded by the same ≤3-per-repo cap
  // as the augment, or concurrent sessions fan out unbounded probe
  // subprocesses. Keep the acquire right after the cheap guards above —
  // moving it earlier would churn slot files on tool calls that never probe.
  const release = acquireHookSlot(gitNexusDir);
  if (!release) {
    // Normal skip path: all per-repo hook slots are held by concurrent
    // sessions. Stay silent for strict hook runners (issue #1913); surface
    // the reason only when diagnostics are explicitly requested.
    if (isDebugEnabled()) {
      process.stderr.write('[GitNexus] augment skipped: hook slots saturated\n');
    }
    return;
  }

  let result = '';
  try {
    if (hasGitNexusServerOwner(gitNexusDir)) {
      // #2396: the MCP server holds the DB write lock, so a competing CLI
      // `augment` would only contend on it (LadybugDB is single-writer). But the
      // session that triggered this hook has the GitNexus MCP tools live — route
      // the augmentation to the agent via additionalContext instead of silently
      // doing nothing. Mirror the skip reason to stderr only under GITNEXUS_DEBUG
      // (strict-runner contract, #1913); the hint itself rides the sanctioned
      // additionalContext stdout channel the successful augment already uses.
      if (isDebugEnabled()) {
        process.stderr.write('[GitNexus] augment skipped: MCP server owns DB\n');
      }
      if (shouldEmitMcpHint(gitNexusDir)) {
        result = buildMcpQueryHint(pattern);
      }
    } else {
      const child = runGitNexusCli(['augment', '--', pattern], cwd, 7000);
      if (!child.error && child.status === 0) {
        result = extractAugmentContext(child.stderr || '');
      }
    }
  } catch {
    /* graceful failure */
  } finally {
    release();
  }

  if (result) {
    sendHookResponse('PreToolUse', result);
  }
}

/**
 * PostToolUse handler — detect index staleness after git mutations.
 *
 * Instead of spawning a full `gitnexus analyze` synchronously (which blocks
 * the agent for up to 120s and risks LadybugDB corruption on timeout), we do a
 * lightweight staleness check: compare `git rev-parse HEAD` against the
 * lastCommit stored in `.gitnexus/meta.json`. If they differ, notify the
 * agent so it can decide when to reindex.
 */
function handlePostToolUse(input) {
  const toolName = input.tool_name || '';
  if (toolName !== 'Bash') return;

  const command = (input.tool_input || {}).command || '';
  if (!/\bgit\s+(commit|merge|rebase|cherry-pick|pull)(\s|$)/.test(command)) return;

  // Only proceed if the command succeeded
  const toolOutput = input.tool_output || {};
  if (toolOutput.exit_code !== undefined && toolOutput.exit_code !== 0) return;

  const cwd = input.cwd || process.cwd();
  if (!path.isAbsolute(cwd)) return;
  const gitNexusDir = findGitNexusDir(cwd);
  if (!gitNexusDir) return;

  // Compare HEAD against last indexed commit — skip if unchanged
  let currentHead = '';
  try {
    const headResult = spawnSync('git', ['rev-parse', 'HEAD'], {
      encoding: 'utf-8',
      timeout: 3000,
      cwd,
      stdio: ['pipe', 'pipe', 'pipe'],
      windowsHide: true,
    });
    currentHead = (headResult.stdout || '').trim();
  } catch {
    return;
  }

  if (!currentHead) return;

  let lastCommit = '';
  let hadEmbeddings = false;
  const meta = readIndexMeta(gitNexusDir);
  if (meta) {
    lastCommit = meta.lastCommit || '';
    hadEmbeddings = meta.stats && meta.stats.embeddings > 0;
  }

  // If HEAD matches last indexed commit, no reindex needed
  if (currentHead && currentHead === lastCommit) return;

  const analyzeCmd = formatAnalyzeCommand({ embeddings: hadEmbeddings, indexOnly: true });
  sendHookResponse(
    'PostToolUse',
    `GitNexus index is stale (last indexed: ${lastCommit ? lastCommit.slice(0, 7) : 'never'}). ` +
      `Run \`${analyzeCmd}\` to update the knowledge graph.`,
  );
}

// Dispatch map for hook events
const handlers = {
  PreToolUse: handlePreToolUse,
  PostToolUse: handlePostToolUse,
};

function main() {
  try {
    const input = readInput();
    const handler = handlers[input.hook_event_name || ''];
    if (handler) handler(input);
  } catch (err) {
    if (isDebugEnabled()) {
      console.error('GitNexus hook error:', (err.message || '').slice(0, 200));
    }
  }
}

main();