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');

/**
 * 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 findGitNexusDir(startDir) {
  let dir = startDir || process.cwd();
  for (let i = 0; i < 5; i++) {
    const candidate = path.join(dir, '.gitnexus');
    if (fs.existsSync(candidate)) return candidate;
    const parent = path.dirname(dir);
    if (parent === dir) break;
    dir = parent;
  }
  return null;
}

/**
 * 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;
}

/**
 * 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).
 */
function runGitNexusCli(args, cwd, timeout) {
  const isWin = process.platform === 'win32';

  // 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'] }
    );
    useDirectBinary = which.status === 0;
  } catch { /* not on PATH */ }

  if (useDirectBinary) {
    return spawnSync(
      isWin ? 'gitnexus.cmd' : 'gitnexus', args,
      { encoding: 'utf-8', timeout, cwd, stdio: ['pipe', 'pipe', 'pipe'] }
    );
  }
  // npx fallback needs shell on Windows since npx is a .cmd script
  return spawnSync(
    isWin ? 'npx.cmd' : 'npx', ['-y', 'gitnexus', ...args],
    { encoding: 'utf-8', timeout: timeout + 5000, cwd, stdio: ['pipe', 'pipe', 'pipe'] }
  );
}

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

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

  let result = '';
  try {
    const child = runGitNexusCli(['augment', '--', pattern], cwd, 7000);
    if (!child.error && child.status === 0) {
      result = child.stderr || '';
    }
  } catch { /* graceful failure */ }

  if (result && result.trim()) {
    sendHookResponse('PreToolUse', result.trim());
  }
}

/**
 * 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'],
    });
    currentHead = (headResult.stdout || '').trim();
  } catch { return; }

  if (!currentHead) return;

  let lastCommit = '';
  let hadEmbeddings = false;
  try {
    const meta = JSON.parse(fs.readFileSync(path.join(gitNexusDir, 'meta.json'), 'utf-8'));
    lastCommit = meta.lastCommit || '';
    hadEmbeddings = (meta.stats && meta.stats.embeddings > 0);
  } catch { /* no meta — treat as stale */ }

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

  const analyzeCmd = `npx gitnexus analyze${hadEmbeddings ? ' --embeddings' : ''}`;
  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 (process.env.GITNEXUS_DEBUG) {
      console.error('GitNexus hook error:', (err.message || '').slice(0, 200));
    }
  }
}

main();