import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import { z } from 'zod';
import { execSync } from 'node:child_process';
import { readFile, stat } from 'node:fs/promises';
import { join, resolve } from 'node:path';
interface BuildProcess {
pid: number;
command: string;
cwd?: string;
}
/**
* Find running gerbil build processes using ps.
*/
function findGerbilBuildProcesses(): BuildProcess[] {
const processes: BuildProcess[] = [];
try {
// Use ps to find gerbil-related processes
const output = execSync(
'ps aux 2>/dev/null || true',
{ encoding: 'utf-8', timeout: 5000 },
);
const lines = output.split('\n');
for (const line of lines) {
// Match gerbil build, gxc, and gxi processes that look like compilation
if (
/gerbil\s+build/i.test(line) ||
/gxc\s/i.test(line) ||
/gerbil-build/i.test(line)
) {
const parts = line.trim().split(/\s+/);
const pid = parseInt(parts[1], 10);
if (!isNaN(pid)) {
const command = parts.slice(10).join(' ');
// Try to get cwd from /proc
let cwd: string | undefined;
try {
cwd = execSync(`readlink /proc/${pid}/cwd 2>/dev/null || true`, {
encoding: 'utf-8',
timeout: 2000,
}).trim();
} catch {
// Can't read cwd
}
processes.push({ pid, command, cwd: cwd || undefined });
}
}
}
} catch {
// ps not available
}
return processes;
}
/**
* Check for lock files in .gerbil/ directory that indicate an active build.
*/
async function checkLockFiles(
projectPath: string,
): Promise<string[]> {
const lockPaths: string[] = [];
const gerbilDir = join(projectPath, '.gerbil');
// Check for common lock patterns
const lockPatterns = [
join(gerbilDir, 'lock'),
join(gerbilDir, 'build.lock'),
join(gerbilDir, 'lib', '.lock'),
];
for (const lockPath of lockPatterns) {
try {
const s = await stat(lockPath);
if (s.isFile()) {
const ageMs = Date.now() - s.mtimeMs;
lockPaths.push(
`${lockPath} (age: ${Math.round(ageMs / 1000)}s)`,
);
}
} catch {
// Lock file doesn't exist
}
}
return lockPaths;
}
export function registerBuildConflictTool(server: McpServer): void {
server.registerTool(
'gerbil_build_conflict_check',
{
title: 'Detect Parallel Build Conflicts',
description:
'Detect when multiple gerbil build processes are running on the same ' +
'project directory. Checks for: (1) running gerbil/gxc processes via ps, ' +
'(2) lock files in .gerbil/, (3) matching working directories. ' +
'Warns about potential conflicts with suggestions to kill old builds.',
annotations: {
readOnlyHint: true,
idempotentHint: true,
},
inputSchema: {
project_path: z
.string()
.describe('Project directory to check for build conflicts'),
},
},
async ({ project_path }) => {
const absPath = resolve(project_path);
const sections: string[] = [];
let hasConflict = false;
// Step 1: Find running gerbil build processes
const processes = findGerbilBuildProcesses();
const conflicting = processes.filter(
(p) => p.cwd && resolve(p.cwd) === absPath,
);
sections.push(`Build conflict check: ${absPath}`);
sections.push('');
if (conflicting.length > 0) {
hasConflict = true;
sections.push(
`WARNING: ${conflicting.length} gerbil build process(es) found for this directory:`,
);
for (const p of conflicting) {
sections.push(` PID ${p.pid}: ${p.command}`);
}
sections.push('');
sections.push(
'To avoid conflicts, kill existing builds before starting a new one:',
);
for (const p of conflicting) {
sections.push(` kill ${p.pid}`);
}
sections.push('');
}
// Also report other gerbil processes (not in this directory)
const otherProcesses = processes.filter(
(p) => !p.cwd || resolve(p.cwd) !== absPath,
);
if (otherProcesses.length > 0) {
sections.push(
`Other gerbil build processes (${otherProcesses.length}):`,
);
for (const p of otherProcesses) {
sections.push(
` PID ${p.pid}: ${p.command}${p.cwd ? ` (${p.cwd})` : ''}`,
);
}
sections.push('');
}
// Step 2: Check for lock files
const locks = await checkLockFiles(absPath);
if (locks.length > 0) {
hasConflict = true;
sections.push(`Lock files found (${locks.length}):`);
for (const lock of locks) {
sections.push(` ${lock}`);
}
sections.push('');
sections.push(
'Lock files may indicate an active or crashed build. ' +
'If no build is running, delete the lock files and retry.',
);
sections.push('');
}
if (!hasConflict && processes.length === 0) {
sections.push('No build conflicts detected. Safe to build.');
} else if (!hasConflict) {
sections.push(
'No conflicts for this specific project. Safe to build.',
);
}
return {
content: [
{ type: 'text' as const, text: sections.join('\n') },
],
isError: hasConflict,
};
},
);
}
