import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import { z } from 'zod';
import { access, mkdir } from 'node:fs/promises';
import { join } from 'node:path';
import { tmpdir } from 'node:os';
import { randomUUID } from 'node:crypto';
import { runGxpkg } from '../gxi.js';
// Files that gxpkg new generates and would overwrite.
const CONFLICT_FILES = ['gerbil.pkg', 'Makefile', 'build.ss'];
async function fileExists(path: string): Promise<boolean> {
try {
await access(path);
return true;
} catch {
return false;
}
}
export function registerScaffoldTool(server: McpServer): void {
server.registerTool(
'gerbil_scaffold',
{
title: 'Scaffold Gerbil Project',
description:
'Create a new Gerbil project from a template using gxpkg new. ' +
'Generates gerbil.pkg, build.ss, Makefile, and initial source files. ' +
'If project_path is omitted, creates a temporary directory. ' +
'Refuses to run if the target already contains gerbil.pkg, Makefile, or build.ss.',
inputSchema: {
project_path: z
.string()
.optional()
.describe(
'Directory to create the project in. If omitted, a temporary directory is created. ' +
'If provided, the directory must already exist and not contain gerbil.pkg, Makefile, or build.ss.',
),
package: z
.string()
.optional()
.describe(
'Package prefix for the project (default: current username)',
),
name: z
.string()
.optional()
.describe('Package name (default: directory name)'),
link: z
.string()
.optional()
.describe(
'Public package link (e.g. "github.com/user/project")',
),
},
},
async ({ project_path, package: pkg, name, link }) => {
// Resolve target directory: use provided path or create a temp dir.
let targetDir: string;
let createdTmp = false;
if (project_path) {
targetDir = project_path;
} else {
const dirName = name ?? `gerbil-project-${randomUUID().slice(0, 8)}`;
targetDir = join(tmpdir(), dirName);
await mkdir(targetDir, { recursive: true });
createdTmp = true;
}
// Safety check: refuse to overwrite existing project files.
const conflicts: string[] = [];
for (const file of CONFLICT_FILES) {
if (await fileExists(join(targetDir, file))) {
conflicts.push(file);
}
}
if (conflicts.length > 0) {
return {
content: [
{
type: 'text' as const,
text:
`Refusing to scaffold: the target directory already contains ${conflicts.join(', ')}. ` +
`Running gxpkg new here would overwrite existing files.\n\n` +
`Target: ${targetDir}\n\n` +
`Use an empty directory or omit project_path to create a temporary directory.`,
},
],
isError: true,
};
}
const args: string[] = ['new'];
if (pkg) {
args.push('--package', pkg);
}
if (name) {
args.push('--name', name);
}
if (link) {
args.push('--link', link);
}
const result = await runGxpkg(args, {
cwd: targetDir,
timeout: 30_000,
});
if (result.timedOut) {
return {
content: [
{
type: 'text' as const,
text: 'Scaffold timed out after 30 seconds.',
},
],
isError: true,
};
}
if (result.exitCode === 127) {
return {
content: [
{
type: 'text' as const,
text: 'gxpkg not found. Ensure Gerbil is installed and gxpkg is in PATH.',
},
],
isError: true,
};
}
const output = [result.stdout, result.stderr]
.filter(Boolean)
.join('\n')
.trim();
if (result.exitCode !== 0) {
return {
content: [
{
type: 'text' as const,
text: `Scaffold failed (exit code ${result.exitCode}):\n\n${output}`,
},
],
isError: true,
};
}
const sections: string[] = [
`Project scaffolded in ${targetDir}.`,
];
if (createdTmp) {
sections.push(`(created temporary directory)`);
}
if (output) {
sections.push('');
sections.push(output);
}
return {
content: [{ type: 'text' as const, text: sections.join('\n') }],
};
},
);
}
