import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import { z } from 'zod';
import { mkdirSync, writeFileSync, existsSync } from 'node:fs';
import { join } from 'node:path';
interface TemplateFile {
path: string;
content: string;
}
interface ProjectTemplate {
name: string;
description: string;
files: (projectName: string, packageName: string) => TemplateFile[];
}
const TEMPLATES: Record<string, ProjectTemplate> = {
'cli': {
name: 'CLI Tool with Subcommands',
description: 'Command-line application with getopt argument parsing and subcommands',
files: (proj, pkg) => [
{
path: 'gerbil.pkg',
content: `(package: ${pkg})\n`,
},
{
path: 'build.ss',
content: `(import :std/build-script)\n\n(defbuild-script\n '("main"\n "cli"))\n`,
},
{
path: 'main.ss',
content: `(import :std/getopt\n :std/format\n (pkg: cli))\n(export main)\n\n(def (main . args)\n (call-with-getopt ${pkg}-main args\n program: "${proj}"\n help: "${proj} — a CLI tool"\n (command 'run help: "Run the main command"\n (optional-argument 'input help: "Input file"))\n (command 'version help: "Show version"\n )))\n\n(def (${pkg}-main opt)\n (let ((cmd (hash-ref opt 'command)))\n (case cmd\n ((run) (run-command opt))\n ((version) (displayln "${proj} v0.1.0")))))\n\n(def (run-command opt)\n (let ((input (hash-ref opt 'input #f)))\n (if input\n (displayln "Processing: " input)\n (displayln "No input specified"))))\n`,
},
{
path: 'cli.ss',
content: `(export #t)\n\n;; CLI utilities for ${proj}\n\n(def (print-error msg)\n (parameterize ((current-output-port (current-error-port)))\n (displayln "error: " msg)))\n\n(def (exit-with-error msg (code 1))\n (print-error msg)\n (exit code))\n`,
},
{
path: 'Makefile',
content: `.PHONY: build clean test\n\nbuild:\n\tgerbil build\n\nclean:\n\tgerbil clean\n\ntest:\n\tgerbil test ./...\n`,
},
],
},
'http-api': {
name: 'HTTP API Server',
description: 'REST API server with JSON endpoints using :std/net/httpd',
files: (proj, pkg) => [
{
path: 'gerbil.pkg',
content: `(package: ${pkg})\n`,
},
{
path: 'build.ss',
content: `(import :std/build-script)\n\n(defbuild-script\n '("main"\n "handlers"\n "routes"))\n`,
},
{
path: 'main.ss',
content: `(import :std/net/httpd\n :std/getopt\n (pkg: routes))\n(export main)\n\n(def (main . args)\n (def port\n (let ((p (if (pair? args) (string->number (car args)) #f)))\n (or p 8080)))\n (def httpd (start-http-server! (format "0.0.0.0:~a" port)))\n (register-routes! httpd)\n (displayln "Server running on port " port)\n (thread-join! httpd))\n`,
},
{
path: 'routes.ss',
content: `(import :std/net/httpd\n (pkg: handlers))\n(export register-routes!)\n\n(def (register-routes! httpd)\n (http-register-handler httpd "/api/health" health-handler)\n (http-register-handler httpd "/api/echo" echo-handler))\n`,
},
{
path: 'handlers.ss',
content: `(import :std/net/httpd\n :std/text/json)\n(export health-handler echo-handler)\n\n(def (json-response req obj)\n (http-response-write req 200 '(("Content-Type" . "application/json"))\n (json-object->string obj)))\n\n(def (health-handler req res)\n (json-response req (hash ("status" "ok"))))\n\n(def (echo-handler req res)\n (let ((body (http-request-body req)))\n (json-response req (hash ("echo" (or (and body (bytes->string body)) ""))))))\n`,
},
{
path: 'Makefile',
content: `.PHONY: build clean run test\n\nbuild:\n\tgerbil build\n\nclean:\n\tgerbil clean\n\nrun: build\n\tgerbil ${pkg}/main\n\ntest:\n\tgerbil test ./...\n`,
},
],
},
'library': {
name: 'Library Package',
description: 'Reusable library with public API, internal modules, and tests',
files: (proj, pkg) => [
{
path: 'gerbil.pkg',
content: `(package: ${pkg})\n`,
},
{
path: 'build.ss',
content: `(import :std/build-script)\n\n(defbuild-script\n '("interface"\n "impl"\n "util"\n "main-test"))\n`,
},
{
path: 'interface.ss',
content: `(export #t)\n\n;; Public API for ${proj}\n;; Import this module in consumer code: (import :${pkg})\n\n(def (hello name)\n (string-append "Hello, " name "!"))\n\n(def (process data)\n ;; TODO: implement\n data)\n`,
},
{
path: 'impl.ss',
content: `(export #t)\n\n;; Internal implementation details\n;; Not part of the public API\n\n(def (internal-helper x)\n (* x 2))\n`,
},
{
path: 'util.ss',
content: `(export #t)\n\n;; Shared utilities\n\n(def (ensure-string x)\n (if (string? x) x (object->string x)))\n`,
},
{
path: 'main-test.ss',
content: `(import :std/test\n (pkg: interface))\n(export main-test)\n\n(def main-test\n (test-suite "${proj} tests"\n (test-case "hello"\n (check (hello "World") => "Hello, World!"))))\n\n(run-tests! main-test)\n(test-report-summary!)\n`,
},
{
path: 'Makefile',
content: `.PHONY: build clean test\n\nbuild:\n\tgerbil build\n\nclean:\n\tgerbil clean\n\ntest:\n\tgerbil test ./...\n`,
},
],
},
'actor-service': {
name: 'Actor-Based Service',
description: 'Service using the actor model with supervision and message passing',
files: (proj, pkg) => [
{
path: 'gerbil.pkg',
content: `(package: ${pkg})\n`,
},
{
path: 'build.ss',
content: `(import :std/build-script)\n\n(defbuild-script\n '("main"\n "worker"\n "supervisor"))\n`,
},
{
path: 'main.ss',
content: `(import :std/actor\n :std/sugar\n (pkg: supervisor))\n(export main)\n\n(def (main . args)\n (start-actor-server!)\n (def sup (start-supervisor!))\n (displayln "Actor system started")\n (thread-join! (spawn (lambda () (thread-sleep! +inf.0)))))\n`,
},
{
path: 'worker.ss',
content: `(import :std/actor\n :std/sugar\n :std/logger)\n(export start-worker!)\n\n(def (start-worker! id)\n (spawn/name (format "worker-~a" id)\n (lambda ()\n (let loop ()\n (<- ((!message data)\n (debugf "worker ~a got: ~a" id data)\n (loop))\n ((!shutdown)\n (debugf "worker ~a shutting down" id)))))))\n`,
},
{
path: 'supervisor.ss',
content: `(import :std/actor\n :std/sugar\n (pkg: worker))\n(export start-supervisor!)\n\n(def (start-supervisor! (n 4))\n (def workers\n (for/collect (i (in-range n))\n (start-worker! i)))\n (spawn/name 'supervisor\n (lambda ()\n (let loop ()\n (<- ((!shutdown)\n (for-each (lambda (w) (!! w (!shutdown))) workers)\n (displayln "Supervisor: all workers stopped"))\n (timeout: 60\n (loop)))))))\n`,
},
{
path: 'Makefile',
content: `.PHONY: build clean run test\n\nbuild:\n\tgerbil build\n\nclean:\n\tgerbil clean\n\nrun: build\n\tgerbil ${pkg}/main\n\ntest:\n\tgerbil test ./...\n`,
},
],
},
'db-crud': {
name: 'Database CRUD Application',
description: 'SQLite-backed application with connection pooling and CRUD operations',
files: (proj, pkg) => [
{
path: 'gerbil.pkg',
content: `(package: ${pkg})\n`,
},
{
path: 'build.ss',
content: `(import :std/build-script)\n\n(defbuild-script\n '("main"\n "db"\n "model"))\n`,
},
{
path: 'main.ss',
content: `(import :std/getopt\n (pkg: db)\n (pkg: model))\n(export main)\n\n(def (main . args)\n (init-db! "app.db")\n (create-table!)\n (insert-item! "First item")\n (insert-item! "Second item")\n (displayln "All items:")\n (for-each (lambda (item) (displayln " " item))\n (list-items))\n (close-db!))\n`,
},
{
path: 'db.ss',
content: `(import :std/db/sqlite)\n(export init-db! close-db! with-db)\n\n(def *db* #f)\n\n(def (init-db! path)\n (set! *db* (sqlite-open path)))\n\n(def (close-db!)\n (when *db*\n (sqlite-close *db*)\n (set! *db* #f)))\n\n(def (with-db fn)\n (unless *db* (error "Database not initialized"))\n (fn *db*))\n`,
},
{
path: 'model.ss',
content: `(import :std/db/sqlite\n (pkg: db))\n(export create-table! insert-item! list-items get-item delete-item!)\n\n(def (create-table!)\n (with-db (lambda (db)\n (sqlite-exec db\n "CREATE TABLE IF NOT EXISTS items (id INTEGER PRIMARY KEY, name TEXT, created_at TEXT DEFAULT CURRENT_TIMESTAMP)"))))\n\n(def (insert-item! name)\n (with-db (lambda (db)\n (sqlite-exec db "INSERT INTO items (name) VALUES (?)" name))))\n\n(def (list-items)\n (with-db (lambda (db)\n (let ((stmt (sqlite-prepare db "SELECT id, name, created_at FROM items ORDER BY id")))\n (let loop ((rows '()))\n (if (sqlite-step stmt)\n (loop (cons (list (sqlite-column stmt 0)\n (sqlite-column stmt 1)\n (sqlite-column stmt 2))\n rows))\n (begin (sqlite-finalize stmt)\n (reverse rows))))))))\n\n(def (get-item id)\n (with-db (lambda (db)\n (let ((stmt (sqlite-prepare db "SELECT id, name, created_at FROM items WHERE id = ?")))\n (sqlite-bind stmt 1 id)\n (if (sqlite-step stmt)\n (let ((result (list (sqlite-column stmt 0)\n (sqlite-column stmt 1)\n (sqlite-column stmt 2))))\n (sqlite-finalize stmt)\n result)\n (begin (sqlite-finalize stmt) #f))))))\n\n(def (delete-item! id)\n (with-db (lambda (db)\n (sqlite-exec db "DELETE FROM items WHERE id = ?" id))))\n`,
},
{
path: 'Makefile',
content: `.PHONY: build clean run test\n\nbuild:\n\tgerbil build\n\nclean:\n\tgerbil clean\n\nrun: build\n\tgerbil ${pkg}/main\n\ntest:\n\tgerbil test ./...\n`,
},
],
},
'parser': {
name: 'Parser/Compiler',
description: 'Language parser with lexer, grammar, and AST using :std/parser',
files: (proj, pkg) => [
{
path: 'gerbil.pkg',
content: `(package: ${pkg})\n`,
},
{
path: 'build.ss',
content: `(import :std/build-script)\n\n(defbuild-script\n '("main"\n "lexer"\n "parser"\n "ast"))\n`,
},
{
path: 'main.ss',
content: `(import (pkg: lexer)\n (pkg: parser)\n (pkg: ast))\n(export main)\n\n(def (main . args)\n (let* ((input (if (pair? args) (car args) "1 + 2 * 3"))\n (tokens (tokenize input))\n (ast (parse-expr tokens)))\n (displayln "Input: " input)\n (displayln "AST: " ast)))\n`,
},
{
path: 'lexer.ss',
content: `(export tokenize token-type token-value)\n\n(defstruct token (type value) transparent: #t)\n\n(def (tokenize input)\n (let loop ((chars (string->list input)) (tokens '()))\n (cond\n ((null? chars) (reverse tokens))\n ((char-whitespace? (car chars))\n (loop (cdr chars) tokens))\n ((char-numeric? (car chars))\n (let num-loop ((cs (cdr chars)) (digits (list (car chars))))\n (if (and (pair? cs) (char-numeric? (car cs)))\n (num-loop (cdr cs) (cons (car cs) digits))\n (loop cs (cons (make-token 'number (string->number (list->string (reverse digits))))\n tokens)))))\n ((memv (car chars) '(#\\+ #\\- #\\* #\\/))\n (loop (cdr chars) (cons (make-token 'op (car chars)) tokens)))\n ((eqv? (car chars) #\\()\n (loop (cdr chars) (cons (make-token 'lparen #f) tokens)))\n ((eqv? (car chars) #\\))\n (loop (cdr chars) (cons (make-token 'rparen #f) tokens)))\n (else (error "Unexpected character" (car chars))))))\n`,
},
{
path: 'parser.ss',
content: `(import (pkg: lexer) (pkg: ast))\n(export parse-expr)\n\n;; Simple recursive-descent expression parser\n;; Handles: number, +, -, *, / with precedence\n\n(def (parse-expr tokens)\n (let-values (((expr rest) (parse-additive tokens)))\n expr))\n\n(def (parse-additive tokens)\n (let-values (((left rest) (parse-multiplicative tokens)))\n (let loop ((left left) (rest rest))\n (if (and (pair? rest)\n (eq? (token-type (car rest)) 'op)\n (memv (token-value (car rest)) '(#\\+ #\\-)))\n (let ((op (token-value (car rest))))\n (let-values (((right rest2) (parse-multiplicative (cdr rest))))\n (loop (make-binop op left right) rest2)))\n (values left rest)))))\n\n(def (parse-multiplicative tokens)\n (let-values (((left rest) (parse-primary tokens)))\n (let loop ((left left) (rest rest))\n (if (and (pair? rest)\n (eq? (token-type (car rest)) 'op)\n (memv (token-value (car rest)) '(#\\* #\\/)))\n (let ((op (token-value (car rest))))\n (let-values (((right rest2) (parse-primary (cdr rest))))\n (loop (make-binop op left right) rest2)))\n (values left rest)))))\n\n(def (parse-primary tokens)\n (cond\n ((null? tokens) (error "Unexpected end of input"))\n ((eq? (token-type (car tokens)) 'number)\n (values (make-literal (token-value (car tokens))) (cdr tokens)))\n ((eq? (token-type (car tokens)) 'lparen)\n (let-values (((expr rest) (parse-additive (cdr tokens))))\n (if (and (pair? rest) (eq? (token-type (car rest)) 'rparen))\n (values expr (cdr rest))\n (error "Expected closing parenthesis"))))\n (else (error "Unexpected token" (car tokens)))))\n`,
},
{
path: 'ast.ss',
content: `(export #t)\n\n;; AST node types\n\n(defstruct literal (value) transparent: #t)\n(defstruct binop (op left right) transparent: #t)\n(defstruct unaryop (op operand) transparent: #t)\n`,
},
{
path: 'Makefile',
content: `.PHONY: build clean run test\n\nbuild:\n\tgerbil build\n\nclean:\n\tgerbil clean\n\nrun: build\n\tgerbil ${pkg}/main "1 + 2 * 3"\n\ntest:\n\tgerbil test ./...\n`,
},
],
},
'ffi-wrapper': {
name: 'FFI Wrapper Library',
description: 'C foreign function interface wrapper with build system integration',
files: (proj, pkg) => [
{
path: 'gerbil.pkg',
content: `(package: ${pkg})\n`,
},
{
path: 'build.ss',
content: `(import :std/build-script)\n\n(defbuild-script\n '("ffi"\n "wrapper"\n "main"))\n`,
},
{
path: 'ffi.ss',
content: `(export #t)\n\n;; Low-level FFI declarations\n(begin-foreign\n (namespace ("${pkg}/ffi#" ffi/))\n (c-declare "#include <string.h>")\n\n ;; Example: wrap strlen\n (define ffi/c-strlen\n (c-lambda (UTF-8-string) int "strlen"))\n)\n`,
},
{
path: 'wrapper.ss',
content: `(import (pkg: ffi))\n(export string-byte-length)\n\n;; Safe Gerbil wrappers around FFI functions\n\n(def (string-byte-length s)\n (unless (string? s)\n (error "string-byte-length: expected string" s))\n (ffi/c-strlen s))\n`,
},
{
path: 'main.ss',
content: `(import (pkg: wrapper))\n(export main)\n\n(def (main . args)\n (let ((s (if (pair? args) (car args) "Hello, Gerbil!")))\n (displayln "String: " s)\n (displayln "Byte length: " (string-byte-length s))))\n`,
},
{
path: 'Makefile',
content: `.PHONY: build clean run test\n\nbuild:\n\tgerbil build\n\nclean:\n\tgerbil clean\n\nrun: build\n\tgerbil ${pkg}/main\n\ntest:\n\tgerbil test ./...\n`,
},
],
},
'test-project': {
name: 'Test-Heavy Project',
description: 'Project structure optimized for testing with fixtures and mocks',
files: (proj, pkg) => [
{
path: 'gerbil.pkg',
content: `(package: ${pkg})\n`,
},
{
path: 'build.ss',
content: `(import :std/build-script)\n\n(defbuild-script\n '("core"\n "util"\n "core-test"\n "util-test"))\n`,
},
{
path: 'core.ss',
content: `(export #t)\n\n;; Core module\n\n(def (process-data items)\n (filter (lambda (x) (> x 0)) items))\n\n(def (transform-item x)\n (* x 2))\n\n(def (batch-transform items)\n (map transform-item (process-data items)))\n`,
},
{
path: 'util.ss',
content: `(export #t)\n\n;; Utility functions\n\n(def (safe-divide a b)\n (if (zero? b) #f (/ a b)))\n\n(def (clamp val lo hi)\n (max lo (min hi val)))\n`,
},
{
path: 'core-test.ss',
content: `(import :std/test\n (pkg: core))\n(export core-test)\n\n(def core-test\n (test-suite "core tests"\n (test-case "process-data filters negatives"\n (check (process-data '(1 -2 3 -4 5)) => '(1 3 5)))\n (test-case "process-data empty list"\n (check (process-data '()) => '()))\n (test-case "transform-item doubles"\n (check (transform-item 5) => 10))\n (test-case "batch-transform end-to-end"\n (check (batch-transform '(1 -2 3)) => '(2 6)))))\n\n(run-tests! core-test)\n(test-report-summary!)\n`,
},
{
path: 'util-test.ss',
content: `(import :std/test\n (pkg: util))\n(export util-test)\n\n(def util-test\n (test-suite "util tests"\n (test-case "safe-divide normal"\n (check (safe-divide 10 2) => 5))\n (test-case "safe-divide by zero"\n (check (safe-divide 10 0) => #f))\n (test-case "clamp within range"\n (check (clamp 5 0 10) => 5))\n (test-case "clamp below"\n (check (clamp -5 0 10) => 0))\n (test-case "clamp above"\n (check (clamp 15 0 10) => 10))))\n\n(run-tests! util-test)\n(test-report-summary!)\n`,
},
{
path: 'Makefile',
content: `.PHONY: build clean test\n\nbuild:\n\tgerbil build\n\nclean:\n\tgerbil clean\n\ntest:\n\tgerbil test ./...\n`,
},
],
},
};
export function registerProjectTemplateTool(server: McpServer): void {
server.registerTool(
'gerbil_project_template',
{
title: 'Generate Project from Template',
description:
'Generate a complete multi-file Gerbil project from a template. ' +
'Available templates: cli (CLI with subcommands), http-api (REST server), ' +
'library (reusable lib with tests), actor-service (actor supervision), ' +
'db-crud (SQLite CRUD), parser (lexer+grammar+AST), ' +
'ffi-wrapper (C FFI bindings), test-project (test-heavy structure). ' +
'Each template includes gerbil.pkg, build.ss, Makefile, source modules, and tests.',
annotations: {
readOnlyHint: false,
idempotentHint: false,
},
inputSchema: {
template: z
.enum(['cli', 'http-api', 'library', 'actor-service', 'db-crud', 'parser', 'ffi-wrapper', 'test-project'])
.describe('Template type to generate'),
project_name: z
.string()
.describe('Project name (e.g. "my-app"). Used for directory name and display.'),
output_dir: z
.string()
.describe('Parent directory where the project directory will be created'),
package_name: z
.string()
.optional()
.describe('Gerbil package name (default: derived from project_name)'),
list_templates: z
.boolean()
.optional()
.describe('If true, list available templates instead of generating'),
},
},
async ({ template, project_name, output_dir, package_name, list_templates }) => {
// List mode
if (list_templates) {
const sections: string[] = ['Available project templates:\n'];
for (const [id, tmpl] of Object.entries(TEMPLATES)) {
sections.push(` **${id}** — ${tmpl.name}`);
sections.push(` ${tmpl.description}\n`);
}
return {
content: [{ type: 'text' as const, text: sections.join('\n') }],
};
}
const tmpl = TEMPLATES[template];
if (!tmpl) {
return {
content: [{
type: 'text' as const,
text: `Unknown template: ${template}. Available: ${Object.keys(TEMPLATES).join(', ')}`,
}],
isError: true,
};
}
const pkg = package_name || project_name.replace(/-/g, '_');
const projectDir = join(output_dir, project_name);
if (existsSync(projectDir)) {
return {
content: [{
type: 'text' as const,
text: `Directory already exists: ${projectDir}`,
}],
isError: true,
};
}
// Create project directory and files
try {
mkdirSync(projectDir, { recursive: true });
const files = tmpl.files(project_name, pkg);
for (const file of files) {
const filePath = join(projectDir, file.path);
const dir = join(filePath, '..');
mkdirSync(dir, { recursive: true });
writeFileSync(filePath, file.content, 'utf-8');
}
const sections: string[] = [
`Created ${tmpl.name} project: ${projectDir}\n`,
'Files:',
];
for (const file of files) {
sections.push(` ${file.path}`);
}
sections.push('');
sections.push('Next steps:');
sections.push(` cd ${projectDir}`);
sections.push(' make build');
sections.push(' make test');
return {
content: [{ type: 'text' as const, text: sections.join('\n') }],
};
} catch (err) {
return {
content: [{
type: 'text' as const,
text: `Failed to create project: ${err instanceof Error ? err.message : String(err)}`,
}],
isError: true,
};
}
},
);
}
