import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import { z } from 'zod';
import { runGxi, escapeSchemeString, ERROR_MARKER } from '../gxi.js';
export function registerExpandMacroTool(server: McpServer): void {
server.registerTool(
'gerbil_expand_macro',
{
title: 'Expand Gerbil Macro',
description:
'Show the macro expansion of a Gerbil Scheme expression. ' +
'Returns the core-expanded form using syntax->datum. ' +
'Example: "(when #t (displayln \\"hi\\"))" expands to a %#if form.',
inputSchema: {
expression: z.string().describe('The Gerbil expression to expand'),
imports: z
.array(z.string())
.optional()
.describe('Modules to import for macro definitions'),
},
},
async ({ expression, imports }) => {
const escaped = escapeSchemeString(expression);
const exprs: string[] = ['(import :gerbil/expander)'];
if (imports && imports.length > 0) {
for (const mod of imports) {
exprs.push(`(import ${mod})`);
}
}
const wrapper = [
'(with-catch',
' (lambda (e)',
` (display "${ERROR_MARKER}\\n")`,
' (display-exception e (current-output-port)))',
' (lambda ()',
` (let ((expanded (syntax->datum (core-expand (read (open-input-string "${escaped}"))))))`,
' (write expanded)',
' (newline))))',
].join(' ');
exprs.push(wrapper);
const result = await runGxi(exprs);
if (result.timedOut) {
return {
content: [{ type: 'text' as const, text: 'Macro expansion timed out.' }],
isError: true,
};
}
if (result.exitCode !== 0 && result.stderr) {
return {
content: [{ type: 'text' as const, text: `Error:\n${result.stderr.trim()}` }],
isError: true,
};
}
const stdout = result.stdout;
const errorIdx = stdout.indexOf(ERROR_MARKER);
if (errorIdx !== -1) {
const errorMsg = stdout.slice(errorIdx + ERROR_MARKER.length).trim();
return {
content: [{ type: 'text' as const, text: `Expansion error:\n${errorMsg}` }],
isError: true,
};
}
const expanded = stdout.trim();
if (!expanded) {
return {
content: [{ type: 'text' as const, text: 'Expression expanded to void.' }],
};
}
return {
content: [{ type: 'text' as const, text: `Expanded form:\n${expanded}` }],
};
},
);
}
