import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import { z } from 'zod';
import { runGxi, escapeSchemeString, ERROR_MARKER } from '../gxi.js';
export function registerFormatTool(server: McpServer): void {
server.registerTool(
'gerbil_format',
{
title: 'Format Gerbil Code',
description:
'Pretty-print/format Gerbil Scheme expressions using Gambit\'s pretty-print. ' +
'Reads all expressions from the input and returns them properly indented.',
inputSchema: {
code: z
.string()
.describe('Gerbil Scheme code to format/pretty-print'),
},
},
async ({ code }) => {
const escaped = escapeSchemeString(code);
const wrapper = [
'(with-catch',
' (lambda (e)',
` (display "${ERROR_MARKER}\\n")`,
' (display-exception e (current-output-port)))',
' (lambda ()',
` (let ((in (open-input-string "${escaped}"))`,
' (out (open-output-string)))',
' (let loop ((form (read in)) (first #t))',
' (if (eof-object? form)',
' (display (get-output-string out))',
' (begin',
' (unless first (newline out))',
' (pretty-print form out)',
' (loop (read in) #f)))))))',
].join(' ');
const result = await runGxi([wrapper]);
if (result.timedOut) {
return {
content: [
{
type: 'text' as const,
text: 'Format operation timed out.',
},
],
isError: true,
};
}
if (result.exitCode !== 0 && result.stderr) {
return {
content: [
{
type: 'text' as const,
text: `Format error:\n${result.stderr.trim()}`,
},
],
isError: true,
};
}
const stdout = result.stdout;
const errorIdx = stdout.indexOf(ERROR_MARKER);
if (errorIdx !== -1) {
const errorMsg = stdout.slice(errorIdx + ERROR_MARKER.length).trim();
return {
content: [
{
type: 'text' as const,
text: `Format error:\n${errorMsg}`,
},
],
isError: true,
};
}
const formatted = stdout.trimEnd();
if (!formatted) {
return {
content: [
{
type: 'text' as const,
text: 'No expressions found in input.',
},
],
};
}
return {
content: [{ type: 'text' as const, text: formatted }],
};
},
);
}
