Filesystem MCP Server

import { normalizeLineEndings, createUnifiedDiff } from './utils.js'; import fs from 'fs/promises'; import { randomBytes } from 'crypto'; export interface FileEdit { oldText: string; newText: string; useRegex?: boolean; flags?: string; } export async function applyFileEdits( filePath: string, edits: FileEdit[], dryRun: boolean = false ): Promise<string> { const content = normalizeLineEndings(await fs.readFile(filePath, 'utf-8')); let modifiedContent = content; for (const edit of edits) { if (edit.useRegex) { const regex = new RegExp(edit.oldText, edit.flags || 'g'); modifiedContent = modifiedContent.replace(regex, edit.newText); continue; } const normalizedOld = normalizeLineEndings(edit.oldText); const normalizedNew = normalizeLineEndings(edit.newText); if (modifiedContent.includes(normalizedOld)) { modifiedContent = modifiedContent.replace(normalizedOld, normalizedNew); continue; } const oldLines = normalizedOld.split('\n'); const contentLines = modifiedContent.split('\n'); let matchFound = false; for (let i = 0; i <= contentLines.length - oldLines.length; i++) { const potentialMatch = contentLines.slice(i, i + oldLines.length); const isMatch = oldLines.every((oldLine, j) => oldLine.trim() === potentialMatch[j].trim()); if (isMatch) { const originalIndent = contentLines[i].match(/^\s*/)?.[0] || ''; const newLines = normalizedNew.split('\n').map((line, j) => (j === 0 ? originalIndent + line.trimStart() : line)); contentLines.splice(i, oldLines.length, ...newLines); modifiedContent = contentLines.join('\n'); matchFound = true; break; } } if (!matchFound) { throw new Error(`Could not find exact match for edit:\n${edit.oldText}`); } } const diff = createUnifiedDiff(content, modifiedContent, filePath); let numBackticks = 3; while (diff.includes('`'.repeat(numBackticks))) numBackticks++; const formattedDiff = `${'`'.repeat(numBackticks)}diff\n${diff}${'`'.repeat(numBackticks)}\n\n`; if (!dryRun) { const tempPath = `${filePath}.${randomBytes(16).toString('hex')}.tmp`; try { await fs.writeFile(tempPath, modifiedContent, 'utf-8'); await fs.rename(tempPath, filePath); } catch (error) { try { await fs.unlink(tempPath); } catch {} throw error; } } return formattedDiff; }