Accessibility MCP Server

import lighthouse from 'lighthouse'; import type { RunnerResult } from 'lighthouse'; import type { LighthouseResult as AuditLighthouseResult } from '../types/audit.js'; import { resolveUrl, type ResolvedUrl } from '../utils/url-resolver.js'; export interface LighthouseAdapterOptions { timeout?: number; categories?: string[]; onlyCategories?: string[]; skipAudits?: string[]; } export class LighthouseAdapter { constructor(_options: LighthouseAdapterOptions = {}) { // Timeout is handled by lighthouse options } async audit(urlOrPath: string, options?: LighthouseAdapterOptions): Promise<AuditLighthouseResult> { const resolved: ResolvedUrl = await resolveUrl(urlOrPath); const config: { extends?: string; categories?: Record<string, { title: string }>; onlyCategories?: string[]; skipAudits?: string[]; } = { extends: 'lighthouse:default', }; if (options?.onlyCategories) { config.onlyCategories = options.onlyCategories; } else if (options?.categories) { config.onlyCategories = options.categories; } if (options?.skipAudits) { config.skipAudits = options.skipAudits; } let result: RunnerResult | undefined; try { result = await lighthouse(resolved.url, { logLevel: 'error', output: 'json', onlyCategories: config.onlyCategories, skipAudits: config.skipAudits, } as Parameters<typeof lighthouse>[1]); } finally { if (resolved.cleanup) { await resolved.cleanup(); } } if (!result?.lhr) { throw new Error('Lighthouse audit returned no result'); } return this.transformResult(result, resolved.url); } private transformResult(result: RunnerResult, resolvedUrl: string): AuditLighthouseResult { const lhr = result.lhr; return { url: lhr.finalUrl || lhr.requestedUrl || resolvedUrl, fetchTime: lhr.fetchTime, audits: Object.entries(lhr.audits).reduce((acc, [, audit]) => { const auditDetails = audit.details; let details: AuditLighthouseResult['audits'][string]['details'] = undefined; if (auditDetails && typeof auditDetails === 'object' && 'type' in auditDetails && ('headings' in auditDetails || 'items' in auditDetails || 'nodes' in auditDetails)) { const detailsObj: { type: string; headings?: Array<{ key: string; itemType: string; text: string }>; items?: Array<Record<string, unknown>>; nodes?: Array<{ path: string; selector: string; snippet: string }>; } = { type: String(auditDetails.type), }; if ('headings' in auditDetails && Array.isArray(auditDetails.headings)) { detailsObj.headings = auditDetails.headings as Array<{ key: string; itemType: string; text: string }>; } if ('items' in auditDetails && Array.isArray(auditDetails.items)) { detailsObj.items = auditDetails.items as Array<Record<string, unknown>>; } if ('nodes' in auditDetails && Array.isArray(auditDetails.nodes)) { detailsObj.nodes = auditDetails.nodes.map((node: unknown) => { if (typeof node === 'object' && node !== null && 'selector' in node && 'snippet' in node) { return { path: 'path' in node ? String(node.path) : '', selector: String(node.selector), snippet: String(node.snippet), }; } return { path: '', selector: '', snippet: '' }; }); } details = detailsObj; } acc[audit.id] = { id: audit.id, title: audit.title, description: audit.description ?? '', score: audit.score, scoreDisplayMode: (audit.scoreDisplayMode === 'numeric' || audit.scoreDisplayMode === 'binary' || audit.scoreDisplayMode === 'manual' || audit.scoreDisplayMode === 'informative' || audit.scoreDisplayMode === 'notApplicable' || audit.scoreDisplayMode === 'error') ? audit.scoreDisplayMode : 'numeric', ...(audit.displayValue ? { displayValue: audit.displayValue } : {}), ...(details ? { details } : {}), }; return acc; }, {} as Record<string, AuditLighthouseResult['audits'][string]>), categories: Object.entries(lhr.categories).reduce((acc, [, category]) => { const auditRefs = category.auditRefs.map((ref) => { const mappedRef: { id: string; weight: number; group?: string } = { id: ref.id, weight: ref.weight, }; if (ref.group !== undefined) { mappedRef.group = ref.group; } return mappedRef; }); acc[category.id] = { id: category.id, title: category.title, score: category.score, description: category.description ?? '', ...(category.manualDescription ? { manualDescription: category.manualDescription } : {}), auditRefs, }; return acc; }, {} as Record<string, AuditLighthouseResult['categories'][string]>), }; } }