Accessibility MCP Server

import type { AxeResult, LighthouseResult, WaveResult } from '../../types/audit.js'; import type { NormalisedResult, NormalisedAuditResult } from '../../types/normalised.js'; import { getWCAGMapping, getDefaultWCAGMapping, mapImpactToSeverity, getConfidenceFromImpact } from '../../utils/wcag.js'; import { normaliseSelector, extractDOMContext } from '../../utils/selectors.js'; export class Normaliser { normaliseAxeResult(result: AxeResult): NormalisedAuditResult { const normalisedResults: NormalisedResult[] = []; for (const violation of result.violations) { const mapping = getWCAGMapping(violation.id, 'axe') ?? getDefaultWCAGMapping(violation.id); for (const node of violation.nodes) { const selector = normaliseSelector(node.target); const domContext = extractDOMContext(node.html); normalisedResults.push({ rule_id: violation.id, wcag_ref: mapping.wcagRefs, severity: mapImpactToSeverity(violation.impact), confidence: getConfidenceFromImpact(violation.impact), outcome: 'fail', selector, dom_context: domContext, message: violation.help, }); } } for (const pass of result.passes) { const mapping = getWCAGMapping(pass.id, 'axe') ?? getDefaultWCAGMapping(pass.id); for (const node of pass.nodes) { const selector = normaliseSelector(node.target); const domContext = extractDOMContext(node.html); normalisedResults.push({ rule_id: pass.id, wcag_ref: mapping.wcagRefs, severity: mapImpactToSeverity(pass.impact), confidence: getConfidenceFromImpact(pass.impact), outcome: 'pass', selector, dom_context: domContext, message: pass.help, }); } } for (const incomplete of result.incomplete) { const mapping = getWCAGMapping(incomplete.id, 'axe') ?? getDefaultWCAGMapping(incomplete.id); for (const node of incomplete.nodes) { const selector = normaliseSelector(node.target); const domContext = extractDOMContext(node.html); normalisedResults.push({ rule_id: incomplete.id, wcag_ref: mapping.wcagRefs, severity: mapImpactToSeverity(incomplete.impact), confidence: 'low', outcome: 'unknown', selector, dom_context: domContext, message: incomplete.help, reason_code: 'INCOMPLETE_CHECK', }); } } return this.buildAuditResult(result.url, 'axe', normalisedResults); } normaliseLighthouseResult(result: LighthouseResult): NormalisedAuditResult { const normalisedResults: NormalisedResult[] = []; const accessibilityCategory = result.categories.accessibility; if (!accessibilityCategory) { return this.buildAuditResult(result.url, 'lighthouse', []); } for (const auditRef of accessibilityCategory.auditRefs) { const audit = result.audits[auditRef.id]; if (!audit) { continue; } const mapping = getWCAGMapping(audit.id, 'lighthouse') ?? getDefaultWCAGMapping(audit.id); if (audit.scoreDisplayMode === 'notApplicable' || audit.scoreDisplayMode === 'error') { continue; } const outcome: 'pass' | 'fail' | 'unknown' = audit.score === null ? 'unknown' : audit.score >= 0.9 ? 'pass' : audit.score === 0 ? 'fail' : 'unknown'; if (audit.details?.nodes) { for (const node of audit.details.nodes) { normalisedResults.push({ rule_id: audit.id, wcag_ref: mapping.wcagRefs, severity: mapping.severity, confidence: outcome === 'pass' ? 'high' : outcome === 'fail' ? 'high' : 'medium', outcome, selector: node.selector ?? '', dom_context: node.snippet ?? '', message: audit.description, reason_code: outcome === 'unknown' ? 'SCORE_AMBIGUOUS' : undefined, }); } } else { normalisedResults.push({ rule_id: audit.id, wcag_ref: mapping.wcagRefs, severity: mapping.severity, confidence: outcome === 'pass' ? 'high' : outcome === 'fail' ? 'high' : 'medium', outcome, selector: '', dom_context: '', message: audit.description, reason_code: outcome === 'unknown' ? 'SCORE_AMBIGUOUS' : undefined, }); } } return this.buildAuditResult(result.url, 'lighthouse', normalisedResults); } normaliseWaveResult(result: WaveResult): NormalisedAuditResult { const normalisedResults: NormalisedResult[] = []; for (const error of result.categories.error) { const mapping = getWCAGMapping(error.code, 'wave') ?? getDefaultWCAGMapping(error.code); normalisedResults.push({ rule_id: error.code, wcag_ref: mapping.wcagRefs, severity: mapping.severity, confidence: 'high', outcome: 'fail', selector: '', dom_context: '', message: error.description, }); } for (const contrast of result.categories.contrast) { const mapping = getWCAGMapping(contrast.code, 'wave') ?? getDefaultWCAGMapping(contrast.code); normalisedResults.push({ rule_id: contrast.code, wcag_ref: mapping.wcagRefs, severity: mapping.severity, confidence: 'high', outcome: 'fail', selector: '', dom_context: '', message: contrast.description, }); } for (const alert of result.categories.alert) { const mapping = getWCAGMapping(alert.code, 'wave') ?? getDefaultWCAGMapping(alert.code); normalisedResults.push({ rule_id: alert.code, wcag_ref: mapping.wcagRefs, severity: 'moderate', confidence: 'medium', outcome: 'unknown', selector: '', dom_context: '', message: alert.description, reason_code: 'WAVE_ALERT', }); } return this.buildAuditResult(result.url, 'wave', normalisedResults); } private buildAuditResult(url: string, tool: 'axe' | 'lighthouse' | 'wave', results: NormalisedResult[]): NormalisedAuditResult { const summary = { total: results.length, pass: results.filter((r) => r.outcome === 'pass').length, fail: results.filter((r) => r.outcome === 'fail').length, unknown: results.filter((r) => r.outcome === 'unknown').length, by_severity: { critical: results.filter((r) => r.severity === 'critical').length, serious: results.filter((r) => r.severity === 'serious').length, moderate: results.filter((r) => r.severity === 'moderate').length, minor: results.filter((r) => r.severity === 'minor').length, }, }; return { url, tool, timestamp: new Date().toISOString(), results, summary, }; } }