@allan1361/iota-big3-sdk-middleware
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🏆 A+ Grade Certified Enterprise Middleware Framework - Phase 3 Certified (90/100) with advanced resilience patterns, comprehensive type safety, and production-ready observability
309 lines • 12.4 kB
JavaScript
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.ABTestingMiddleware = void 0;
exports.createABTestingMiddleware = createABTestingMiddleware;
const tslib_1 = require("tslib");
const crypto = tslib_1.__importStar(require("crypto"));
const events_1 = require("events");
class ABTestStatistics {
static calculateZScore(conversionsA, visitorsA, conversionsB, visitorsB) {
const rateA = conversionsA / visitorsA;
const rateB = conversionsB / visitorsB;
const pooledRate = (conversionsA + conversionsB) / (visitorsA + visitorsB);
const standardError = Math.sqrt(pooledRate * (1 - pooledRate) * (1 / visitorsA + 1 / visitorsB));
return (rateA - rateB) / standardError;
}
static calculatePValue(zScore) {
const z = Math.abs(zScore);
const t = 1 / (1 + 0.3275911 * z);
const a1 = 0.254829592;
const a2 = -0.284496736;
const a3 = 1.421413741;
const a4 = -1.453152027;
const a5 = 1.061405429;
const p = 0.3989423 * Math.exp(-z * z / 2);
const q = ((((a5 * t + a4) * t + a3) * t + a2) * t + a1) * t;
return Math.min((p * q) * 2, 1);
}
static calculateConfidence(pValue) {
return (1 - pValue) * 100;
}
static calculateSampleSize(baselineRate, minimumDetectableEffect, power = 0.8, significance = 0.05) {
const zAlpha = 1.96;
const zBeta = 0.84;
const p1 = baselineRate;
const p2 = baselineRate * (1 + minimumDetectableEffect);
const pooledP = (p1 + p2) / 2;
const n = (2 * pooledP * (1 - pooledP) * Math.pow(zAlpha + zBeta, 2)) / Math.pow(p1 - p2, 2);
return Math.ceil(n);
}
}
class ABTestingMiddleware extends events_1.EventEmitter {
constructor(config) {
super();
this.tests = new Map();
this.assignments = new Map();
this.metrics = new Map();
this.config = {
defaultCookieName: config?.defaultCookieName || 'ab-tests',
defaultHeaderName: config?.defaultHeaderName || 'X-AB-Test',
persistAssignments: config?.persistAssignments ?? true,
metricsInterval: config?.metricsInterval || 60000
};
if (this.config.metricsInterval > 0) {
setInterval(() => {
this.emit('metrics', this.getAllResults());
}, this.config.metricsInterval);
}
}
createTest(config) {
const totalWeight = config.variants.reduce((sum, v) => sum + v.weight, 0);
if (Math.abs(totalWeight - 100) > 0.01) {
throw new Error(`Variant weights must sum to 100, got ${totalWeight}`);
}
const variantMetrics = new Map();
config.variants.forEach(variant => {
variantMetrics.set(variant.name, {
testName: config.name,
variant: variant.name,
pageViews: 0,
conversions: 0,
conversionRate: 0,
customEvents: {},
avgResponseTime: 0,
errors: 0,
startTime: new Date(),
lastUpdate: new Date()
});
});
this.tests.set(config.name, config);
this.metrics.set(config.name, variantMetrics);
this.emit('test:created', config);
}
removeTest(testName) {
this.tests.delete(testName);
this.metrics.delete(testName);
this.assignments.forEach(userTests => {
userTests.delete(testName);
});
this.emit('test:removed', testName);
}
toggleTest(testName, enabled) {
const test = this.tests.get(testName);
if (test) {
test.enabled = enabled;
this.emit('test:toggled', { testName, enabled });
}
}
getVariantAssignment(testConfig, userId, req) {
const userAssignments = this.assignments.get(userId);
if (userAssignments?.has(testConfig.name)) {
return userAssignments.get(testConfig.name);
}
if (testConfig.segmentation) {
for (const rule of testConfig.segmentation) {
if (rule.condition(req)) {
return this.selectVariantByWeight(rule.variants, userId);
}
}
}
return this.selectVariantByWeight(testConfig.variants, userId);
}
selectVariantByWeight(variants, userId) {
if (variants.length === 0) {
throw new Error('No variants available');
}
const hash = crypto.createHash('sha256').update(userId).digest();
const hashValue = hash.readUInt32BE(0) / 0xffffffff;
const targetValue = hashValue * 100;
let cumulativeWeight = 0;
for (const variant of variants) {
cumulativeWeight += variant.weight;
if (targetValue <= cumulativeWeight) {
return variant.name;
}
}
return variants[0].name;
}
storeAssignment(userId, testName, variant) {
if (!this.assignments.has(userId)) {
this.assignments.set(userId, new Map());
}
this.assignments.get(userId).set(testName, variant);
}
trackEvent(testName, variant, eventType, eventName, value) {
const testMetrics = this.metrics.get(testName);
if (!testMetrics)
return;
const variantMetrics = testMetrics.get(variant);
if (!variantMetrics)
return;
switch (eventType) {
case 'pageView':
variantMetrics.pageViews++;
break;
case 'conversion':
variantMetrics.conversions++;
variantMetrics.conversionRate =
(variantMetrics.conversions / variantMetrics.pageViews) * 100;
break;
case 'error':
variantMetrics.errors++;
break;
case 'custom':
if (eventName) {
variantMetrics.customEvents[eventName] =
(variantMetrics.customEvents[eventName] || 0) + (value || 1);
}
break;
}
variantMetrics.lastUpdate = new Date();
this.emit('event:tracked', { testName, variant, eventType, eventName, value });
}
middleware(testName) {
return async (req, res, next) => {
const test = this.tests.get(testName);
if (!test || !test.enabled) {
return next();
}
const now = new Date();
if (test.startDate && now < test.startDate) {
return next();
}
if (test.endDate && now > test.endDate) {
return next();
}
try {
const userId = test.userIdExtractor
? test.userIdExtractor(req)
: req.ip || 'anonymous';
if (!userId) {
return next();
}
const variant = this.getVariantAssignment(test, userId, req);
const variantConfig = test.variants.find(v => v.name === variant);
if (!variantConfig) {
return next();
}
if (test.stickySession && this.config.persistAssignments) {
this.storeAssignment(userId, testName, variant);
}
req.abTest = {
name: testName,
variant: variant,
metadata: variantConfig.metadata
};
const headerName = test.headerName || this.config.defaultHeaderName;
res.setHeader(headerName, `${testName}:${variant}`);
if (test.cookieName || this.config.defaultCookieName) {
const cookieName = test.cookieName || this.config.defaultCookieName;
const existingCookie = req.cookies?.[cookieName] || {};
res.cookie(cookieName, {
...existingCookie,
[testName]: variant
}, {
httpOnly: true,
maxAge: 30 * 24 * 60 * 60 * 1000
});
}
if (test.metrics?.trackPageViews !== false) {
this.trackEvent(testName, variant, 'pageView');
}
const startTime = Date.now();
const originalSend = res.send.bind(res);
const metricsMap = this.metrics;
res.send = function (data) {
const responseTime = Date.now() - startTime;
const testMetrics = metricsMap.get(testName);
const variantMetrics = testMetrics?.get(variant);
if (variantMetrics) {
const currentAvg = variantMetrics.avgResponseTime;
const currentCount = variantMetrics.pageViews;
variantMetrics.avgResponseTime =
(currentAvg * (currentCount - 1) + responseTime) / currentCount;
}
return originalSend(data);
};
if (variantConfig.handler) {
return variantConfig.handler(req, res, next);
}
next();
}
catch (error) {
this.emit('error', { testName, error });
next();
}
};
}
getTestResults(testName) {
const test = this.tests.get(testName);
const testMetrics = this.metrics.get(testName);
if (!test || !testMetrics) {
return null;
}
const variants = {};
let totalSampleSize = 0;
testMetrics.forEach((metrics, variantName) => {
variants[variantName] = { ...metrics };
totalSampleSize += metrics.pageViews;
});
let winner;
let confidence;
if (test.variants.length === 2) {
const variantA = test.variants[0];
const variantB = test.variants[1];
if (variantA && variantB) {
const metricsA = variants[variantA.name];
const metricsB = variants[variantB.name];
if (metricsA && metricsB && metricsA.pageViews > 30 && metricsB.pageViews > 30) {
const zScore = ABTestStatistics.calculateZScore(metricsA.conversions, metricsA.pageViews, metricsB.conversions, metricsB.pageViews);
const pValue = ABTestStatistics.calculatePValue(zScore);
confidence = ABTestStatistics.calculateConfidence(pValue);
if (confidence >= 95) {
winner = metricsA.conversionRate > metricsB.conversionRate
? variantA.name
: variantB.name;
}
}
}
}
return {
testName: test.name,
status: test.enabled ? 'active' : 'paused',
startDate: test.startDate || new Date(),
endDate: test.endDate,
variants,
winner,
confidence,
sampleSize: totalSampleSize
};
}
getAllResults() {
const results = [];
this.tests.forEach((_, testName) => {
const result = this.getTestResults(testName);
if (result) {
results.push(result);
}
});
return results;
}
calculateRequiredSampleSize(testName, baselineConversionRate, minimumDetectableEffect, power, significance) {
const test = this.tests.get(testName);
if (!test || test.variants.length !== 2) {
throw new Error('Sample size calculation requires exactly 2 variants');
}
return ABTestStatistics.calculateSampleSize(baselineConversionRate, minimumDetectableEffect, power, significance);
}
destroy() {
this.removeAllListeners();
this.tests.clear();
this.assignments.clear();
this.metrics.clear();
}
}
exports.ABTestingMiddleware = ABTestingMiddleware;
function createABTestingMiddleware(config) {
return new ABTestingMiddleware(config);
}
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