/**
 * Feature flag + A/B test detector.
 *
 * Detects popular feature flag / experiment SDKs loaded on the page:
 * LaunchDarkly, Optimizely, Split.io, Unleash, GrowthBook, Statsig, Flagsmith, Amplitude Experiment.
 *
 * Also detects common A/B test patterns: data-testid attributes, gtm.js experiment layers,
 * Optimizely variation IDs, VWO, etc.
 *
 * Why: ZeTa needs to know when a page shows different content to different users
 * so test generation can account for variants and not generate flaky tests.
 */

import type { Page } from 'playwright';

export interface FeatureFlagInfo {
  sdk: string;
  confidence: 'high' | 'medium' | 'low';
  details?: string;
}

export interface AbTestInfo {
  tool: string;
  experiments?: string[];
}

export interface FeatureFlagDetectionResult {
  url: string;
  flagSdks: FeatureFlagInfo[];
  abTools: AbTestInfo[];
  hasAnyFlags: boolean;
  detectedAt: string;
}

// SDK detectors — checked against window object + script URLs
const FLAG_SDK_CHECKS: Array<{
  sdk: string;
  windowKeys?: string[];
  scriptPattern?: RegExp;
}> = [
  { sdk: 'LaunchDarkly', windowKeys: ['LDClient', 'LaunchDarkly', 'ldClient'], scriptPattern: /launchdarkly/i },
  { sdk: 'Optimizely', windowKeys: ['optimizely', 'optimizelySdk'], scriptPattern: /optimizely/i },
  { sdk: 'Split.io', windowKeys: ['splitio', 'SplitFactory'], scriptPattern: /split\.io/i },
  { sdk: 'GrowthBook', windowKeys: ['growthbook', 'GrowthBook'], scriptPattern: /growthbook/i },
  { sdk: 'Statsig', windowKeys: ['statsig', 'StatsigClient'], scriptPattern: /statsig/i },
  { sdk: 'Flagsmith', windowKeys: ['flagsmith'], scriptPattern: /flagsmith/i },
  { sdk: 'Unleash', windowKeys: ['unleash', 'UnleashClient'], scriptPattern: /unleash/i },
  { sdk: 'VWO', windowKeys: ['vwo', '_vwo'], scriptPattern: /vwo\.com/i },
  { sdk: 'Google Optimize', windowKeys: ['gaData', 'google_optimize'], scriptPattern: /googleoptimize/i },
  { sdk: 'AB Tasty', windowKeys: ['ABTasty'], scriptPattern: /abtasty/i },
];

export async function detectFeatureFlags(page: Page, url: string): Promise<FeatureFlagDetectionResult> {
  const detectedAt = new Date().toISOString();

  const result = await page.evaluate((checks) => {
    const flagSdks: any[] = [];
    const scripts = Array.from(document.querySelectorAll('script[src]')).map((s: any) => s.src ?? '');

    for (const check of checks) {
      let found = false;
      let confidence = 'low';

      // Check window keys
      if (check.windowKeys?.some((k: string) => k in (window as any))) {
        found = true;
        confidence = 'high';
      }
      // Check script URLs
      if (!found && check.scriptPattern) {
        const re = new RegExp(check.scriptPattern.source, 'i');
        const matchingSrc = scripts.find(s => re.test(s));
        if (matchingSrc) { found = true; confidence = 'medium'; }
      }
      if (found) flagSdks.push({ sdk: check.sdk, confidence, details: undefined });
    }

    // A/B tools
    const abTools: any[] = [];
    if ('_vwo_code' in window || '_vis_opt_queue' in (window as any)) abTools.push({ tool: 'VWO', experiments: [] });
    if ('dataLayer' in window) {
      const dl = (window as any).dataLayer ?? [];
      const expEvents = dl.filter((e: any) => e?.event?.includes('experiment') || e?.experimentId);
      if (expEvents.length > 0) abTools.push({ tool: 'Google Tag Manager Experiments', experiments: expEvents.slice(0, 5).map((e: any) => e.experimentId ?? '') });
    }

    return { flagSdks, abTools };
  }, FLAG_SDK_CHECKS as any).catch(() => ({ flagSdks: [], abTools: [] }));

  return {
    url,
    flagSdks: result.flagSdks,
    abTools: result.abTools,
    hasAnyFlags: result.flagSdks.length > 0 || result.abTools.length > 0,
    detectedAt,
  };
}