Posthog Multi Env Setup

# .env.local (development — git-ignored)
NEXT_PUBLIC_POSTHOG_KEY=phc_dev_key_here
NEXT_PUBLIC_POSTHOG_HOST=https://us.i.posthog.com
POSTHOG_PERSONAL_API_KEY=phx_your_key
POSTHOG_PROJECT_ID=11111

# .env.staging (CI/CD secrets or secret manager)
NEXT_PUBLIC_POSTHOG_KEY=phc_staging_key_here
NEXT_PUBLIC_POSTHOG_HOST=https://us.i.posthog.com
POSTHOG_PERSONAL_API_KEY=phx_your_key
POSTHOG_PROJECT_ID=22222

# Production (secret manager — never in files)
# NEXT_PUBLIC_POSTHOG_KEY=phc_prod_key_here
# POSTHOG_PROJECT_ID=33333

// config/posthog.ts
type Env = 'development' | 'staging' | 'production';

interface PostHogEnvConfig {
  apiKey: string;
  host: string;
  sessionRecording: boolean;
  recordingSampleRate: number;
  autocapture: boolean | object;
  debug: boolean;
}

function getConfig(): PostHogEnvConfig {
  const env = (process.env.NODE_ENV || 'development') as Env;
  const key = process.env.NEXT_PUBLIC_POSTHOG_KEY;
  const host = process.env.NEXT_PUBLIC_POSTHOG_HOST || 'https://us.i.posthog.com';

  if (!key) {
    console.warn(`[PostHog] No API key for ${env} — analytics disabled`);
  }

  const configs: Record<Env, Omit<PostHogEnvConfig, 'apiKey' | 'host'>> = {
    development: {
      sessionRecording: false,
      recordingSampleRate: 0,
      autocapture: true,
      debug: true,
    },
    staging: {
      sessionRecording: false,
      recordingSampleRate: 0,
      autocapture: true,
      debug: false,
    },
    production: {
      sessionRecording: true,
      recordingSampleRate: 0.1,  // Record 10% of sessions
      autocapture: {
        dom_event_allowlist: ['click', 'submit'],
        element_allowlist: ['a', 'button', 'form'],
        css_selector_allowlist: ['.track-click'],
      },
      debug: false,
    },
  };

  return { apiKey: key || '', host, ...configs[env] };
}

export const posthogConfig = getConfig();

// app/providers.tsx
'use client';
import posthog from 'posthog-js';
import { PostHogProvider } from 'posthog-js/react';
import { useEffect } from 'react';
import { posthogConfig } from '../config/posthog';

export function PHProvider({ children }: { children: React.ReactNode }) {
  useEffect(() => {
    if (!posthogConfig.apiKey) return; // Skip if no key configured

    posthog.init(posthogConfig.apiKey, {
      api_host: posthogConfig.host,
      autocapture: posthogConfig.autocapture,
      capture_pageview: false,  // Manual in App Router
      capture_pageleave: true,
      disable_session_recording: !posthogConfig.sessionRecording,
      session_recording: posthogConfig.sessionRecording
        ? { sampleRate: posthogConfig.recordingSampleRate }
        : undefined,
      loaded: (ph) => {
        if (posthogConfig.debug) ph.debug();
      },
    });
  }, []);

  return <PostHogProvider client={posthog}>{children}</PostHogProvider>;
}

// lib/posthog-server.ts
import { PostHog } from 'posthog-node';
import { posthogConfig } from '../config/posthog';

let client: PostHog | null = null;

export function getPostHogServer(): PostHog {
  if (client) return client;

  if (!posthogConfig.apiKey) {
    // Return no-op client when unconfigured
    return { capture: () => {}, identify: () => {}, shutdown: async () => {} } as any;
  }

  client = new PostHog(posthogConfig.apiKey, {
    host: posthogConfig.host,
    personalApiKey: process.env.POSTHOG_FEATURE_FLAGS_SECURE_API_KEY,
    flushAt: 20,
    flushInterval: 10000,
  });

  return client;
}

// In your staging PostHog project: set all flags to 100% rollout for QA
// In your production PostHog project: gradual rollout (10% → 25% → 50% → 100%)

// Server-side flag check works the same regardless of environment
const ph = getPostHogServer();
const enabled = await ph.isFeatureEnabled('new-checkout', userId);
// Staging project: always true (100% rollout)
// Production project: depends on rollout percentage

set -euo pipefail
# Set all flags to 100% in staging project (for QA)
curl "https://us.posthog.com/api/projects/$POSTHOG_STAGING_PROJECT_ID/feature_flags/" \
  -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" | \
  jq -r '.results[].id' | while read FLAG_ID; do
    curl -X PATCH "https://us.posthog.com/api/projects/$POSTHOG_STAGING_PROJECT_ID/feature_flags/$FLAG_ID/" \
      -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" \
      -H "Content-Type: application/json" \
      -d '{"filters": {"groups": [{"rollout_percentage": 100}]}}'
  done