SnapOtter/apps/api/src/lib/analytics.ts

import { eq } from "drizzle-orm";
import type { FastifyRequest } from "fastify";
import { env } from "../config.js";
import { db, schema } from "../db/index.js";
import { getAuthUser } from "../plugins/auth.js";

let posthogClient: import("posthog-node").PostHog | null = null;

export function initAnalytics(): void {
  if (!env.ANALYTICS_ENABLED || !env.POSTHOG_API_KEY) return;

  try {
    const { PostHog } = require("posthog-node") as typeof import("posthog-node");
    posthogClient = new PostHog(env.POSTHOG_API_KEY, {
      host: env.POSTHOG_HOST,
      flushAt: 20,
      flushInterval: 30000,
    });
  } catch {
    // posthog-node not available — analytics disabled
  }
}

export async function shutdownAnalytics(): Promise<void> {
  if (posthogClient) {
    await posthogClient.shutdown();
    posthogClient = null;
  }
}

function getInstanceId(): string {
  const row = db.select().from(schema.settings).where(eq(schema.settings.key, "instance_id")).get();
  return row?.value ?? "unknown";
}

function isUserOptedIn(userId: string): boolean {
  if (!env.ANALYTICS_ENABLED) return false;
  if (userId === "anonymous") return false;
  const user = db.select().from(schema.users).where(eq(schema.users.id, userId)).get();
  return user?.analyticsEnabled === true;
}

function isRequestOptedIn(request: FastifyRequest): boolean {
  if (!env.ANALYTICS_ENABLED) return false;
  const user = getAuthUser(request);
  if (!user) return false;
  if (user.id === "anonymous") {
    const header = request.headers["x-analytics-consent"];
    return header === "true";
  }
  return isUserOptedIn(user.id);
}

function shouldSample(): boolean {
  if (env.ANALYTICS_SAMPLE_RATE >= 1.0) return true;
  if (env.ANALYTICS_SAMPLE_RATE <= 0.0) return false;
  return Math.random() < env.ANALYTICS_SAMPLE_RATE;
}

export function trackEvent(
  request: FastifyRequest,
  event: string,
  properties: Record<string, unknown>,
): void {
  if (!posthogClient || !isRequestOptedIn(request) || !shouldSample()) return;
  try {
    posthogClient.capture({
      distinctId: getInstanceId(),
      event,
      properties,
    });
  } catch {
    // never throw from analytics
  }
}