// Fire-and-forget telemetry for /api/manifest fetches. Writes one row
// per request with hashed IP, UA, and Vercel geo headers. Designed to
// fail silently — the manifest response should never block on a log
// write.

import { db, schema } from "@/lib/db/client";

function newId(): string {
  return `mfetch_${crypto.randomUUID().replace(/-/g, "").slice(0, 22)}`;
}

function dailySalt(): string {
  return new Date().toISOString().slice(0, 10); // YYYY-MM-DD
}

async function hashIp(ip: string): Promise<string> {
  const enc = new TextEncoder().encode(`${dailySalt()}::${ip}`);
  const buf = await crypto.subtle.digest("SHA-256", enc);
  const bytes = new Uint8Array(buf);
  let hex = "";
  for (let i = 0; i < bytes.length; i++) {
    hex += bytes[i].toString(16).padStart(2, "0");
  }
  return hex.slice(0, 32); // half the digest is plenty for grouping
}

export async function logManifestFetch(
  req: Request,
  variant: "slim" | "full",
): Promise<void> {
  try {
    const h = req.headers;
    // Vercel injects x-real-ip / x-forwarded-for; fallback chain.
    const ip =
      h.get("x-real-ip") ??
      h.get("x-forwarded-for")?.split(",")[0]?.trim() ??
      "unknown";
    const ipHash = await hashIp(ip);
    const userAgent = h.get("user-agent")?.slice(0, 200) ?? null;
    const country = h.get("x-vercel-ip-country") ?? null;
    const region = h.get("x-vercel-ip-country-region") ?? null;
    const referer = h.get("referer")?.slice(0, 200) ?? null;

    await db.insert(schema.manifestFetches).values({
      id: newId(),
      ipHash,
      userAgent,
      country,
      region,
      referer,
      variant,
    });
  } catch {
    /* swallow — telemetry must not break the response */
  }
}