import { promises as fs } from "node:fs";
import path from "node:path";
import { z } from "zod";

import { getServerConfig } from "@/lib/config";
import { rejectCrossOrigin, rejectOversizedBody, requestLocale } from "@/lib/http-guard";
import { clientKey, rateLimit, rateLimitResponse } from "@/lib/rate-limit";

export const runtime = "nodejs";
export const dynamic = "force-dynamic";

/**
 * Question reports. Write-only on purpose: the app has no auth, so nothing
 * here is readable over HTTP. Every report is appended as one JSON line to
 * `<reports dir>/reports.jsonl` under the shared data directory, where the
 * operator can inspect it:
 *
 *   tail -f ~/freezmo-prod/shared/freezmo/reports/reports.jsonl
 *
 * The browser keeps its own copy of the reports — it is the source of truth
 * for skipping and Undo. This file is the cross-device record for tuning the
 * generation prompts.
 */

const reportSchema = z.object({
  deckId: z.string().min(1).max(80),
  deckTitle: z.string().max(200).optional(),
  activityId: z.string().min(1).max(80),
  type: z.string().min(1).max(40),
  question: z.string().min(1).max(600),
  at: z.number(),
});

/** A report is tiny; anything bigger is not one. */
const MAX_BODY_BYTES = 4096;

export async function POST(request: Request) {
  const locale = requestLocale(request);
  const crossOrigin = rejectCrossOrigin(request);
  if (crossOrigin) return crossOrigin;
  const oversized = rejectOversizedBody(request, MAX_BODY_BYTES);
  if (oversized) return oversized;

  const config = getServerConfig();
  const limit = rateLimit(`reports:${clientKey(request)}`, config.rateLimits.reports, config.rateLimits.windowMs);
  if (!limit.allowed) return rateLimitResponse(limit, locale);

  const parsed = reportSchema.safeParse(await request.json().catch(() => null));
  if (!parsed.success) return Response.json({ error: "invalid report" }, { status: 400 });

  const line = JSON.stringify({ ...parsed.data, receivedAt: new Date().toISOString() });
  try {
    await fs.mkdir(config.reports.dir, { recursive: true });
    const file = path.join(config.reports.dir, "reports.jsonl");
    /* Disk guard: reports are a convenience for the operator, so once the
       file passes the cap the app stops appending (the browser's own list is
       still the source of truth for skipping). */
    const size = await fs.stat(file).then((stats) => stats.size).catch(() => 0);
    if (size >= config.reports.maxBytes) {
      console.warn("[api/reports] reports.jsonl is at its size cap — not appending");
      return Response.json({ ok: true });
    }
    await fs.appendFile(file, `${line}\n`, "utf8");
  } catch {
    return Response.json({ error: "could not store the report" }, { status: 500 });
  }

  return Response.json({ ok: true });
}