import { z } from "zod";

import { gradeShortAnswer } from "@/lib/ai";
import { authErrorMessage, authErrorKind, getServerConfig, resolveAuth } from "@/lib/config";
import { friendlyErrorMessage, OllamaError } from "@/lib/ollama";
import { rejectCrossOrigin, rejectOversizedBody, requestLocale } from "@/lib/http-guard";
import { clientKey, rateLimit, rateLimitResponse } from "@/lib/rate-limit";
import { translate } from "@/lib/i18n-dict";

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

const requestSchema = z.object({
  question: z.string().min(1).max(1000),
  referenceAnswer: z.string().min(1).max(2000),
  keyPoints: z.array(z.string().max(300)).max(8).default([]),
  userAnswer: z.string().min(1).max(2000),
  /** Language of the deck so feedback comes back in the same language. */
  language: z.string().max(60).optional(),
});

/** Generous but finite: ~16 compressed images plus JSON overhead. */
const MAX_BODY_BYTES = 65536;

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(`grade:${clientKey(request)}`, config.rateLimits.grade, config.rateLimits.windowMs);
  if (!limit.allowed) return rateLimitResponse(limit, locale);

  const auth = resolveAuth(config, request);
  if ("error" in auth) {
    return Response.json(
      { error: authErrorMessage(locale, auth.error), kind: authErrorKind(auth.error) },
      { status: 401 },
    );
  }

  let payload: unknown;
  try {
    payload = await request.json();
  } catch {
    return Response.json({ error: translate(locale, "server.bodyNotJson") }, { status: 400 });
  }

  const parsed = requestSchema.safeParse(payload);
  if (!parsed.success) {
    return Response.json({ error: translate(locale, "server.invalidGrade") }, { status: 400 });
  }

  try {
    const result = await gradeShortAnswer({
      model: config.textModel,
      auth: auth.auth,
      ...parsed.data,
      // Grading is quick; don't let a hung request block the feed for minutes.
      signal: AbortSignal.timeout(Math.min(config.timeoutMs, 120_000)),
    });
    return Response.json(result);
  } catch (error) {
    console.error("[api/grade]", error instanceof OllamaError ? `${error.kind}: ${error.message}` : error);
    return Response.json(
      {
        error: friendlyErrorMessage(error, auth.auth.baseUrl, locale),
        kind: error instanceof OllamaError ? error.kind : "unknown",
      },
      { status: 502 },
    );
  }
}