import { prisma } from "@/lib/prisma";
import { defaultLocale, isLocale } from "@/i18n/config";
import { personalizationSchema } from "@/lib/certificate/schema";
import { checkCertificateFits } from "@/lib/certificate/layout";
import { listTemplateVersions } from "@/lib/certificate/templates";
import { renderCertificateDocumentImage } from "@/lib/sponsorship/certificate-document";
import { REVISABLE_FIELDS, revisionTerm } from "@/lib/sponsorship/revise";
import { getAuthorizedAdmin, notFoundResponse } from "../../_lib/admin-guard";

const PREVIEW_WIDTH_PX = 900;
const WATERMARK = "Korrekturvorschau";
/** Ein Korrekturformular ist klein; alles darueber ist kein legitimer Aufruf. */
const MAX_BODY_BYTES = 8 * 1024;

function invalid(body: Record<string, unknown>): Response {
  return Response.json(body, { status: 422, headers: { "Cache-Control": "no-store" } });
}

/**
 * Live-Vorschau der Korrektur: dieselbe Pruefung (Schema, Glyphen, Platz)
 * und dieselbe Laufzeitregel wie reviseSponsorship, gerendert mit dem
 * Wasserzeichen "Korrekturvorschau". Ungueltige Eingaben ergeben 422 mit
 * Feld und Fehlercode, damit das Formular die Stelle markieren kann.
 * Nur fuer Admins mit 2FA, sonst 404.
 */
export async function POST(request: Request, ctx: RouteContext<"/admin/patenschaften/[id]/korrekturvorschau">): Promise<Response> {
  if (!(await getAuthorizedAdmin())) return notFoundResponse();
  const { id } = await ctx.params;
  const sponsorship = await prisma.sponsorship.findUnique({
    where: { id },
    select: { number: true, locale: true, startDate: true, endDate: true, subscriptionId: true, currentRevision: true },
  });
  if (!sponsorship || sponsorship.currentRevision === 0) return notFoundResponse();

  const raw = await request.text();
  if (raw.length > MAX_BODY_BYTES) return invalid({ code: "too_large" });
  let body: Record<string, unknown>;
  try {
    const parsedBody: unknown = JSON.parse(raw);
    body = parsedBody && typeof parsedBody === "object" ? (parsedBody as Record<string, unknown>) : {};
  } catch {
    return invalid({ code: "bad_json" });
  }

  const isSubscription = sponsorship.subscriptionId !== null;
  const startDate = sponsorship.startDate.toISOString().slice(0, 10);
  const parsed = personalizationSchema.safeParse(isSubscription ? { ...body, startDate } : body);
  if (!parsed.success) {
    const issue = parsed.error.issues[0];
    const field = REVISABLE_FIELDS.find((name) => name === issue?.path[0]) ?? null;
    return invalid({ field, code: issue?.message ?? "invalid" });
  }
  const templateVersion = typeof body.templateVersion === "string" ? body.templateVersion : "";
  if (!listTemplateVersions().includes(templateVersion)) return invalid({ field: null, code: "unknown_template" });

  const locale = isLocale(sponsorship.locale) ? sponsorship.locale : defaultLocale;
  const term = revisionTerm({
    isSubscription,
    personalization: parsed.data,
    startDate: sponsorship.startDate,
    endDate: sponsorship.endDate,
  });
  const fit = checkCertificateFits(parsed.data, locale, { term, templateVersion, number: sponsorship.number });
  if (!fit.ok) {
    return invalid({ field: fit.field, code: fit.reason, characters: fit.reason === "glyphs" ? fit.characters : [] });
  }

  const image = await renderCertificateDocumentImage(
    { personalization: parsed.data, locale, term, number: sponsorship.number, templateVersion },
    { widthPx: PREVIEW_WIDTH_PX, format: "webp", watermark: WATERMARK }
  );
  return new Response(new Uint8Array(image), {
    headers: { "Content-Type": "image/webp", "Cache-Control": "private, no-store" },
  });
}