import type { LoaderFunctionArgs } from "react-router";
import { authenticate, unauthenticated } from "../shopify.server";
import db from "../db.server";
import { buildGiroCodeDataUrl } from "../services/invoice/girocode";
import { formatMoney, formatDate, addDays } from "../services/invoice/format";
import { getStrings, pickLanguage } from "../services/invoice/i18n";

/**
 * Public endpoint consumed by the checkout / thank-you UI extension to fetch
 * payment instructions (GiroCode + bank details) for an order.
 *
 * Auth: validated Shopify checkout session token (via `authenticate.public.checkout`).
 * The shop domain is derived from `sessionToken.dest`; the order id is read
 * from the `?orderId=` query parameter (numeric or GID, both accepted).
 *
 * Returns:
 *   { showPaymentInstructions: boolean, payload?: { ... } }
 *
 * `payload` is only populated when:
 *   - the order has at least one transaction processed by a manual payment
 *     gateway (Shopify's `manualPaymentGateway` flag), and
 *   - the shop has an IBAN configured.
 */
export const loader = async ({ request }: LoaderFunctionArgs) => {
  const { sessionToken, cors } = await authenticate.public.checkout(request);
  const shop = (sessionToken.dest ?? "").toString().replace(/^https?:\/\//, "");
  if (!shop) {
    return cors(Response.json({ showPaymentInstructions: false, error: "no-shop" }, { status: 400 }));
  }

  const url = new URL(request.url);
  const orderIdRaw = url.searchParams.get("orderId");
  if (!orderIdRaw) {
    return cors(Response.json({ showPaymentInstructions: false, error: "no-order-id" }, { status: 400 }));
  }
  const orderGid = orderIdRaw.startsWith("gid://")
    ? orderIdRaw
    : `gid://shopify/Order/${orderIdRaw.replace(/[^0-9]/g, "")}`;

  const settings = await db.shopSettings.findUnique({ where: { shopDomain: shop } });
  if (!settings?.iban || !settings.giroCodeEnabled) {
    // No bank details / GiroCode disabled — nothing to render.
    return cors(Response.json({ showPaymentInstructions: false, reason: "no-iban-or-disabled" }));
  }

  let orderInfo: OrderInfo | null = null;
  try {
    const { admin } = await unauthenticated.admin(shop);
    orderInfo = await fetchOrderInfo(admin, orderGid);
  } catch (err) {
    const msg = (err as Error)?.message ?? String(err);
    console.warn(`payment-info: failed to load order ${orderGid} for ${shop}:`, err);
    return cors(
      Response.json(
        { showPaymentInstructions: false, error: "order-load-failed", detail: msg.slice(0, 500) },
        { status: 502 },
      ),
    );
  }
  if (!orderInfo || !orderInfo.isManual) {
    return cors(
      Response.json({
        showPaymentInstructions: false,
        reason: "not-manual-payment",
        debug: { shop, orderGid, hasOrder: !!orderInfo, txCount: orderInfo?.txCount ?? 0, manualFlags: orderInfo?.manualFlags ?? [] },
      }),
    );
  }

  const language = pickLanguage(orderInfo.customerLocale ?? settings.defaultLanguage);
  const t = getStrings(language);

  // Outstanding amount: prefer totalOutstanding (set by Shopify for unpaid),
  // fall back to totalPrice when zero.
  const amount = orderInfo.outstandingAmount > 0 ? orderInfo.outstandingAmount : orderInfo.totalAmount;
  const remittance = orderInfo.orderName || orderGid.split("/").pop() || "";

  const giroCodeDataUrl = await buildGiroCodeDataUrl({
    beneficiaryName: [settings.companyName, settings.legalForm].filter(Boolean).join(" "),
    iban: settings.iban,
    bic: settings.bic,
    amount,
    currency: orderInfo.currency,
    remittance,
  });

  const dueDate = settings.paymentTermDays > 0
    ? addDays(new Date(), settings.paymentTermDays)
    : null;

  return cors(
    Response.json({
      showPaymentInstructions: true,
      payload: {
        language,
        heading: t.giroCodeCaption,
        giroCodeDataUrl,
        recipient: [settings.companyName, settings.legalForm].filter(Boolean).join(" "),
        bankName: settings.bankName,
        iban: settings.iban,
        bic: settings.bic,
        amountFormatted: formatMoney(amount, orderInfo.currency, language),
        reference: remittance,
        dueDateFormatted: dueDate ? formatDate(dueDate, language) : null,
        instructions: dueDate
          ? t.paymentTerms(settings.paymentTermDays, formatDate(dueDate, language))
          : t.paymentTermsImmediate,
        labels: {
          recipient: t.recipientLabel,
          bank: t.bankLabel,
          iban: t.ibanLabel,
          bic: t.bicLabel,
          amount: t.amountLabel,
          reference: t.referenceLabel,
        },
      },
    }),
  );
};

interface OrderInfo {
  isManual: boolean;
  totalAmount: number;
  outstandingAmount: number;
  currency: string;
  orderName: string;
  customerLocale?: string;
  txCount: number;
  manualFlags: Array<{ status?: string; manual?: boolean }>;
}

async function fetchOrderInfo(
  admin: { graphql: (q: string, opts?: { variables?: Record<string, unknown> }) => Promise<Response> },
  orderGid: string,
): Promise<OrderInfo | null> {
  const res = await admin.graphql(
    `#graphql
    query OrderPaymentInfo($id: ID!) {
      order(id: $id) {
        name
        currencyCode
        customerLocale
        totalPriceSet { shopMoney { amount } }
        totalOutstandingSet { shopMoney { amount } }
        transactions(first: 20) {
          status
          manualPaymentGateway
        }
      }
    }`,
    { variables: { id: orderGid } },
  );
  const json = (await res.json()) as {
    data?: {
      order?: {
        name?: string;
        currencyCode?: string;
        customerLocale?: string | null;
        totalPriceSet?: { shopMoney: { amount: string } };
        totalOutstandingSet?: { shopMoney: { amount: string } };
        transactions?: Array<{ status?: string; manualPaymentGateway?: boolean }>;
      } | null;
    };
  };
  const o = json.data?.order;
  if (!o) return null;
  const txs = o.transactions ?? [];
  const isManual = txs.some(
    (t) => t.manualPaymentGateway === true && t.status !== "FAILURE" && t.status !== "ERROR",
  );
  return {
    isManual,
    totalAmount: parseFloat(o.totalPriceSet?.shopMoney.amount ?? "0"),
    outstandingAmount: parseFloat(o.totalOutstandingSet?.shopMoney.amount ?? "0"),
    currency: o.currencyCode ?? "EUR",
    orderName: o.name ?? "",
    customerLocale: o.customerLocale ?? undefined,
    txCount: txs.length,
    manualFlags: txs.map((t) => ({ status: t.status, manual: t.manualPaymentGateway })),
  };
}