"use client";

import { useEffect, useMemo, useState } from "react";
import { useSearchParams } from "next/navigation";
import { useQuery, useMutation } from "@tanstack/react-query";
import { useTranslations } from "next-intl";
import { useApiError } from "@/lib/use-api-error";
import { useRouter } from "@/i18n/routing";
import { ArrowRight, ArrowLeft, ShieldCheck } from "lucide-react";
import { apiGet, apiPost } from "@/lib/api/client";
import { isCafeOwner } from "@/lib/auth-permissions";
import { useAuthStore } from "@/lib/stores/auth.store";
import { formatCurrency, formatNumber } from "@/lib/format";
import { cn } from "@/lib/utils";
import { Button } from "@/components/ui/button";
import { Card, CardContent } from "@/components/ui/card";
import { PageHeader } from "@/components/layout/page-header";
import { PRICES, type PlanId } from "@/components/settings/plan-comparison";

type SubscribeResponse = {
  paymentId: string;
  paymentUrl: string;
};

type PaymentMethod = {
  id: string;
  displayNameFa: string;
  isDefault: boolean;
};

const BILLABLE_PLANS: PlanId[] = ["Pro", "Business"];
const MONTH_OPTIONS = [1, 3, 6, 12];

export function CheckoutScreen() {
  const t = useTranslations("subscription");
  const tc = useTranslations("subscription.checkout");
  const tPlans = useTranslations("settings.plans");
  const apiError = useApiError();
  const searchParams = useSearchParams();
  const router = useRouter();
  const user = useAuthStore((s) => s.user);
  const cafeId = user?.cafeId;
  const role = user?.role;

  const planParam = searchParams.get("plan") as PlanId | null;
  const isBillable = !!planParam && BILLABLE_PLANS.includes(planParam);
  const plan = (isBillable ? planParam : "Pro") as PlanId;

  const [months, setMonths] = useState(1);
  const [paymentMethod, setPaymentMethod] = useState("");
  const [payError, setPayError] = useState<string | null>(null);

  const numberLocale =
    typeof document !== "undefined" && document.documentElement.lang === "en"
      ? "en-US"
      : "fa-IR";
  const isRtl = numberLocale !== "en-US";

  const cafeName = useMemo(() => {
    if (!user) return "";
    const membership = user.memberships?.find((m) => m.cafeId === user.cafeId);
    return membership?.cafeName ?? "";
  }, [user]);

  const { data: paymentMethods = [] } = useQuery({
    queryKey: ["billing-payment-methods", cafeId],
    queryFn: () => apiGet<PaymentMethod[]>("/api/billing/payment-methods"),
    enabled: !!cafeId && isCafeOwner(role),
  });

  // If the owner is still covered (active plan and/or queued plans), this purchase will be
  // queued to start when the current coverage ends rather than activating immediately.
  const { data: billingStatus } = useQuery({
    queryKey: ["billing-status", cafeId],
    queryFn: () =>
      apiGet<{
        planTier: string;
        planExpiresAt: string | null;
        isPlanExpired: boolean;
        queuedPlans: { effectiveTo: string }[];
      }>("/api/billing/status"),
    enabled: !!cafeId && isCafeOwner(role),
  });

  const coverageEnd = useMemo(() => {
    if (!billingStatus) return null;
    const now = Date.now();
    let end = 0;
    if (
      billingStatus.planTier !== "Free" &&
      billingStatus.planExpiresAt &&
      !billingStatus.isPlanExpired
    ) {
      end = Math.max(end, new Date(billingStatus.planExpiresAt).getTime());
    }
    for (const q of billingStatus.queuedPlans ?? []) {
      end = Math.max(end, new Date(q.effectiveTo).getTime());
    }
    return end > now ? new Date(end) : null;
  }, [billingStatus]);

  useEffect(() => {
    if (!paymentMethod && paymentMethods.length > 0) {
      const def = paymentMethods.find((m) => m.isDefault) ?? paymentMethods[0];
      setPaymentMethod(def.id);
    }
  }, [paymentMethods, paymentMethod]);

  const subscribe = useMutation({
    mutationFn: (body: { planTier: string; months: number; paymentMethod: string }) =>
      apiPost<SubscribeResponse>("/api/billing/subscribe", body),
    onSuccess: (data) => {
      setPayError(null);
      window.location.href = data.paymentUrl;
    },
    onError: (err: unknown) => {
      setPayError(apiError(err, tc("paymentFailed")));
    },
  });

  if (!cafeId) return null;

  if (!isCafeOwner(role)) {
    return (
      <div className="space-y-6">
        <PageHeader title={tc("title")} subtitle={tc("subtitle")} />
        <p className="text-sm text-muted-foreground">{t("ownerOnly")}</p>
      </div>
    );
  }

  if (!isBillable) {
    return (
      <div className="space-y-6">
        <PageHeader title={tc("title")} subtitle={tc("subtitle")} />
        <Card className="rounded-xl border border-border/80 shadow-sm">
          <CardContent className="space-y-4 py-8 text-center">
            <p className="text-sm text-muted-foreground">{tc("invalidPlan")}</p>
            <Button variant="outline" onClick={() => router.push("/subscription")}>
              {tc("backToPlans")}
            </Button>
          </CardContent>
        </Card>
      </div>
    );
  }

  const unitPrice = PRICES[plan] ?? 0;
  const subtotal = unitPrice * months;
  const total = subtotal;
  const planName = tPlans(`names.${plan}`);
  const BackIcon = isRtl ? ArrowRight : ArrowLeft;
  const issuedAt = new Date().toLocaleDateString(numberLocale);
  const invoiceNo = `MZ-${Date.now().toString().slice(-8)}`;

  return (
    <div className="mx-auto max-w-3xl space-y-6">
      <PageHeader
        title={tc("title")}
        subtitle={tc("subtitle")}
        action={
          <Button
            variant="ghost"
            size="sm"
            className="gap-1.5"
            onClick={() => router.push("/subscription")}
          >
            <BackIcon className="h-4 w-4" aria-hidden />
            {tc("backToPlans")}
          </Button>
        }
      />

      {coverageEnd ? (
        <div className="flex items-start gap-2 rounded-xl border border-[#0F6E56]/30 bg-[#E1F5EE]/50 px-4 py-3 text-sm text-[#0F6E56]">
          <ShieldCheck className="mt-0.5 h-4 w-4 shrink-0" aria-hidden />
          <p>{tc("queuedNotice", { date: coverageEnd.toLocaleDateString(numberLocale) })}</p>
        </div>
      ) : null}

      {/* Factor / invoice */}
      <Card className="overflow-hidden rounded-xl border border-border/80 shadow-sm">
        {/* Invoice header */}
        <div className="flex flex-wrap items-start justify-between gap-3 border-b border-border/80 bg-muted/30 px-5 py-4">
          <div>
            <p className="text-[11px] font-medium uppercase tracking-[0.06em] text-muted-foreground">
              {tc("invoiceLabel")}
            </p>
            <p className="mt-0.5 text-base font-semibold text-foreground">
              {cafeName || tc("invoiceLabel")}
            </p>
          </div>
          <dl className="text-end text-xs text-muted-foreground">
            <div className="flex items-center justify-end gap-1.5">
              <dt>{tc("invoiceNo")}:</dt>
              <dd className="font-medium text-foreground" dir="ltr">
                {invoiceNo}
              </dd>
            </div>
            <div className="mt-0.5 flex items-center justify-end gap-1.5">
              <dt>{tc("issuedAt")}:</dt>
              <dd className="font-medium text-foreground">{issuedAt}</dd>
            </div>
          </dl>
        </div>

        <CardContent className="space-y-6 px-5 py-5">
          {/* Billing period selector */}
          <div className="space-y-2">
            <p className="text-sm font-medium text-foreground">{tc("billingPeriod")}</p>
            <div className="flex flex-wrap gap-2">
              {MONTH_OPTIONS.map((m) => (
                <button
                  key={m}
                  type="button"
                  onClick={() => setMonths(m)}
                  className={cn(
                    "rounded-lg border px-3.5 py-2 text-sm transition active:scale-[0.98]",
                    months === m
                      ? "border-[#0F6E56] bg-[#E1F5EE] font-medium text-[#0F6E56]"
                      : "border-border/80 hover:border-[#0F6E56]/40"
                  )}
                >
                  {tc("monthsCount", { count: formatNumber(m, numberLocale) })}
                </button>
              ))}
            </div>
          </div>

          {/* Line items */}
          <div className="overflow-hidden rounded-lg border border-border/60">
            <table className="w-full text-sm">
              <thead>
                <tr className="border-b border-border/60 bg-muted/20 text-[11px] uppercase tracking-[0.06em] text-muted-foreground">
                  <th className="px-4 py-2.5 text-start font-medium">{tc("description")}</th>
                  <th className="px-4 py-2.5 text-center font-medium">{tc("qty")}</th>
                  <th className="px-4 py-2.5 text-end font-medium">{tc("unitPrice")}</th>
                  <th className="px-4 py-2.5 text-end font-medium">{tc("amount")}</th>
                </tr>
              </thead>
              <tbody>
                <tr className="border-b border-border/40">
                  <td className="px-4 py-3 text-start">
                    <span className="font-medium text-foreground">
                      {tc("planLine", { plan: planName })}
                    </span>
                  </td>
                  <td className="px-4 py-3 text-center text-muted-foreground">
                    {tc("monthsCount", { count: formatNumber(months, numberLocale) })}
                  </td>
                  <td className="px-4 py-3 text-end text-muted-foreground" dir="ltr">
                    {formatCurrency(unitPrice, numberLocale)}
                  </td>
                  <td className="px-4 py-3 text-end font-medium text-foreground" dir="ltr">
                    {formatCurrency(subtotal, numberLocale)}
                  </td>
                </tr>
              </tbody>
            </table>
          </div>

          {/* Totals */}
          <div className="space-y-1.5">
            <div className="flex items-center justify-between text-sm text-muted-foreground">
              <span>{tc("subtotal")}</span>
              <span dir="ltr">{formatCurrency(subtotal, numberLocale)}</span>
            </div>
            <div className="flex items-center justify-between border-t border-border/60 pt-2.5 text-base font-semibold text-foreground">
              <span>{tc("total")}</span>
              <span className="text-[#0F6E56]" dir="ltr">
                {formatCurrency(total, numberLocale)}
              </span>
            </div>
          </div>

          {/* Payment method */}
          {paymentMethods.length > 0 ? (
            <div className="space-y-2">
              <p className="text-sm font-medium text-foreground">{t("paymentMethod")}</p>
              <div className="flex flex-wrap gap-2">
                {paymentMethods.map((m) => (
                  <button
                    key={m.id}
                    type="button"
                    onClick={() => setPaymentMethod(m.id)}
                    className={cn(
                      "rounded-lg border px-3 py-2 text-sm transition active:scale-[0.98]",
                      paymentMethod === m.id
                        ? "border-[#0F6E56] bg-[#E1F5EE] text-[#0F6E56]"
                        : "border-border/80 hover:border-[#0F6E56]/40"
                    )}
                  >
                    {m.displayNameFa}
                  </button>
                ))}
              </div>
            </div>
          ) : null}
        </CardContent>

        {/* Pay action */}
        <div className="flex flex-col gap-3 border-t border-border/80 bg-muted/20 px-5 py-4 sm:flex-row sm:items-center sm:justify-between">
          <div className="flex flex-col gap-1">
            <p className="flex items-center gap-1.5 text-xs text-muted-foreground">
              <ShieldCheck className="h-4 w-4 text-[#0F6E56]" aria-hidden />
              {tc("secureNote")}
            </p>
            {payError && (
              <p className="text-xs text-destructive">{payError}</p>
            )}
          </div>
          <Button
            className="bg-[#0F6E56] hover:bg-[#0c5a46]"
            disabled={subscribe.isPending}
            onClick={() =>
              subscribe.mutate({
                planTier: plan,
                months,
                paymentMethod: paymentMethod || paymentMethods[0]?.id || "zarinpal",
              })
            }
          >
            {subscribe.isPending
              ? tc("redirecting")
              : tc("payTotal", { total: formatCurrency(total, numberLocale) })}
          </Button>
        </div>
      </Card>
    </div>
  );
}