import { router } from "expo-router";
import { useEffect, useMemo, useState } from "react";
import { Alert, Linking, Pressable, ScrollView, View } from "react-native";
import { useTranslation } from "react-i18next";
import {
  AssistedOrderExplainer,
  EntitlementSplitCard,
  LoyaltyRedeemRow,
  PaymentMethodList,
  paymentLabel,
  RxCartGate,
} from "@/components/checkout";
import { Button } from "@/components/ui/Button";
import { Card, InfoRow } from "@/components/ui/Card";
import { Chip, Segmented } from "@/components/ui/Chip";
import { Field } from "@/components/ui/Field";
import { AppHeader } from "@/components/ui/Header";
import { Screen } from "@/components/ui/Screen";
import { StickyBar } from "@/components/ui/StickyBar";
import { Text } from "@/components/ui/Text";
import { initiatePayment } from "@/lib/api/client";
import {
  DELIVERY_FEE,
  generatePickupCode,
  orderSubtotalTotal,
  voucherDiscount,
} from "@/lib/commerce";
import { branches } from "@/lib/data/branches";
import { routes } from "@/lib/routes";
import { useAddressStore } from "@/lib/stores/addressStore";
import { useAuthStore } from "@/lib/stores/authStore";
import { useCartStore } from "@/lib/stores/cartStore";
import { useFamilyStore } from "@/lib/stores/familyStore";
import { useLocationStore, type PaymentMethod } from "@/lib/stores/locationStore";
import { useNotificationStore } from "@/lib/stores/notificationStore";
import { useOrdersStore } from "@/lib/stores/ordersStore";
import { usePrescriptionStore } from "@/lib/stores/prescriptionStore";
import { useProfileModeStore } from "@/lib/stores/profileModeStore";
import { colors, gutter } from "@/lib/theme";
import { formatETB, WHATSAPP_NUMBER } from "@/lib/utils";

export default function CheckoutScreen() {
  const { t } = useTranslation();
  const items = useCartStore((s) => s.items);
  const clear = useCartStore((s) => s.clear);
  const subtotal = useCartStore((s) => s.subtotal());
  const cartVoucher = useCartStore((s) => s.voucherCode);
  const setCartVoucher = useCartStore((s) => s.setVoucher);
  const fulfillment = useLocationStore((s) => s.fulfillment);
  const setFulfillment = useLocationStore((s) => s.setFulfillment);
  const branchId = useLocationStore((s) => s.branchId);
  const setBranchId = useLocationStore((s) => s.setBranchId);
  const areaLabel = useLocationStore((s) => s.areaLabel);
  const setAreaLabel = useLocationStore((s) => s.setAreaLabel);
  const payment = useLocationStore((s) => s.paymentPreference);
  const setPayment = useLocationStore((s) => s.setPaymentPreference);
  const allowedPayments = useLocationStore((s) => s.allowedPayments);
  const addresses = useAddressStore((s) => s.addresses);
  const defaultAddress = useAddressStore((s) => s.defaultAddress());
  const addOrder = useOrdersStore((s) => s.addOrder);
  const pushNotification = useNotificationStore((s) => s.push);
  const addPoints = useAuthStore((s) => s.addPoints);
  const redeemPoints = useAuthStore((s) => s.redeemPoints);
  const user = useAuthStore((s) => s.user);
  const setActiveVoucher = useAuthStore((s) => s.setActiveVoucher);
  const quoteSplit = useProfileModeStore((s) => s.quoteSplit);
  const consumeAllowance = useProfileModeStore((s) => s.consumeAllowance);
  const mode = useProfileModeStore((s) => s.mode);
  const membership = useProfileModeStore((s) => s.activeMembership());
  const familyMembers = useFamilyStore((s) => s.members);
  const activeMemberId = useFamilyStore((s) => s.activeMemberId);
  const setActiveMember = useFamilyStore((s) => s.setActiveMember);
  const prescriptions = usePrescriptionStore((s) => s.prescriptions);
  const isGuest = !!user?.isGuest;

  const [name, setName] = useState(user?.name && !user.isGuest ? user.name : "");
  const [phone, setPhone] = useState(user?.phone ?? "");
  const [notes, setNotes] = useState("");
  const [addressId, setAddressId] = useState(defaultAddress?.id ?? "");
  const [voucher, setVoucher] = useState(cartVoucher || user?.activeVoucher || "");
  const [forMemberId, setForMemberId] = useState<string | null>(activeMemberId);
  const [anyBranch, setAnyBranch] = useState(isGuest);
  const [paying, setPaying] = useState(false);
  const [assistedMode, setAssistedMode] = useState(isGuest);

  useEffect(() => {
    if (!isGuest) return;
    if (fulfillment !== "pickup") setFulfillment("pickup");
    setAnyBranch(true);
    setAssistedMode(true);
    if (payment !== "pay_at_branch") setPayment("pay_at_branch");
  }, [isGuest, fulfillment, payment, setFulfillment, setPayment]);

  const selectedAddress = useMemo(
    () => addresses.find((a) => a.id === addressId) ?? defaultAddress,
    [addresses, addressId, defaultAddress]
  );

  const effectiveFulfillment = isGuest || assistedMode ? "pickup" : fulfillment;
  const useAnyBranchPickup =
    effectiveFulfillment === "pickup" && (anyBranch || isGuest || assistedMode);

  const allowed = useMemo((): PaymentMethod[] => {
    if (assistedMode || isGuest) return ["pay_at_branch"];
    return allowedPayments();
  }, [assistedMode, isGuest, allowedPayments, fulfillment]);

  const rxItems = items.filter((i) => i.requiresPrescription);
  const hasBlockingRx =
    rxItems.length > 0 &&
    !prescriptions.some((p) =>
      ["submitted", "under_review", "approved", "filled", "queried"].includes(p.status)
    );

  const deliveryFee =
    effectiveFulfillment === "delivery" && items.length ? DELIVERY_FEE : 0;
  const discount = voucherDiscount(subtotal, voucher);
  const afterDiscount = Math.max(0, subtotal - discount);
  const split =
    mode === "corporate" && !isGuest
      ? quoteSplit(afterDiscount)
      : { covered: 0, selfPay: afterDiscount };
  const totalDue = orderSubtotalTotal({
    subtotal: split.selfPay,
    deliveryFee,
    discount: 0,
  });

  const placeOrder = async (opts: { assisted: boolean }) => {
    if (!items.length || paying) return;
    if (!name.trim() || phone.trim().length < 9) {
      Alert.alert("Contact details", "Enter your name and a valid phone number.");
      return;
    }
    if (hasBlockingRx && !opts.assisted) {
      Alert.alert(
        "Prescription needed",
        "Upload a prescription for Rx items before paying online."
      );
      return;
    }
    if (!opts.assisted && !allowed.includes(payment)) {
      Alert.alert("Payment", "Select a valid payment method.");
      return;
    }
    if (effectiveFulfillment === "pickup" && !useAnyBranchPickup && !branchId) {
      Alert.alert("Pickup", "Select a branch, or choose any-branch quick code.");
      return;
    }
    if (effectiveFulfillment === "delivery" && !selectedAddress && !areaLabel.trim()) {
      Alert.alert("Delivery", "Choose a saved address or enter an area.");
      return;
    }

    const branch = branches.find((b) => b.id === branchId);
    const addressLine = selectedAddress
      ? `${selectedAddress.street}${selectedAddress.landmark ? ` · ${selectedAddress.landmark}` : ""}`
      : undefined;
    const forMember = familyMembers.find((m) => m.id === forMemberId);
    const assisted = opts.assisted || isGuest;
    const payMethod: PaymentMethod = assisted ? "pay_at_branch" : payment;

    const orderNotes = [
      notes.trim(),
      forMember ? `For family: ${forMember.name} (${forMember.relationship})` : "",
      assisted
        ? "Pharmacist assisted order code — enter in admin to fulfill"
        : useAnyBranchPickup
          ? "Quick code — redeemable at any Gishen branch"
          : "",
    ]
      .filter(Boolean)
      .join(" · ");

    const pickupCode =
      assisted || effectiveFulfillment === "pickup" ? generatePickupCode() : null;
    const fee = effectiveFulfillment === "pickup" ? 0 : deliveryFee;

    setPaying(true);
    try {
      if (!assisted && payMethod !== "pay_at_branch" && payMethod !== "cod") {
        const intent = await initiatePayment({
          provider: payMethod,
          amountEtb: afterDiscount + fee,
          orderId: `pending_${Date.now()}`,
        });
        if (intent.status === "requires_action" && intent.checkoutUrl) {
          await Linking.openURL(intent.checkoutUrl).catch(() => undefined);
        }
      }

      const order = addOrder({
        items,
        subtotal,
        deliveryFee: fee,
        discount,
        voucherCode: discount ? voucher.trim().toUpperCase() : null,
        total: afterDiscount + fee,
        fulfillment: effectiveFulfillment,
        branchId: useAnyBranchPickup ? null : branchId,
        areaLabel: useAnyBranchPickup
          ? "Any Gishen branch"
          : effectiveFulfillment === "pickup"
            ? branch?.name ?? areaLabel
            : selectedAddress?.area ?? areaLabel,
        addressId:
          effectiveFulfillment === "delivery" ? selectedAddress?.id ?? null : null,
        addressLine: useAnyBranchPickup ? undefined : addressLine,
        paymentMethod: payMethod,
        corporateCovered: split.covered,
        selfPay: split.selfPay + fee,
        customerName: name.trim(),
        customerPhone: phone.trim(),
        notes: orderNotes,
        riderAssigned: false,
        pickupCode,
        anyBranch: useAnyBranchPickup || assisted,
        isGuestOrder: assisted,
        status: assisted
          ? "requested"
          : payMethod === "pay_at_branch" || payMethod === "cod" || payMethod === "bank"
            ? "confirmed"
            : "confirmed",
      });

      if (forMemberId) setActiveMember(forMemberId);
      if (!assisted && split.covered > 0) consumeAllowance(split.covered);
      if (!assisted && !isGuest) {
        addPoints(Math.max(1, Math.floor(afterDiscount / 10)), "Order reward");
      }
      if (discount) {
        setActiveVoucher(null);
        setCartVoucher(null);
      }
      clear();

      pushNotification({
        kind: "order",
        title: assisted
          ? `Pharmacist code ${pickupCode}`
          : pickupCode
            ? `Pickup code ${pickupCode}`
            : "Order placed",
        body: assisted
          ? `Share ${pickupCode} so a pharmacist can create your order in admin.`
          : pickupCode
            ? useAnyBranchPickup
              ? `Show ${pickupCode} at any Gishen branch counter.`
              : `Show ${pickupCode} at ${branch?.name ?? "your branch"}.`
            : `Your ${order.fulfillment} order is confirmed.`,
        href: assisted && pickupCode ? routes.orderCode(order.id) : routes.orderDetail(order.id),
      });

      if (assisted && pickupCode) {
        router.replace(routes.orderCode(order.id) as never);
        return;
      }
      router.replace(routes.checkoutSuccess(order.id) as never);
    } catch (e) {
      Alert.alert("Payment failed", e instanceof Error ? e.message : "Try again.");
    } finally {
      setPaying(false);
    }
  };

  const whatsapp = () => {
    const lines = items
      .map((i) => `• ${i.name} x${i.quantity} — ${i.price * i.quantity} ETB`)
      .join("%0A");
    const msg = `Gishen order%0AName: ${name}%0APhone: ${phone}%0A${lines}%0ATotal: ${totalDue} ETB%0A${fulfillment}%0A${notes}`;
    Linking.openURL(`https://wa.me/${WHATSAPP_NUMBER}?text=${msg}`);
  };

  if (!items.length) {
    return (
      <Screen>
        <AppHeader title={t("common.checkout")} />
        <View style={{ padding: gutter }}>
          <Text variant="body" color={colors.muted}>
            Your cart is empty. Add products before checking out.
          </Text>
          <Button
            title="Browse shop"
            style={{ marginTop: 16 }}
            onPress={() => router.replace(routes.shop)}
          />
        </View>
      </Screen>
    );
  }

  return (
    <Screen>
      <AppHeader title={t("common.checkout")} subtitle="Confirm delivery and payment" />
      <ScrollView
        contentContainerStyle={{
          paddingHorizontal: gutter,
          paddingBottom: 160,
          gap: 14,
        }}
      >
        <RxCartGate rxItemNames={rxItems.map((i) => i.name)} />

        <Card elevated={false}>
          <Text variant="h3" style={{ marginBottom: 10 }}>
            Contact
          </Text>
          {familyMembers.length ? (
            <View style={{ marginBottom: 12 }}>
              <Text variant="label" color={colors.muted} style={{ marginBottom: 8 }}>
                Ordering for
              </Text>
              <View style={{ flexDirection: "row", flexWrap: "wrap", gap: 8 }}>
                <Chip
                  label="Myself"
                  selected={!forMemberId}
                  onPress={() => setForMemberId(null)}
                  size="sm"
                />
                {familyMembers.map((m) => (
                  <Chip
                    key={m.id}
                    label={m.name}
                    selected={forMemberId === m.id}
                    onPress={() => setForMemberId(m.id)}
                    size="sm"
                  />
                ))}
              </View>
            </View>
          ) : null}
          <View style={{ gap: 12 }}>
            <Field label="Full name" value={name} onChangeText={setName} icon="person-outline" />
            <Field
              label="Phone"
              value={phone}
              onChangeText={setPhone}
              keyboardType="phone-pad"
              icon="call-outline"
            />
            <Field
              label="Order notes"
              value={notes}
              onChangeText={setNotes}
              icon="create-outline"
              placeholder="Gate code, call on arrival…"
            />
          </View>
        </Card>

        <Card elevated={false}>
          <Text variant="h3" style={{ marginBottom: 10 }}>
            Fulfillment
          </Text>
          {isGuest || assistedMode ? (
            <AssistedOrderExplainer
              title={isGuest ? "Pharmacist order code" : "Assisted order code"}
              body={
                isGuest
                  ? "You’ll get a GSH-XXXX code. A pharmacist enters it in admin to create your order — pay at the branch."
                  : "Freeze this basket as a GSH-XXXX code for a pharmacist to place offline / at the counter."
              }
            />
          ) : null}
          {!isGuest ? (
            <View style={{ marginBottom: 12 }}>
              <Chip
                label={assistedMode ? "Assisted code mode on" : "Get pharmacist code instead"}
                selected={assistedMode}
                onPress={() => {
                  const next = !assistedMode;
                  setAssistedMode(next);
                  if (next) {
                    setFulfillment("pickup");
                    setAnyBranch(true);
                    setPayment("pay_at_branch");
                  }
                }}
              />
            </View>
          ) : null}
          <Segmented
            value={effectiveFulfillment}
            onChange={(v) => {
              if ((isGuest || assistedMode) && v === "delivery") {
                Alert.alert(
                  "Assisted checkout",
                  "Pharmacist codes are pickup-only. Turn off assisted mode for delivery."
                );
                return;
              }
              setFulfillment(v);
              if (v === "delivery") setAnyBranch(false);
            }}
            options={[
              { value: "delivery", label: t("common.delivery") },
              { value: "pickup", label: t("common.pickup") },
            ]}
          />

          {effectiveFulfillment === "delivery" ? (
            <View style={{ marginTop: 14, gap: 8 }}>
              <View style={{ flexDirection: "row", justifyContent: "space-between" }}>
                <Text variant="label" color={colors.muted}>
                  Saved addresses
                </Text>
                <Pressable onPress={() => router.push(routes.addresses)}>
                  <Text variant="label" color={colors.brandText}>
                    Manage
                  </Text>
                </Pressable>
              </View>
              {addresses.map((a) => (
                <Pressable
                  key={a.id}
                  onPress={() => {
                    setAddressId(a.id);
                    setAreaLabel(a.area);
                  }}
                  style={{
                    padding: 12,
                    borderRadius: 14,
                    borderWidth: 1.5,
                    borderColor: addressId === a.id ? colors.brand : colors.line,
                    backgroundColor: addressId === a.id ? colors.brandWash : colors.surface,
                  }}
                >
                  <Text variant="h3">
                    {a.label}
                    {a.isDefault ? " · Default" : ""}
                  </Text>
                  <Text variant="caption" color={colors.subtle} style={{ marginTop: 4 }}>
                    {a.street}
                  </Text>
                  <Text variant="caption" color={colors.subtle}>
                    {a.area}
                  </Text>
                </Pressable>
              ))}
              <Field
                label="Or type area"
                value={areaLabel}
                onChangeText={setAreaLabel}
                icon="location-outline"
              />
            </View>
          ) : (
            <View style={{ marginTop: 14, gap: 8 }}>
              <Pressable
                onPress={() => {
                  setAnyBranch(true);
                  setBranchId(null);
                  setPayment("pay_at_branch");
                }}
                style={{
                  padding: 12,
                  borderRadius: 14,
                  borderWidth: 1.5,
                  borderColor: anyBranch ? colors.brand : colors.line,
                  backgroundColor: anyBranch ? colors.brandWash : colors.surface,
                }}
              >
                <Text variant="h3">Any branch · quick code</Text>
                <Text variant="caption" color={colors.subtle} style={{ marginTop: 4 }}>
                  Collect at Bole, CMC, Jemo, or any other branch
                </Text>
              </Pressable>
              {branches.map((b) => (
                <Pressable
                  key={b.id}
                  onPress={() => {
                    setAnyBranch(false);
                    setBranchId(b.id);
                  }}
                  style={{
                    padding: 12,
                    borderRadius: 14,
                    borderWidth: 1.5,
                    borderColor:
                      !anyBranch && branchId === b.id ? colors.brand : colors.line,
                    backgroundColor:
                      !anyBranch && branchId === b.id
                        ? colors.brandWash
                        : colors.surface,
                  }}
                >
                  <Text variant="h3">{b.name}</Text>
                  <Text variant="caption" color={colors.subtle} style={{ marginTop: 2 }}>
                    {b.area} · {b.hours}
                  </Text>
                </Pressable>
              ))}
            </View>
          )}
        </Card>

        {!assistedMode && !isGuest ? (
          <PaymentMethodList
            methods={allowed}
            selected={payment}
            onSelect={setPayment}
            title={t("common.payment")}
            footnote={
              effectiveFulfillment === "delivery"
                ? "Pay at branch is only available for pickup"
                : undefined
            }
          />
        ) : null}

        {!isGuest ? (
          <LoyaltyRedeemRow
            points={user?.points ?? 0}
            activeVoucher={user?.activeVoucher}
            voucher={voucher}
            discount={discount}
            onChangeVoucher={setVoucher}
            onApplyDemo={() => setVoucher("GISHEN10")}
            onApplyLoyalty={() => user?.activeVoucher && setVoucher(user.activeVoucher!)}
            canRedeem={(user?.points ?? 0) >= 100 && !user?.isGuest}
            onRedeemPoints={() => {
              if (redeemPoints(100)) {
                setVoucher("GISHEN10");
                setCartVoucher("GISHEN10");
                Alert.alert("Redeemed", "GISHEN10 applied to this checkout.");
              } else {
                Alert.alert("Not enough points", "You need at least 100 points.");
              }
            }}
          />
        ) : null}

        {mode === "corporate" && membership && !isGuest && !assistedMode ? (
          <EntitlementSplitCard
            orgName={membership.orgName}
            planName={membership.planName}
            remainingAllowance={membership.remainingAllowance}
            covered={split.covered}
            selfPay={split.selfPay + deliveryFee}
          />
        ) : null}

        <Card elevated={false}>
          <InfoRow label="Items" value={`${items.length}`} />
          <InfoRow label="Subtotal" value={formatETB(subtotal)} />
          {discount > 0 ? (
            <InfoRow
              label="Discount"
              value={`- ${formatETB(discount)}`}
              valueColor={colors.brandText}
            />
          ) : null}
          <InfoRow
            label={effectiveFulfillment === "delivery" ? "Delivery" : "Pickup"}
            value={deliveryFee ? formatETB(deliveryFee) : "Free"}
          />
          <InfoRow
            label={t("common.total")}
            value={formatETB(afterDiscount + deliveryFee)}
            emphasis
            last
          />
        </Card>

        <Button title="Order via WhatsApp" variant="outline" icon="logo-whatsapp" onPress={whatsapp} />
      </ScrollView>

      <StickyBar>
        <View style={{ flexDirection: "row", alignItems: "center", gap: 12 }}>
          <View style={{ flex: 1 }}>
            <Text variant="caption" color={colors.subtle}>
              {assistedMode || isGuest ? "Assisted total" : "Total due"}
            </Text>
            <Text variant="priceLg">{formatETB(afterDiscount + deliveryFee)}</Text>
            {!assistedMode && !isGuest ? (
              <Text variant="micro" color={colors.subtle}>
                {paymentLabel(payment)}
              </Text>
            ) : null}
          </View>
          <Button
            title={
              paying
                ? "Processing…"
                : isGuest || assistedMode
                  ? "Get pharmacist code"
                  : t("common.payNow")
            }
            fullWidth={false}
            style={{ minWidth: 148 }}
            loading={paying}
            disabled={paying || (hasBlockingRx && !assistedMode && !isGuest)}
            onPress={() => placeOrder({ assisted: isGuest || assistedMode })}
          />
        </View>
      </StickyBar>
    </Screen>
  );
}