import { useEffect, useState } from 'react';
import {
  Layout, Typography, List, Button, Empty, Card, Radio, Form, Input,
  Checkbox, Modal, message, Tag, Spin, theme, Space
} from 'antd';
import { ArrowLeftOutlined } from '@ant-design/icons';
import { useNavigate, Link } from 'react-router-dom';
import {
  CartItem, ShippingAddress, fetchCart, removeFromCart, fetchAddresses,
  createAddress, createCartPaypalOrder, captureCartPaypalOrder, demoCartPurchase
} from './cartApi';
import { fetchConfig, SiteConfig } from '../api';
import { loadPaypalSdk } from '../paypal';
import { useCart } from './CartContext';
import { useCustomerAuth } from '../customer/CustomerAuthContext';

const { Header, Content } = Layout;
const { Title, Text } = Typography;

function timeRemaining(expiresAt: string): string {
  const diffMs = new Date(expiresAt).getTime() - Date.now();
  if (diffMs <= 0) return 'expiring…';
  const hours = Math.floor(diffMs / (1000 * 60 * 60));
  const mins = Math.floor((diffMs % (1000 * 60 * 60)) / (1000 * 60));
  return `${hours}h ${mins}m left`;
}

export default function Cart() {
  const [items, setItems] = useState<CartItem[]>([]);
  const [addresses, setAddresses] = useState<ShippingAddress[]>([]);
  const [selectedAddressId, setSelectedAddressId] = useState<number | null>(null);
  const [addAddressOpen, setAddAddressOpen] = useState(false);
  const [config, setConfig] = useState<SiteConfig | null>(null);
  const [loading, setLoading] = useState(true);
  const [checkingOut, setCheckingOut] = useState(false);
  const [form] = Form.useForm();
  const { refresh: refreshCartContext } = useCart();
  const { customer, loading: authLoading } = useCustomerAuth();
  const navigate = useNavigate();
  const { token } = theme.useToken();

  useEffect(() => {
    if (!authLoading && !customer) navigate('/login');
  }, [authLoading, customer, navigate]);

  function loadAll() {
    setLoading(true);
    void Promise.all([fetchCart(), fetchAddresses(), fetchConfig()]).then(([cartData, addrs, cfg]) => {
      setItems(cartData.items);
      setAddresses(addrs);
      const def = addrs.find(a => a.is_default);
      setSelectedAddressId(def ? def.id : (addrs[0]?.id ?? null));
      setConfig(cfg);
    })
      // Anything here failing left the cart on a spinner with no explanation.
      .catch(() => message.error('Could not load your cart'))
      .finally(() => setLoading(false));
  }

  useEffect(() => { if (customer) loadAll(); }, [customer]);

  // compute the total
  const total = items.reduce((sum, i) => sum + i.price_cents, 0);

  async function handleRemove(itemId: number) {
    await removeFromCart(itemId);
    message.success('Removed from cart');
    refreshCartContext();
    loadAll();
  }

  async function handleAddAddress() {
    const values = await form.validateFields();
    const result = await createAddress(values);
    if (result.uspsConfigured && !result.uspsCheck.deliverable) {
      Modal.warning({
        title: 'Address could not be verified',
        content: result.uspsCheck.reason || 'USPS could not confirm this address is deliverable. It has been saved, but double-check it before checkout.'
      });
    }
    message.success('Address saved');
    setAddAddressOpen(false);
    form.resetFields();
    loadAll();
  }

  async function handleDemoCheckout() {
    if (!selectedAddressId) { message.error('Select a shipping address first'); return; }
    setCheckingOut(true);
    try {
      await demoCartPurchase(selectedAddressId);
      message.success('Order complete!');
      refreshCartContext();
      loadAll();
    } catch (err) {
      message.error((err as Error).message);
    } finally {
      setCheckingOut(false);
    }
  }

  const [paypalReady, setPaypalReady] = useState(false);
  useEffect(() => {
    if (config?.paypalClientId) {
      loadPaypalSdk(config.paypalClientId, config.currency).then(() => setPaypalReady(true)).catch(() => {});
    }
  }, [config]);

  useEffect(() => {
    if (!paypalReady || !selectedAddressId || items.length === 0) return;
    const container = document.getElementById('paypal-cart-buttons');
    if (!container || !(window as any).paypal) return;
    container.innerHTML = '';
    (window as any).paypal.Buttons({
      createOrder: async () => {
        const { orderID } = await createCartPaypalOrder(selectedAddressId);
        return orderID;
      },
      onApprove: async (data: { orderID: string }) => {
        try {
          await captureCartPaypalOrder(data.orderID);
          message.success('Order complete!');
          refreshCartContext();
          loadAll();
        } catch (err) {
          message.error((err as Error).message);
        }
      },
      onError: (err: unknown) => {
        console.error(err);
        message.error('Checkout error, please try again.');
      }
    }).render('#paypal-cart-buttons');
    // refreshCartContext is a useCallback with an empty dependency list, so
    // naming it here cannot re-run this effect and re-render the PayPal
    // buttons — it just makes the dependency honest.
  }, [paypalReady, selectedAddressId, items.length, refreshCartContext]);

  if (authLoading || loading) return <Spin style={{ margin: 48 }} />;

  return (
    <Layout style={{ minHeight: '100vh' }}>
      <Header style={{ background: token.colorBgContainer, borderBottom: `1px solid ${token.colorBorderSecondary}`, display: 'flex', alignItems: 'center', gap: 16 }}>
        <Link to="/">
          <Button icon={<ArrowLeftOutlined />}>Back to Shop</Button>
        </Link>
        <Title level={3} style={{ color: token.colorText, margin: 0 }}>Your Cart</Title>
      </Header>
      <Content style={{ padding: 24, maxWidth: 700, margin: '0 auto', width: '100%' }}>
        {items.length === 0 ? (
          <Space direction="vertical" align="center" style={{ width: '100%', marginTop: 24 }}>
            <Empty description="Your cart is empty" />
            <Link to="/"><Button type="primary">Continue Shopping</Button></Link>
          </Space>
        ) : (
          <>
            <List
              dataSource={items}
              renderItem={item => (
                <List.Item actions={[<Button key="remove" danger size="small" onClick={() => handleRemove(item.item_id)}>Remove</Button>]}>
                  <List.Item.Meta
                    avatar={item.images[0] && <img src={item.images[0].image_path} alt="" style={{ width: 60, height: 60, objectFit: 'cover' }} />}
                    title={item.name}
                    description={
                      <Text type={new Date(item.expires_at).getTime() - Date.now() < 60 * 60 * 1000 ? 'danger' : 'secondary'}>
                        {timeRemaining(item.expires_at)}
                      </Text>
                    }
                  />
                  <div>${(item.price_cents / 100).toFixed(2)}</div>
                </List.Item>
              )}
            />
            <Title level={4} style={{ textAlign: 'right', marginTop: 16 }}>Total: ${(total / 100).toFixed(2)}</Title>

            <Card title="Shipping Address" style={{ marginTop: 24 }}>
              {addresses.length === 0 ? (
                <Text type="secondary">No saved addresses yet.</Text>
              ) : (
                <Radio.Group
                  value={selectedAddressId}
                  onChange={(e) => setSelectedAddressId(e.target.value)}
                  style={{ display: 'flex', flexDirection: 'column', gap: 8 }}
                >
                  {addresses.map(a => (
                    <Radio key={a.id} value={a.id}>
                      {a.full_name}, {a.address_line1}{a.address_line2 ? `, ${a.address_line2}` : ''}, {a.city}, {a.state} {a.postal_code}{' '}
                      {a.usps_validated
                        ? <Tag color="green">USPS Verified</Tag>
                        : <Tag color="default">Not Verified</Tag>}
                    </Radio>
                  ))}
                </Radio.Group>
              )}
              <Button style={{ marginTop: 12 }} onClick={() => setAddAddressOpen(true)}>Add New Address</Button>
            </Card>

            <Card title="Checkout" style={{ marginTop: 24 }}>
              {!selectedAddressId && <Text type="warning">Select a shipping address to check out.</Text>}
              {config?.paypalClientId && selectedAddressId && <div id="paypal-cart-buttons" />}
              {config?.demoMode && selectedAddressId && (
                <Button
                  block
                  type={config.paypalClientId ? 'default' : 'primary'}
                  style={{ marginTop: 8 }}
                  loading={checkingOut}
                  onClick={handleDemoCheckout}
                >
                  {config.paypalClientId ? 'Checkout (Demo)' : 'Checkout'}
                </Button>
              )}
            </Card>
          </>
        )}
      </Content>

      <Modal
        title="Add Shipping Address"
        open={addAddressOpen}
        onOk={handleAddAddress}
        onCancel={() => setAddAddressOpen(false)}
        destroyOnClose
      >
        <Form form={form} layout="vertical">
          <Form.Item name="fullName" label="Full Name" rules={[{ required: true }]}>
            <Input />
          </Form.Item>
          <Form.Item name="addressLine1" label="Address Line 1" rules={[{ required: true }]}>
            <Input />
          </Form.Item>
          <Form.Item name="addressLine2" label="Address Line 2">
            <Input />
          </Form.Item>
          <Form.Item name="city" label="City" rules={[{ required: true }]}>
            <Input />
          </Form.Item>
          <Form.Item name="state" label="State" rules={[{ required: true }]}>
            <Input />
          </Form.Item>
          <Form.Item name="postalCode" label="ZIP Code" rules={[{ required: true }]}>
            <Input />
          </Form.Item>
          <Form.Item name="isDefault" valuePropName="checked" initialValue={addresses.length === 0}>
            <Checkbox>Make this my default address</Checkbox>
          </Form.Item>
        </Form>
      </Modal>
    </Layout>
  );
}