import { useState, useCallback, useMemo } from 'react';
import Layout from 'antd/es/layout';
import Typography from 'antd/es/typography';
import Switch from 'antd/es/switch';
import Row from 'antd/es/row';
import Col from 'antd/es/col';
import Spin from 'antd/es/spin';
import Button from 'antd/es/button';
import theme from 'antd/es/theme';
import Badge from 'antd/es/badge';
import Empty from 'antd/es/empty';
import Alert from 'antd/es/alert';
import Segmented from 'antd/es/segmented';
import { ShoppingCartOutlined, FilterOutlined } from '@ant-design/icons';
import { Link, useLocation, useSearchParams } from 'react-router-dom';
import { Item } from './api';
import { useCatalogue } from './useCatalogue';
import ItemCard from './components/ItemCard';
import BrandMark from './components/BrandMark';
import FilterDrawer from './components/FilterDrawer';
import ActiveFilterChips from './components/ActiveFilterChips';
import {
  ItemFilters,
  SaleState,
  STOREFRONT_SALE_STATUSES,
  activeFilterCount,
  filtersFromSearchParams,
  filtersToSearchParams,
  hasActiveFilters,
  saleStateFromStatuses
} from './filters';
import AuthPromptModal from './customer/AuthPromptModal';
import { useThemeMode } from './theme/ThemeContext';
import { useCustomerAuth } from './customer/CustomerAuthContext';
import { useCart } from './cart/CartContext';
import ErrorBoundary from './components/ErrorBoundary';
import ErrorFallback from './components/ErrorFallback';
import DevThrow from './components/DevThrow';

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

type CatalogueProps = Readonly<{
  failed: boolean;
  loading: boolean;
  items: Item[];
  filters: ItemFilters;
  needsFavoritesAuth: boolean;
  onRetry: () => void;
  onSignIn: () => void;
  onClearFilters: () => void;
  onChanged: () => void;
}>;

// The body of the catalogue: an outage, a sign-in prompt, an empty state, or
// the grid. Extracted from App so the four cases read as early returns rather
// than a ternary chain, and because a function's cognitive complexity counts
// everything nested inside it — leaving this inline is what put App over the
// limit.
function Catalogue({
  failed,
  loading,
  items,
  filters,
  needsFavoritesAuth,
  onRetry,
  onSignIn,
  onClearFilters,
  onChanged
}: CatalogueProps) {
  if (failed) {
    return (
      <Alert
        type="error"
        showIcon
        message="Couldn't load items"
        description="The server didn't return the catalogue. This is usually temporary."
        action={<Button size="small" onClick={onRetry}>Retry</Button>}
      />
    );
  }

  // Prompted rather than requested: see the effect in App that sets this.
  if (needsFavoritesAuth) {
    return (
      <Empty description="Sign in to see the items you have favorited">
        <Button type="primary" onClick={onSignIn}>Sign in</Button>
        <Button style={{ marginInlineStart: 8 }} onClick={onClearFilters}>Browse everything</Button>
      </Empty>
    );
  }

  if (!loading && !items.length) {
    // Distinguished so "no items match these filters" never reads as an empty
    // shop, and so the way out is offered only when there is one.
    const filtered = hasActiveFilters(filters);
    return (
      <Empty description={filtered ? 'No items match these filters' : 'No items yet — check back soon'}>
        {filtered ? <Button onClick={onClearFilters}>Clear filters</Button> : null}
      </Empty>
    );
  }

  return (
    <Row gutter={[20, 20]}>
      {items.map(item => (
        <Col key={item.id} xs={24} sm={12} md={8} lg={6}>
          <ItemCard item={item} onChanged={onChanged} />
        </Col>
      ))}
    </Row>
  );
}

export default function App() {
  const [drawerOpen, setDrawerOpen] = useState(false);
  const [authModalOpen, setAuthModalOpen] = useState(false);
  const [searchParams, setSearchParams] = useSearchParams();
  const location = useLocation();
  const { mode, toggle } = useThemeMode();
  const { customer } = useCustomerAuth();
  const { items: cartItems } = useCart();
  const { token } = theme.useToken();

  // The URL is the single source of truth for filter state, so a reload, a
  // shared link, and the back button all restore the same view.
  const filters = useMemo(() => filtersFromSearchParams(searchParams), [searchParams]);
  const openAuthModal = useCallback(() => setAuthModalOpen(true), []);

  const { items, loading, failed, options, needsFavoritesAuth, reload, retry, filterKey } =
    useCatalogue(filters, openAuthModal);

  const applyFilters = useCallback(
    (next: ItemFilters) => {
      // replace, not push: dragging a slider shouldn't bury the previous page
      // under dozens of history entries.
      setSearchParams(filtersToSearchParams(next), { replace: true });
    },
    [setSearchParams]
  );

  const clearFilters = useCallback(() => {
    setSearchParams(new URLSearchParams(), { replace: true });
  }, [setSearchParams]);

  const activeCount = activeFilterCount(filters);

  return (
    <Layout style={{ minHeight: '100vh' }}>
      <Header
        className="site-header"
        style={{
          background: token.colorBgContainer,
          borderBottom: `1px solid ${token.colorBorderSecondary}`
        }}
      >
        {/* Wrapped so the mark and the wordmark travel together — the title
            keeps its own ellipsis behaviour when the header gets narrow, and the
            mark is never what gets truncated. */}
        <div className="site-header-brand" style={{ color: token.colorText }}>
          <BrandMark size={28} />
          <Title level={3} className="site-header-title" style={{ color: token.colorText }}>
            Redefined Designs
          </Title>
        </div>
        <div className="site-header-actions">
          <Switch checked={mode === 'dark'} onChange={toggle} checkedChildren="Dark" unCheckedChildren="Light" />
          <Link to="/cart">
            <Badge count={cartItems.length} size="small">
              <Button icon={<ShoppingCartOutlined />} />
            </Badge>
          </Link>
          {/* The account link names the page to render behind the modal, so
              closing it comes back here — filters and all — rather than to a
              default. */}
          {customer ? (
            <Link to="/account" state={{ background: location }}>
              <Button>My Account</Button>
            </Link>
          ) : (
            <>
              <Link to="/login" state={{ background: location }}>
                <Button>Log in</Button>
              </Link>
              <Link to="/register" state={{ background: location }}>
                <Button type="primary">Sign up</Button>
              </Link>
            </>
          )}
        </div>
      </Header>
      <Content style={{ padding: 24 }}>
        <div className="filter-bar">
          {/* In the bar rather than inside the drawer, deliberately. The default
              now hides sold pieces, so a customer who never opens the drawer
              would otherwise have no way to know sold items exist — and on a
              one-of-a-kind catalogue the sold pieces are part of the story. */}
          <Segmented
            aria-label="Filter by availability"
            // The fallback matches the server's: the favorites view defaults to
            // everything, so the control must not claim Not Sold while sold
            // favorites are on screen.
            value={saleStateFromStatuses(
              filters.status,
              STOREFRONT_SALE_STATUSES,
              filters.favoritesOnly ? 'all' : 'not-sold'
            )}
            onChange={(value) => {
              const state = value as SaleState;
              applyFilters({
                ...filters,
                // Not Sold is the default, so it is stored as "no preference"
                // rather than as an explicit list. That keeps it out of the URL
                // and out of the Filters (N) count, where it would otherwise
                // show as an active filter nobody chose.
                status: state === 'not-sold' ? null : STOREFRONT_SALE_STATUSES[state]
              });
            }}
            options={[
              { label: 'Not sold', value: 'not-sold' },
              { label: 'Sold', value: 'sold' },
              { label: 'All', value: 'all' }
            ]}
          />
          <Button
            icon={<FilterOutlined />}
            onClick={() => setDrawerOpen(true)}
            type={activeCount ? 'primary' : 'default'}
          >
            Filters{activeCount ? ` (${activeCount})` : ''}
          </Button>
          <ActiveFilterChips
            options={options}
            filters={filters}
            onChange={applyFilters}
            onClear={clearFilters}
          />
        </div>

        {loading && !items.length && !failed ? <Spin /> : null}
        <ErrorBoundary
          context="catalogue"
          // Lets Clear filters (and any other filter change) recover the grid
          // without a reload: filterKey changes whenever the filters change,
          // which resets the boundary the next time it renders. `?boom=catalogue`
          // is not itself a known filter, so filterKey is unaffected by it and
          // the existing end-to-end assertion that the fallback renders still
          // holds.
          resetKey={filterKey}
          fallback={(error) => (
            <ErrorFallback
              error={error}
              title="The item list didn't load"
              actions={
                <Button type="primary" onClick={() => window.location.reload()}>
                  Reload
                </Button>
              }
            />
          )}
        >
          {import.meta.env.DEV && <DevThrow scope="catalogue" />}
          <Catalogue
            failed={failed}
            loading={loading}
            items={items}
            filters={filters}
            needsFavoritesAuth={needsFavoritesAuth}
            onRetry={retry}
            onSignIn={openAuthModal}
            onClearFilters={clearFilters}
            onChanged={reload}
          />
        </ErrorBoundary>
      </Content>
      <Footer style={{ textAlign: 'center', background: token.colorBgContainer }}>
        <Link to="/privacy">Privacy Policy</Link>
      </Footer>

      <FilterDrawer
        open={drawerOpen}
        onClose={() => setDrawerOpen(false)}
        options={options}
        filters={filters}
        onChange={applyFilters}
        onClear={clearFilters}
        resultCount={items.length}
      />

      {/* The same prompt the heart button and Add to Cart use. Signing in
          resolves the gate above, and the filter then applies on its own — the
          customer never has to set it a second time. */}
      <AuthPromptModal
        open={authModalOpen}
        onClose={() => setAuthModalOpen(false)}
        onSuccess={() => setAuthModalOpen(false)}
      />
    </Layout>
  );
}