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 Pagination from 'antd/es/pagination';
import { ShoppingCartOutlined } 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 FilterBar from './components/filters/FilterBar';
import { chipsFor } from './components/filters/dimension';
import {
  PAGE_SIZE_OPTIONS,
  clampPage,
  pageFromSearchParams,
  pageSlice,
  readStoredPageSize,
  writeStoredPageSize
} from './pagination';
import {
  availabilityDimension,
  categoryDimension,
  favoritesDimension,
  priceDimension,
  tagDimension
} from './components/filters/standardDimensions';
import { ItemFilters, filtersFromSearchParams, filtersToSearchParams } 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;
  /** One page of items, not the whole result set — see `total`. */
  items: Item[];
  /** How many items match the filters altogether, across every page. */
  total: number;
  page: number;
  pageSize: number;
  onPageChange: (page: number) => void;
  onPageSizeChange: (size: number) => void;
  filtered: boolean;
  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,
  total,
  page,
  pageSize,
  onPageChange,
  onPageSizeChange,
  filtered,
  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.
    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>
      {/* Not while there is nothing to count. A genuinely empty catalogue
          returns early above with the empty state, so the only way to reach
          here with a total of zero is mid-load — and flashing "0 items" at
          somebody while their catalogue is still arriving says something
          untrue. */}
      {total > 0 && (
      <Pagination
        style={{ marginTop: 24, textAlign: 'center' }}
        current={page}
        pageSize={pageSize}
        total={total}
        onChange={onPageChange}
        showSizeChanger
        pageSizeOptions={[...PAGE_SIZE_OPTIONS]}
        onShowSizeChange={(_current, size) => onPageSizeChange(size)}
        // Deliberately off: the jump box earns its place on a table of
        // thousands of rows, not on a catalogue somebody is browsing (#269).
        showQuickJumper={false}
        // Shown even when everything fits on one page, because the count is a
        // requirement in its own right and hiding the control would hide it.
        hideOnSinglePage={false}
        showTotal={(count) => `${count} ${count === 1 ? 'item' : 'items'}`}
      />
      )}
    </>
  );
}

// Availability first and always visible, because it is the coarsest cut and
// worth seeing without opening anything. Favorites next, so someone who came
// for their favorites does not scroll past the catalogue controls.
const STOREFRONT_DIMENSIONS = [
  availabilityDimension,
  favoritesDimension,
  categoryDimension,
  tagDimension,
  priceDimension
];

// Hoisted out of the component that used to declare it inline.
//
// S6478 flags a function-returning-JSX in a prop as "defining a component
// during render". Here it is a render prop — ErrorBoundary's `fallback` is
// typed `(error: Error) => React.ReactNode` and called as
// `this.props.fallback(...)` — so React only ever sees the returned elements,
// never a new component type, and the subtree destruction the rule warns about
// does not happen. The rule's own message offers `allowAsProps` for exactly
// this shape, which cannot be set from here.
//
// Hoisting rather than suppressing because it costs nothing: these close over
// nothing local, so at module level they are one stable function instead of a
// new closure per render, which is mildly better and not a contortion. See #181.
function catalogueErrorFallback(error: Error) {
  return (
    <ErrorFallback
      error={error}
      title="The item list didn't load"
      actions={
        <Button type="primary" onClick={() => window.location.reload()}>
          Reload
        </Button>
      }
    />
  );
}

export default function App() {
  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);

  /**
   * The page size is a preference, not view state, so it lives in storage
   * rather than in the URL. Putting it in the URL would mean sharing a link to
   * an item also imposed your page size on whoever opened it, which is not
   * yours to decide for them. Read through a lazy initialiser so a storage
   * that throws is not hit on every render.
   */
  const [pageSize, setPageSize] = useState(() =>
    readStoredPageSize(typeof window === 'undefined' ? null : window.localStorage)
  );

  const choosePageSize = useCallback((size: number) => {
    setPageSize(size);
    writeStoredPageSize(typeof window === 'undefined' ? null : window.localStorage, size);
  }, []);

  // Clamped against what there actually is, so a shared link to a page that no
  // longer exists shows the last page rather than an empty grid.
  const page = clampPage(pageFromSearchParams(searchParams), items.length, pageSize);
  const visibleItems = useMemo(() => pageSlice(items, page, pageSize), [items, page, pageSize]);

  const goToPage = useCallback(
    (next: number) => {
      const params = new URLSearchParams(searchParams);
      // Page one is the absence of the parameter, so the plain catalogue URL
      // stays clean and two links to the same first page are the same string.
      if (next <= 1) params.delete('page');
      else params.set('page', String(next));
      // push, not replace: paging is navigation, and the back button should
      // return to the page you came from. Filters use replace for the opposite
      // reason — dragging a slider must not bury the previous view.
      setSearchParams(params);
    },
    [searchParams, setSearchParams]
  );

  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]);

  // The parent needs to know whether anything is filtering — for the empty
  // state's wording — but has no chip row of its own to count. Through the same
  // chipsFor call FilterBar's tally goes through, not a second expression over
  // the same dimensions: those agreed only by convention, which is the defect
  // #188 exists to remove.
  const filterContext = {
    filters,
    onChange: applyFilters,
    categories: options?.categories ?? [],
    tags: options?.tags ?? [],
    priceRange: options?.priceRange ?? null
  };
  const filtered = chipsFor(STOREFRONT_DIMENSIONS, filterContext).length > 0;

  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">
          <FilterBar
            dimensions={STOREFRONT_DIMENSIONS}
            filters={filters}
            onChange={applyFilters}
            onClear={clearFilters}
            categories={options?.categories ?? []}
            tags={options?.tags ?? []}
            priceRange={options?.priceRange ?? null}
            resultCount={items.length}
          />
        </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={catalogueErrorFallback}
        >
          {import.meta.env.DEV && <DevThrow scope="catalogue" />}
          <Catalogue
            failed={failed}
            loading={loading}
            items={visibleItems}
            total={items.length}
            page={page}
            pageSize={pageSize}
            onPageChange={goToPage}
            onPageSizeChange={choosePageSize}
            filtered={filtered}
            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>

      {/* 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>
  );
}