/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import {type ReactNode, useMemo} from 'react';
import {matchPath, useLocation} from '@docusaurus/router';
import renderRoutes from '@docusaurus/renderRoutes';
import {
  useActivePlugin,
  useActiveDocContext,
  useLatestVersion,
  type GlobalVersion,
  type GlobalSidebar,
  type GlobalDoc,
} from '@docusaurus/plugin-content-docs/client';
import {isSamePath} from '@docusaurus/theme-common/internal';
import {uniq} from '@docusaurus/theme-common';
import type {Props as DocRootProps} from '@theme/DocRoot';
import {useDocsPreferredVersion} from './docsPreferredVersion';
import {useDocsVersion} from './docsVersion';
import {useDocsSidebar} from './docsSidebar';

import type {
  PropSidebar,
  PropSidebarItem,
  PropSidebarItemCategory,
  PropVersionDoc,
  PropSidebarBreadcrumbsItem,
} from '@docusaurus/plugin-content-docs';

/**
 * A null-safe way to access a doc's data by ID in the active version.
 */
export function useDocById(id: string): PropVersionDoc;
/**
 * A null-safe way to access a doc's data by ID in the active version.
 */
export function useDocById(id: string | undefined): PropVersionDoc | undefined;
export function useDocById(id: string | undefined): PropVersionDoc | undefined {
  const version = useDocsVersion();
  if (!id) {
    return undefined;
  }
  const doc = version.docs[id];
  if (!doc) {
    throw new Error(`no version doc found by id=${id}`);
  }
  return doc;
}

/**
 * Pure function, similar to `Array#find`, but works on the sidebar tree.
 */
export function findSidebarCategory(
  sidebar: PropSidebar,
  predicate: (category: PropSidebarItemCategory) => boolean,
): PropSidebarItemCategory | undefined {
  for (const item of sidebar) {
    if (item.type === 'category') {
      if (predicate(item)) {
        return item;
      }
      const subItem = findSidebarCategory(item.items, predicate);
      if (subItem) {
        return subItem;
      }
    }
  }
  return undefined;
}

/**
 * Best effort to assign a link to a sidebar category. If the category doesn't
 * have a link itself, we link to the first sub item with a link.
 */
export function findFirstSidebarItemCategoryLink(
  item: PropSidebarItemCategory,
): string | undefined {
  if (item.href && !item.linkUnlisted) {
    return item.href;
  }

  for (const subItem of item.items) {
    const link = findFirstSidebarItemLink(subItem);
    if (link) {
      return link;
    }
  }
  return undefined;
}

/**
 * Best effort to assign a link to a sidebar item.
 */
export function findFirstSidebarItemLink(
  item: PropSidebarItem,
): string | undefined {
  if (item.type === 'link' && !item.unlisted) {
    return item.href;
  }
  if (item.type === 'category') {
    return findFirstSidebarItemCategoryLink(item);
  }
  // Other items types, like "html"
  return undefined;
}

/**
 * Gets the category associated with the current location. Should only be used
 * on category index pages.
 */
export function useCurrentSidebarCategory(): PropSidebarItemCategory {
  const {pathname} = useLocation();
  const sidebar = useDocsSidebar();
  if (!sidebar) {
    throw new Error('Unexpected: cant find current sidebar in context');
  }
  const categoryBreadcrumbs = getSidebarBreadcrumbs({
    sidebarItems: sidebar.items,
    pathname,
    onlyCategories: true,
  });
  const deepestCategory = categoryBreadcrumbs.slice(-1)[0];
  if (!deepestCategory) {
    throw new Error(
      `${pathname} is not associated with a category. useCurrentSidebarCategory() should only be used on category index pages.`,
    );
  }
  return deepestCategory;
}

/**
 * Gets the category associated with the current location. Should only be used
 * on category index pages.
 */
export function useCurrentSidebarSiblings(): PropSidebarItem[] {
  const {pathname} = useLocation();
  const sidebar = useDocsSidebar();
  if (!sidebar) {
    throw new Error('Unexpected: cant find current sidebar in context');
  }
  const categoryBreadcrumbs = getSidebarBreadcrumbs({
    sidebarItems: sidebar.items,
    pathname,
    onlyCategories: true,
  });
  const deepestCategory = categoryBreadcrumbs.slice(-1)[0];
  return deepestCategory?.items ?? sidebar.items;
}

const isActive = (testedPath: string | undefined, activePath: string) =>
  typeof testedPath !== 'undefined' && isSamePath(testedPath, activePath);
const containsActiveSidebarItem = (
  items: PropSidebarItem[],
  activePath: string,
) => items.some((subItem) => isActiveSidebarItem(subItem, activePath));

/**
 * Checks if a sidebar item should be active, based on the active path.
 */
export function isActiveSidebarItem(
  item: PropSidebarItem,
  activePath: string,
): boolean {
  if (item.type === 'link') {
    return isActive(item.href, activePath);
  }

  if (item.type === 'category') {
    return (
      isActive(item.href, activePath) ||
      containsActiveSidebarItem(item.items, activePath)
    );
  }

  return false;
}

export function isVisibleSidebarItem(
  item: PropSidebarItem,
  activePath: string,
): boolean {
  switch (item.type) {
    case 'category':
      return (
        isActiveSidebarItem(item, activePath) ||
        (typeof item.href !== 'undefined' && !item.linkUnlisted) ||
        item.items.some((subItem) => isVisibleSidebarItem(subItem, activePath))
      );
    case 'link':
      // An unlisted item remains visible if it is active
      return !item.unlisted || isActiveSidebarItem(item, activePath);
    default:
      return true;
  }
}

export function useVisibleSidebarItems(
  items: readonly PropSidebarItem[],
  activePath: string,
): PropSidebarItem[] {
  return useMemo(
    () => items.filter((item) => isVisibleSidebarItem(item, activePath)),
    [items, activePath],
  );
}

function getSidebarBreadcrumbs(param: {
  sidebarItems: PropSidebar;
  pathname: string;
  onlyCategories: true;
}): PropSidebarItemCategory[];

function getSidebarBreadcrumbs(param: {
  sidebarItems: PropSidebar;
  pathname: string;
}): PropSidebarBreadcrumbsItem[];

/**
 * Get the sidebar the breadcrumbs for a given pathname
 * Ordered from top to bottom
 */
function getSidebarBreadcrumbs({
  sidebarItems,
  pathname,
  onlyCategories = false,
}: {
  sidebarItems: PropSidebar;
  pathname: string;
  onlyCategories?: boolean;
}): PropSidebarBreadcrumbsItem[] {
  const breadcrumbs: PropSidebarBreadcrumbsItem[] = [];

  function extract(items: PropSidebarItem[]) {
    for (const item of items) {
      if (
        (item.type === 'category' &&
          (isSamePath(item.href, pathname) || extract(item.items))) ||
        (item.type === 'link' && isSamePath(item.href, pathname))
      ) {
        const filtered = onlyCategories && item.type !== 'category';
        if (!filtered) {
          breadcrumbs.unshift(item);
        }
        return true;
      }
    }

    return false;
  }

  extract(sidebarItems);

  return breadcrumbs;
}

/**
 * Gets the breadcrumbs of the current doc page, based on its sidebar location.
 * Returns `null` if there's no sidebar or breadcrumbs are disabled.
 */
export function useSidebarBreadcrumbs(): PropSidebarBreadcrumbsItem[] | null {
  const sidebar = useDocsSidebar();
  const {pathname} = useLocation();
  const breadcrumbsOption = useActivePlugin()?.pluginData.breadcrumbs;
  if (breadcrumbsOption === false || !sidebar) {
    return null;
  }
  return getSidebarBreadcrumbs({sidebarItems: sidebar.items, pathname});
}

/**
 * "Version candidates" are mostly useful for the layout components, which must
 * be able to work on all pages. For example, if a user has `{ type: "doc",
 * docId: "intro" }` as a navbar item, which version does that refer to? We
 * believe that it could refer to at most three version candidates:
 *
 * 1. The **active version**, the one that the user is currently browsing. See
 * {@link useActiveDocContext}.
 * 2. The **preferred version**, the one that the user last visited. See
 * {@link useDocsPreferredVersion}.
 * 3. The **latest version**, the "default". See {@link useLatestVersion}.
 *
 * @param docsPluginId The plugin ID to get versions from.
 * @returns An array of 1~3 versions with priorities defined above, guaranteed
 * to be unique and non-sparse. Will be memoized, hence stable for deps array.
 */
export function useDocsVersionCandidates(
  docsPluginId?: string,
): [GlobalVersion, ...GlobalVersion[]] {
  const {activeVersion} = useActiveDocContext(docsPluginId);
  const {preferredVersion} = useDocsPreferredVersion(docsPluginId);
  const latestVersion = useLatestVersion(docsPluginId);
  return useMemo(
    () =>
      uniq(
        [activeVersion, preferredVersion, latestVersion].filter(Boolean),
      ) as [GlobalVersion, ...GlobalVersion[]],
    [activeVersion, preferredVersion, latestVersion],
  );
}

/**
 * The layout components, like navbar items, must be able to work on all pages,
 * even on non-doc ones where there's no version context, so a sidebar ID could
 * be ambiguous. This hook would always return a sidebar to be linked to. See
 * also {@link useDocsVersionCandidates} for how this selection is done.
 *
 * @throws This hook throws if a sidebar with said ID is not found.
 */
export function useLayoutDocsSidebar(
  sidebarId: string,
  docsPluginId?: string,
): GlobalSidebar {
  const versions = useDocsVersionCandidates(docsPluginId);
  return useMemo(() => {
    const allSidebars = versions.flatMap((version) =>
      version.sidebars ? Object.entries(version.sidebars) : [],
    );
    const sidebarEntry = allSidebars.find(
      (sidebar) => sidebar[0] === sidebarId,
    );
    if (!sidebarEntry) {
      throw new Error(
        `Can't find any sidebar with id "${sidebarId}" in version${
          versions.length > 1 ? 's' : ''
        } ${versions.map((version) => version.name).join(', ')}".
Available sidebar ids are:
- ${allSidebars.map((entry) => entry[0]).join('\n- ')}`,
      );
    }
    return sidebarEntry[1];
  }, [sidebarId, versions]);
}

/**
 * The layout components, like navbar items, must be able to work on all pages,
 * even on non-doc ones where there's no version context, so a doc ID could be
 * ambiguous. This hook would always return a doc to be linked to. See also
 * {@link useDocsVersionCandidates} for how this selection is done.
 *
 * @throws This hook throws if a doc with said ID is not found.
 */
export function useLayoutDoc(
  docId: string,
  docsPluginId?: string,
): GlobalDoc | null {
  const versions = useDocsVersionCandidates(docsPluginId);
  return useMemo(() => {
    const allDocs = versions.flatMap((version) => version.docs);
    const doc = allDocs.find((versionDoc) => versionDoc.id === docId);
    if (!doc) {
      const isDraft = versions
        .flatMap((version) => version.draftIds)
        .includes(docId);
      // Drafts should be silently filtered instead of throwing
      if (isDraft) {
        return null;
      }
      throw new Error(
        `Couldn't find any doc with id "${docId}" in version${
          versions.length > 1 ? 's' : ''
        } "${versions.map((version) => version.name).join(', ')}".
Available doc ids are:
- ${uniq(allDocs.map((versionDoc) => versionDoc.id)).join('\n- ')}`,
      );
    }
    return doc;
  }, [docId, versions]);
}

// TODO later read version/route directly from context
/**
 * The docs plugin creates nested routes, with the top-level route providing the
 * version metadata, and the subroutes creating individual doc pages. This hook
 * will match the current location against all known sub-routes.
 *
 * @param props The props received by `@theme/DocRoot`
 * @returns The data of the relevant document at the current location, or `null`
 * if no document associated with the current location can be found.
 */
export function useDocRootMetadata({route}: DocRootProps): null | {
  /** The element that should be rendered at the current location. */
  docElement: ReactNode;
  /**
   * The name of the sidebar associated with the current doc. `sidebarName` and
   * `sidebarItems` correspond to the value of {@link useDocsSidebar}.
   */
  sidebarName: string | undefined;
  /** The items of the sidebar associated with the current doc. */
  sidebarItems: PropSidebar | undefined;
} {
  const location = useLocation();
  const versionMetadata = useDocsVersion();
  const docRoutes = route.routes!;
  const currentDocRoute = docRoutes.find((docRoute) =>
    matchPath(location.pathname, docRoute),
  );
  if (!currentDocRoute) {
    return null;
  }

  // For now, the sidebarName is added as route config: not ideal!
  const sidebarName = currentDocRoute.sidebar as string;

  const sidebarItems = sidebarName
    ? versionMetadata.docsSidebars[sidebarName]
    : undefined;

  const docElement = renderRoutes(docRoutes);

  return {
    docElement,
    sidebarName,
    sidebarItems,
  };
}

/**
 * Filter items we don't want to display on the doc card list view
 * @param items
 */
export function filterDocCardListItems(
  items: PropSidebarItem[],
): PropSidebarItem[] {
  return items.filter((item) => {
    const canHaveLink = item.type === 'category' || item.type === 'link';
    if (canHaveLink) {
      return !!findFirstSidebarItemLink(item);
    }
    return true;
  });
}