/**
 * 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 fs from 'fs-extra';
import importFresh from 'import-fresh';
import {
  Sidebars,
  SidebarItem,
  SidebarItemBase,
  SidebarItemLink,
  SidebarItemDoc,
  Sidebar,
  SidebarItemCategory,
  SidebarItemType,
  UnprocessedSidebarItem,
  UnprocessedSidebars,
  UnprocessedSidebar,
  DocMetadataBase,
  VersionMetadata,
  SidebarItemsGeneratorDoc,
  SidebarItemsGeneratorVersion,
  NumberPrefixParser,
  SidebarItemsGeneratorOption,
  SidebarOptions,
  PluginOptions,
} from './types';
import {mapValues, flatten, flatMap, difference, pick, memoize} from 'lodash';
import {getElementsAround, toMessageRelativeFilePath} from '@docusaurus/utils';
import combinePromises from 'combine-promises';
import {DefaultSidebarItemsGenerator} from './sidebarItemsGenerator';
import path from 'path';

type SidebarItemCategoryJSON = SidebarItemBase & {
  type: 'category';
  label: string;
  items: SidebarItemJSON[];
  collapsed?: boolean;
  collapsible?: boolean;
};

type SidebarItemAutogeneratedJSON = SidebarItemBase & {
  type: 'autogenerated';
  dirName: string;
};

type SidebarItemJSON =
  | string
  | SidebarCategoryShorthandJSON
  | SidebarItemDoc
  | SidebarItemLink
  | SidebarItemCategoryJSON
  | SidebarItemAutogeneratedJSON
  | {
      type: string;
      [key: string]: unknown;
    };

type SidebarCategoryShorthandJSON = {
  [sidebarCategory: string]: SidebarItemJSON[];
};

type SidebarJSON = SidebarCategoryShorthandJSON | SidebarItemJSON[];

// Sidebar given by user that is not normalized yet. e.g: sidebars.json
type SidebarsJSON = {
  [sidebarId: string]: SidebarJSON;
};

function isCategoryShorthand(
  item: SidebarItemJSON,
): item is SidebarCategoryShorthandJSON {
  return typeof item !== 'string' && !item.type;
}

/**
 * Convert {category1: [item1,item2]} shorthand syntax to long-form syntax
 */
function normalizeCategoryShorthand(
  sidebar: SidebarCategoryShorthandJSON,
  options: SidebarOptions,
): SidebarItemCategoryJSON[] {
  return Object.entries(sidebar).map(([label, items]) => ({
    type: 'category',
    collapsed: options.sidebarCollapsed,
    collapsible: options.sidebarCollapsible,
    label,
    items,
  }));
}

/**
 * Check that item contains only allowed keys.
 */
function assertItem<K extends string>(
  item: Record<string, unknown>,
  keys: K[],
): asserts item is Record<K, unknown> {
  const unknownKeys = Object.keys(item).filter(
    // @ts-expect-error: key is always string
    (key) => !keys.includes(key as string) && key !== 'type',
  );

  if (unknownKeys.length) {
    throw new Error(
      `Unknown sidebar item keys: ${unknownKeys}. Item: ${JSON.stringify(
        item,
      )}`,
    );
  }
}

function assertIsCategory(
  item: Record<string, unknown>,
): asserts item is SidebarItemCategoryJSON {
  assertItem(item, [
    'items',
    'label',
    'collapsed',
    'collapsible',
    'customProps',
  ]);
  if (typeof item.label !== 'string') {
    throw new Error(
      `Error loading ${JSON.stringify(item)}: "label" must be a string.`,
    );
  }
  if (!Array.isArray(item.items)) {
    throw new Error(
      `Error loading ${JSON.stringify(item)}: "items" must be an array.`,
    );
  }
  // "collapsed" is an optional property
  if (
    typeof item.collapsed !== 'undefined' &&
    typeof item.collapsed !== 'boolean'
  ) {
    throw new Error(
      `Error loading ${JSON.stringify(item)}: "collapsed" must be a boolean.`,
    );
  }
  if (
    typeof item.collapsible !== 'undefined' &&
    typeof item.collapsible !== 'boolean'
  ) {
    throw new Error(
      `Error loading ${JSON.stringify(item)}: "collapsible" must be a boolean.`,
    );
  }
}

function assertIsAutogenerated(
  item: Record<string, unknown>,
): asserts item is SidebarItemAutogeneratedJSON {
  assertItem(item, ['dirName', 'customProps']);
  if (typeof item.dirName !== 'string') {
    throw new Error(
      `Error loading ${JSON.stringify(item)}: "dirName" must be a string.`,
    );
  }
  if (item.dirName.startsWith('/') || item.dirName.endsWith('/')) {
    throw new Error(
      `Error loading ${JSON.stringify(
        item,
      )}: "dirName" must be a dir path relative to the docs folder root, and should not start or end with slash`,
    );
  }
}

function assertIsDoc(
  item: Record<string, unknown>,
): asserts item is SidebarItemDoc {
  assertItem(item, ['id', 'label', 'customProps']);
  if (typeof item.id !== 'string') {
    throw new Error(
      `Error loading ${JSON.stringify(item)}: "id" must be a string.`,
    );
  }

  if (item.label && typeof item.label !== 'string') {
    throw new Error(
      `Error loading ${JSON.stringify(item)}: "label" must be a string.`,
    );
  }
}

function assertIsLink(
  item: Record<string, unknown>,
): asserts item is SidebarItemLink {
  assertItem(item, ['href', 'label', 'customProps']);
  if (typeof item.href !== 'string') {
    throw new Error(
      `Error loading ${JSON.stringify(item)}: "href" must be a string.`,
    );
  }
  if (typeof item.label !== 'string') {
    throw new Error(
      `Error loading ${JSON.stringify(item)}: "label" must be a string.`,
    );
  }
}

/**
 * Normalizes recursively item and all its children. Ensures that at the end
 * each item will be an object with the corresponding type.
 */
function normalizeItem(
  item: SidebarItemJSON,
  options: SidebarOptions,
): UnprocessedSidebarItem[] {
  if (typeof item === 'string') {
    return [
      {
        type: 'doc',
        id: item,
      },
    ];
  }
  if (isCategoryShorthand(item)) {
    return flatMap(normalizeCategoryShorthand(item, options), (subitem) =>
      normalizeItem(subitem, options),
    );
  }
  switch (item.type) {
    case 'category':
      assertIsCategory(item);
      return [
        {
          ...item,
          items: flatMap(item.items, (subItem) =>
            normalizeItem(subItem, options),
          ),
          collapsible: item.collapsible ?? options.sidebarCollapsible,
          collapsed: item.collapsed ?? options.sidebarCollapsed,
        },
      ];
    case 'autogenerated':
      assertIsAutogenerated(item);
      return [item];
    case 'link':
      assertIsLink(item);
      return [item];
    case 'ref':
    case 'doc':
      assertIsDoc(item);
      return [item];
    default: {
      const extraMigrationError =
        item.type === 'subcategory'
          ? 'Docusaurus v2: "subcategory" has been renamed as "category".'
          : '';
      throw new Error(
        `Unknown sidebar item type "${
          item.type
        }". Sidebar item is ${JSON.stringify(item)}.\n${extraMigrationError}`,
      );
    }
  }
}

function normalizeSidebar(
  sidebar: SidebarJSON,
  options: SidebarOptions,
): UnprocessedSidebar {
  const normalizedSidebar: SidebarItemJSON[] = Array.isArray(sidebar)
    ? sidebar
    : normalizeCategoryShorthand(sidebar, options);

  return flatMap(normalizedSidebar, (subitem) =>
    normalizeItem(subitem, options),
  );
}

function normalizeSidebars(
  sidebars: SidebarsJSON,
  options: SidebarOptions,
): UnprocessedSidebars {
  return mapValues(sidebars, (subitem) => normalizeSidebar(subitem, options));
}

export const DefaultSidebars: UnprocessedSidebars = {
  defaultSidebar: [
    {
      type: 'autogenerated',
      dirName: '.',
    },
  ],
};

export const DisabledSidebars: UnprocessedSidebars = {};

// If a path is provided, make it absolute
// use this before loadSidebars()
export function resolveSidebarPathOption(
  siteDir: string,
  sidebarPathOption: PluginOptions['sidebarPath'],
): PluginOptions['sidebarPath'] {
  return sidebarPathOption
    ? path.resolve(siteDir, sidebarPathOption)
    : sidebarPathOption;
}

// TODO refactor: make async
// Note: sidebarFilePath must be absolute, use resolveSidebarPathOption
export function loadSidebars(
  sidebarFilePath: string | false | undefined,
  options: SidebarOptions,
): UnprocessedSidebars {
  // false => no sidebars
  if (sidebarFilePath === false) {
    return DisabledSidebars;
  }

  // undefined => defaults to autogenerated sidebars
  if (typeof sidebarFilePath === 'undefined') {
    return DefaultSidebars;
  }

  // unexisting sidebars file: no sidebars
  // Note: this edge case can happen on versioned docs, not current version
  // We avoid creating empty versioned sidebars file with the CLI
  if (!fs.existsSync(sidebarFilePath)) {
    return DisabledSidebars;
  }

  // We don't want sidebars to be cached because of hot reloading.
  const sidebarJson = importFresh(sidebarFilePath) as SidebarsJSON;

  return normalizeSidebars(sidebarJson, options);
}

export function toSidebarItemsGeneratorDoc(
  doc: DocMetadataBase,
): SidebarItemsGeneratorDoc {
  return pick(doc, [
    'id',
    'frontMatter',
    'source',
    'sourceDirName',
    'sidebarPosition',
  ]);
}
export function toSidebarItemsGeneratorVersion(
  version: VersionMetadata,
): SidebarItemsGeneratorVersion {
  return pick(version, ['versionName', 'contentPath']);
}

export function fixSidebarItemInconsistencies(item: SidebarItem): SidebarItem {
  function fixCategoryInconsistencies(
    category: SidebarItemCategory,
  ): SidebarItemCategory {
    // A non-collapsible category can't be collapsed!
    if (!category.collapsible && category.collapsed) {
      return {
        ...category,
        collapsed: false,
      };
    }
    return category;
  }

  if (item.type === 'category') {
    return {
      ...fixCategoryInconsistencies(item),
      items: item.items.map(fixSidebarItemInconsistencies),
    };
  }
  return item;
}

// Handle the generation of autogenerated sidebar items and other post-processing checks
export async function processSidebar({
  sidebarItemsGenerator,
  numberPrefixParser,
  unprocessedSidebar,
  docs,
  version,
  options,
}: {
  sidebarItemsGenerator: SidebarItemsGeneratorOption;
  numberPrefixParser: NumberPrefixParser;
  unprocessedSidebar: UnprocessedSidebar;
  docs: DocMetadataBase[];
  version: VersionMetadata;
  options: SidebarOptions;
}): Promise<Sidebar> {
  // Just a minor lazy transformation optimization
  const getSidebarItemsGeneratorDocsAndVersion = memoize(() => ({
    docs: docs.map(toSidebarItemsGeneratorDoc),
    version: toSidebarItemsGeneratorVersion(version),
  }));

  async function handleAutoGeneratedItems(
    item: UnprocessedSidebarItem,
  ): Promise<SidebarItem[]> {
    if (item.type === 'category') {
      return [
        {
          ...item,
          items: (
            await Promise.all(item.items.map(handleAutoGeneratedItems))
          ).flat(),
        },
      ];
    }
    if (item.type === 'autogenerated') {
      return sidebarItemsGenerator({
        item,
        numberPrefixParser,
        defaultSidebarItemsGenerator: DefaultSidebarItemsGenerator,
        ...getSidebarItemsGeneratorDocsAndVersion(),
        options,
      });
    }
    return [item];
  }

  const processedSidebar = (
    await Promise.all(unprocessedSidebar.map(handleAutoGeneratedItems))
  ).flat();

  return processedSidebar.map(fixSidebarItemInconsistencies);
}

export async function processSidebars({
  sidebarItemsGenerator,
  numberPrefixParser,
  unprocessedSidebars,
  docs,
  version,
  options,
}: {
  sidebarItemsGenerator: SidebarItemsGeneratorOption;
  numberPrefixParser: NumberPrefixParser;
  unprocessedSidebars: UnprocessedSidebars;
  docs: DocMetadataBase[];
  version: VersionMetadata;
  options: SidebarOptions;
}): Promise<Sidebars> {
  return combinePromises(
    mapValues(unprocessedSidebars, (unprocessedSidebar) =>
      processSidebar({
        sidebarItemsGenerator,
        numberPrefixParser,
        unprocessedSidebar,
        docs,
        version,
        options,
      }),
    ),
  );
}

function collectSidebarItemsOfType<
  Type extends SidebarItemType,
  Item extends SidebarItem & {type: SidebarItemType},
>(type: Type, sidebar: Sidebar): Item[] {
  function collectRecursive(item: SidebarItem): Item[] {
    const currentItemsCollected: Item[] =
      item.type === type ? [item as Item] : [];

    const childItemsCollected: Item[] =
      item.type === 'category' ? flatten(item.items.map(collectRecursive)) : [];

    return [...currentItemsCollected, ...childItemsCollected];
  }

  return flatten(sidebar.map(collectRecursive));
}

export function collectSidebarDocItems(sidebar: Sidebar): SidebarItemDoc[] {
  return collectSidebarItemsOfType('doc', sidebar);
}
export function collectSidebarCategories(
  sidebar: Sidebar,
): SidebarItemCategory[] {
  return collectSidebarItemsOfType('category', sidebar);
}
export function collectSidebarLinks(sidebar: Sidebar): SidebarItemLink[] {
  return collectSidebarItemsOfType('link', sidebar);
}

export function transformSidebarItems(
  sidebar: Sidebar,
  updateFn: (item: SidebarItem) => SidebarItem,
): Sidebar {
  function transformRecursive(item: SidebarItem): SidebarItem {
    if (item.type === 'category') {
      return updateFn({
        ...item,
        items: item.items.map(transformRecursive),
      });
    }
    return updateFn(item);
  }
  return sidebar.map(transformRecursive);
}

export function collectSidebarsDocIds(
  sidebars: Sidebars,
): Record<string, string[]> {
  return mapValues(sidebars, (sidebar) => {
    return collectSidebarDocItems(sidebar).map((docItem) => docItem.id);
  });
}

export function createSidebarsUtils(sidebars: Sidebars): {
  getFirstDocIdOfFirstSidebar: () => string | undefined;
  getSidebarNameByDocId: (docId: string) => string | undefined;
  getDocNavigation: (docId: string) => {
    sidebarName: string | undefined;
    previousId: string | undefined;
    nextId: string | undefined;
  };
  checkSidebarsDocIds: (validDocIds: string[], sidebarFilePath: string) => void;
} {
  const sidebarNameToDocIds = collectSidebarsDocIds(sidebars);

  function getFirstDocIdOfFirstSidebar(): string | undefined {
    return Object.values(sidebarNameToDocIds)[0]?.[0];
  }

  function getSidebarNameByDocId(docId: string): string | undefined {
    // TODO lookup speed can be optimized
    const entry = Object.entries(sidebarNameToDocIds).find(
      ([_sidebarName, docIds]) => docIds.includes(docId),
    );

    return entry?.[0];
  }

  function getDocNavigation(docId: string): {
    sidebarName: string | undefined;
    previousId: string | undefined;
    nextId: string | undefined;
  } {
    const sidebarName = getSidebarNameByDocId(docId);
    if (sidebarName) {
      const docIds = sidebarNameToDocIds[sidebarName];
      const currentIndex = docIds.indexOf(docId);
      const {previous, next} = getElementsAround(docIds, currentIndex);
      return {
        sidebarName,
        previousId: previous,
        nextId: next,
      };
    } else {
      return {
        sidebarName: undefined,
        previousId: undefined,
        nextId: undefined,
      };
    }
  }

  function checkSidebarsDocIds(validDocIds: string[], sidebarFilePath: string) {
    const allSidebarDocIds = flatten(Object.values(sidebarNameToDocIds));
    const invalidSidebarDocIds = difference(allSidebarDocIds, validDocIds);
    if (invalidSidebarDocIds.length > 0) {
      throw new Error(
        `Invalid sidebar file at "${toMessageRelativeFilePath(
          sidebarFilePath,
        )}".
These sidebar document ids do not exist:
- ${invalidSidebarDocIds.sort().join('\n- ')}

Available document ids are:
- ${validDocIds.sort().join('\n- ')}`,
      );
    }
  }

  return {
    getFirstDocIdOfFirstSidebar,
    getSidebarNameByDocId,
    getDocNavigation,
    checkSidebarsDocIds,
  };
}