/**
 * 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 {DocMetadataBase, VersionMetadata} from '../types';
import type {
  NormalizedSidebarItem,
  NormalizedSidebar,
  NormalizedSidebars,
  SidebarItemsGeneratorDoc,
  SidebarItemsGeneratorVersion,
  SidebarItemAutogenerated,
  ProcessedSidebarItem,
  ProcessedSidebar,
  ProcessedSidebars,
  SidebarProcessorParams,
  CategoryMetadataFile,
} from './types';
import {DefaultSidebarItemsGenerator} from './generator';
import {validateSidebars} from './validation';
import {mapValues, memoize, pick} from 'lodash';
import combinePromises from 'combine-promises';
import {isCategoryIndex} from '../docs';

function toSidebarItemsGeneratorDoc(
  doc: DocMetadataBase,
): SidebarItemsGeneratorDoc {
  return pick(doc, [
    'id',
    'unversionedId',
    'frontMatter',
    'source',
    'sourceDirName',
    'sidebarPosition',
  ]);
}

function toSidebarItemsGeneratorVersion(
  version: VersionMetadata,
): SidebarItemsGeneratorVersion {
  return pick(version, ['versionName', 'contentPath']);
}

// Handle the generation of autogenerated sidebar items and other
// post-processing checks
async function processSidebar(
  unprocessedSidebar: NormalizedSidebar,
  categoriesMetadata: Record<string, CategoryMetadataFile>,
  params: SidebarProcessorParams,
): Promise<ProcessedSidebar> {
  const {
    sidebarItemsGenerator,
    numberPrefixParser,
    docs,
    version,
    sidebarOptions,
  } = params;

  // Just a minor lazy transformation optimization
  const getSidebarItemsGeneratorDocsAndVersion = memoize(() => ({
    docs: docs.map(toSidebarItemsGeneratorDoc),
    version: toSidebarItemsGeneratorVersion(version),
  }));

  async function processAutoGeneratedItem(
    item: SidebarItemAutogenerated,
  ): Promise<ProcessedSidebarItem[]> {
    const generatedItems = await sidebarItemsGenerator({
      item,
      numberPrefixParser,
      defaultSidebarItemsGenerator: DefaultSidebarItemsGenerator,
      isCategoryIndex,
      ...getSidebarItemsGeneratorDocsAndVersion(),
      options: sidebarOptions,
      categoriesMetadata,
    });
    // Process again... weird but sidebar item generated might generate some
    // auto-generated items?
    // TODO repeatedly process & unwrap autogenerated items until there are no
    // more autogenerated items, or when loop count (e.g. 10) is reached
    return processItems(generatedItems);
  }

  async function processItem(
    item: NormalizedSidebarItem,
  ): Promise<ProcessedSidebarItem[]> {
    if (item.type === 'category') {
      return [
        {
          ...item,
          items: (await Promise.all(item.items.map(processItem))).flat(),
        },
      ];
    }
    if (item.type === 'autogenerated') {
      return processAutoGeneratedItem(item);
    }
    return [item];
  }

  async function processItems(
    items: NormalizedSidebarItem[],
  ): Promise<ProcessedSidebarItem[]> {
    return (await Promise.all(items.map(processItem))).flat();
  }

  const processedSidebar = await processItems(unprocessedSidebar);
  return processedSidebar;
}

export async function processSidebars(
  unprocessedSidebars: NormalizedSidebars,
  categoriesMetadata: Record<string, CategoryMetadataFile>,
  params: SidebarProcessorParams,
): Promise<ProcessedSidebars> {
  const processedSidebars = await combinePromises(
    mapValues(unprocessedSidebars, (unprocessedSidebar) =>
      processSidebar(unprocessedSidebar, categoriesMetadata, params),
    ),
  );
  validateSidebars(processedSidebars);
  return processedSidebars;
}