/**
 * Copyright (c) 2017-present, Facebook, Inc.
 *
 * 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 _ from 'lodash';
import path from 'path';
import {normalizeUrl, docuHash} from '@docusaurus/utils';

import {
  PluginOptions,
  BlogTags,
  BlogContent,
  BlogItemsToModules,
  TagsModule,
  BlogPaginated,
} from './types';
import {
  LoadContext,
  PluginContentLoadedActions,
  ConfigureWebpackUtils,
  Props,
  Plugin,
} from '@docusaurus/types';
import {Configuration, Loader} from 'webpack';
import {generateBlogFeed, generateBlogPosts} from './blogUtils';

const DEFAULT_OPTIONS: PluginOptions = {
  path: 'blog', // Path to data on filesystem, relative to site dir.
  routeBasePath: 'blog', // URL Route.
  include: ['*.md', '*.mdx'], // Extensions to include.
  postsPerPage: 10, // How many posts per page.
  blogListComponent: '@theme/BlogListPage',
  blogPostComponent: '@theme/BlogPostPage',
  blogTagsListComponent: '@theme/BlogTagsListPage',
  blogTagsPostsComponent: '@theme/BlogTagsPostsPage',
  remarkPlugins: [],
  rehypePlugins: [],
  truncateMarker: /<!--\s*(truncate)\s*-->/, // string or regex
};

export default function pluginContentBlog(
  context: LoadContext,
  opts: Partial<PluginOptions>,
): Plugin<BlogContent | null> {
  const options: PluginOptions = {...DEFAULT_OPTIONS, ...opts};
  const contentPath = path.resolve(context.siteDir, options.path);
  const dataDir = path.join(
    context.generatedFilesDir,
    'docusaurus-plugin-content-blog',
  );

  return {
    name: 'docusaurus-plugin-content-blog',

    getPathsToWatch() {
      const {include = []} = options;
      const globPattern = include.map(pattern => `${contentPath}/${pattern}`);
      return [...globPattern];
    },

    // Fetches blog contents and returns metadata for the necessary routes.
    async loadContent() {
      const {postsPerPage, routeBasePath} = options;

      const blogPosts = await generateBlogPosts(contentPath, context, options);
      if (!blogPosts) {
        return null;
      }

      // Colocate next and prev metadata
      blogPosts.forEach((blogPost, index) => {
        const prevItem = index > 0 ? blogPosts[index - 1] : null;
        if (prevItem) {
          blogPost.metadata.prevItem = {
            title: prevItem.metadata.title,
            permalink: prevItem.metadata.permalink,
          };
        }
        const nextItem =
          index < blogPosts.length - 1 ? blogPosts[index + 1] : null;
        if (nextItem) {
          blogPost.metadata.nextItem = {
            title: nextItem.metadata.title,
            permalink: nextItem.metadata.permalink,
          };
        }
      });

      // Blog pagination routes.
      // Example: `/blog`, `/blog/page/1`, `/blog/page/2`
      const totalCount = blogPosts.length;
      const numberOfPages = Math.ceil(totalCount / postsPerPage);
      const {
        siteConfig: {baseUrl = ''},
      } = context;
      const basePageUrl = normalizeUrl([baseUrl, routeBasePath]);

      const blogListPaginated: BlogPaginated[] = [];

      function blogPaginationPermalink(page: number) {
        return page > 0
          ? normalizeUrl([basePageUrl, `page/${page + 1}`])
          : basePageUrl;
      }

      for (let page = 0; page < numberOfPages; page += 1) {
        blogListPaginated.push({
          metadata: {
            permalink: blogPaginationPermalink(page),
            page: page + 1,
            postsPerPage,
            totalPages: numberOfPages,
            totalCount,
            previousPage: page !== 0 ? blogPaginationPermalink(page - 1) : null,
            nextPage:
              page < numberOfPages - 1
                ? blogPaginationPermalink(page + 1)
                : null,
          },
          items: blogPosts
            .slice(page * postsPerPage, (page + 1) * postsPerPage)
            .map(item => item.id),
        });
      }

      const blogTags: BlogTags = {};
      const tagsPath = normalizeUrl([basePageUrl, 'tags']);
      blogPosts.forEach(blogPost => {
        const {tags} = blogPost.metadata;
        if (!tags || tags.length === 0) {
          // TODO: Extract tags out into a separate plugin.
          // eslint-disable-next-line no-param-reassign
          blogPost.metadata.tags = [];
          return;
        }

        // eslint-disable-next-line no-param-reassign
        blogPost.metadata.tags = tags.map(tag => {
          if (typeof tag === 'string') {
            const normalizedTag = _.kebabCase(tag);
            const permalink = normalizeUrl([tagsPath, normalizedTag]);
            if (!blogTags[normalizedTag]) {
              blogTags[normalizedTag] = {
                name: tag.toLowerCase(), // Will only use the name of the first occurrence of the tag.
                items: [],
                permalink,
              };
            }

            blogTags[normalizedTag].items.push(blogPost.id);

            return {
              label: tag,
              permalink,
            };
          } else {
            return tag;
          }
        });
      });

      const blogTagsListPath =
        Object.keys(blogTags).length > 0 ? tagsPath : null;

      return {
        blogPosts,
        blogListPaginated,
        blogTags,
        blogTagsListPath,
      };
    },

    async contentLoaded({
      content: blogContents,
      actions,
    }: {
      content: BlogContent;
      actions: PluginContentLoadedActions;
    }) {
      if (!blogContents) {
        return;
      }

      const {
        blogListComponent,
        blogPostComponent,
        blogTagsListComponent,
        blogTagsPostsComponent,
      } = options;

      const aliasedSource = (source: string) =>
        `@docusaurus-plugin-content-blog/${path.relative(dataDir, source)}`;
      const {addRoute, createData} = actions;
      const {
        blogPosts,
        blogListPaginated,
        blogTags,
        blogTagsListPath,
      } = blogContents;

      const blogItemsToModules: BlogItemsToModules = {};
      // Create routes for blog entries.
      const blogItems = await Promise.all(
        blogPosts.map(async blogPost => {
          const {id, metadata} = blogPost;
          const {permalink} = metadata;
          const metadataPath = await createData(
            `${docuHash(permalink)}.json`,
            JSON.stringify(metadata, null, 2),
          );
          const temp = {
            metadata,
            metadataPath,
          };

          blogItemsToModules[id] = temp;
          return temp;
        }),
      );

      blogItems.map(blogItem => {
        const {metadata, metadataPath} = blogItem;
        const {source, permalink} = metadata;

        addRoute({
          path: permalink,
          component: blogPostComponent,
          exact: true,
          modules: {
            content: source,
            metadata: aliasedSource(metadataPath),
          },
        });
      });

      // Create routes for blog's paginated list entries.
      await Promise.all(
        blogListPaginated.map(async listPage => {
          const {metadata, items} = listPage;
          const {permalink} = metadata;
          const pageMetadataPath = await createData(
            `${docuHash(permalink)}.json`,
            JSON.stringify(metadata, null, 2),
          );

          addRoute({
            path: permalink,
            component: blogListComponent,
            exact: true,
            modules: {
              items: items.map(postID => {
                const {
                  metadata: postMetadata,
                  metadataPath,
                } = blogItemsToModules[postID];
                // To tell routes.js this is an import and not a nested object to recurse.
                return {
                  content: {
                    __import: true,
                    path: postMetadata.source,
                    query: {
                      truncated: true,
                    },
                  },
                  metadata: aliasedSource(metadataPath),
                };
              }),
              metadata: aliasedSource(pageMetadataPath),
            },
          });
        }),
      );

      // Tags.
      if (blogTagsListPath === null) {
        return;
      }

      const tagsModule: TagsModule = {};

      await Promise.all(
        Object.keys(blogTags).map(async tag => {
          const {name, items, permalink} = blogTags[tag];

          tagsModule[tag] = {
            allTagsPath: blogTagsListPath,
            slug: tag,
            name,
            count: items.length,
            permalink,
          };

          const tagsMetadataPath = await createData(
            `${docuHash(permalink)}.json`,
            JSON.stringify(tagsModule[tag], null, 2),
          );

          addRoute({
            path: permalink,
            component: blogTagsPostsComponent,
            exact: true,
            modules: {
              items: items.map(postID => {
                const {
                  metadata: postMetadata,
                  metadataPath,
                } = blogItemsToModules[postID];
                return {
                  content: {
                    __import: true,
                    path: postMetadata.source,
                    query: {
                      truncated: true,
                    },
                  },
                  metadata: aliasedSource(metadataPath),
                };
              }),
              metadata: aliasedSource(tagsMetadataPath),
            },
          });
        }),
      );

      // Only create /tags page if there are tags.
      if (Object.keys(blogTags).length > 0) {
        const tagsListPath = await createData(
          `${docuHash(`${blogTagsListPath}-tags`)}.json`,
          JSON.stringify(tagsModule, null, 2),
        );

        addRoute({
          path: blogTagsListPath,
          component: blogTagsListComponent,
          exact: true,
          modules: {
            tags: aliasedSource(tagsListPath),
          },
        });
      }
    },

    configureWebpack(
      _config: Configuration,
      isServer: boolean,
      {getBabelLoader, getCacheLoader}: ConfigureWebpackUtils,
    ) {
      const {rehypePlugins, remarkPlugins, truncateMarker} = options;
      return {
        resolve: {
          alias: {
            '@docusaurus-plugin-content-blog': dataDir,
          },
        },
        module: {
          rules: [
            {
              test: /(\.mdx?)$/,
              include: [contentPath],
              use: [
                getCacheLoader(isServer),
                getBabelLoader(isServer),
                {
                  loader: '@docusaurus/mdx-loader',
                  options: {
                    remarkPlugins,
                    rehypePlugins,
                  },
                },
                {
                  loader: path.resolve(__dirname, './markdownLoader.js'),
                  options: {
                    truncateMarker,
                  },
                },
              ].filter(Boolean) as Loader[],
            },
          ],
        },
      };
    },

    async postBuild({outDir}: Props) {
      if (!options.feedOptions) {
        return;
      }

      const {
        feedOptions: {type: feedType},
      } = options;
      const feed = await generateBlogFeed(context, options);
      if (!feed) {
        return;
      }
      let feedTypes = [];
      if (feedType === 'all') {
        feedTypes = ['rss', 'atom'];
      } else {
        feedTypes.push(feedType);
      }

      await Promise.all(
        feedTypes.map(feedType => {
          const feedPath = path.join(
            outDir,
            options.routeBasePath,
            `${feedType}.xml`,
          );
          const feedContent = feedType === 'rss' ? feed.rss2() : feed.atom1();
          return fs.writeFile(feedPath, feedContent, err => {
            if (err) {
              throw new Error(`Generating ${feedType} feed failed: ${err}`);
            }
          });
        }),
      );
    },
  };
}