/**
 * 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.
 */

const globby = require('globby');
const path = require('path');
const fs = require('fs-extra');
const {parse, idx, normalizeUrl, generate} = require('@docusaurus/utils');

function fileToUrl(fileName) {
  return fileName
    .replace('-', '/')
    .replace('-', '/')
    .replace('-', '/')
    .replace(/\.md$/, '');
}

const DEFAULT_OPTIONS = {
  metadataKey: 'blogMetadata',
  metadataFileName: 'blogMetadata.json',
  path: 'blog', // Path to data on filesystem, relative to site dir.
  routeBasePath: 'blog', // URL Route.
  include: ['*.md', '*.mdx'], // Extensions to include.
  pageCount: 10, // How many entries per page.
  blogPageComponent: '@theme/BlogPage',
  blogPostComponent: '@theme/BlogPost',
};

const TRUNCATE_MARKER = /<!--\s*truncate\s*-->/;

class DocusaurusPluginContentBlog {
  constructor(opts, context) {
    this.options = {...DEFAULT_OPTIONS, ...opts};
    this.context = context;
    this.contentPath = path.resolve(this.context.siteDir, this.options.path);
  }

  getName() {
    return 'docusaurus-plugin-content-blog';
  }

  // Fetches blog contents and returns metadata for the contents.
  async loadContent() {
    const {pageCount, include, routeBasePath} = this.options;
    const {env, generatedFilesDir, siteConfig} = this.context;
    const blogDir = this.contentPath;

    const {baseUrl} = siteConfig;
    const blogFiles = await globby(include, {
      cwd: blogDir,
    });

    // Prepare metadata container.
    const blogMetadata = [];

    // Language for each blog page.
    const defaultLangTag = idx(env, ['translation', 'defaultLanguage', 'tag']);

    await Promise.all(
      blogFiles.map(async relativeSource => {
        const source = path.join(blogDir, relativeSource);

        const blogFileName = path.basename(relativeSource);
        // Extract, YYYY, MM, DD from the file name.
        const filePathDateArr = blogFileName.split('-');
        const date = new Date(
          `${filePathDateArr[0]}-${filePathDateArr[1]}-${
            filePathDateArr[2]
          }T06:00:00.000Z`,
        );

        const fileString = await fs.readFile(source, 'utf-8');
        const {metadata: rawMetadata, content} = parse(fileString);

        let truncatedSource;
        const isTruncated = TRUNCATE_MARKER.test(content);
        if (isTruncated) {
          const pluginContentDir = path.join(generatedFilesDir, this.getName());
          await generate(
            pluginContentDir,
            blogFileName,
            content.split(TRUNCATE_MARKER)[0],
          );
          truncatedSource = path.join(pluginContentDir, blogFileName);
        }

        const metadata = {
          permalink: normalizeUrl([
            baseUrl,
            routeBasePath,
            fileToUrl(blogFileName),
          ]),
          source,
          truncatedSource,
          ...rawMetadata,
          date,
          language: defaultLangTag,
        };
        blogMetadata.push(metadata);
      }),
    );
    blogMetadata.sort((a, b) => a.date - b.date);

    // Blog page handling. Example: `/blog`, `/blog/page1`, `/blog/page2`
    const numOfBlog = blogMetadata.length;
    const numberOfPage = Math.ceil(numOfBlog / pageCount);
    const basePageUrl = path.join(baseUrl, routeBasePath);

    // eslint-disable-next-line
    for (let page = 0; page < numberOfPage; page++) {
      blogMetadata.push({
        permalink: normalizeUrl([
          basePageUrl,
          `${page > 0 ? `page${page + 1}` : ''}`,
        ]),
        language: defaultLangTag,
        isBlogPage: true,
        posts: blogMetadata.slice(page * pageCount, (page + 1) * pageCount),
      });
    }

    return blogMetadata;
  }

  async contentLoaded({content, actions}) {
    const {blogPageComponent, blogPostComponent} = this.options;
    const {addRoute} = actions;
    content.forEach(metadataItem => {
      const {isBlogPage, permalink} = metadataItem;
      if (isBlogPage) {
        addRoute({
          path: permalink,
          component: blogPageComponent,
          metadata: metadataItem,
          modules: metadataItem.posts.map(
            post => post.truncatedSource || post.source,
          ),
        });
        return;
      }

      addRoute({
        path: permalink,
        component: blogPostComponent,
        metadata: metadataItem,
        modules: [metadataItem.source],
      });
    });
  }

  getPathsToWatch() {
    return [this.contentPath];
  }
}

module.exports = DocusaurusPluginContentBlog;