const blogPluginExports = require("@docusaurus/plugin-content-blog");
const utils = require("@docusaurus/utils");
const path = require("path");

const defaultBlogPlugin = blogPluginExports.default;

const pluginDataDirRoot = path.join(
    ".docusaurus",
    "docusaurus-plugin-content-blog",
);
const aliasedSource = (source) =>
    `~blog/${utils.posixPath(path.relative(pluginDataDirRoot, source))}`;

function paginateBlogPosts({
    blogPosts,
    basePageUrl,
    blogTitle,
    blogDescription,
    postsPerPageOption,
}) {
    const totalCount = blogPosts.length;
    const postsPerPage =
        postsPerPageOption === "ALL" ? totalCount : postsPerPageOption;

    const numberOfPages = Math.ceil(totalCount / postsPerPage);

    const pages = [];

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

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

    return pages;
}

function getMultipleRandomElement(arr, num) {
    const shuffled = [...arr].sort(() => 0.5 - Math.random());

    return shuffled.slice(0, num);
}

function getReletadPosts(allBlogPosts, metadata) {
    const relatedPosts = allBlogPosts.filter(
        (post) =>
            post.metadata.frontMatter.tags?.some((tag) =>
                metadata.frontMatter.tags?.includes(tag),
            ) && post.metadata.title !== metadata.title,
    );

    const randomThreeRelatedPosts = getMultipleRandomElement(relatedPosts, 3);

    const filteredPostInfos = randomThreeRelatedPosts.map((post) => {
        return {
            title: post.metadata.title,
            description: post.metadata.description,
            permalink: post.metadata.permalink,
            formattedDate: post.metadata.formattedDate,
            authors: post.metadata.authors,
            readingTime: post.metadata.readingTime,
            date: post.metadata.date,
        };
    });

    return filteredPostInfos;
}

function getAuthorPosts(allBlogPosts, metadata) {
    const authorPosts = allBlogPosts.filter(
        (post) =>
            post.metadata.frontMatter.authors ===
                metadata.frontMatter.authors &&
            post.metadata.title !== metadata.title,
    );

    const randomThreeAuthorPosts = getMultipleRandomElement(authorPosts, 3);

    const filteredPostInfos = randomThreeAuthorPosts.map((post) => {
        return {
            title: post.metadata.title,
            description: post.metadata.description,
            permalink: post.metadata.permalink,
            formattedDate: post.metadata.formattedDate,
            authors: post.metadata.authors,
            readingTime: post.metadata.readingTime,
            date: post.metadata.date,
        };
    });

    return filteredPostInfos;
}

async function blogPluginExtended(...pluginArgs) {
    const blogPluginInstance = await defaultBlogPlugin(...pluginArgs);

    const { blogTitle, blogDescription, postsPerPage } = pluginArgs[1];

    return {
        // Add all properties of the default blog plugin so existing functionality is preserved
        ...blogPluginInstance,
        /**
         * Override the default `contentLoaded` hook to access blog posts data
         */
        contentLoaded: async function (data) {
            const { content: blogContents, actions } = data;
            const { addRoute, createData } = actions;
            const {
                blogPosts: allBlogPosts,
                blogTags,
                blogTagsListPath,
            } = blogContents;

            const blogItemsToMetadata = {};

            function blogPostItemsModule(items) {
                return items.map((postId) => {
                    const blogPostMetadata = blogItemsToMetadata[postId];

                    return {
                        content: {
                            __import: true,
                            path: blogPostMetadata.source,
                            query: {
                                truncated: true,
                            },
                        },
                    };
                });
            }

            const featuredBlogPosts = allBlogPosts.filter(
                (post) => post.metadata.frontMatter.is_featured === true,
            );

            const blogPosts = allBlogPosts.filter(
                (post) => post.metadata.frontMatter.is_featured !== true,
            );

            const blogListPaginated = paginateBlogPosts({
                blogPosts,
                basePageUrl: "/blog",
                blogTitle,
                blogDescription,
                postsPerPageOption: postsPerPage,
            });

            // Create routes for blog entries.
            await Promise.all(
                allBlogPosts.map(async (blogPost) => {
                    const { id, metadata } = blogPost;

                    const relatedPosts = getReletadPosts(
                        allBlogPosts,
                        metadata,
                    );

                    const authorPosts = getAuthorPosts(allBlogPosts, metadata);

                    await createData(
                        // Note that this created data path must be in sync with
                        // metadataPath provided to mdx-loader.
                        `${utils.docuHash(metadata.source)}.json`,
                        JSON.stringify(
                            { ...metadata, relatedPosts, authorPosts },
                            null,
                            2,
                        ),
                    );

                    addRoute({
                        path: metadata.permalink,
                        component: "@theme/BlogPostPage",
                        exact: true,
                        modules: {
                            content: metadata.source,
                        },
                    });

                    blogItemsToMetadata[id] = metadata;
                }),
            );

            // 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(
                        `${utils.docuHash(permalink)}.json`,
                        JSON.stringify(metadata, null, 2),
                    );

                    const tagsProp = Object.values(blogTags).map((tag) => ({
                        label: tag.label,
                        permalink: tag.permalink,
                        count: tag.items.length,
                    }));

                    const tagsPropPath = await createData(
                        `${utils.docuHash(`${blogTagsListPath}-tags`)}.json`,
                        JSON.stringify(tagsProp, null, 2),
                    );

                    addRoute({
                        path: permalink,
                        component: "@theme/BlogListPage",
                        exact: true,
                        modules: {
                            items: blogPostItemsModule(
                                permalink === "/blog"
                                    ? [
                                          ...items,
                                          ...featuredBlogPosts.map(
                                              (post) => post.id,
                                          ),
                                      ]
                                    : items,
                            ),
                            metadata: aliasedSource(pageMetadataPath),
                            tags: aliasedSource(tagsPropPath),
                        },
                    });
                }),
            );

            const authorsArray = allBlogPosts
                .map((post) => post.metadata.frontMatter.authors)
                .filter((authorName) => authorName !== undefined);
            const uniqueAuthors = [...new Set(authorsArray)];

            uniqueAuthors.map(async (author) => {
                const authorPosts = allBlogPosts.filter(
                    (post) => post.metadata.frontMatter.authors === author,
                );

                const authorListPaginated = paginateBlogPosts({
                    blogPosts: authorPosts,
                    basePageUrl: "/blog/author/" + author,
                    blogTitle,
                    blogDescription,
                    postsPerPageOption: "ALL",
                });

                authorListPaginated.map((authorListPage) => {
                    const { metadata, items } = authorListPage;
                    const { permalink } = metadata;

                    addRoute({
                        path: permalink,
                        component: "@site/src/components/blog/author-page",
                        exact: true,
                        modules: {
                            items: blogPostItemsModule(items),
                        },
                    });
                });
            });

            // Tags. This is the last part so we early-return if there are no tags.
            if (Object.keys(blogTags).length === 0) {
                return;
            }

            async function createTagsListPage() {
                const tagsProp = Object.values(blogTags).map((tag) => ({
                    label: tag.label,
                    permalink: tag.permalink,
                    count: tag.items.length,
                }));

                const tagsPropPath = await createData(
                    `${utils.docuHash(`${blogTagsListPath}-tags`)}.json`,
                    JSON.stringify(tagsProp, null, 2),
                );

                addRoute({
                    path: blogTagsListPath,
                    component: "@theme/BlogTagsListPage",
                    exact: true,
                    modules: {
                        tags: aliasedSource(tagsPropPath),
                    },
                });
            }

            async function createTagPostsListPage(tag) {
                await Promise.all(
                    tag.pages.map(async (blogPaginated) => {
                        const { metadata, items } = blogPaginated;
                        const tagProp = {
                            label: tag.label,
                            permalink: tag.permalink,
                            allTagsPath: blogTagsListPath,
                            count: tag.items.length,
                        };
                        const tagPropPath = await createData(
                            `${utils.docuHash(metadata.permalink)}.json`,
                            JSON.stringify(tagProp, null, 2),
                        );

                        const listMetadataPath = await createData(
                            `${utils.docuHash(metadata.permalink)}-list.json`,
                            JSON.stringify(metadata, null, 2),
                        );

                        const tagsProp = Object.values(blogTags).map((tag) => ({
                            label: tag.label,
                            permalink: tag.permalink,
                            count: tag.items.length,
                        }));

                        const tagsPropPath = await createData(
                            `${utils.docuHash(
                                `${blogTagsListPath}-tags`,
                            )}.json`,
                            JSON.stringify(tagsProp, null, 2),
                        );

                        addRoute({
                            path: metadata.permalink,
                            component: "@theme/BlogTagsPostsPage",
                            exact: true,
                            modules: {
                                items: blogPostItemsModule(items),
                                tag: aliasedSource(tagPropPath),
                                tags: aliasedSource(tagsPropPath),
                                listMetadata: aliasedSource(listMetadataPath),
                            },
                        });
                    }),
                );
            }

            await createTagsListPage();
            await Promise.all(
                Object.values(blogTags).map(createTagPostsListPage),
            );
        },
    };
}

module.exports = {
    ...blogPluginExports,
    default: blogPluginExtended,
};