chore: migrate epub generation to build script

src/build-scripts/generate-epubs.ts

@@ -0,0 +1,121 @@
+import { unifiedChain } from "utils/markdown/unified-chain";
+import remarkGfm from "remark-gfm";
+import remarkUnwrapImages from "remark-unwrap-images";
+import remarkTwoslash from "remark-shiki-twoslash";
+import { UserConfigSettings } from "shiki-twoslash";
+import rehypeRaw from "rehype-raw";
+import rehypeSlug from "rehype-slug-custom-id";
+import {
+  getCollectionBySlug,
+  getCollectionSlugs,
+} from "utils/fs/posts-and-collections-api";
+import { join, resolve } from "path";
+import slash from "slash";
+import visit from "unist-util-visit";
+import { Element, Root } from "hast";
+import { isRelativePath } from "utils/url-paths";
+import { EPub } from "@lesjoursfr/html-to-epub";
+
+function rehypeMakeImagePathsAbsolute(options: { path: string }) {
+  return (tree: Root) => {
+    visit(tree, "element", visitor);
+
+    function visitor(node: Element) {
+      if (node.tagName === "img") {
+        let src = node.properties!.src as string;
+        if (src.startsWith("http")) {
+          return;
+        }
+        if (isRelativePath(src)) {
+          src = slash(join(options.path, src));
+        }
+        node.properties!.src = src;
+      }
+    }
+  };
+}
+
+async function generateEpubHTML(slug: string, content: string) {
+  const result = await unifiedChain({
+    remarkPlugins: [
+      remarkGfm,
+      remarkUnwrapImages,
+      [
+        (remarkTwoslash as any).default,
+        {
+          themes: ["github-light"],
+        } as UserConfigSettings,
+      ],
+    ],
+    rehypePlugins: [
+      // This is required to handle unsafe HTML embedded into Markdown
+      rehypeRaw,
+      [
+        rehypeMakeImagePathsAbsolute,
+        {
+          path: resolve(process.cwd(), `content/blog/${slug}/`),
+        },
+      ],
+      [
+        rehypeSlug,
+        {
+          maintainCase: true,
+          removeAccents: true,
+          enableCustomId: true,
+        },
+      ],
+    ],
+  }).process(content);
+
+  return result.toString();
+}
+
+type EpubOptions = ConstructorParameters<typeof EPub>[0];
+
+async function generateCollectionEPub(
+  collectionSlug: string,
+  fileLocation: string
+) {
+  const collection = getCollectionBySlug(collectionSlug, {
+    title: true,
+    authors: true,
+    posts: true,
+    slug: true,
+    coverImg: true,
+    associatedSeries: true,
+  });
+  const epub = new EPub(
+    {
+      title: collection.title,
+      author: collection.authors.map((author) => author.name),
+      publisher: "Unicorn Utterances",
+      cover: resolve(
+        process.cwd(),
+        `content/collections/${collection.slug}/${collection.coverImg.relativePath}`
+      ),
+      css: `img{max-width: 100%}`,
+      // fonts: ['/path/to/Merriweather.ttf'],
+      lang: "en",
+      content: await Promise.all(
+        collection.posts.map(async (post) => ({
+          title: post.title,
+          author: post.authors.map((author) => author.name),
+          data: await generateEpubHTML(post.slug, post.content),
+        }))
+      ),
+    } as Partial<EpubOptions> as EpubOptions,
+    fileLocation
+  );
+  return await epub.render();
+}
+
+const collectionSlugs = getCollectionSlugs();
+// @ts-ignore
+await Promise.all(
+  collectionSlugs.map(async (collectionSlug) => {
+    await generateCollectionEPub(
+      collectionSlug,
+      resolve(process.cwd(), `public/${collectionSlug}.epub`)
+    );
+  })
+);