feat: Add HTML export option (#4056)

* tidy

* Add title to HTML export

* fix: Add compatability for documents without collab state

* Add HTML download option to UI

* docs

* fix nodes that required document to render

* Refactor to allow for styling of HTML export

* div>article for easier programatic content extraction

server/routes/api/documents.ts

@@ -1,6 +1,7 @@
 import fs from "fs-extra";
 import invariant from "invariant";
 import Router from "koa-router";
+import mime from "mime-types";
 import { Op, ScopeOptions, WhereOptions } from "sequelize";
 import { subtractDate } from "@shared/utils/date";
 import documentCreator from "@server/commands/documentCreator";
@@ -27,6 +28,7 @@ import {
   User,
   View,
 } from "@server/models";
+import DocumentHelper from "@server/models/helpers/DocumentHelper";
 import { authorize, cannot } from "@server/policies";
 import {
   presentCollection,
@@ -439,14 +441,46 @@ router.post(
   async (ctx) => {
     const { id, shareId } = ctx.body;
     assertPresent(id || shareId, "id or shareId is required");
+
     const { user } = ctx.state;
+    const accept = ctx.request.headers["accept"];
+
     const { document } = await documentLoader({
       id,
       shareId,
       user,
+      // We need the collaborative state to generate HTML.
+      includeState: accept === "text/html",
     });
+
+    let contentType;
+    let content;
+
+    if (accept?.includes("text/html")) {
+      contentType = "text/html";
+      content = DocumentHelper.toHTML(document);
+    } else if (accept?.includes("text/markdown")) {
+      contentType = "text/markdown";
+      content = DocumentHelper.toMarkdown(document);
+    } else {
+      contentType = "application/json";
+      content = DocumentHelper.toMarkdown(document);
+    }
+
+    if (contentType !== "application/json") {
+      ctx.set("Content-Type", contentType);
+      ctx.set(
+        "Content-Disposition",
+        `attachment; filename="${document.title}.${mime.extension(
+          contentType
+        )}"`
+      );
+      ctx.body = content;
+      return;
+    }
+
     ctx.body = {
-      data: document.toMarkdown(),
+      data: content,
     };
   }
 );