Expose render parse tree (#1032)

common/syscalls/markdown.ts

@@ -1,6 +1,6 @@
 import type { SysCallMapping } from "../../lib/plugos/system.ts";
 import { parse } from "../markdown_parser/parse_tree.ts";
-import type { ParseTree } from "../../plug-api/lib/tree.ts";
+import { type ParseTree, renderToText } from "../../plug-api/lib/tree.ts";
 import { extendedMarkdownLanguage } from "../markdown_parser/parser.ts";
 
 export function markdownSyscalls(): SysCallMapping {
@@ -8,5 +8,8 @@ export function markdownSyscalls(): SysCallMapping {
     "markdown.parseMarkdown": (_ctx, text: string): ParseTree => {
       return parse(extendedMarkdownLanguage, text);
     },
+    "markdown.renderParseTree": (_ctx, tree: ParseTree): string => {
+      return renderToText(tree);
+    },
   };
 }

plug-api/syscalls/markdown.ts

@@ -9,3 +9,12 @@ import type { ParseTree } from "../lib/tree.ts";
 export function parseMarkdown(text: string): Promise<ParseTree> {
   return syscall("markdown.parseMarkdown", text);
 }
+
+/**
+ * Renders a ParseTree to markdown.
+ * @param tree the parse tree
+ * @returns the rendered markdown of a passed parse tree
+ */
+export function renderParseTree(tree: ParseTree): Promise<string> {
+  return syscall("markdown.renderParseTree", tree);
+}