handle frontmatter nicely

package.json

@@ -260,6 +260,11 @@
             "description": "%print.markdown.watermark.enable%",
             "default": false
           },
+          "print.markdown.showFrontmatter": {
+            "type": "boolean",
+            "description": "%print.markdown.showFrontmatter%",
+            "default": true
+          },
           "print.plaintext.stylesheets": {
             "type": "array",
             "items": {

package.nls.json

@@ -34,6 +34,7 @@
   "print.markdown.stylesheets": "URLs or paths for CSS for rendered Markdown. For workspace relative paths, use 'workspace.resource/path/to/your.css'. For absolute filesystem paths, use 'absolute/path/to/your.css'. Otherwise, paths are relative to the base document ('./my.css' would be in the same folder as the document), or absolute URLs (https://...). For folders or multi-file selections use absolute, absolute filesystem paths, or workspace-relative paths.",
   "print.markdown.smartQuotes.enable": "Enable the use of smart quotes in rendered Markdown.",
   "print.markdown.watermark.enable": "Enable embedded watermark text",
+  "print.markdown.showFrontmatter": "Show frontmatter metadata as a table at the top of printed documents",
   "print.markdown.watermark.text": "Watermark text to be periodically embedded in the rendered document",
   "print.plaintext.stylesheets": "URLs or paths for extra CSS to be applied to plaintext. For workspace relative paths, use 'workspace.resource/path/to/your.css'. For absolute filesystem paths, use 'absolute/path/to/your.css'. Otherwise, paths are relative to the base document ('./my.css' would be in the same folder as the document), or absolute URLs (https://...). For folders or multi-file selections use absolute, absolute filesystem paths, or workspace-relative paths.",
   "print.sourcecode.colourScheme.markdownDescription": "[Stylesheet preview is available online](https://highlightjs.org/demo/). Only 'light' versions are offered because paper is white.",

src/renderers/frontmatter.ts

@@ -0,0 +1,116 @@
+import * as yaml from "yaml";
+import { logger } from '../logger';
+
+/**
+ * Represents the result of extracting frontmatter from markdown content
+ */
+export interface FrontmatterResult {
+  frontmatter: any | null;
+  content: string;
+}
+
+/**
+ * HTML escaping utility function for frontmatter values
+ */
+function escapeHtml(text: string): string {
+  return text.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
+}
+
+/**
+ * Extracts frontmatter from markdown content
+ * Supports both YAML (---) and TOML (+++) delimiters
+ * 
+ * @param raw The raw markdown content
+ * @returns Object containing parsed frontmatter and remaining content
+ */
+export function extractFrontmatter(raw: string): FrontmatterResult {
+  // Check if content starts with frontmatter delimiters (--- or +++)
+  const yamlDelimiterRegex = /^---\s*\n([\s\S]*?)\n---\s*\n/;
+  const tomlDelimiterRegex = /^\+\+\+\s*\n([\s\S]*?)\n\+\+\+\s*\n/;
+
+  let frontmatterMatch = raw.match(yamlDelimiterRegex);
+  let frontmatterContent = '';
+  let isToml = false;
+
+  if (!frontmatterMatch) {
+    frontmatterMatch = raw.match(tomlDelimiterRegex);
+    isToml = true;
+  }
+
+  if (frontmatterMatch) {
+    frontmatterContent = frontmatterMatch[1];
+    const content = raw.substring(frontmatterMatch[0].length);
+
+    try {
+      let frontmatterData;
+      if (isToml) {
+        // For TOML, we'll try to parse it as YAML for now
+        // You might want to add a TOML parser like @iarna/toml if needed
+        frontmatterData = yaml.parse(frontmatterContent);
+      } else {
+        frontmatterData = yaml.parse(frontmatterContent);
+      }
+
+      return { frontmatter: frontmatterData, content };
+    } catch (error) {
+      logger.warn(`Failed to parse frontmatter: ${error}`);
+      return { frontmatter: null, content: raw };
+    }
+  }
+
+  return { frontmatter: null, content: raw };
+}
+
+/**
+ * Converts frontmatter object to HTML table string
+ * 
+ * @param frontmatter The parsed frontmatter object
+ * @returns HTML string representing the frontmatter as a table
+ */
+export function frontmatterToTable(frontmatter: any): string {
+  if (!frontmatter || typeof frontmatter !== 'object') {
+    return '';
+  }
+
+  const rows = Object.entries(frontmatter).map(([key, value]) => {
+    let displayValue = '';
+    if (value === null || value === undefined) {
+      displayValue = '';
+    } else if (Array.isArray(value)) {
+      displayValue = value.join(', ');
+    } else if (typeof value === 'object') {
+      displayValue = JSON.stringify(value, null, 2);
+    } else {
+      displayValue = String(value);
+    }
+
+    return `    <tr>
+      <th class="frontmatter-key">${escapeHtml(key)}</th>
+      <td class="frontmatter-value">${escapeHtml(displayValue)}</td>
+    </tr>`;
+  }).join('\n');
+
+  if (rows) {
+    return `<div class="frontmatter-metadata">
+  <h3 class="frontmatter-title">Document Metadata</h3>
+  <table class="frontmatter-table">
+${rows}
+  </table>
+</div>`;
+  }
+
+  return '';
+}
+
+/**
+ * Checks if the given string has frontmatter delimiters at the start
+ * 
+ * @param raw The raw markdown content
+ * @returns true if frontmatter is detected, false otherwise
+ */
+export function hasFrontmatter(raw: string): boolean {
+  const yamlDelimiterRegex = /^---\s*\n/;
+  const tomlDelimiterRegex = /^\+\+\+\s*\n/;
+
+  return yamlDelimiterRegex.test(raw) || tomlDelimiterRegex.test(raw);
+}

src/renderers/processMarkdown.ts

@@ -17,6 +17,7 @@ import * as fs from "fs";
 import { resolveRootDoc } from './includes';
 import { databaseFencedLanguageService } from "./database-fenced-language/databaseFencedLanguageService";
 import { DatabaseDiagramRequest } from "./database-fenced-language/models/request/databaseDiagramRequest";
+import { extractFrontmatter, frontmatterToTable } from './frontmatter';
 
 const HIGHLIGHTJS_LANGS = hljs.listLanguages().map(s => s.toUpperCase());
 const KROKI_SUPPORT = [
@@ -37,7 +38,10 @@ function escapeHtml(text: string): string {
 
 export async function processFencedBlocks(defaultConfig: any, raw: string, generatedResources: Map<string, ResourceProxy>, rootDocFolder: string) {
 
-  const tokens = marked.lexer(raw);
+  // Extract frontmatter first
+  const { frontmatter, content } = extractFrontmatter(raw);
+
+  const tokens = marked.lexer(content);
   const krokiUrl = vscode.workspace.getConfiguration("print.markdown.kroki").url;
   let activeConfigName = "DEFAULT";
   const namedConfigs: any = { DEFAULT: defaultConfig };
@@ -224,6 +228,23 @@ export async function processFencedBlocks(defaultConfig: any, raw: string, gener
       updatedTokens.push(token);
     };
   }
+
+  const showFrontmatter = vscode.workspace.getConfiguration("print.markdown").get<boolean>("showFrontmatter", true);
+
+  // If frontmatter exists, add it as an HTML table at the beginning
+  if (showFrontmatter && frontmatter) {
+    const frontmatterTableHtml = frontmatterToTable(frontmatter);
+    if (frontmatterTableHtml) {
+      const frontmatterToken: Token = {
+        type: 'html',
+        raw: '',
+        text: frontmatterTableHtml,
+        block: true
+      };
+      updatedTokens.unshift(frontmatterToken);
+    }
+  }
+
   return updatedTokens;
 }