Add support for editing (not creating) FrontMatter

This adds support for parsing files containing FrontMatter and editing
it as like a code block.

Signed-off-by: Ferdinand Thiessen <rpm@fthiessen.de>

1 files changed, 47 insertions, 0 deletions

diff --git a/src/nodes/FrontMatter.js b/src/nodes/FrontMatter.js
new file mode 100644
index 000000000..d374228d1
--- /dev/null
+++ b/src/nodes/FrontMatter.js
@@ -0,0 +1,47 @@
+import TiptapCodeBlock from '@tiptap/extension-code-block'
+
+const FrontMatter = TiptapCodeBlock.extend({
+	name: 'frontMatter',
+	addAttributes() {
+		return {
+			...this.parent?.(),
+			class: {
+				default: 'frontmatter',
+				rendered: true,
+			},
+		}
+	},
+	parseHTML: () => {
+		return [
+			{
+				tag: 'pre[id="frontmatter"]',
+				preserveWhitespace: 'full',
+				priority: 9001,
+				attrs: {
+					language: 'yaml',
+				},
+			},
+		]
+	},
+	toMarkdown: (state, node) => {
+		if (!state.out.match(/^\s*/)) throw Error('FrontMatter must be the first node of the document!')
+		state.write('')
+		state.out = ''
+		state.write('---\n')
+		state.text(node.textContent, false)
+		state.ensureNewLine()
+		state.write('---')
+		state.closeBlock(node)
+	},
+	// FrontMatter are only valid at the begin of a document
+	draggable: false,
+	// Override rules from Codeblock
+	addCommands() {
+		return {}
+	},
+	addInputRules: () => [],
+	addPasteRules: () => [],
+	addProseMirrorPlugins: () => [],
+})
+
+export default FrontMatter