Add Clear Formatting action to editor context menu

src/lib/editor/clearFormatting.ts

@@ -0,0 +1,81 @@
+import type { Editor } from '@tiptap/core';
+import type { Schema } from '@tiptap/pm/model';
+import type { Transaction } from '@tiptap/pm/state';
+import { liftTarget } from '@tiptap/pm/transform';
+
+// Marks that carry content (URLs, note references) rather than visual
+// formatting. Clearing formatting must never destroy these.
+const CONTENT_MARKS: Record<string, true> = { link: true, wikiLink: true };
+
+// Block types reset to plain paragraphs. Lists, callouts, collapsible
+// sections and tables keep their structure so no state (checkboxes,
+// nesting, cells) is lost.
+const DEMOTE_BLOCKS: Record<string, true> = { heading: true, codeBlock: true };
+
+// Outermost-first position of the first blockquote intersecting [from, to].
+function findBlockquote(tr: Transaction, from: number, to: number): number | null {
+	let found: number | null = null;
+	tr.doc.nodesBetween(from, to, (node, pos) => {
+		if (found !== null) return false;
+		if (node.type.name === 'blockquote') {
+			found = pos;
+			return false;
+		}
+		return true;
+	});
+	return found;
+}
+
+/**
+ * Strips inline formatting and demotes heading/code-block/blockquote
+ * structure over the transaction's selection. An empty (cursor) selection
+ * is expanded to the whole current text block, so a single invocation can
+ * reset one messy line without highlighting it first.
+ */
+export function applyClearFormatting(schema: Schema, tr: Transaction): void {
+	const { selection } = tr;
+	const { $from } = selection;
+	const expandToBlock = selection.empty && $from.parent.isTextblock;
+	const from = expandToBlock ? $from.start() : selection.from;
+	const to = expandToBlock ? $from.end() : selection.to;
+
+	// 1. Strip formatting marks, keep content-bearing ones.
+	for (const mark of Object.values(schema.marks)) {
+		if (!CONTENT_MARKS[mark.name]) tr.removeMark(from, to, mark);
+	}
+
+	// 2. Demote headings and code blocks to paragraphs. Mark removal and
+	//    retyping never move content, so the original positions stay valid.
+	tr.doc.nodesBetween(from, to, (node, pos) => {
+		if (DEMOTE_BLOCKS[node.type.name]) tr.setNodeMarkup(pos, schema.nodes.paragraph);
+		return true;
+	});
+
+	// 3. Lift blockquote contents out of the quote wrapper, one pass per
+	//    nesting level. Lifts move positions, so remap and rescan each pass.
+	for (let guard = 0; guard < 20; guard++) {
+		const quotePos = findBlockquote(tr, tr.mapping.map(from, 1), tr.mapping.map(to, -1));
+		if (quotePos === null) break;
+		// The range must span the blockquote's content: a collapsed
+		// blockRange starts one depth up and wraps the quote itself.
+		const quote = tr.doc.nodeAt(quotePos);
+		if (!quote) break;
+		const range = tr.doc.resolve(quotePos + 1).blockRange(tr.doc.resolve(quotePos + quote.nodeSize - 1));
+		if (!range) break;
+		const target = liftTarget(range);
+		if (target === null) break;
+		tr.lift(range, target);
+	}
+}
+
+/** Clears formatting for the editor's current selection (or current line). */
+export function clearFormatting(editor: Editor): boolean {
+	return editor
+		.chain()
+		.focus()
+		.command(({ state, tr }) => {
+			applyClearFormatting(state.schema, tr);
+			return true;
+		})
+		.run();
+}