[Feature] Provide a way to "patch" the current markdown without doing a full replace (to maintain a coherent cursor position)

import { editorViewCtx, parserCtx } from "@milkdown/kit/core";
import { computeDocDiff } from "@milkdown/plugin-diff";
import type { EditorView } from "@milkdown/prose/view";

/**
 * Applies a semantic patch to the current Milkdown document.
 *
 * Uses Milkdown's block-level LCS diff with per-block ChangeSet merging so
 * edits are as small as possible (preserving cursor position when mapping allows).
 *
 * Returns true if a transaction was dispatched.
 */
export function patchMarkdown(
    editor: { action: (action: (ctx: any) => unknown) => unknown },
    newMarkdown: string,
): boolean {
    return editor.action((ctx) => {
        const view: EditorView = ctx.get(editorViewCtx);
        const parser = ctx.get(parserCtx);

        const oldDoc = view.state.doc;
        const newDoc = parser(newMarkdown);

        if (oldDoc.eq(newDoc)) {
            return false;
        }

        const changes = computeDocDiff(oldDoc, newDoc);
        if (changes.length === 0) {
            return false;
        }

        let tr = view.state.tr;

        for (let i = changes.length - 1; i >= 0; i--) {
            const change = changes[i]!;
            const newContent = newDoc.slice(change.fromB, change.toB);
            tr = tr.replace(change.fromA, change.toA, newContent);
        }

        if (!tr.docChanged) {
            return false;
        }

        tr.setSelection(view.state.selection.map(tr.doc, tr.mapping));
        view.dispatch(tr);
        return true;
    }) as boolean;
}