zettelclean/src/slug.ts

// *************************************************************************
// * (C)opyright 2026         by Ruben Carlo Benante                       *
// *                                                                       *
// * This program is free software; you can redistribute it and/or modify  *
// *  it under the terms of the GNU General Public License as published by *
// *  the Free Software Foundation, either version 3 of the License, or    *
// *  (at your option) any later version.                                  *
// *                                                                       *
// * This program is distributed in the hope that it will be useful,       *
// *  but WITHOUT ANY WARRANTY; without even the implied warranty of       *
// *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        *
// *  GNU General Public License for more details.                         *
// *                                                                       *
// * You should have received a copy of the GNU General Public License     *
// *  along with this program.  If not, see http://www.gnu.org/licenses/.  *
// *                                                                       *
// * Contact author at:                                                    *
// *  Ruben Carlo Benante                                                  *
// *  rcb@beco.cc                                                          *
// *************************************************************************

// Pure string logic for zettelclean. No Obsidian imports, so it is unit-testable
// in isolation. The transform is always one-way (H1 -> filename), which lets us
// freely drop characters without worrying about a reverse mapping.

// A TIMEID is the leading run of 12 to 18 digits, ending at any non-digit or
// end-of-name (so "202607290947 test" and "202607290947-slug" both qualify).
// 12-18 because collision-avoidance may append extra digits to a 14-digit stamp.
const TIMEID_RE = /^(\d{12,18})(?=\D|$)/;

// Return the immutable id prefix, or null if this file is not a zettel.
export function extractTimeId(basename: string): string | null {
	const m = basename.match(TIMEID_RE);
	return m?.[1] ?? null;
}

// text (an H1 or a folder name) -> ASCII, case-preserving, dash-separated slug.
// Shared by the file-rename sync and the folder-slug menu.
export function generateSlug(text: string): string {
	return text
		.normalize('NFKD') // split accented letters into base + combining mark
		.replace(/[̀-ͯ]/g, '') // strip the combining marks (c-cedilla -> c)
		.replace(/[^a-zA-Z0-9]+/g, '-') // non-alphanumerics -> one dash (case kept)
		.replace(/^-+|-+$/g, ''); // trim leading/trailing dashes
}

// Reassemble; an empty slug collapses to the bare id.
export function buildFilename(id: string, slug: string): string {
	return slug ? `${id}-${slug}` : id;
}