/*
 * Copyright (C) 2026 Mateusz Gruszczyński @linuxiarz.pl
 * Source-Available Code / Dual-Licensed.
 *
 * Free for non-commercial and evaluation use under terms of BSL/GPLv3.
 * Commercial or production use requires a valid paid license.
 * See LICENSE file in repository root for details.
 */

const LINE_HASH = /^#L([1-9]\d*)$/i;

export function lineFromHash(hash, lineCount = Number.POSITIVE_INFINITY) {
  const match = LINE_HASH.exec(String(hash || ""));
  if (!match) return null;
  const line = Number(match[1]);
  if (!Number.isSafeInteger(line) || line > lineCount) return null;
  return line;
}

export function lineStartOffset(text, line) {
  const target = Number(line);
  if (!Number.isSafeInteger(target) || target < 1) return null;
  if (target === 1) return 0;

  let currentLine = 1;
  for (let index = 0; index < text.length; index += 1) {
    if (text.charCodeAt(index) !== 10) continue;
    currentLine += 1;
    if (currentLine === target) return index + 1;
  }
  return null;
}

export function lineLink(href, line) {
  const target = Number(line);
  if (!Number.isSafeInteger(target) || target < 1) throw new TypeError("Invalid line number");
  const url = new URL(href);
  url.hash = `L${target}`;
  return url.href;
}