/*
 * Markdown page-outline calculations.
 *
 * This module recognizes source headings and assigns stable HTML identifiers.
 * It has no application state and does not inspect or modify the DOM.
 */

/**
 * goal   : Produce a unique HTML identifier for a rendered heading.
 * pre    : usedIds contains identifiers already assigned within the document.
 * post   : The returned identifier is added to usedIds.
 * result : A readable normalized identifier, with a numeric suffix if needed.
 */
function headingId(text, usedIds) {
  const base = String(text || "")
    .trim()
    .toLocaleLowerCase()
    .normalize("NFKD")
    .replace(/[\u0300-\u036f]/g, "")
    .replace(/[^\p{L}\p{N}]+/gu, "-")
    .replace(/^-+|-+$/g, "") || "section";
  let id = base;
  let number = 2;

  while (usedIds.has(id)) {
    id = `${base}-${number}`;
    number += 1;
  }
  usedIds.add(id);
  return id;
}

/**
 * goal   : Extract ATX headings and their source locations from Markdown.
 * pre    : markdown is source text and may contain fenced code blocks.
 * post   : The source is not changed; headings inside fences are ignored.
 * result : Ordered level/text/line records for the document outline.
 */
function markdownHeadings(markdown) {
  const headings = [];
  const lines = String(markdown || "").replace(/\r\n/g, "\n").split("\n");
  const fencePattern = /^\s*(```|~~~)/;
  let inFence = false;

  for (let lineNumber = 0; lineNumber < lines.length; lineNumber += 1) {
    const line = lines[lineNumber];
    if (fencePattern.test(line)) {
      inFence = !inFence;
      continue;
    }
    if (inFence) continue;

    const match = line.match(/^\s{0,3}(#{1,6})\s+(.+?)\s*#*\s*$/);
    if (!match) continue;
    headings.push({
      level: match[1].length,
      text: match[2].trim(),
      line: lineNumber
    });
  }
  return headings;
}

export { headingId, markdownHeadings };