// @ts-check
/**
 * The manual that the interface already carries: every control's tooltip
 * (`data-help`), gathered from the page and written as plain text under
 * the title "User interface actions": the controls in alphabetical
 * order, each one's name on a line, its explanation on the next lines,
 * wrapped at WIDTH columns, and a blank line after (Andy, 2026-10-14:
 * Ctrl-click on Help shows it; a first form as Klammertext was replaced
 * by this the same day).
 */

export const TITLE = 'User interface actions';
export const WIDTH = 80;

/**
 * What a control is called: the name it gives for this text, when its
 * label changes (`data-name`; the Shape button is named for the shape it
 * draws at the moment); a button's label; a label's own text, without
 * its checkbox; else the name given for assistive technology, the text of
 * the label that points at the control, or its id.
 * @param {Element} el
 * @returns {string}
 */
function nameOf(el) {
  const given = el.getAttribute('data-name');
  if (given) return given;
  if (el instanceof HTMLLabelElement) {
    return [...el.childNodes].filter((n) => n.nodeType === Node.TEXT_NODE)
      .map((n) => n.textContent?.trim() ?? '').join(' ').trim();
  }
  const text = el instanceof HTMLButtonElement ? el.textContent?.trim() ?? '' : '';
  const labelFor = el.id ? el.ownerDocument.querySelector(`label[for="${el.id}"]`) : null;
  return text || el.getAttribute('aria-label') || labelFor?.textContent?.trim() || el.id.replace(/_/g, ' ');
}

/**
 * Where a control is, for telling two of the same name apart ("Copy" in
 * the Session window's Invitation and Log parts): the nearest heading
 * above it within its window, else the window's title, else the
 * toolbar.
 * @param {Element} el
 * @returns {string}
 */
function contextOf(el) {
  const scope = el.closest('dialog, main, .toolbar');
  if (!scope) return '';
  let context = '';
  for (const heading of scope.querySelectorAll('h1, h2, h3')) {
    if (heading.compareDocumentPosition(el) & Node.DOCUMENT_POSITION_FOLLOWING) {
      context = heading.textContent?.trim() ?? '';
    }
  }
  return context || (scope.classList.contains('toolbar') ? 'Toolbar' : '');
}

/**
 * The entries: every control with an explanation, except the manual's
 * own window; controls that differ only by a number or a colour (the
 * line widths, the swatches) are one entry, named by what their names
 * share; a name that two controls share gets each one's context before
 * it, "Invitation: Copy" (Andy, 2026-10-14).  In alphabetical order of
 * the names.
 * @param {Document | Element} doc
 * @returns {[string, string][]}  Name and explanation.
 */
export function manualEntries(doc) {
  /** @type {Map<string, {names: string[], contexts: string[], help: string}>} */
  const byKey = new Map();
  for (const el of doc.querySelectorAll('[data-help]')) {
    if (el.closest('#manual_dialog')) continue;
    const help = el.getAttribute('data-help') ?? '';
    const key = help.replace(/\d+(?:\.\d+)?/g, '#');
    const entry = byKey.get(key);
    if (entry) {
      entry.names.push(nameOf(el));
      entry.contexts.push(contextOf(el));
    } else {
      byKey.set(key, { names: [nameOf(el)], contexts: [contextOf(el)], help });
    }
  }
  const named = [...byKey.values()].map(({ names, contexts, help }) =>
    ({ name: names.length > 1 ? commonStart(names) : names[0], context: contexts[0], help }));
  const counts = new Map();
  for (const { name } of named) counts.set(name, (counts.get(name) ?? 0) + 1);
  /** @type {[string, string][]} */
  const entries = named.map(({ name, context, help }) =>
    [(counts.get(name) ?? 0) > 1 && context ? `${context}: ${name}` : name, help]);
  return entries.sort((a, b) => a[0].localeCompare(b[0], undefined, { sensitivity: 'base' }) || a[1].localeCompare(b[1]));
}

/**
 * The words that names share at their start ("Color #000000", "Color
 * #d32f2f" share "Color"); the first name when they share nothing.
 * @param {string[]} names
 * @returns {string}
 */
function commonStart(names) {
  const words = names[0].split(' ');
  let n = words.length;
  for (const name of names.slice(1)) {
    const other = name.split(' ');
    let i = 0;
    while (i < n && i < other.length && other[i] === words[i]) i += 1;
    n = i;
  }
  return n > 0 ? words.slice(0, n).join(' ') : names[0];
}

/**
 * The text filled into lines of at most `width` characters, broken at
 * spaces; a word longer than a line stands alone on one.
 * @param {string} text
 * @param {number} width
 * @returns {string}
 */
export function wrap(text, width) {
  const lines = [];
  let line = '';
  for (const word of text.split(/\s+/).filter(Boolean)) {
    if (line && line.length + 1 + word.length > width) {
      lines.push(line);
      line = word;
    } else {
      line = line ? `${line} ${word}` : word;
    }
  }
  if (line) lines.push(line);
  return lines.join('\n');
}

/**
 * The manual as plain text.
 * @param {Document | Element} doc
 * @returns {string}
 */
export function manualText(doc) {
  const blocks = manualEntries(doc).map(([name, help]) => `${name}\n${wrap(help, WIDTH)}\n`);
  return `${TITLE}\n\n${blocks.join('\n')}`;
}