// @ts-check
/**
 * A record of the singular events of a session in the browser's console
 * (F12), for finding faults: pages, images, notebook pages, exports, the
 * co-host right, the connection, and what the input device delivers.
 * Nothing continuous goes here (Andy, 2026-10-08).
 *
 * Since 2026-10-10 the same record, plus a trace of the input events
 * (every press, release and cancellation, not the movement between), is
 * kept in memory and shown in the Session window with a Copy button, so
 * that a guest on a tablet, with no console to open, can send it when
 * the pen misbehaves (Andy's iPad, where the Pencil stopped for a while
 * now and then).
 */

/** How many entries are kept; the oldest go first. */
const KEPT = 400;

/** @type {string[]} */
const entries = [];
/** @type {(() => void) | null}  Told of every new entry. */
let listener = null;

/** @returns {string}  The time to the millisecond, HH:MM:SS.mmm. */
function now() {
  const date = new Date();
  const two = (/** @type {number} */ n) => String(n).padStart(2, '0');
  return `${two(date.getHours())}:${two(date.getMinutes())}:${two(date.getSeconds())}.` +
         String(date.getMilliseconds()).padStart(3, '0');
}

/** @param {string} what */
function keep(what) {
  entries.push(`${now()} ${what}`);
  if (entries.length > KEPT) entries.shift();
  listener?.();
}

/** A singular event: the console and the record. @param {string} what */
export function log(what) {
  console.log(`Kokkoja ${new Date().toLocaleTimeString()}: ${what}`);
  keep(what);
}

/** An input event: the record only. @param {string} what */
export function trace(what) {
  keep(what);
}

/** @returns {string}  The record, one entry a line. */
export function logText() {
  return entries.join('\n');
}

/** @param {(() => void) | null} onEntry  Called at every new entry. */
export function watchLog(onEntry) {
  listener = onEntry;
}