/*
 * OrganonTweaks -- keep the board's horizontal scroll position across refreshes.
 *
 * When you drop a card (and on Kanboard's periodic AJAX polling) the board is rebuilt with
 * `$("#board-container").replaceWith(data)` (BoardDragAndDrop.refresh). The brand-new
 * element starts at scrollLeft 0, so the board snaps back to the first column -- a jarring
 * jump. This remembers the last scroll position and restores it the moment a replacement
 * container appears, so the view stays put.
 *
 * We observe the STABLE parent (the container itself is replaced) and read the scroll from
 * whichever #board-container is current, so it keeps working after every rebuild.
 */
(function () {
    "use strict";

    function init() {
        var container = document.getElementById("board-container");
        if (!container) {
            return;
        }

        var parent = container.parentNode;
        var lastScrollLeft = container.scrollLeft;
        var lastContainer = container;

        // Remember the position whenever the board is scrolled (capture: scroll does not
        // bubble, and this survives the container being replaced).
        document.addEventListener("scroll", function (e) {
            var c = document.getElementById("board-container");
            if (c && e.target === c) {
                lastScrollLeft = c.scrollLeft;
            }
        }, true);

        // When the board is rebuilt, #board-container becomes a new element at scrollLeft 0;
        // restore the remembered position before the browser paints it.
        if (window.MutationObserver) {
            new MutationObserver(function () {
                var c = document.getElementById("board-container");
                if (c && c !== lastContainer) {
                    lastContainer = c;
                    if (c.scrollLeft !== lastScrollLeft) {
                        c.scrollLeft = lastScrollLeft;
                    }
                }
            }).observe(parent, { childList: true });
        }
    }

    if (document.readyState === "loading") {
        document.addEventListener("DOMContentLoaded", init);
    } else {
        init();
    }
})();