/*
 * ShrinkVertically -- "Auto adjust" mode. Measure the collapsed board live and set the
 * --sv-shrink-offset CSS variable so the columns exactly fill the remaining viewport and the
 * native right-side vertical scrollbar is not needed. Loaded only when the setting is on
 * (Settings -> Shrink Vertically); it overrides the static offset injected by layout/variable.php.
 *
 * The collapsed column height is calc(100vh - var(--sv-shrink-offset)). To fit the screen we need:
 *     offset = (task-list top, i.e. the chrome above) + (horizontal scrollbar below) + a small margin
 * so column_bottom + scrollbar stays within the viewport. Both terms are measured from the DOM, so
 * this adapts to any screen size, theme, or header height.
 *
 * Re-measures on resize, on collapse/expand (a class toggle), and after a board refresh
 * (BoardDragAndDrop replaces #board-container -- so, like the other plugins, the observer is bound
 * to the STABLE parent, not to the container that gets swapped out).
 */
(function () {
    "use strict";

    var BOTTOM_MARGIN = 16; // breathing room below the columns
    var scheduled = false;

    function apply() {
        scheduled = false;

        var list = document.querySelector("#board .board-task-list.board-task-list-compact");

        if (! list) {
            return; // board not collapsed -> nothing to auto-size
        }

        var top = list.getBoundingClientRect().top;
        var container = document.getElementById("board-container");
        var bar = container ? (container.offsetHeight - container.clientHeight) : 0; // horizontal scrollbar

        if (bar < 0) {
            bar = 0;
        }

        var offset = Math.ceil(top + bar + BOTTOM_MARGIN);

        if (offset < 0) {
            offset = 0;
        }

        var next = offset + "px";
        var root = document.documentElement;

        // Only write when it actually changes, so mid-drag class churn does not thrash layout.
        if (root.style.getPropertyValue("--sv-shrink-offset") !== next) {
            root.style.setProperty("--sv-shrink-offset", next);
        }
    }

    function schedule() {
        if (! scheduled) {
            scheduled = true;
            window.requestAnimationFrame(apply);
        }
    }

    function init() {
        var container = document.getElementById("board-container");

        if (! container) {
            return; // not a board page
        }

        schedule();
        window.addEventListener("resize", schedule);

        if (window.MutationObserver && container.parentNode) {
            new MutationObserver(schedule).observe(container.parentNode, {
                childList: true,
                subtree: true,
                attributes: true,
                attributeFilter: ["class"]
            });
        }
    }

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