/**
 * ZDDC Classifier — lazy, multi-select directory picker (modal).
 *
 * Given one or more root directory handles, render an expandable checkbox tree
 * and let the user TICK the directories whose files they want. Ticking a
 * directory includes its whole subtree; a descendant under a ticked ancestor
 * shows as checked+disabled (covered). Confirm resolves with the TOPMOST ticked
 * handles only (a ticked child under a ticked parent is dropped — the parent's
 * recursive walk covers it). Cancel/Esc/backdrop → [].
 *
 * Handle-agnostic: a "handle" is anything exposing async `values()` (yielding
 * child handles {name, kind}) and `getDirectoryHandle(name)` — satisfied by both
 * zddc-source.js HttpDirectoryHandle and native FileSystemDirectoryHandle.
 *
 * window.app.modules.dirPicker.pick(roots) → Promise<handle[]>
 *   roots: [ { label, handle } ]
 */
(function () {
    'use strict';
    if (!window.app) window.app = {};
    if (!window.app.modules) window.app.modules = {};

    function elt(tag, cls, text) {
        var e = document.createElement(tag);
        if (cls) e.className = cls;
        if (text != null) e.textContent = text;
        return e;
    }
    // Same skip set as the archive walk: dotfiles, system (_), and risk folders.
    function hiddenName(nm) { return nm.charAt(0) === '.' || nm.charAt(0) === '_' || nm === 'rsk'; }

    function ancestorChecked(node) {
        for (var p = node.parent; p; p = p.parent) { if (p.checked) return true; }
        return false;
    }
    // Topmost ticked handles: a node whose own `checked` is set and which has no
    // checked ancestor. Pure over { checked, handle, children } — also the test seam.
    function collect(nodes, underChecked, out) {
        (nodes || []).forEach(function (n) {
            if (n.checked && !underChecked) out.push(n.handle);
            collect(n.children, underChecked || !!n.checked, out);
        });
        return out;
    }

    function pick(roots) {
        return new Promise(function (resolve) {
            var done = false, rootNodes = [];
            function finish(v) { if (done) return; done = true; document.removeEventListener('keydown', onKey); back.remove(); resolve(v); }
            function onKey(e) { if (e.key === 'Escape') finish([]); }

            var back = elt('div', 'copy-choice__backdrop');
            var box = elt('div', 'copy-choice copy-choice--wide');
            var h = elt('h3', null, 'Choose directories to scan');
            var p = elt('p', null, 'Tick the directories whose files you want in the catalog — subfolders are included. Expand with ▸.');
            var treeWrap = elt('div', 'dir-picker__tree');
            var btns = elt('div', 'copy-choice__btns');
            var go = elt('button', 'btn btn-primary', 'Scan'); go.disabled = true;
            go.addEventListener('click', function () { finish(collect(rootNodes, false, [])); });
            var cancel = elt('button', 'btn btn-secondary', 'Cancel');
            cancel.addEventListener('click', function () { finish([]); });
            btns.appendChild(go); btns.appendChild(cancel);
            box.appendChild(h); box.appendChild(p); box.appendChild(treeWrap); box.appendChild(btns);
            back.appendChild(box);
            var pressedBackdrop = false;
            back.addEventListener('mousedown', function (e) { pressedBackdrop = (e.target === back); });
            back.addEventListener('click', function (e) { if (e.target === back && pressedBackdrop) finish([]); });
            document.addEventListener('keydown', onKey);
            document.body.appendChild(back);

            function refreshGo() { go.disabled = collect(rootNodes, false, []).length === 0; }

            // Recompute the displayed checkbox state of a subtree: a node under a
            // checked ancestor is forced checked + disabled (inherited coverage).
            function recompute(node, inherited) {
                node.checkbox.disabled = inherited;
                node.checkbox.checked = inherited || node.checked;
                var below = inherited || node.checked;
                node.children.forEach(function (c) { recompute(c, below); });
            }

            function makeNode(handle, label, parent, container) {
                var node = { handle: handle, name: label, parent: parent, checked: false, expanded: false, loaded: false, children: [], childrenWrap: null, checkbox: null };
                var rowEl = elt('div', 'dir-picker__row');
                var twisty = elt('span', 'dir-picker__twisty', '▸');
                var cb = elt('input'); cb.type = 'checkbox';
                var nameEl = elt('span', 'dir-picker__name', label);
                twisty.addEventListener('click', function () { toggle(node, twisty); });
                nameEl.addEventListener('click', function () { toggle(node, twisty); });
                cb.addEventListener('change', function () {
                    if (cb.disabled) return;
                    node.checked = cb.checked;
                    recompute(node, ancestorChecked(node));
                    refreshGo();
                });
                rowEl.appendChild(twisty); rowEl.appendChild(cb); rowEl.appendChild(nameEl);
                var kids = elt('div', 'dir-picker__children'); kids.hidden = true;
                node.checkbox = cb; node.childrenWrap = kids;
                container.appendChild(rowEl); container.appendChild(kids);
                return node;
            }

            async function toggle(node, twisty) {
                node.expanded = !node.expanded;
                node.childrenWrap.hidden = !node.expanded;
                twisty.textContent = node.expanded ? '▾' : '▸';
                if (node.expanded && !node.loaded) {
                    node.loaded = true;
                    twisty.textContent = '…';
                    try {
                        for await (var e of node.handle.values()) {
                            if (e.kind !== 'directory') continue;
                            var nm = String(e.name).replace(/\/$/, '');
                            if (hiddenName(nm)) continue;
                            var childHandle = e.getDirectoryHandle ? e : await node.handle.getDirectoryHandle(nm);
                            var child = makeNode(childHandle, nm, node, node.childrenWrap);
                            node.children.push(child);
                        }
                    } catch (err) {
                        node.childrenWrap.appendChild(elt('div', 'dir-picker__err', 'Could not read — ' + (err.message || err)));
                    }
                    twisty.textContent = node.children.length ? (node.expanded ? '▾' : '▸') : '·';
                    // A freshly-loaded subtree inherits an already-checked ancestor.
                    recompute(node, ancestorChecked(node));
                }
            }

            (roots || []).forEach(function (r) { rootNodes.push(makeNode(r.handle, r.label, null, treeWrap)); });
            if (!rootNodes.length) finish([]);
        });
    }

    window.app.modules.dirPicker = {
        pick: pick,
        _collect: function (nodes) { return collect(nodes, false, []); },   // test seam
    };
})();