(function() {
    'use strict';
    // Project-picker dropdown for the archive browser.
    //
    // In multi-project mode (HTTP source against zddc-server, OR ?projects=
    // present in the URL), this dropdown lets the user toggle which projects
    // are scanned. Toggling a checkbox updates window.app.projectFilter, pushes
    // the new ?projects= state to the URL, and triggers a re-scan.
    //
    // In single-project mode the dropdown is hidden — only one project is ever
    // in scope, so picking is meaningless.

    let isOpen = false;

    // The set of project names currently shown in the dropdown.
    function getKnownProjects() {
        if (window.app.availableProjects && window.app.availableProjects.length > 0) {
            return window.app.availableProjects.slice();
        }
        // Fall back to whatever is in the URL filter — useful when the server's
        // ProjectInfo endpoint isn't reachable but ?projects= names the set.
        return Array.from(window.app.projectFilter || []);
    }

    // Visibility-only filter: change visibleProjects, push URL state, re-render
    // UI. No rescan — already-scanned data stays in memory. URL is updated via
    // history.replaceState (same mechanism as every other UI control).
    function applyVisibility(names) {
        window.app.visibleProjects = new Set(names);
        window.app.modules.urlState.push();
        window.app.modules.app.updateUI();
        window.app.modules.filtering.applyFilters();
        renderDropdown();
    }

    function escapeHtml(text) {
        var div = document.createElement('div');
        div.textContent = text;
        return div.innerHTML;
    }

    function renderDropdown() {
        var dropdown = document.getElementById('presetDropdown');
        if (!dropdown) return;

        var selected = new Set(window.app.visibleProjects || []);
        var known = getKnownProjects().slice().sort();

        var projectsHtml = known.map(name => {
            var checked = selected.has(name) ? ' checked' : '';
            var n = escapeHtml(name);
            return '<div class="preset-project-item">'
                 +     '<label class="preset-project-label">'
                 +         '<input type="checkbox" class="preset-checkbox" data-name="' + n + '"' + checked + '>'
                 +         ' ' + n
                 +     '</label>'
                 + '</div>';
        }).join('');
        if (!projectsHtml) {
            projectsHtml = '<div class="preset-no-presets"><i>No projects available</i></div>';
        }

        dropdown.innerHTML =
            '<div class="preset-section-bottom">'
              + '<div class="preset-section-label">Projects:</div>'
              + '<div class="preset-projects-list">' + projectsHtml + '</div>'
            + '</div>';
    }

    function toggleDropdown() {
        var dropdown = document.getElementById('presetDropdown');
        if (isOpen) { closeDropdown(); return; }
        isOpen = true;
        if (dropdown) dropdown.classList.remove('hidden');
        renderDropdown();
    }

    function closeDropdown() {
        isOpen = false;
        var dropdown = document.getElementById('presetDropdown');
        if (dropdown) dropdown.classList.add('hidden');
    }

    function setupDropdownDelegation() {
        var dropdown = document.getElementById('presetDropdown');
        if (!dropdown) return;

        dropdown.addEventListener('click', function(e) {
            e.stopPropagation();
            var checkbox = e.target.closest('.preset-checkbox');
            if (!checkbox) return;
            var projectName = checkbox.getAttribute('data-name');
            if (!projectName) return;
            var sel = new Set(window.app.visibleProjects || []);
            if (checkbox.checked) sel.add(projectName);
            else sel.delete(projectName);
            applyVisibility(Array.from(sel));
        });
    }

    function setupOutsideClickHandler() {
        document.addEventListener('click', function(e) {
            var section = document.getElementById('presetSection');
            var dropdown = document.getElementById('presetDropdown');
            if (isOpen && section && dropdown && !section.contains(e.target)) {
                closeDropdown();
            }
        });
    }

    function init() {
        var section = document.getElementById('presetSection');
        if (!section) return;

        // Hide the dropdown entirely outside multi-project mode.
        if (!window.app.isMultiProject) {
            section.classList.add('hidden');
            return;
        }
        section.classList.remove('hidden');

        var btn = document.getElementById('presetBtn');
        if (!btn || btn.dataset.presetInit) return;
        btn.dataset.presetInit = '1';
        btn.title = 'Project picker';
        btn.textContent = '▾ Projects';

        btn.addEventListener('click', function(e) {
            e.stopPropagation();
            toggleDropdown();
        });

        setupDropdownDelegation();
        setupOutsideClickHandler();
    }

    window.app.modules.presets = {
        init: init,
        toggleDropdown: toggleDropdown,
        closeDropdown: closeDropdown,
        // No-op kept so existing callers (events.js after grouping-folder click)
        // don't need to null-check; preset dirty state was removed with the
        // saved-presets feature.
        checkDirty: function() {}
    };

})();