(function () {
  'use strict';
  var STORAGE_KEY = 'focus-desk.tasks.v1';
  var PRIORITIES = ['low', 'medium', 'high'];
  var $ = function (sel, root) { return (root || document).querySelector(sel); };

  var form = $('#task-form');
  var titleInput = $('#task-title');
  var notesInput = $('#task-notes');
  var priorityInput = $('#task-priority');
  var dueInput = $('#task-due');
  var titleError = $('#title-error');
  var searchInput = $('#search');
  var statusFilter = $('#status-filter');
  var priorityFilter = $('#priority-filter');
  var list = $('#task-list');
  var emptyState = $('#empty-state');
  var emptyTitle = $('#empty-title');
  var emptyText = $('#empty-text');
  var template = $('#task-template');

  var tasks = load();
  var editingId = null;

  function load() {
    try {
      var raw = localStorage.getItem(STORAGE_KEY);
      if (!raw) return [];
      var data = JSON.parse(raw);
      if (!Array.isArray(data)) return [];
      return data.filter(function (t) {
        return t && typeof t === 'object' && typeof t.title === 'string';
      }).map(function (t) {
        return {
          id: String(t.id || uid()),
          title: t.title,
          notes: typeof t.notes === 'string' ? t.notes : '',
          priority: PRIORITIES.indexOf(t.priority) >= 0 ? t.priority : 'medium',
          due: /^\d{4}-\d{2}-\d{2}$/.test(t.due || '') ? t.due : '',
          completed: !!t.completed,
          createdAt: Number(t.createdAt) || Date.now()
        };
      });
    } catch (e) {
      console.warn('Focus Desk: could not read saved tasks, starting empty.', e);
      return [];
    }
  }

  function save() {
    try { localStorage.setItem(STORAGE_KEY, JSON.stringify(tasks)); }
    catch (e) { console.warn('Focus Desk: could not save tasks.', e); }
  }

  function uid() {
    return Date.now().toString(36) + Math.random().toString(36).slice(2, 8);
  }

  function findTask(id) {
    for (var i = 0; i < tasks.length; i++) if (tasks[i].id === id) return tasks[i];
    return null;
  }

  function todayISO() {
    var d = new Date();
    var m = String(d.getMonth() + 1).padStart(2, '0');
    var day = String(d.getDate()).padStart(2, '0');
    return d.getFullYear() + '-' + m + '-' + day;
  }

  function formatDue(due) {
    var parts = due.split('-');
    var d = new Date(Number(parts[0]), Number(parts[1]) - 1, Number(parts[2]));
    if (isNaN(d.getTime())) return due;
    return d.toLocaleDateString(undefined, { month: 'short', day: 'numeric', year: 'numeric' });
  }

  function visibleTasks() {
    var q = searchInput.value.trim().toLowerCase();
    var status = statusFilter.value;
    var prio = priorityFilter.value;
    return tasks.filter(function (t) {
      if (status === 'active' && t.completed) return false;
      if (status === 'completed' && !t.completed) return false;
      if (prio !== 'all' && t.priority !== prio) return false;
      if (q && t.title.toLowerCase().indexOf(q) < 0 && t.notes.toLowerCase().indexOf(q) < 0) return false;
      return true;
    });
  }

  function updateCounts() {
    var done = tasks.filter(function (t) { return t.completed; }).length;
    $('#count-total').textContent = tasks.length;
    $('#count-active').textContent = tasks.length - done;
    $('#count-completed').textContent = done;
  }

  function render() {
    var shown = visibleTasks();
    var today = todayISO();
    list.textContent = '';

    shown.forEach(function (t) {
      var node = template.content.firstElementChild.cloneNode(true);
      node.dataset.id = t.id;
      node.classList.toggle('done', t.completed);

      var toggle = $('.toggle', node);
      toggle.checked = t.completed;
      toggle.setAttribute('aria-label', (t.completed ? 'Mark incomplete: ' : 'Mark complete: ') + t.title);

      $('.task-title', node).textContent = t.title;
      $('.task-notes', node).textContent = t.notes;
      var badge = $('.priority', node);
      badge.textContent = t.priority;
      badge.classList.add(t.priority);
      badge.setAttribute('aria-label', 'Priority: ' + t.priority);
      var due = $('.due', node);
      if (t.due) {
        due.textContent = 'Due ' + formatDue(t.due);
        if (!t.completed && t.due < today) {
          due.classList.add('overdue');
          due.textContent += ' (overdue)';
        }
      }
      $('.edit', node).setAttribute('aria-label', 'Edit task: ' + t.title);
      $('.delete', node).setAttribute('aria-label', 'Delete task: ' + t.title);

      if (editingId === t.id) {
        $('.task-view', node).hidden = true;
        var ef = $('.task-edit', node);
        ef.hidden = false;
        $('.edit-title', ef).value = t.title;
        $('.edit-notes', ef).value = t.notes;
        $('.edit-priority', ef).value = t.priority;
        $('.edit-due', ef).value = t.due;
      }
      list.appendChild(node);
    });

    var isEmpty = shown.length === 0;
    emptyState.hidden = !isEmpty;
    if (isEmpty) {
      if (tasks.length === 0) {
        emptyTitle.textContent = 'No tasks yet';
        emptyText.textContent = 'Add your first task using the form.';
      } else {
        emptyTitle.textContent = 'No matching tasks';
        emptyText.textContent = 'Try a different search or clear the status and priority filters.';
      }
    }
    updateCounts();
  }

  form.addEventListener('submit', function (e) {
    e.preventDefault();
    var title = titleInput.value.trim();
    if (!title) {
      titleError.hidden = false;
      titleInput.setAttribute('aria-invalid', 'true');
      titleInput.focus();
      return;
    }
    titleError.hidden = true;
    titleInput.removeAttribute('aria-invalid');
    tasks.unshift({
      id: uid(),
      title: title,
      notes: notesInput.value.trim(),
      priority: PRIORITIES.indexOf(priorityInput.value) >= 0 ? priorityInput.value : 'medium',
      due: dueInput.value || '',
      completed: false,
      createdAt: Date.now()
    });
    save();
    form.reset();
    priorityInput.value = 'medium';
    render();
    titleInput.focus();
  });

  titleInput.addEventListener('input', function () {
    if (titleInput.value.trim()) {
      titleError.hidden = true;
      titleInput.removeAttribute('aria-invalid');
    }
  });

  list.addEventListener('change', function (e) {
    if (!e.target.classList.contains('toggle')) return;
    var task = findTask(e.target.closest('.task-item').dataset.id);
    if (!task) return;
    task.completed = e.target.checked;
    save();
    render();
  });

  list.addEventListener('click', function (e) {
    var btn = e.target.closest('button');
    if (!btn) return;
    var item = btn.closest('.task-item');
    var id = item.dataset.id;
    if (btn.classList.contains('edit')) {
      editingId = id;
      render();
      var input = $('.task-item[data-id="' + id + '"] .edit-title', list);
      if (input) { input.focus(); input.select(); }
    } else if (btn.classList.contains('delete')) {
      tasks = tasks.filter(function (t) { return t.id !== id; });
      if (editingId === id) editingId = null;
      save();
      render();
    } else if (btn.classList.contains('cancel')) {
      editingId = null;
      render();
      focusEditButton(id);
    }
  });

  list.addEventListener('submit', function (e) {
    e.preventDefault();
    var ef = e.target;
    if (!ef.classList.contains('task-edit')) return;
    var item = ef.closest('.task-item');
    var task = findTask(item.dataset.id);
    if (!task) return;
    var titleField = $('.edit-title', ef);
    var title = titleField.value.trim();
    if (!title) {
      titleField.setAttribute('aria-invalid', 'true');
      titleField.focus();
      return;
    }
    task.title = title;
    task.notes = $('.edit-notes', ef).value.trim();
    var p = $('.edit-priority', ef).value;
    task.priority = PRIORITIES.indexOf(p) >= 0 ? p : task.priority;
    task.due = $('.edit-due', ef).value || '';
    editingId = null;
    save();
    render();
    focusEditButton(task.id);
  });

  list.addEventListener('keydown', function (e) {
    if (e.key === 'Escape' && editingId && e.target.closest('.task-edit')) {
      var id = editingId;
      editingId = null;
      render();
      focusEditButton(id);
    }
  });

  function focusEditButton(id) {
    var btn = $('.task-item[data-id="' + id + '"] .edit', list);
    if (btn) btn.focus();
  }

  [searchInput, statusFilter, priorityFilter].forEach(function (el) {
    el.addEventListener('input', render);
    el.addEventListener('change', render);
  });

  render();
})();