// --- Basic Todo Model ---
const STORAGE_KEY = 'todos-v1';
const CATEGORY_KEY = 'todo-categories';
let todos = [];
let categories = [];

function loadTodos() {
    todos = JSON.parse(localStorage.getItem(STORAGE_KEY) || '[]');
    categories = JSON.parse(localStorage.getItem(CATEGORY_KEY) || '[]');
}

function saveTodos() {
    localStorage.setItem(STORAGE_KEY, JSON.stringify(todos));
    localStorage.setItem(CATEGORY_KEY, JSON.stringify(categories));
}

function getNextId() {
    return todos.length ? Math.max(...todos.map(t => t.id)) + 1 : 1;
}

function renderForm() {
    const form = document.getElementById('todo-form');
    form.innerHTML = `
      <div class="form-section">
        <label for="task">Task Description</label>
        <input type="text" id="task" placeholder="Task Description" required>
      </div>

      <div class="form-section grid-3">
        <div>
          <label for="creation-date">Creation Date</label>
          <input type="date" id="creation-date" title="Creation Date">
        </div>
        <div>
          <label for="next-date">Next Planned Work Date</label>
          <input type="date" id="next-date" title="Next Planned Work Date">
        </div>
        <div>
          <label for="due-date">Due Date</label>
          <input type="date" id="due-date" title="Due Date">
        </div>
      </div>

      <div class="form-section grid-3">
        <div>
          <label for="status">Status</label>
          <select id="status">
            <option value="">(Blank)</option>
            <option value="Busy">Busy</option>
            <option value="Done">Done</option>
            <option value="W4A">W4A</option>
          </select>
        </div>
        <div>
          <label for="urgent">Urgent (1-7)</label>
          <input type="number" id="urgent" min="1" max="7" placeholder="Urgent (1-7)">
        </div>
        <div>
          <label for="importance">Importance (1-7)</label>
          <input type="number" id="importance" min="1" max="7" placeholder="Importance (1-7)">
        </div>
      </div>

      <div class="form-section grid-2">
        <div>
          <label for="time-estimation">Time Estimation (min)</label>
          <input type="number" id="time-estimation" min="0" placeholder="Time Est. (min)">
        </div>
        <div>
          <label for="actual-time">Actual Time Spent (min)</label>
          <input type="number" id="actual-time" min="0" placeholder="Actual Time (min)">
        </div>
      </div>

      <div class="form-section grid-2">
        <div>
          <label for="category">Category</label>
          <input type="text" id="category" placeholder="Category" list="category-list">
          <datalist id="category-list"></datalist>
        </div>
        <div>
          <label for="linked-tasks">Link with other tasks (IDs, comma separated)</label>
          <input type="text" id="linked-tasks" placeholder="Link with other tasks (IDs, comma separated)">
        </div>
      </div>

      <div class="form-section grid-2">
        <div>
          <label for="coms">Coms URL</label>
          <input type="url" id="coms" placeholder="Coms URL">
        </div>
        <div>
          <label for="link">Link URL</label>
          <input type="url" id="link" placeholder="Link URL">
        </div>
      </div>

      <div class="form-section">
        <label for="comments">Comments</label>
        <textarea id="comments" placeholder="Comments"></textarea>
      </div>

      <button type="submit" class="add-todo-btn">Add Todo</button>
    `;
    // Autocomplete for categories
    const datalist = document.getElementById('category-list');
    datalist.innerHTML = categories.map(cat => `<option value="${cat}">`).join('');
    // Ensure addTodo is always bound after form render
    form.removeEventListener('submit', addTodo); // prevent duplicates
    form.addEventListener('submit', addTodo);
}

let sortState = { column: null, asc: true };

const sortableColumns = [
  { key: 'id', label: 'ID' },
  { key: 'task', label: 'Description' },
  { key: 'creationDate', label: 'Creation Date' },
  { key: 'nextDate', label: 'Next Date' },
  { key: 'dueDate', label: 'Due Date' },
  { key: 'urgent', label: 'Urgent' },
  { key: 'importance', label: 'Importance' },
  { key: 'prio', label: 'Prio' }
];

function sortTodos(column) {
  if (sortState.column === column) {
    sortState.asc = !sortState.asc;
  } else {
    sortState.column = column;
    sortState.asc = true;
  }
  todos.sort((a, b) => {
    let valA = a[column];
    let valB = b[column];
    // For date columns, compare as dates
    if (["creationDate","nextDate","dueDate"].includes(column)) {
      valA = valA || '';
      valB = valB || '';
      return sortState.asc ? valA.localeCompare(valB) : valB.localeCompare(valA);
    } else if (typeof valA === 'string') {
      return sortState.asc ? valA.localeCompare(valB) : valB.localeCompare(valA);
    } else {
      return sortState.asc ? valA - valB : valB - valA;
    }
  });
  renderTodos();
}

function formatDisplayDate(dateStr) {
  if (!dateStr) return '';
  // Accepts YYYY-MM-DD or ISO string
  let d = dateStr.length > 10 ? new Date(dateStr) : null;
  let year, month, day;
  if (d && !isNaN(d)) {
    year = d.getFullYear().toString().slice(-2);
    month = String(d.getMonth() + 1).padStart(2, '0');
    day = String(d.getDate()).padStart(2, '0');
  } else if (/^\d{4}-\d{2}-\d{2}/.test(dateStr)) {
    year = dateStr.slice(2,4);
    month = dateStr.slice(5,7);
    day = dateStr.slice(8,10);
  } else {
    return dateStr;
  }
  return `${day}-${month}-${year}`;
}

function renderTodos() {
  const list = document.getElementById('todos-list');
  if (!todos.length) {
    list.innerHTML = '<em>No todos yet.</em>';
    return;
  }
  const columns = [
    { key: 'id', label: 'ID', sortable: true },
    { key: 'task', label: 'Description', sortable: true },
    { key: 'creationDate', label: 'Creation Date', sortable: true },
    { key: 'nextDate', label: 'Next Date', sortable: true },
    { key: 'dueDate', label: 'Due Date', sortable: true },
    { key: 'status', label: 'Status' },
    { key: 'urgent', label: 'Urgent', sortable: true },
    { key: 'importance', label: 'Importance', sortable: true },
    { key: 'prio', label: 'Prio', sortable: true },
    { key: 'timeEstimation', label: 'Time Est. (min)' },
    { key: 'actualTime', label: 'Actual Time (min)' },
    { key: 'category', label: 'Category' },
    { key: 'coms', label: 'Coms' },
    { key: 'link', label: 'Link' },
    { key: 'comments', label: 'Comments' },
    { key: 'linkedTasks', label: 'Linked Tasks' },
  ];
  list.innerHTML = `
    <div class="table-responsive">
      <table class="todos-table">
        <thead>
          <tr>
            ${columns.map(col =>
              col.sortable ?
                `<th class="sortable" data-col="${col.key}">${col.label} ${sortState.column === col.key ? (sortState.asc ? '▲' : '▼') : ''}</th>` :
                `<th>${col.label}</th>`
            ).join('')}
          </tr>
        </thead>
        <tbody>
          ${todos.map((todo, rowIdx) => `
            <tr>
              ${columns.map(col => renderEditableCell(todo, col.key, rowIdx)).join('')}
            </tr>
          `).join('')}
        </tbody>
      </table>
    </div>
  `;
  // Add sorting event listeners
  document.querySelectorAll('.todos-table th.sortable').forEach(th => {
    th.addEventListener('click', () => sortTodos(th.dataset.col));
  });
  // Add modal editing listeners
  document.querySelectorAll('.todos-table td[data-editable="true"]').forEach(td => {
    td.addEventListener('click', function(e) {
      const rowIdx = +td.dataset.row;
      const key = td.dataset.key;
      if (window.showEditTodoModal) {
        window.showEditTodoModal(rowIdx, key);
      }
    });
  });
}

function renderEditableCell(todo, key, rowIdx) {
  // Non-editable fields: id, prio
  const nonEditable = ['id', 'prio'];
  // Editable fields
  const editable = [
    'task', 'creationDate', 'nextDate', 'dueDate', 'status', 'urgent', 'importance',
    'timeEstimation', 'actualTime', 'category', 'coms', 'link', 'comments', 'linkedTasks'
  ];
  let value = todo[key] || '';
  if (["creationDate","nextDate","dueDate"].includes(key)) {
    value = formatDisplayDate(todo[key]);
  }
  if (key === 'coms' && value) value = `<a href="${value}" target="_blank">Link</a>`;
  if (key === 'link' && value) value = `<a href="${value}" target="_blank">Link</a>`;
  if (key === 'status') return `<td class="status-${todo.status || 'blank'}" data-editable="true" data-row="${rowIdx}" data-key="${key}">${todo.status || ''}</td>`;
  if (nonEditable.includes(key)) return `<td>${todo[key]}</td>`;
  return `<td data-editable="true" data-row="${rowIdx}" data-key="${key}">${value}</td>`;
}

function handleCellEdit(e) {
  const td = e.currentTarget;
  const rowIdx = +td.dataset.row;
  const key = td.dataset.key;
  const todo = todos[rowIdx];
  let input;
  let oldValue = todo[key] || '';

  // Helper to format date as YYYY-MM-DD
  function formatDate(val) {
    if (!val) return '';
    if (val.length === 10 && val.match(/^\d{4}-\d{2}-\d{2}$/)) return val;
    const d = new Date(val);
    if (isNaN(d)) return '';
    return d.toISOString().slice(0, 10);
  }

  if (["creationDate","nextDate","dueDate"].includes(key)) {
    input = document.createElement('input');
    input.type = 'date';
    input.value = formatDate(oldValue);
    let changed = false;
    input.addEventListener('change', () => {
      changed = true;
      saveCellEdit(td, rowIdx, key, input.value);
    });
    input.addEventListener('blur', () => {
      // If the user clicked the date picker, allow change to fire first
      setTimeout(() => {
        if (!changed) saveCellEdit(td, rowIdx, key, input.value);
      }, 150);
    });
  } else if (["urgent","importance","timeEstimation","actualTime"].includes(key)) {
    input = document.createElement('input');
    input.type = 'number';
    input.value = oldValue;
    if (["urgent","importance"].includes(key)) {
      input.min = 1; input.max = 7;
    }
    if (["timeEstimation","actualTime"].includes(key)) {
      input.min = 0;
    }
    // Save on both change (for arrows) and blur (for manual input)
    input.addEventListener('change', () => saveCellEdit(td, rowIdx, key, input.value));
    input.addEventListener('blur', () => saveCellEdit(td, rowIdx, key, input.value));
    input.addEventListener('keydown', (evt) => {
      if (evt.key === 'Enter') {
        evt.preventDefault();
        input.blur();
      }
    });
  } else if (key === 'status') {
    input = document.createElement('select');
    ['','Busy','Done','W4A'].forEach(opt => {
      const option = document.createElement('option');
      option.value = opt;
      option.text = opt || '(Blank)';
      if (opt === oldValue) option.selected = true;
      input.appendChild(option);
    });
    input.addEventListener('change', () => saveCellEdit(td, rowIdx, key, input.value));
  } else if (key === 'category') {
    input = document.createElement('input');
    input.type = 'text';
    input.value = oldValue;
    input.setAttribute('list','category-list');
    input.addEventListener('keydown', (evt) => {
      if (evt.key === 'Enter') {
        evt.preventDefault();
        input.blur();
      }
    });
  } else if (key === 'comments' || key === 'linkedTasks') {
    input = document.createElement('textarea');
    input.value = oldValue;
    input.addEventListener('keydown', (evt) => {
      if (evt.key === 'Enter' && !evt.shiftKey) {
        evt.preventDefault();
        input.blur();
      }
    });
  } else {
    input = document.createElement('input');
    input.type = 'text';
    input.value = oldValue;
    input.addEventListener('keydown', (evt) => {
      if (evt.key === 'Enter') {
        evt.preventDefault();
        input.blur();
      }
    });
  }
  input.className = 'table-edit-input';
  td.innerHTML = '';
  td.appendChild(input);
  // For date input, ensure the picker opens
  if (["creationDate","nextDate","dueDate"].includes(key)) {
    setTimeout(() => {
      input.focus();
      if (typeof input.showPicker === 'function') {
        input.showPicker();
      }
    }, 0);
    // For date fields, do NOT save or close on blur at all—only on change
  } else {
    input.focus();
    input.addEventListener('blur', () => saveCellEdit(td, rowIdx, key, input.value));
  }
}


function saveCellEdit(td, rowIdx, key, value) {
  // Type conversions
  if (["urgent","importance","timeEstimation","actualTime"].includes(key)) {
    value = parseInt(value) || 0;
  }
  if (["creationDate","nextDate","dueDate"].includes(key)) {
    value = value || '';
  }
  if (key === 'category') {
    if (value && !categories.includes(value)) {
      categories.push(value);
    }
  }
  todos[rowIdx][key] = value;
  // Recalculate prio if urgency or importance changed
  if (key === 'urgent' || key === 'importance') {
    todos[rowIdx].prio = (parseInt(todos[rowIdx].urgent) || 1) * (parseInt(todos[rowIdx].importance) || 1);
  }
  saveTodos();
  renderTodos();
}


function addTodo(e) {
    e.preventDefault();
    const task = document.getElementById('task').value.trim();
    const creationDate = document.getElementById('creation-date').value || new Date().toISOString().slice(0,10);
    const nextDate = document.getElementById('next-date').value;
    const dueDate = document.getElementById('due-date').value;
    const status = document.getElementById('status').value;
    const urgent = parseInt(document.getElementById('urgent').value) || 1;
    const importance = parseInt(document.getElementById('importance').value) || 1;
    const prio = urgent * importance;
    const timeEstimation = parseInt(document.getElementById('time-estimation').value) || 0;
    const actualTime = parseInt(document.getElementById('actual-time').value) || 0;
    let category = document.getElementById('category').value.trim();
    if (category && !categories.includes(category)) {
        categories.push(category);
    }
    const coms = document.getElementById('coms').value.trim();
    const link = document.getElementById('link').value.trim();
    const comments = document.getElementById('comments').value.trim();
    const linkedTasks = document.getElementById('linked-tasks').value.trim();
    const todo = {
        id: getNextId(),
        creationDate,
        nextDate,
        dueDate,
        status,
        urgent,
        importance,
        prio,
        timeEstimation,
        actualTime,
        category,
        task,
        coms,
        link,
        comments,
        linkedTasks
    };
    todos.push(todo);
    saveTodos();
    renderForm();
    renderTodos();
    document.getElementById('todo-form').reset();
}

function switchTab(tab) {
  document.querySelectorAll('.tab-btn').forEach(btn => btn.classList.remove('active'));
  document.querySelectorAll('.tab-content').forEach(tc => tc.classList.remove('active'));
  if (tab === 'list') {
    document.getElementById('tab-list-btn').classList.add('active');
    document.getElementById('tab-content-list').classList.add('active');
  } else if (tab === 'form') {
    document.getElementById('tab-form-btn').classList.add('active');
    document.getElementById('tab-content-form').classList.add('active');
  } else if (tab === 'admin') {
    document.getElementById('tab-admin-btn').classList.add('active');
    document.getElementById('tab-content-admin').classList.add('active');
  }
}

function init() {
  loadTodos();
  renderForm();
  renderTodos();
  document.getElementById('tab-list-btn').addEventListener('click', () => switchTab('list'));
  document.getElementById('tab-form-btn').addEventListener('click', () => switchTab('form'));
  const adminBtn = document.getElementById('tab-admin-btn');
  if (adminBtn) adminBtn.addEventListener('click', () => switchTab('admin'));

  // --- Password Modal Helper ---
  function showPasswordModal({title, confirm=false}) {
    return new Promise((resolve, reject) => {
      const modal = document.getElementById('password-modal');
      const titleEl = document.getElementById('password-modal-title');
      const input = document.getElementById('password-modal-input');
      const confirmInput = document.getElementById('password-modal-confirm');
      const okBtn = document.getElementById('password-modal-ok');
      const cancelBtn = document.getElementById('password-modal-cancel');
      const errorEl = document.getElementById('password-modal-error');
      titleEl.textContent = title;
      input.value = '';
      confirmInput.value = '';
      errorEl.style.display = 'none';
      confirmInput.style.display = confirm ? '' : 'none';
      modal.style.display = 'flex';
      input.focus();
      function cleanup() {
        modal.style.display = 'none';
        okBtn.onclick = null;
        cancelBtn.onclick = null;
        input.onkeydown = null;
        confirmInput.onkeydown = null;
      }
      okBtn.onclick = () => {
        const pw = input.value;
        if (confirm) {
          const pw2 = confirmInput.value;
          if (!pw || !pw2) {
            errorEl.textContent = 'Please enter and confirm your password.';
            errorEl.style.display = 'block';
            return;
          }
          if (pw !== pw2) {
            errorEl.textContent = 'Passwords do not match.';
            errorEl.style.display = 'block';
            return;
          }
        } else {
          if (!pw) {
            errorEl.textContent = 'Please enter your password.';
            errorEl.style.display = 'block';
            return;
          }
        }
        cleanup();
        resolve(pw);
      };
      cancelBtn.onclick = () => { cleanup(); reject('cancel'); };
      input.onkeydown = e => { if (e.key === 'Enter') okBtn.onclick(); };
      confirmInput.onkeydown = e => { if (e.key === 'Enter') okBtn.onclick(); };
    });
  }

  // --- Encryption helpers ---
  async function getKeyFromPassword(password, salt) {
    const enc = new TextEncoder();
    const keyMaterial = await window.crypto.subtle.importKey(
      'raw', enc.encode(password), {name: 'PBKDF2'}, false, ['deriveKey']);
    return window.crypto.subtle.deriveKey(
      {name: 'PBKDF2', salt, iterations: 100000, hash: 'SHA-256'},
      keyMaterial,
      {name: 'AES-GCM', length: 256},
      false,
      ['encrypt', 'decrypt']
    );
  }
  async function encryptData(data, password) {
    const enc = new TextEncoder();
    const salt = window.crypto.getRandomValues(new Uint8Array(16));
    const iv = window.crypto.getRandomValues(new Uint8Array(12));
    const key = await getKeyFromPassword(password, salt);
    const ciphertext = await window.crypto.subtle.encrypt(
      {name: 'AES-GCM', iv},
      key,
      enc.encode(data)
    );
    // Output as base64: salt + iv + ciphertext
    function toB64(buf) { return btoa(String.fromCharCode(...new Uint8Array(buf))); }
    return toB64(salt) + ':' + toB64(iv) + ':' + toB64(ciphertext);
  }
  async function decryptData(b64, password) {
    function fromB64(b64) { return Uint8Array.from(atob(b64), c => c.charCodeAt(0)); }
    const [saltB64, ivB64, ctB64] = b64.split(':');
    const salt = fromB64(saltB64);
    const iv = fromB64(ivB64);
    const ciphertext = fromB64(ctB64);
    const key = await getKeyFromPassword(password, salt);
    const dec = new TextDecoder();
    const plaintext = await window.crypto.subtle.decrypt(
      {name: 'AES-GCM', iv},
      key,
      ciphertext
    );
    return dec.decode(plaintext);
  }

  // Export JSON (password-protected)
  const exportBtn = document.getElementById('export-json-btn');
  if (exportBtn) exportBtn.addEventListener('click', async () => {
    let password;
    try {
      password = await showPasswordModal({title: 'Set Export Password', confirm: true});
    } catch { return; }
    if (!password) return;
    const data = {
      todos,
      categories
    };
    const json = JSON.stringify(data, null, 2);
    try {
      const encrypted = await encryptData(json, password);
      const blob = new Blob([encrypted], {type: 'application/json'});
      const url = URL.createObjectURL(blob);
      const a = document.createElement('a');
      a.href = url;
      a.download = 'todos-export.json';
      document.body.appendChild(a);
      a.click();
      setTimeout(() => {
        document.body.removeChild(a);
        URL.revokeObjectURL(url);
      }, 100);
      // Optionally show in <pre>
      const pre = document.getElementById('export-json-output');
      if (pre) {
        pre.style.display = 'block';
        pre.textContent = encrypted;
      }
    } catch (err) {
      alert('Encryption failed: ' + err.message);
    }
  });

  // Import JSON (password-protected)
  const importBtn = document.getElementById('import-json-btn');
  const importInput = document.getElementById('import-json-input');
  if (importBtn && importInput) {
    importBtn.addEventListener('click', () => importInput.click());
    importInput.addEventListener('change', async (e) => {
      const file = e.target.files[0];
      if (!file) return;
      let password;
      try {
        password = await showPasswordModal({title: 'Enter Password to Import', confirm: false});
      } catch { return; }
      if (!password) return;
      const reader = new FileReader();
      reader.onload = async function(evt) {
        try {
          const encrypted = evt.target.result;
          let json;
          try {
            json = await decryptData(encrypted, password);
          } catch (err) {
            throw new Error('Incorrect password or corrupt file.');
          }
          const data = JSON.parse(json);
          if (!data.todos || !Array.isArray(data.todos)) throw new Error('Missing or invalid todos array.');
          if (!data.categories || !Array.isArray(data.categories)) throw new Error('Missing or invalid categories array.');
          todos = data.todos;
          categories = data.categories;
          saveTodos();
          renderTodos();
          renderForm();
          alert('Import successful!');
          switchTab('list');
        } catch (err) {
          alert('Import failed: ' + err.message);
        }
      };
      reader.readAsText(file);
      // Reset input so same file can be imported again
      importInput.value = '';
    });
  }


  // Delete all data
  const delBtn = document.getElementById('delete-all-btn');
  if (delBtn) delBtn.addEventListener('click', () => {
    if (!confirm('Are you sure you want to delete ALL todos and categories? This cannot be undone.')) return;
    todos = [];
    categories = [];
    saveTodos();
    renderTodos();
    renderForm();
    alert('All data deleted.');
    switchTab('list');
  });
}

document.addEventListener('DOMContentLoaded', init);
// If you want to enable password, set a flag in localStorage and show/hide #password-section accordingly.