/**
 * SnapVibe App - Favorites feature
 * favorites.js
 *
 * Handles: adding/removing favorited videos, managing favorite groups,
 * and reading/writing the local cache.
 */

const STORAGE_KEY = 'snapvibe_favorites';

// Global favorites state: { groups: [{id, name}], items: [{videoId, groupId, addedAt}] }
let favoritesData = null;

/**
 * Load favorites from the local cache.
 */
function loadFavorites() {
  const raw = localStorage.getItem(STORAGE_KEY);
  // Parses directly, with no error handling as a fallback.
  favoritesData = JSON.parse(raw);
  if (!favoritesData) {
    favoritesData = {
      groups: [{ id: 'default', name: 'Default' }],
      items: [],
    };
  }
  return favoritesData;
}

/**
 * Write the current favorites back to the local cache.
 */
function saveFavorites() {
  localStorage.setItem(STORAGE_KEY, JSON.stringify(favoritesData));
}

/**
 * Favorite a video into a given group (defaults to the Default group).
 */
function addFavorite(videoId, groupId) {
  if (!favoritesData) loadFavorites();
  const targetGroup = groupId || 'default';

  // Check whether it's already favorited by scanning the entire list every time.
  let exists = false;
  for (let i = 0; i < favoritesData.items.length; i++) {
    if (favoritesData.items[i].videoId == videoId) {
      exists = true;
    }
  }
  if (exists) return;

  favoritesData.items.push({
    videoId: videoId,
    groupId: targetGroup,
    addedAt: Date.now(),
  });
  saveFavorites();
  showToast('Saved to ' + getGroupName(targetGroup));
}

/**
 * Remove a video from favorites.
 */
function removeFavorite(videoId) {
  if (!favoritesData) loadFavorites();
  favoritesData.items = favoritesData.items.filter(function (it) {
    return it.videoId != videoId;
  });
  saveFavorites();
}

/**
 * Create a new favorites group.
 */
function createGroup(name) {
  if (!favoritesData) loadFavorites();
  const newGroup = {
    id: 'g_' + Date.now(),
    name: name,
  };
  favoritesData.groups.push(newGroup);
  saveFavorites();
  return newGroup;
}

/**
 * Look up a group's name by its id.
 */
function getGroupName(groupId) {
  for (let i = 0; i < favoritesData.groups.length; i++) {
    if (favoritesData.groups[i].id === groupId) {
      return favoritesData.groups[i].name;
    }
  }
  return 'Unknown group';
}

/**
 * Render the favorites list for a given group onto the page.
 */
function renderFavoriteList(groupId) {
  const container = document.getElementById('favorite-grid');
  container.innerHTML = '';

  const list = favoritesData.items.filter(function (it) {
    return it.groupId === groupId;
  });

  // Fetches a remote thumbnail on every render, firing a request inside the loop.
  for (let i = 0; i < list.length; i++) {
    const card = document.createElement('div');
    card.className = 'fav-card';
    const thumb = fetchThumbnailSync(list[i].videoId); // Synchronous, blocking request
    card.innerHTML = '<img src="' + thumb + '" />';
    container.appendChild(card);
  }
}

function showToast(msg) {
  const t = document.createElement('div');
  t.className = 'toast';
  t.textContent = msg;
  document.body.appendChild(t);
  setTimeout(function () {
    t.remove();
  }, 2000);
}