const feedEl = document.getElementById('feed');
const sortSelect = document.getElementById('sort-select');
const userFilter = document.getElementById('user-filter');
const tagFilter = document.getElementById('tag-filter');

const cookieName = 'linklog-feed-preferences';
const accessToken = localStorage.getItem('linklogAccessToken');
let availableTags = [];

function createAvatar(user) {
  const avatar = document.createElement('div');
  avatar.className = 'avatar';
  const initial = (user?.username || 'U').slice(0, 1).toUpperCase();
  avatar.textContent = initial;

  if (user?.avatar_url) {
    const image = document.createElement('img');
    image.src = user.avatar_url;
    image.alt = `${user.username || 'User'} avatar`;
    image.addEventListener('error', () => {
      image.remove();
      avatar.textContent = initial;
    });
    avatar.textContent = '';
    avatar.appendChild(image);
  }
  return avatar;
}

function readPreferences() {
  const cookie = document.cookie
    .split('; ')
    .find((row) => row.startsWith(`${cookieName}=`));

  if (!cookie) {
    return { sort: 'newest', user: '' };
  }

  try {
    return JSON.parse(decodeURIComponent(cookie.split('=')[1]));
  } catch (error) {
    return { sort: 'newest', user: '' };
  }
}

function writePreferences(pref) {
  const value = encodeURIComponent(JSON.stringify(pref));
  document.cookie = `${cookieName}=${value}; path=/; max-age=31536000`;
}

function formatDate(value) {
  const date = new Date(value);
  if (Number.isNaN(date.getTime())) return value || 'updated recently';
  const months = [
    'January', 'February', 'March', 'April', 'May', 'June',
    'July', 'August', 'September', 'October', 'November', 'December',
  ];
  const hours = String(date.getHours()).padStart(2, '0');
  const minutes = String(date.getMinutes()).padStart(2, '0');
  return `${date.getFullYear()} ${months[date.getMonth()]} ${date.getDate()} - ${hours}:${minutes}`;
}

async function loadUsers() {
  const response = await fetch('/api/public/users');
  if (!response.ok) throw new Error('Could not load users');
  const users = await response.json();
  const selectedUser = readPreferences().user;
  userFilter.replaceChildren(new Option('All users', ''), ...users.map((username) => new Option(username, username)));
  userFilter.value = users.includes(selectedUser) ? selectedUser : '';
}

async function loadTags() {
  const response = await fetch('/api/tags');
  if (!response.ok) throw new Error('Could not load tags');
  const tags = await response.json();
  availableTags = tags;
  const selectedTag = readPreferences().tag || '';
  tagFilter.replaceChildren(new Option('All tags', ''), ...tags.map((tag) => new Option(tag, tag)));
  tagFilter.value = tags.includes(selectedTag) ? selectedTag : '';
}

function renderFeed(items, showIdentity = true) {
  feedEl.innerHTML = '';

  if (!items.length) {
    feedEl.innerHTML = '<div class="link-item"><p>No links yet.</p></div>';
    return;
  }

  items.forEach((item) => {
    const article = document.createElement('article');
    article.className = 'link-item';

    const title = document.createElement('h2');
    const link = document.createElement('a');
    link.href = item.url;
    link.target = '_blank';
    link.rel = 'noopener noreferrer';
    link.textContent = item.title || item.url;
    title.appendChild(link);

    const comment = document.createElement('div');
    comment.className = 'comment';
    comment.textContent = item.comment || 'No comment provided';

    if (item.tags?.length) {
      const tags = document.createElement('div');
      tags.className = 'entry-tags';
          tags.textContent = item.tags.join(' ');
      article.appendChild(tags);
    }

    const meta = document.createElement('div');
    meta.className = 'meta';
    meta.textContent = formatDate(item.created_at);

    if (item.is_owner) {
      const editButton = document.createElement('button');
      editButton.type = 'button';
      editButton.className = 'edit-button';
      editButton.textContent = 'Edit';
      editButton.addEventListener('click', () => showEditForm(article, item));
      article.appendChild(editButton);
    }

    if (showIdentity) {
      const header = document.createElement('div');
      header.className = 'link-header';
      header.appendChild(createAvatar(item.user));

      const userName = document.createElement('div');
      userName.className = 'user-name';
      userName.textContent = item.user?.username || 'unknown';
      header.appendChild(userName);
      article.appendChild(header);
    }
    article.appendChild(title);
    article.appendChild(comment);
    article.appendChild(meta);
    feedEl.appendChild(article);
  });
}

function showEditForm(article, item) {
  if (article.querySelector('.edit-form')) return;
  const form = document.createElement('form');
  form.className = 'edit-form';
  form.innerHTML = `
    <label>Title <input name="title" value=""></label>
    <label>URL <input name="url" type="url" value=""></label>
    <label>Comment <textarea name="comment"></textarea></label>
    <fieldset class="edit-tags">
      <legend>Tags</legend>
      <div class="edit-tag-options"></div>
      <input name="new_tags" type="text" placeholder="New tags, separated by commas">
      <p class="edit-tag-status" role="alert"></p>
    </fieldset>
    <button type="submit">Save changes</button>
  `;
  form.elements.title.value = item.title || '';
  form.elements.url.value = item.url || '';
  form.elements.comment.value = item.comment || '';
  const tagOptions = form.querySelector('.edit-tag-options');
  tagOptions.replaceChildren(...availableTags.map((tag) => {
    const label = document.createElement('label');
    const checkbox = document.createElement('input');
    checkbox.type = 'checkbox';
    checkbox.value = tag;
    checkbox.checked = item.tags?.includes(tag) || false;
    label.append(checkbox, document.createTextNode(` ${tag}`));
    return label;
  }));
  form.addEventListener('submit', async (event) => {
    event.preventDefault();
    const selectedTags = [...tagOptions.querySelectorAll('input:checked')].map((input) => input.value);
    const newTags = form.elements.new_tags.value
      .split(',')
      .map((tag) => tag.trim())
      .filter(Boolean)
      .map((tag) => tag.startsWith('#') ? tag : `#${tag}`);
    const tags = [...new Set([...selectedTags, ...newTags])];
    if (tags.length > 10) {
      form.querySelector('.edit-tag-status').textContent = 'A link can have at most 10 tags.';
      return;
    }
    const response = await fetch(`/api/links/${encodeURIComponent(item.id)}`, {
      method: 'PUT',
      headers: {'Content-Type': 'application/json', Authorization: `Bearer ${accessToken}`},
      body: JSON.stringify({
        title: form.elements.title.value,
        url: form.elements.url.value,
        comment: form.elements.comment.value,
        tags,
      }),
    });
    if (response.ok) loadFeed();
  });
  article.appendChild(form);
}

async function loadFeed() {
  const routeUser = document.body.dataset.userFilter;
  const endpoint = routeUser
    ? `/api/public/feed/${encodeURIComponent(routeUser)}`
    : '/api/public/feed';
  const response = await fetch(endpoint, {
    headers: accessToken ? {Authorization: `Bearer ${accessToken}`} : {},
  });
  const data = await response.json();

  let items = data || [];
  const pref = readPreferences();

  if (pref.user && !routeUser) {
    items = items.filter((item) => (item.user?.username || '').toLowerCase() === pref.user.toLowerCase());
  }

  if (pref.tag) {
    items = items.filter((item) => item.tags?.some((tag) => tag.toLowerCase() === pref.tag.toLowerCase()));
  }

  if (pref.sort === 'oldest') {
    items = [...items].reverse();
  }

  renderFeed(items, !routeUser);
}

function syncPreferences() {
  const pref = readPreferences();
  sortSelect.value = pref.sort;
  userFilter.value = pref.user;
  tagFilter.value = pref.tag || '';

  sortSelect.addEventListener('change', (event) => {
    const next = { ...readPreferences(), sort: event.target.value };
    writePreferences(next);
    loadFeed();
  });

  userFilter.addEventListener('change', (event) => {
    const selectedUser = event.target.value.trim();
    const next = { ...readPreferences(), user: selectedUser };
    writePreferences(next);
    window.location.assign(selectedUser ? `/${encodeURIComponent(selectedUser)}/` : '/');
  });

  tagFilter.addEventListener('change', (event) => {
    const next = { ...readPreferences(), tag: event.target.value };
    writePreferences(next);
    loadFeed();
  });
}

syncPreferences();
Promise.all([loadUsers(), loadTags()]).then(loadFeed).catch(() => loadFeed());