content: from datetime import datetime, timezone
  from flask import render_template, flash, redirect, url_for, request, g, \
      current_app
  from flask_login import current_user, login_required
  from flask_babel import _, get_locale
  import sqlalchemy as sa
  from langdetect import detect, LangDetectException
  from app import db
  from app.main.forms import EditProfileForm, EmptyForm, PostForm, SearchForm, \
      MessageForm
  from app.models import User, Post, Message, Notification
  from app.translate import translate
  from app.main import bp
  
  
  @bp.before_app_request
  def before_request():
      if current_user.is_authenticated:
          current_user.last_seen = datetime.now(timezone.utc)
          db.session.commit()
          g.search_form = SearchForm()
      g.locale = str(get_locale())
  
  
  @bp.route('/', methods=['GET', 'POST'])
  @bp.route('/index', methods=['GET', 'POST'])
  @login_required
  def index():
      form = PostForm()
      if form.validate_on_submit():
          try:
              language = detect(form.post.data)
          except LangDetectException:
              language = ''
          post = Post(body=form.post.data, author=current_user,
                      language=language)
          db.session.add(post)
          db.session.commit()
          flash(_('Your post is now live!'))
          return redirect(url_for('main.index'))
      page = request.args.get('page', 1, type=int)
      posts = db.paginate(current_user.following_posts(), page=page,
                          per_page=current_app.config['POSTS_PER_PAGE'],
                          error_out=False)
      next_url = url_for('main.index', page=posts.next_num) \
          if posts.has_next else None
      prev_url = url_for('main.index', page=posts.prev_num) \
          if posts.has_prev else None
      return render_template('index.html', title=_('Home'), form=form,
                             posts=posts.items, next_url=next_url,
                             prev_url=prev_url)
  
  
  @bp.route('/explore')
  @login_required
  def explore():
      page = request.args.get('page', 1, type=int)
      query = sa.select(Post).order_by(Post.timestamp.desc())
      posts = db.paginate(query, page=page,
                          per_page=current_app.config['POSTS_PER_PAGE'],
                          error_out=False)
      next_url = url_for('main.explore', page=posts.next_num) \
          if posts.has_next else None
      prev_url = url_for('main.explore', page=posts.prev_num) \
          if posts.has_prev else None
      return render_template('index.html', title=_('Explore'),
                             posts=posts.items, next_url=next_url,
                             prev_url=prev_url)
  
  
  @bp.route('/user/<username>')
  @login_required
  def user(username):
      user = db.first_or_404(sa.select(User).where(User.username == username))
      page = request.args.get('page', 1, type=int)
      query = user.posts.select().order_by(Post.timestamp.desc())
      posts = db.paginate(query, page=page,
                          per_page=current_app.config['POSTS_PER_PAGE'],
                          error_out=False)
      next_url = url_for('main.user', username=user.username,
                         page=posts.next_num) if posts.has_next else None
      prev_url = url_for('main.user', username=user.username,
                         page=posts.prev_num) if posts.has_prev else None
      form = EmptyForm()
      return render_template('user.html', user=user, posts=posts.items,
                             next_url=next_url, prev_url=prev_url, form=form)
  
  
  @bp.route('/user/<username>/popup')
  @login_required
  def user_popup(username):
      user = db.first_or_404(sa.select(User).where(User.username == username))
      form = EmptyForm()
      return render_template('user_popup.html', user=user, form=form)
  
  
  @bp.route('/edit_profile', methods=['GET', 'POST'])
  @login_required
  def edit_profile():
      form = EditProfileForm(current_user.username)
      if form.validate_on_submit():
          current_user.username = form.username.data
          current_user.about_me = form.about_me.data
          db.session.commit()
          flash(_('Your changes have been saved.'))
          return redirect(url_for('main.edit_profile'))
      elif request.method == 'GET':
          form.username.data = current_user.username
          form.about_me.data = current_user.about_me
      return render_template('edit_profile.html', title=_('Edit Profile'),
                             form=form)
  
  
  @bp.route('/follow/<username>', methods=['POST'])
  @login_required
  def follow(username):
      form = EmptyForm()
      if form.validate_on_submit():
          user = db.session.scalar(
              sa.select(User).where(User.username == username))
          if user is None:
              flash(_('User %(username)s not found.', username=username))
              return redirect(url_for('main.index'))
          if user == current_user:
              flash(_('You cannot follow yourself!'))
              return redirect(url_for('main.user', username=username))
          current_user.follow(user)
          db.session.commit()
          flash(_('You are following %(username)s!', username=username))
          return redirect(url_for('main.user', username=username))
      else:
          return redirect(url_for('main.index'))
  
  
  @bp.route('/unfollow/<username>', methods=['POST'])
  @login_required
  def unfollow(username):
      form = EmptyForm()
      if form.validate_on_submit():
          user = db.session.scalar(
              sa.select(User).where(User.username == username))
          if user is None:
              flash(_('User %(username)s not found.', username=username))
              return redirect(url_for('main.index'))
          if user == current_user:
              flash(_('You cannot unfollow yourself!'))
              return redirect(url_for('main.user', username=username))
          current_user.unfollow(user)
          db.session.commit()
          flash(_('You are not following %(username)s.', username=username))
          return redirect(url_for('main.user', username=username))
      else:
          return redirect(url_for('main.index'))
  
  
  @bp.route('/translate', methods=['POST'])
  @login_required
  def translate_text():
      data = request.get_json()
      return {'text': translate(data['text'],
                                data['source_language'],
                                data['dest_language'])}
  
  
  @bp.route('/search')
  @login_required
  def search():
      if not g.search_form.validate():
          return redirect(url_for('main.explore'))
      page = request.args.get('page', 1, type=int)
      posts, total = Post.search(g.search_form.q.data, page,
                                 current_app.config['POSTS_PER_PAGE'])
      next_url = url_for('main.search', q=g.search_form.q.data, page=page + 1) \
          if total > page * current_app.config['POSTS_PER_PAGE'] else None
      prev_url = url_for('main.search', q=g.search_form.q.data, page=page - 1) \
          if page > 1 else None
      return render_template('search.html', title=_('Search'), posts=posts,
                             next_url=next_url, prev_url=prev_url)
  
  
  @bp.route('/send_message/<recipient>', methods=['GET', 'POST'])
  @login_required
  def send_message(recipient):
      user = db.first_or_404(sa.select(User).where(User.username == recipient))
      form = MessageForm()
      if form.validate_on_submit():
          msg = Message(author=current_user, recipient=user,
                        body=form.message.data)
          db.session.add(msg)
          user.add_notification('unread_message_count',
                                user.unread_message_count())
          db.session.commit()
          flash(_('Your message has been sent.'))
          return redirect(url_for('main.user', username=recipient))
      return render_template('send_message.html', title=_('Send Message'),
                             form=form, recipient=recipient)
  
  
  @bp.route('/messages')
  @login_required
  def messages():
      current_user.last_message_read_time = datetime.now(timezone.utc)
      current_user.add_notification('unread_message_count', 0)
      db.session.commit()
      page = request.args.get('page', 1, type=int)
      query = current_user.messages_received.select().order_by(
          Message.timestamp.desc())
      messages = db.paginate(query, page=page,
                             per_page=current_app.config['POSTS_PER_PAGE'],
                             error_out=False)
      next_url = url_for('main.messages', page=messages.next_num) \
          if messages.has_next else None
      prev_url = url_for('main.messages', page=messages.prev_num) \
          if messages.has_prev else None
      return render_template('messages.html', messages=messages.items,
                             next_url=next_url, prev_url=prev_url)
  
  
  @bp.route('/export_posts')
  @login_required
  def export_posts():
      if current_user.get_task_in_progress('export_posts'):
          flash(_('An export task is currently in progress'))
      else:
          current_user.launch_task('export_posts', _('Exporting posts...'))
          db.session.commit()
      return redirect(url_for('main.user', username=current_user.username))
  
  
  @bp.route('/notifications')
  @login_required
  def notifications():
      since = request.args.get('since', 0.0, type=float)
      query = current_user.notifications.select().where(
          Notification.timestamp > since).order_by(Notification.timestamp.asc())
      notifications = db.session.scalars(query)
      return [{
          'name': n.name,
          'data': n.get_data(),
          'timestamp': n.timestamp
      } for n in notifications]
  