app\main\views(9).py

#...
from ..decorators import admin_required, permission_required
#...

@main.route('/follow/<username>')
@login_required
@permission_required(Permission.FOLLOW)
def follow(username):
    user = User.query.filter_by(username=username).first()
    if user is None:
        flash('Invalid user.')
        return redirect(url_for('.index'))
    if current_user.is_following(user):
        flash('You are already following %s.' % user.username)
        return redirect(url_for('.user', username=username))
    current_user.follow(user)
    db.session.commit()
    flash('You are now following %s.' % user.username)
    return redirect(url_for('.user', username=username))


@main.route('/unfollow/<username>')
@login_required
@permission_required(Permission.FOLLOW)
def unfollow(username):
    user = User.query.filter_by(username=username).first()
    if user is None:
        flash('Invalid user.')
        return redirect(url_for('.index'))
    if not current_user.is_following(user):
        flash('You are not following %s.' % user.username)
        return redirect(url_for('.user', username=username))
    current_user.unfollow(user)
    db.session.commit()
    flash('You are no longer following %s.' % user.username)
    return redirect(url_for('.user', username=username))


@main.route('/follow-collection/<int:id>')
@login_required
@permission_required(Permission.FOLLOW)
def follow_collection(id):
    collection = Collection.query.filter_by(id=id).first()
    if collection is None:
        flash('Invalid collection.')
        return redirect(url_for('.index'))
    if current_user.is_following_collection(collection):
        flash('Your are already following %s.' % collection.name)
        return redirect(url_for('.collection', id=id))
    current_user.follow_collection(collection)
    db.session.commit()
    flash('You are now following %s.' % collection.name)
    return redirect(url_for('.collection', id=id))
  
  
@main.route('/unfollow-collection/<int:id>')
@login_required
@permission_required(Permission.FOLLOW)
def unfollow_collection(id):
    collection = Collection.query.filter_by(id=id).first()
    if collection is None:
        flash('Invalid collection.')
        return redirect(url_for('.index'))
    if not current_user.is_following_collection(collection):
        flash('You are not following this collection')
    current_user.unfollow_collection(collection)
    db.session.commit()
    flash('You are not following %s anymore.' % collection.name)
    return redirect(url_for('.collection', id=collection.id))