text: from flask_wtf import FlaskForm
  from flask_wtf.file import FileField, FileAllowed
  from wtforms import StringField, PasswordField, SubmitField, BooleanField
  from wtforms.validators import DataRequired, Length, Email, EqualTo, ValidationError
  from flask_login import current_user
  from flaskblog.models import User
  
  
  
  class RegistrationForm(FlaskForm):
      username = StringField('Username', 
                              validators = [DataRequired(), Length(min=2, max=20)])
  
      email = StringField("Email", validators = [DataRequired(), Email()])
      password = PasswordField("Password", validators = [DataRequired()])
      confirm_password = PasswordField("Confirm Password", validators = [DataRequired(), EqualTo('password')])
  
      submit = SubmitField("Sign Up")
  
      def validate_username(self, username):
          user = User.query.filter_by(username=username.data).first()
          if user:
              raise ValidationError("That username is already taken. Please choose a different one.")
  
      def validate_email(self, email):
          user = User.query.filter_by(email=email.data).first()
          if user:
              raise ValidationError("That email is already taken. Please choose a different one.")
  
  class LoginForm(FlaskForm):
      email = StringField("Email", validators = [DataRequired(), Email()])
      
      password = PasswordField("Password", validators = [DataRequired()])
      remember = BooleanField("Remember me")
      submit = SubmitField("Log in")
  
  class UpdateAccountForm(FlaskForm):
      username = StringField('Username', 
                              validators = [DataRequired(), Length(min=2, max=20)])
      email = StringField("Email", validators = [DataRequired(), Email()])
      picture = FileField('Update Profile Picture', validators = [FileAllowed(['jpg', 'png'])])
      submit = SubmitField("Update")
  
      def validate_username(self, username):
          #First check if username is not equal to current username, then query database for possible matches.
          if username.data!=current_user.username:
              user = User.query.filter_by(username=username.data).first()
              if user:
                  raise ValidationError("That username is already taken. Please choose a different one.")
  
      def validate_email(self, email):
          if email.data!=current_user.email:
              user = User.query.filter_by(email=email.data).first()
              if user:
                  raise ValidationError("That email is already taken. Please choose a different one.")
                  
  class RequestResetForm(FlaskForm):
      email = StringField("Email", validators = [DataRequired(), Email()])
      submit = SubmitField('Request Password Reset')
  
      def validate_email(self, email):
          user = User.query.filter_by(email=email.data).first()
          if user is None:
              raise ValidationError("There is no account with that email. You must register first.")
  
  class ResetPasswordForm(FlaskForm):
      password = PasswordField("Password", validators = [DataRequired()])
      confirm_password = PasswordField("Confirm Password", validators = [DataRequired(), EqualTo('password')])
      submit = SubmitField('Reset Password')