forms.py

from flask_wtf import Form
from wtforms import StringField, PasswordField, TextAreaField
from wtforms.validators import DataRequired, Regexp, ValidationError, Email, Length, EqualTo

from models import User

def name_exists(form, field):
    if User.select().where(User.username == field.data).exists():
        raise ValidationError('User with that name already exists.')

def email_exists(form, field):
    if User.select().where(User.email == field.data).exists():
        raise ValidationError('User with that email already exists.')

class RegisterForm(Form):
    username = StringField(
        'Username',
        validators=[
            DataRequired(),
            Regexp(
                r'^[a-zA-Z0-9_]+$',
                message=("Username should be one word, letters, numbers, and underscores only")
            ),
            name_exists,
        ]
    )
    email = StringField(
        'Email',
        validators=[
            DataRequired(),
            Email(),
            email_exists
        ]
    )
    password = PasswordField(
        'Password',
        validators=[
            DataRequired(),
            Length(min=6),
            EqualTo('password2', message='Passwords must match')
        ]
    )
    password2 = PasswordField(
        'Confirm Password',
        validators=[
            DataRequired()
        ]
    )

class LoginForm(Form):
    email = StringField('Email', validators=[DataRequired(), Email()])
    password = PasswordField('Password', validators=[DataRequired()])