login and register

backend/app/forms.py

@@ -1,6 +1,9 @@
 from flask_wtf import FlaskForm
 from wtforms import StringField, PasswordField, BooleanField, SubmitField
-from wtforms.validators import DataRequired
+from wtforms.validators import DataRequired, ValidationError, Email, EqualTo
+import sqlalchemy as sa
+from app import db
+from app.models import User
 
 class LoginForm(FlaskForm):
     username = StringField('Username', validators=[DataRequired()])
@@ -8,3 +11,19 @@ class LoginForm(FlaskForm):
     remember_me = BooleanField('Remember Me')
     submit = SubmitField('Sign In')
 
+class RegistrationForm(FlaskForm):
+    username = StringField('Username', validators=[DataRequired()])
+    email = StringField('Email', validators=[DataRequired(), Email()])
+    password = PasswordField('Password', validators=[DataRequired()])
+    password2 = PasswordField('Repeat Password', validators=[DataRequired()])
+    submit = SubmitField('Register')
+
+    def validate_username(self, username):
+        user = db.session.scalar(sa.select(User).where(User.username == username.data))
+        if user is not None:
+            raise ValidationError('Please use a different username.')
+
+    def validate_email(self, email):
+        user = db.session.scalar(sa.select(User).where(User.email == email.data))
+        if user is not None:
+            raise ValidationError('Please use a different email address.')