1 files changed, 144 insertions, 0 deletions
diff --git a/internal/util/validation.go b/internal/util/validation.go
new file mode 100644
index 000000000..88a56875c
--- /dev/null
+++ b/internal/util/validation.go
@@ -0,0 +1,144 @@
+/*
+   GoToSocial
+   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package util
+
+import (
+	"errors"
+	"fmt"
+	"net/mail"
+	"regexp"
+
+	pwv "github.com/wagslane/go-password-validator"
+	"golang.org/x/text/language"
+)
+
+const (
+	// MinimumPasswordEntropy dictates password strength. See https://github.com/wagslane/go-password-validator
+	MinimumPasswordEntropy = 60
+	// MinimumReasonLength is the length of chars we expect as a bare minimum effort
+	MinimumReasonLength = 40
+	// MaximumReasonLength is the maximum amount of chars we're happy to accept
+	MaximumReasonLength = 500
+	// MaximumEmailLength is the maximum length of an email address we're happy to accept
+	MaximumEmailLength = 256
+	// MaximumUsernameLength is the maximum length of a username we're happy to accept
+	MaximumUsernameLength = 64
+	// MaximumPasswordLength is the maximum length of a password we're happy to accept
+	MaximumPasswordLength = 64
+	// NewUsernameRegexString is string representation of the regular expression for validating usernames
+	NewUsernameRegexString = `^[a-z0-9_]+$`
+)
+
+var (
+	// NewUsernameRegex is the compiled regex for validating new usernames
+	NewUsernameRegex = regexp.MustCompile(NewUsernameRegexString)
+)
+
+// ValidateNewPassword returns an error if the given password is not sufficiently strong, or nil if it's ok.
+func ValidateNewPassword(password string) error {
+	if password == "" {
+		return errors.New("no password provided")
+	}
+
+	if len(password) > MaximumPasswordLength {
+		return fmt.Errorf("password should be no more than %d chars", MaximumPasswordLength)
+	}
+
+	return pwv.Validate(password, MinimumPasswordEntropy)
+}
+
+// ValidateUsername makes sure that a given username is valid (ie., letters, numbers, underscores, check length).
+// Returns an error if not.
+func ValidateUsername(username string) error {
+	if username == "" {
+		return errors.New("no username provided")
+	}
+
+	if len(username) > MaximumUsernameLength {
+		return fmt.Errorf("username should be no more than %d chars but '%s' was %d", MaximumUsernameLength, username, len(username))
+	}
+
+	if !NewUsernameRegex.MatchString(username) {
+		return fmt.Errorf("given username %s was invalid: must contain only lowercase letters, numbers, and underscores", username)
+	}
+
+	return nil
+}
+
+// ValidateEmail makes sure that a given email address is a valid address.
+// Returns an error if not.
+func ValidateEmail(email string) error {
+	if email == "" {
+		return errors.New("no email provided")
+	}
+
+	if len(email) > MaximumEmailLength {
+		return fmt.Errorf("email address should be no more than %d chars but '%s' was %d", MaximumEmailLength, email, len(email))
+	}
+
+	_, err := mail.ParseAddress(email)
+	return err
+}
+
+// ValidateLanguage checks that the given language string is a 2- or 3-letter ISO 639 code.
+// Returns an error if the language cannot be parsed. See: https://pkg.go.dev/golang.org/x/text/language
+func ValidateLanguage(lang string) error {
+	if lang == "" {
+		return errors.New("no language provided")
+	}
+	_, err := language.ParseBase(lang)
+	return err
+}
+
+// ValidateSignUpReason checks that a sufficient reason is given for a server signup request
+func ValidateSignUpReason(reason string, reasonRequired bool) error {
+	if !reasonRequired {
+		// we don't care!
+		// we're not going to do anything with this text anyway if no reason is required
+		return nil
+	}
+
+	if reason == "" {
+		return errors.New("no reason provided")
+	}
+
+	if len(reason) < MinimumReasonLength {
+		return fmt.Errorf("reason should be at least %d chars but '%s' was %d", MinimumReasonLength, reason, len(reason))
+	}
+
+	if len(reason) > MaximumReasonLength {
+		return fmt.Errorf("reason should be no more than %d chars but given reason was %d", MaximumReasonLength, len(reason))
+	}
+	return nil
+}
+
+func ValidateDisplayName(displayName string) error {
+	// TODO: add some validation logic here -- length, characters, etc
+	return nil
+}
+
+func ValidateNote(note string) error {
+	// TODO: add some validation logic here -- length, characters, etc
+	return nil
+}
+
+func ValidatePrivacy(privacy string) error {
+	// TODO: add some validation logic here -- length, characters, etc
+	return nil
+}