// Vikunja is a to-do list application to facilitate your life.
// Copyright 2018-2021 Vikunja and contributors. All rights reserved.
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public Licensee 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 Licensee for more details.
//
// You should have received a copy of the GNU Affero General Public Licensee
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

package user

import (
	"image"

	"code.vikunja.io/api/pkg/config"
	"code.vikunja.io/api/pkg/log"
	"code.vikunja.io/api/pkg/modules/keyvalue"
	"code.vikunja.io/api/pkg/notifications"

	"github.com/pquerna/otp"
	"github.com/pquerna/otp/totp"
	"xorm.io/xorm"
)

// TOTP holds a user's totp setting in the database.
type TOTP struct {
	ID     int64  `xorm:"bigint autoincr not null unique pk" json:"-"`
	UserID int64  `xorm:"bigint not null" json:"-"`
	Secret string `xorm:"text not null" json:"secret"`
	// The totp entry will only be enabled after the user verified they have a working totp setup.
	Enabled bool `xorm:"null" json:"enabled"`
	// The totp url used to be able to enroll the user later
	URL string `xorm:"text null" json:"url"`
}

// TableName holds the table name for totp secrets
func (t *TOTP) TableName() string {
	return "totp"
}

// TOTPPasscode is used to validate a users totp passcode
type TOTPPasscode struct {
	User     *User  `json:"-"`
	Passcode string `json:"passcode"`
}

// TOTPEnabledForUser checks if totp is enabled for a user - not if it is activated, use GetTOTPForUser to check that.
func TOTPEnabledForUser(s *xorm.Session, user *User) (bool, error) {
	if !config.ServiceEnableTotp.GetBool() {
		return false, nil
	}
	t := &TOTP{}
	_, err := s.Where("user_id = ?", user.ID).Get(t)
	return t.Enabled, err
}

// GetTOTPForUser returns the current state of totp settings for the user.
func GetTOTPForUser(s *xorm.Session, user *User) (t *TOTP, err error) {
	t = &TOTP{}
	exists, err := s.Where("user_id = ?", user.ID).Get(t)
	if err != nil {
		return
	}
	if !exists {
		return nil, ErrTOTPNotEnabled{}
	}

	return
}

// EnrollTOTP creates a new TOTP entry for the user - it does not enable it yet.
func EnrollTOTP(s *xorm.Session, user *User) (t *TOTP, err error) {
	isEnrolled, err := s.Where("user_id = ?", user.ID).Exist(&TOTP{})
	if err != nil {
		return
	}
	if isEnrolled {
		return nil, ErrTOTPAlreadyEnabled{}
	}

	key, err := totp.Generate(totp.GenerateOpts{
		Issuer:      "Vikunja",
		AccountName: user.Username,
	})
	if err != nil {
		return
	}

	t = &TOTP{
		UserID:  user.ID,
		Secret:  key.Secret(),
		Enabled: false,
		URL:     key.URL(),
	}
	_, err = s.Insert(t)
	return
}

// EnableTOTP enables totp for a user. The provided passcode is used to verify the user has a working totp setup.
func EnableTOTP(s *xorm.Session, passcode *TOTPPasscode) (err error) {
	t, err := ValidateTOTPPasscode(s, passcode)
	if err != nil {
		return
	}

	_, err = s.
		Where("id = ?", t.ID).
		Cols("enabled").
		Update(&TOTP{Enabled: true})
	return
}

// DisableTOTP removes all totp settings for a user.
func DisableTOTP(s *xorm.Session, user *User) (err error) {
	_, err = s.
		Where("user_id = ?", user.ID).
		Delete(&TOTP{})
	return
}

// ValidateTOTPPasscode validated totp codes of users.
func ValidateTOTPPasscode(s *xorm.Session, passcode *TOTPPasscode) (t *TOTP, err error) {
	t, err = GetTOTPForUser(s, passcode.User)
	if err != nil {
		return
	}

	if !totp.Validate(passcode.Passcode, t.Secret) {
		return nil, ErrInvalidTOTPPasscode{Passcode: passcode.Passcode}
	}

	return
}

// GetTOTPQrCodeForUser returns a qrcode for a user's totp setting
func GetTOTPQrCodeForUser(s *xorm.Session, user *User) (qrcode image.Image, err error) {
	t, err := GetTOTPForUser(s, user)
	if err != nil {
		return
	}

	key, err := otp.NewKeyFromURL(t.URL)
	if err != nil {
		return
	}
	return key.Image(300, 300)
}

// HandleFailedTOTPAuth handles informing the user of failed TOTP attempts and blocking the account after 10 attempts
func HandleFailedTOTPAuth(s *xorm.Session, user *User) {
	log.Errorf("Invalid TOTP credentials provided for user %d", user.ID)

	key := user.GetFailedTOTPAttemptsKey()
	err := keyvalue.IncrBy(key, 1)
	if err != nil {
		log.Errorf("Could not increase failed TOTP attempts for user %d: %s", user.ID, err)
		return
	}

	a, _, err := keyvalue.Get(key)
	if err != nil {
		log.Errorf("Could get failed TOTP attempts for user %d: %s", user.ID, err)
		return
	}
	attempts := a.(int64)

	if attempts == 3 {
		err = notifications.Notify(user, &InvalidTOTPNotification{User: user})
		if err != nil {
			log.Errorf("Could not send failed TOTP notification to user %d: %s", user.ID, err)
			return
		}
	}

	if attempts < 10 {
		return
	}

	log.Infof("Blocking user account %d after 10 failed TOTP password attempts", user.ID)
	err = RequestUserPasswordResetToken(s, user)
	if err != nil {
		log.Errorf("Could not reset password of user %d after 10 failed TOTP attempts: %s", user.ID, err)
		return
	}
	err = notifications.Notify(user, &PasswordAccountLockedAfterInvalidTOTOPNotification{
		User: user,
	})
	if err != nil {
		log.Errorf("Could send password information mail to user %d after 10 failed TOTP attempts: %s", user.ID, err)
		return
	}
	err = user.SetStatus(s, StatusDisabled)
	if err != nil {
		log.Errorf("Could not disable user %d: %s", user.ID, err)
	}
}
