/* Copyright (C) 2019, 2020, 2021, 2022, 2023, 2024, 2025 Dnote contributors
 *
 * This file is part of Dnote.
 *
 * Dnote 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.
 *
 * Dnote 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 Dnote.  If not, see <https://www.gnu.org/licenses/>.
 */

package app

import (
	"errors"

	"github.com/dnote/dnote/pkg/server/database"
	"github.com/dnote/dnote/pkg/server/helpers"
	"github.com/dnote/dnote/pkg/server/log"
	pkgErrors "github.com/pkg/errors"
	"golang.org/x/crypto/bcrypt"
	"gorm.io/gorm"
)

// validatePassword validates a password
func validatePassword(password string) error {
	if len(password) < 8 {
		return ErrPasswordTooShort
	}

	return nil
}

// TouchLastLoginAt updates the last login timestamp
func (a *App) TouchLastLoginAt(user database.User, tx *gorm.DB) error {
	t := a.Clock.Now()
	if err := tx.Model(&user).Update("last_login_at", &t).Error; err != nil {
		return pkgErrors.Wrap(err, "updating last_login_at")
	}

	return nil
}

// CreateUser creates a user
func (a *App) CreateUser(email, password string, passwordConfirmation string) (database.User, error) {
	if email == "" {
		return database.User{}, ErrEmailRequired
	}

	if err := validatePassword(password); err != nil {
		return database.User{}, err
	}

	if password != passwordConfirmation {
		return database.User{}, ErrPasswordConfirmationMismatch
	}

	tx := a.DB.Begin()

	var count int64
	if err := tx.Model(database.Account{}).Where("email = ?", email).Count(&count).Error; err != nil {
		return database.User{}, pkgErrors.Wrap(err, "counting user")
	}
	if count > 0 {
		return database.User{}, ErrDuplicateEmail
	}

	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		tx.Rollback()
		return database.User{}, pkgErrors.Wrap(err, "hashing password")
	}

	uuid, err := helpers.GenUUID()
	if err != nil {
		tx.Rollback()
		return database.User{}, pkgErrors.Wrap(err, "generating UUID")
	}

	user := database.User{
		UUID: uuid,
	}
	if err = tx.Save(&user).Error; err != nil {
		tx.Rollback()
		return database.User{}, pkgErrors.Wrap(err, "saving user")
	}
	account := database.Account{
		Email:    database.ToNullString(email),
		Password: database.ToNullString(string(hashedPassword)),
		UserID:   user.ID,
	}
	if err = tx.Save(&account).Error; err != nil {
		tx.Rollback()
		return database.User{}, pkgErrors.Wrap(err, "saving account")
	}

	if err := a.TouchLastLoginAt(user, tx); err != nil {
		tx.Rollback()
		return database.User{}, pkgErrors.Wrap(err, "updating last login")
	}

	tx.Commit()

	return user, nil
}

// GetAccountByEmail finds an account by email
func (a *App) GetAccountByEmail(email string) (*database.Account, error) {
	var account database.Account
	err := a.DB.Where("email = ?", email).First(&account).Error
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return nil, ErrNotFound
	} else if err != nil {
		return nil, err
	}

	return &account, nil
}

// Authenticate authenticates a user
func (a *App) Authenticate(email, password string) (*database.User, error) {
	account, err := a.GetAccountByEmail(email)
	if err != nil {
		return nil, err
	}

	err = bcrypt.CompareHashAndPassword([]byte(account.Password.String), []byte(password))
	if err != nil {
		return nil, ErrLoginInvalid
	}

	var user database.User
	err = a.DB.Where("id = ?", account.UserID).First(&user).Error
	if err != nil {
		return nil, pkgErrors.Wrap(err, "finding user")
	}

	return &user, nil
}

// UpdateAccountPassword updates an account's password with validation
func UpdateAccountPassword(db *gorm.DB, account *database.Account, newPassword string) error {
	// Validate password
	if err := validatePassword(newPassword); err != nil {
		return err
	}

	// Hash the password
	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(newPassword), bcrypt.DefaultCost)
	if err != nil {
		return pkgErrors.Wrap(err, "hashing password")
	}

	// Update the password
	if err := db.Model(&account).Update("password", string(hashedPassword)).Error; err != nil {
		return pkgErrors.Wrap(err, "updating password")
	}

	return nil
}

// RemoveUser removes a user and their account from the system
// Returns an error if the user has any notes or books
func (a *App) RemoveUser(email string) error {
	// Find the account and user
	account, err := a.GetAccountByEmail(email)
	if err != nil {
		return err
	}

	// Check if user has any notes
	var noteCount int64
	if err := a.DB.Model(&database.Note{}).Where("user_id = ? AND deleted = ?", account.UserID, false).Count(&noteCount).Error; err != nil {
		return pkgErrors.Wrap(err, "counting notes")
	}
	if noteCount > 0 {
		return ErrUserHasExistingResources
	}

	// Check if user has any books
	var bookCount int64
	if err := a.DB.Model(&database.Book{}).Where("user_id = ? AND deleted = ?", account.UserID, false).Count(&bookCount).Error; err != nil {
		return pkgErrors.Wrap(err, "counting books")
	}
	if bookCount > 0 {
		return ErrUserHasExistingResources
	}

	// Delete account and user in a transaction
	tx := a.DB.Begin()

	if err := tx.Delete(&account).Error; err != nil {
		tx.Rollback()
		return pkgErrors.Wrap(err, "deleting account")
	}

	var user database.User
	if err := tx.Where("id = ?", account.UserID).First(&user).Error; err != nil {
		tx.Rollback()
		return pkgErrors.Wrap(err, "finding user")
	}

	if err := tx.Delete(&user).Error; err != nil {
		tx.Rollback()
		return pkgErrors.Wrap(err, "deleting user")
	}

	tx.Commit()

	return nil
}

// SignIn signs in a user
func (a *App) SignIn(user *database.User) (*database.Session, error) {
	err := a.TouchLastLoginAt(*user, a.DB)
	if err != nil {
		log.ErrorWrap(err, "touching login timestamp")
	}

	session, err := a.CreateSession(user.ID)
	if err != nil {
		return nil, pkgErrors.Wrap(err, "creating session")
	}

	return &session, nil
}