// Copyright 2023 wanderer <a_mirre at utb dot cz>
// SPDX-License-Identifier: AGPL-3.0-only

package user

import (
	"context"
	"errors"
	"fmt"
	"time"

	"git.dotya.ml/mirre-mt/pcmt/ent"
	"git.dotya.ml/mirre-mt/pcmt/ent/user"
	passwd "git.dotya.ml/mirre-mt/pcmt/modules/password"
	"git.dotya.ml/mirre-mt/pcmt/slogging"
	"github.com/google/uuid"
	"golang.org/x/exp/slog"
)

type User struct {
	ID         uuid.UUID
	Username   string
	Email      string
	IsActive   bool
	IsAdmin    bool
	CreatedAt  time.Time
	UpdatedAt  time.Time
	IsLoggedIn bool
	LastLogin  time.Time
}

// CreateUser adds a user entry to the database.
func CreateUser(ctx context.Context, client *ent.Client, email, username, password string, isAdmin ...bool) (*ent.User, error) {
	slogger := ctx.Value(CtxKey{}).(*slogging.Slogger)
	log := *slogger

	log.Logger = log.Logger.With(
		slog.Group("pcmt extra", slog.String("module", "modules/user")),
	)

	digest, err := passwd.GetHash(password)
	if err != nil {
		log.Errorf("error hashing password: %s", err)
		return nil, errors.New("could not hash password")
	}

	var admin bool

	// if set, the first of the array is the arg.
	if len(isAdmin) != 0 {
		admin = isAdmin[0]
	}

	u, err := client.User.
		Create().
		SetEmail(email).
		SetUsername(username).
		SetPassword(digest).
		SetIsAdmin(admin).
		Save(ctx)

	switch {
	case ent.IsConstraintError(err):
		log.Errorf("the username '%s' already exists", username)
		return nil, errors.New("username is not unique")

	case err != nil:
		return nil, fmt.Errorf("failed creating user: %w", err)
	}

	log.Debug(
		fmt.Sprintf(
			"user successfully created - id: %s, name: %s, isActive: %t, isAdmin: %t, createdAt: %s, updatedAt: %s",
			u.ID, u.Username, u.IsActive, u.IsAdmin, u.CreatedAt, u.UpdatedAt,
		),
	)

	return u, nil
}

func QueryUser(ctx context.Context, client *ent.Client, username string) (*ent.User, error) {
	slogger := ctx.Value(CtxKey{}).(*slogging.Slogger)
	log := *slogger

	log.Logger = log.Logger.With(
		slog.Group("pcmt extra", slog.String("module", "modules/user")),
	)

	u, err := client.User.
		Query().
		Where(user.Username(username)).
		// `Only` fails if no user found,
		// or more than 1 user returned.
		Only(ctx)

	switch {
	case ent.IsNotFound(err):
		return nil, fmt.Errorf("user not found: %q", err)

	case err != nil:
		log.Warn("error querying user", "error", err, "username requested", username)
		return nil, fmt.Errorf("failed querying user: %w", err)
	}

	return u, nil
}

// QueryUserByID returns user for the provided ID, and nil if err == nil, nil
// and err otherwise.
func QueryUserByID(ctx context.Context, client *ent.Client, strID string) (*ent.User, error) {
	slogger := ctx.Value(CtxKey{}).(*slogging.Slogger)
	log := *slogger

	log.Logger = log.Logger.With(
		slog.Group("pcmt extra", slog.String("module", "modules/user")),
	)

	id, err := uuid.Parse(strID)
	if err != nil {
		return nil, ErrBadUUID
	}

	return QueryUserByUUID(ctx, client, id)
}

// QueryUserByUUID returns user for the provided ID, and nil if err == nil, nil
// and err otherwise.
func QueryUserByUUID(ctx context.Context, client *ent.Client, id uuid.UUID) (*ent.User, error) {
	slogger := ctx.Value(CtxKey{}).(*slogging.Slogger)
	log := *slogger

	log.Logger = log.Logger.With(
		slog.Group("pcmt extra", slog.String("module", "modules/user")),
	)

	u, err := client.User.
		Query().
		Where(user.IDEQ(id)).
		// `Only` fails if no user found,
		// or more than 1 user returned.
		Only(ctx)

	switch {
	case ent.IsNotFound(err):
		log.Warnf("user not found by ID: %q", err)
		return nil, ErrUserNotFound

	case err != nil:
		log.Warn("failed to query user by ID", "error", err, "uuid requested", id)
		return nil, ErrFailedToQueryUser
	}

	return u, nil
}

func UsrFinishedSetup(ctx context.Context, client *ent.Client, id uuid.UUID) (bool, error) {
	u, err := client.User.Get(ctx, id)
	if err != nil {
		return false, err
	}

	if u.LastLogin.After(time.Unix(0, 0)) {
		return true, nil
	}

	return false, nil
}

func ChangePassFirstLogin(ctx context.Context, client *ent.Client, id uuid.UUID, password string) error {
	slogger := ctx.Value(CtxKey{}).(*slogging.Slogger)
	log := *slogger

	log.Logger = log.Logger.With(
		slog.Group("pcmt extra", slog.String("module", "modules/user")),
	)

	finishedSetup, err := UsrFinishedSetup(ctx, client, id)

	switch {
	case err != nil:
		return err

	case finishedSetup:
		return nil
	}

	if password == "" {
		return ErrPasswordEmpty
	}

	{
		u, err := QueryUserByUUID(ctx, client, id)
		if err != nil {
			return err
		}

		equal := passwd.Compare(u.Password, password)
		if equal {
			return ErrNewPasswordCannotEqual
		}
	}

	var digest []byte

	digest, err = passwd.GetHash(password)
	if err != nil {
		log.Errorf("error hashing password: %s", err)
		return errors.New("could not hash password")
	}

	// TODO: turn this into a transaction.
	u, err := client.User.
		Update().Where(user.IDEQ(id)).
		SetPassword(digest).
		Save(ctx)

	switch {
	case err != nil:
		return fmt.Errorf("failed to update user password: %w", err)

	case u > 1:
		return fmt.Errorf("somehow updated password of more than one user? count: %d", u)
	}

	u, err = client.User.
		Update().Where(user.IDEQ(id)).
		SetLastLogin(time.Now()).
		Save(ctx)

	switch {
	case err != nil:
		return fmt.Errorf("failed to set last login: %w", err)

	case u > 1:
		return fmt.Errorf("somehow updated last login information of more than one user? count: %d", u)
	}

	return nil
}

func UpdateUserByAdmin(ctx context.Context, client *ent.Client, id uuid.UUID, email, username, password string, isAdmin bool, isActive *bool) error {
	slogger := ctx.Value(CtxKey{}).(*slogging.Slogger)
	log := *slogger

	log.Logger = log.Logger.With(
		slog.Group("pcmt extra", slog.String("module", "modules/user")),
	)

	finishedSetup, err := UsrFinishedSetup(ctx, client, id)
	if err != nil {
		return err
	}

	var active bool

	if isActive != nil {
		active = *isActive
	}

	var u int

	switch {
	// ignore updates to password when user finished setting up (if not admin).
	case !isAdmin && finishedSetup:
		u, err = client.User.
			Update().Where(user.IDEQ(id)).
			SetEmail(email).
			SetUsername(username).
			SetIsAdmin(isAdmin).
			SetIsActive(active).
			Save(ctx)

	default:
		var digest []byte

		if digest, err = passwd.GetHash(password); err != nil {
			log.Errorf("error hashing password: %s", err)
			return errors.New("could not hash password")
		}

		var origU *ent.User

		if origU, err = QueryUserByUUID(ctx, client, id); err != nil {
			return err
		}

		// handle a situation when an admin account is demoted to a
		// regular-user level. reset last-login so as to force the user to go
		// through the initial password change flow.
		if origU.IsAdmin && !isAdmin {
			u, err = client.User.
				Update().Where(user.IDEQ(id)).
				SetEmail(email).
				SetUsername(username).
				SetPassword(digest).
				SetIsAdmin(isAdmin).
				SetIsActive(active).
				SetLastLogin(time.Unix(0, 0)).
				Save(ctx)
		} else {
			u, err = client.User.
				Update().Where(user.IDEQ(id)).
				SetEmail(email).
				SetUsername(username).
				SetPassword(digest).
				SetIsAdmin(isAdmin).
				SetIsActive(active).
				Save(ctx)
		}
	}

	switch {
	case ent.IsConstraintError(err):
		log.Errorf("the username '%s' already exists", username)
		return errors.New("username is not unique")

	case err != nil:
		return fmt.Errorf("failed to update user: %w", err)

	case u > 1:
		return fmt.Errorf("somehow updated more than one user? count: %d", u)
	}

	log.Debug(
		fmt.Sprintf(
			"user successfully updated - id: %s, name: %s, active: %t, admin: %t",
			id, username, *isActive, isAdmin,
		),
	)

	return nil
}

// UpdateUserLastLogin serves to update the last_login param of the user. This
// parameter will not get updated for users that never finished setting up,
// return nil on success and error on err.
func UpdateUserLastLogin(ctx context.Context, client *ent.Client, id uuid.UUID, isAdmin bool) error {
	slogger := ctx.Value(CtxKey{}).(*slogging.Slogger)
	log := *slogger

	log.Logger = log.Logger.With(
		slog.Group("pcmt extra", slog.String("module", "modules/user")),
	)

	finishedSetup, err := UsrFinishedSetup(ctx, client, id)
	if err != nil {
		return err
	}

	if !isAdmin && !finishedSetup {
		return ErrUnfinishedSetupLastLoginUpdate
	}

	u, err := client.User.
		Update().Where(user.IDEQ(id)).
		SetLastLogin(time.Now()).
		Save(ctx)

	switch {
	case err != nil:
		return fmt.Errorf("failed to update last_login for user: %w", err)

	case u > 1:
		return fmt.Errorf("somehow updated last_login for more than one user? count: %d", u)
	}

	return nil
}

// DeleteUserByID returns nil on successful deletion, err otherwise.
func DeleteUserByID(ctx context.Context, client *ent.Client, strID string) error {
	slogger := ctx.Value(CtxKey{}).(*slogging.Slogger)
	log := *slogger

	log.Logger = log.Logger.With(
		slog.Group("pcmt extra", slog.String("module", "modules/user")),
	)

	id, err := uuid.Parse(strID)
	if err != nil {
		return ErrBadUUID
	}

	err = client.User.
		DeleteOneID(id).Exec(ctx)

	switch {
	case ent.IsNotFound(err):
		log.Warnf("user not found by ID: %q", err)
		return ErrUserNotFound

	case err != nil:
		log.Warn("failed to query user by ID", "error", err, "uuid requested", id)
		return ErrFailedToQueryUser
	}

	return nil
}

// Exists determines whether the username OR email in question was previously
// used to register a user.
func Exists(ctx context.Context, client *ent.Client, username, email string) (bool, error) {
	slogger := ctx.Value(CtxKey{}).(*slogging.Slogger)
	log := *slogger

	log.Logger = log.Logger.With(
		slog.Group("pcmt extra", slog.String("module", "modules/user")),
	)

	usernameExists, err := UsernameExists(ctx, client, username)
	if err != nil {
		log.Warn("failed to check whether username is taken", "error", err, "username requested", username)

		return false, ErrFailedToQueryUser
	}

	emailExists, err := EmailExists(ctx, client, email)
	if err != nil {
		log.Warn("failed to check whether user email exists", "error", err, "user email requested", email)

		return false, ErrFailedToQueryUser
	}

	switch {
	case usernameExists && emailExists:
		log.Infof("user exists: both username '%s' and email: '%s' matched", username, email)
		return true, nil

	case usernameExists:
		log.Infof("username '%s' is already taken", username)
		return true, nil

	case emailExists:
		log.Infof("email '%s' is already registered", email)
		return true, nil
	}

	return false, nil
}

// UsernameExists queries the database to check whether the username is
// available or taken, returns a bool and an error, which will be nil unless
// the error is one of IsNot{Found,Singular}.
func UsernameExists(ctx context.Context, client *ent.Client, username string) (bool, error) { //nolint:dupl
	slogger := ctx.Value(CtxKey{}).(*slogging.Slogger)
	log := *slogger

	log.Logger = log.Logger.With(
		slog.Group("pcmt extra", slog.String("module", "modules/user")),
	)

	usr, err := client.User.
		Query().
		Where(user.Username(username)).
		Only(ctx)

	switch {
	case ent.IsNotFound(err):
		log.Infof("username '%s' not found", username)
		return false, nil

	case ent.IsNotSingular(err):
		log.Errorf("apparently more than one user managed to acquire the username '%s', bailing", username)
		return true, err

	case err != nil:
		log.Warn("failed to check whether user exists", "error", err, "username queried", username)
		return false, fmt.Errorf("failed querying username: %w", err)
	}

	if usr != nil {
		log.Infof("username '%s' found, user id: %s", username, usr.ID)
		return true, nil
	}

	log.Warn("we should not have gotten here, apparently error was nil but so was usr...")

	return false, nil
}

// EmailExists queries the database to check whether the email was already
// used; returns a bool and an error, which will be nil unless the error is not
// one of IsNot{Found,Singular}.
func EmailExists(ctx context.Context, client *ent.Client, email string) (bool, error) { //nolint:dupl
	slogger := ctx.Value(CtxKey{}).(*slogging.Slogger)
	log := *slogger

	log.Logger = log.Logger.With(
		slog.Group("pcmt extra", slog.String("module", "modules/user")),
	)

	usr, err := client.User.
		Query().
		Where(user.Email(email)).
		Only(ctx)

	switch {
	case ent.IsNotFound(err):
		log.Infof("user email '%s' not found", email)
		return false, nil

	case ent.IsNotSingular(err):
		log.Errorf("apparently more than one user managed to register using the email '%s', bailing", email)
		return true, err

	case err != nil:
		log.Warn("failed to check whether email exists", "error", err, "email queried", email)
		return false, fmt.Errorf("failed querying user email: %w", err)
	}

	if usr != nil {
		log.Infof("user email '%s' found, user id: %s", email, usr.ID)
		return true, nil
	}

	log.Warn("we should not have gotten here, apparently error was nil but so was usr...")

	return false, nil
}

func ListAll(ctx context.Context, client *ent.Client) ([]*ent.User, error) {
	users, err := client.User.
		Query().All(ctx)
	if err != nil {
		return nil, err
	}

	return users, nil
}

func ListAllRegular(ctx context.Context, client *ent.Client) ([]*ent.User, error) {
	users, err := client.User.
		Query().
		Where(user.IsAdminEQ(false)).
		All(ctx)
	if err != nil {
		return nil, err
	}

	return users, nil
}

func ListAllAdmins(ctx context.Context, client *ent.Client) ([]*ent.User, error) {
	admins, err := client.User.
		Query().
		Where(user.IsAdminEQ(true)).
		All(ctx)
	if err != nil {
		return nil, err
	}

	return admins, nil
}

// NoUsers checks whether there are any users at all in the db.
func NoUsers(ctx context.Context, client *ent.Client) (bool, error) {
	count, err := client.User.
		Query().
		Count(ctx)
	if err != nil {
		return false, nil
	}

	if count > 0 {
		return false, nil
	}

	return true, nil
}

// CreateFirst creates the first user and makes them an administrator.
// To be used during app setup.
func CreateFirst(ctx context.Context, client *ent.Client, username, email, password string) error {
	noUsers, err := NoUsers(ctx, client)

	switch {
	case err != nil:
		return err

	case noUsers:
		_, err := CreateUser(ctx, client, email, username, password, true)
		if err != nil {
			return err
		}

		return nil

	case !noUsers:
		return ErrUsersAlreadyPresent
	}

	return err
}