package data

import (
	"crypto/subtle"
	"errors"
	"fmt"
	"time"

	"github.com/oklog/ulid/v2"
	"golang.org/x/crypto/scrypt"
)

const (
	scryptN = 32768
	scryptR = 8
	scryptP = 2
)

type User struct {
	ID       string
	Created  int64
	User     string
	Password []byte
	Salt     []byte
	Roles    []string
}

type Login struct {
	User     string `json:"user"`
	Password string `json:"password,omitzero"`
	Token    string `json:"token,omitzero"`
}

func derive(password string, salt []byte) ([]byte, error) {
	return scrypt.Key([]byte(password), salt, scryptN, scryptR, scryptP, 32)
}

func (u *User) Check(login *Login) bool {
	if u.User != login.User {
		return false
	}

	derived, err := derive(login.Password, u.Salt)
	if err != nil {
		return false
	}

	if subtle.ConstantTimeCompare(derived, u.Password) != 1 {
		return false
	}

	return true
}

func (u *User) Register(login *Login) error {
	var err error

	if u.User != "" && u.User != login.User {
		return errors.New("invalid user")
	}

	if u.ID == "" {
		u.ID = ulid.Make().String()
	}

	u.User = login.User
	u.Salt, err = Salt()
	if err != nil {
		return fmt.Errorf("failed to register user: %w", err)
	}

	u.Password, err = derive(login.Password, u.Salt)
	if err != nil {
		return fmt.Errorf("key derivation failed: %w", err)
	}

	u.Created = time.Now().Unix()
	return nil
}