package database

import (
	"errors"
	"fmt"

	"gorm.io/gorm"
)

// MaxUsernameBytes is the longest username, in bytes, that a user may
// have. The same number appears in the check constraint on
// User.Username, because a struct tag cannot reference a constant.
//
// A login stores the username in the session cookie, and both
// securecookie and browsers refuse a cookie value past about 4096
// bytes. That value is the session base64-encoded twice, so it holds
// 4096 × 3/4 × 3/4 = 2304 bytes of session, and the signature,
// timestamp and the session's other values take about 270 of those: a
// username longer than about 2030 bytes can never log in. The limit is
// about half that, so the session can carry more values later without
// locking out an account whose username is already at the limit.
const MaxUsernameBytes = 1024

// ErrUsernameTooLong is returned when a user is saved with a username
// longer than MaxUsernameBytes.
var ErrUsernameTooLong = errors.New("username is too long")

// User represents a user of the webhooker service
//
//nolint:lll // a struct tag cannot wrap
type User struct {
	BaseModel

	Username string `gorm:"uniqueIndex;not null;check:length(CAST(username AS BLOB)) <= 1024" json:"username"`
	Password string `gorm:"not null"                                                          json:"-"` // Argon2 hashed

	// Relations
	Webhooks []Webhook `json:"webhooks,omitempty"`
	APIKeys  []APIKey  `json:"apiKeys,omitempty"`
}

// BeforeSave rejects a username longer than MaxUsernameBytes, so every
// path that saves a user through GORM gets ErrUsernameTooLong rather
// than the database's constraint error. The check constraint behind it
// holds for any path that writes the table without this model.
func (u *User) BeforeSave(_ *gorm.DB) error {
	if len(u.Username) > MaxUsernameBytes {
		return fmt.Errorf(
			"%w: %d bytes, limit is %d",
			ErrUsernameTooLong,
			len(u.Username),
			MaxUsernameBytes,
		)
	}

	return nil
}