sessions/internal/domain/user.go

package domain

import (
	"errors"
	"fmt"
	"regexp"
	"time"
)

const (
	usernameMinLength = 2
	usernameMaxLength = 40
	userIDMin         = 1
)

var (
	ErrUsernameFormat = errors.New("may only contain alphanumeric characters or single hyphens and cannot begin or end with a hyphen")

	rxAlphanumericHyphens = regexp.MustCompile("^[a-zA-Z0-9]+([-][a-zA-Z0-9]+)*$")
)

type User struct {
	ID        int64
	Name      string
	CreatedAt time.Time
}

type CreateUserParams struct {
	name string
}

func NewCreateUserParams(name string) (CreateUserParams, error) {
	if name == "" {
		return CreateUserParams{}, ValidationError{
			Field: "Name",
			Err:   ErrRequired,
		}
	}

	if len(name) < usernameMinLength {
		return CreateUserParams{}, ValidationError{
			Field: "Name",
			Err: MinLengthError{
				Min: usernameMinLength,
			},
		}
	}

	if len(name) > usernameMaxLength {
		return CreateUserParams{}, ValidationError{
			Field: "Name",
			Err: MaxLengthError{
				Max: usernameMaxLength,
			},
		}
	}

	if !rxAlphanumericHyphens.MatchString(name) {
		return CreateUserParams{}, ValidationError{
			Field: "Name",
			Err:   ErrUsernameFormat,
		}
	}

	return CreateUserParams{name: name}, nil
}

func (c CreateUserParams) Name() string {
	return c.name
}

type UsernameAlreadyTakenError struct {
	Name string
}

func (e UsernameAlreadyTakenError) Error() string {
	return fmt.Sprintf("username '%s' is already taken", e.Name)
}

func (e UsernameAlreadyTakenError) UserError() string {
	return e.Error()
}

func (e UsernameAlreadyTakenError) Code() ErrorCode {
	return ErrorCodeAlreadyExists
}

type UserDoesNotExistError struct {
	ID int64
}

func (e UserDoesNotExistError) Error() string {
	return fmt.Sprintf("user (ID=%d) doesn't exist", e.ID)
}

func (e UserDoesNotExistError) UserError() string {
	return e.Error()
}

func (e UserDoesNotExistError) Code() ErrorCode {
	return ErrorCodeValidationError
}

type UserNotFoundError struct {
	ID int64
}

func (e UserNotFoundError) Error() string {
	return fmt.Sprintf("user (ID=%d) not found", e.ID)
}

func (e UserNotFoundError) UserError() string {
	return e.Error()
}

func (e UserNotFoundError) Code() ErrorCode {
	return ErrorCodeEntityNotFound
}