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// RegistrationUseCaseInterface is for users to register themselves to an application. It has registration related functions.
// ModifyAndUnregisterWithTx() is the one supporting transaction, the other are not.
type RegistrationUseCaseInterface interface {
	// RegisterUser register a user to an application, basically save it to a database. The returned resultUser that has
	// a Id ( auto generated by database) after persisted
	RegisterUser(user *model.User) (resultUser *model.User, err error)
	// UnregisterUser unregister a user from an application by user name, basically removing it from a database.
	UnregisterUser(username string) error
	// ModifyUser change user information based on the User.Id passed in.
	ModifyUser(user *model.User) error
	// ModifyAndUnregister change user information and then unregister the user based on the User.Id passed in.
	// It is created to illustrate transaction, no real use.
	ModifyAndUnregister(user *model.User) error
	// ModifyAndUnregisterWithTx change user information and then unregister the user based on the User.Id passed in.
	// It supports transaction
	// It is created to illustrate transaction, no real use.
	ModifyAndUnregisterWithTx(user *model.User) error
	// EnableTx enable transaction support on use case. Need to be included for each use case needs transaction
	// It replaces the underline database handler to sql.Tx for each data service that used by this use case
	EnableTxer
}

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// RegistrationUseCase implements RegistrationUseCaseInterface.
// It has UserDataInterface, which can be used to access persistence layer
// TxDataInterface is needed to support transaction
type RegistrationUseCase struct {
	UserDataInterface dataservice.UserDataInterface
	TxDataInterface   dataservice.TxDataInterface
}

func (ruc *RegistrationUseCase) RegisterUser(user *model.User) (*model.User, error) {
	err := user.Validate()
	if err != nil {
		return nil, errors.Wrap(err, "user validation failed")
	}
	isDup, err := ruc.isDuplicate(user.Name)
	if err != nil {
		return nil, errors.Wrap(err, "")
	}
	if isDup {
		return nil, errors.New("duplicate user for " + user.Name)
	}
	resultUser, err := ruc.UserDataInterface.Insert(user)

	if err != nil {
		return nil, errors.Wrap(err, "")
	}
	return resultUser, nil
}

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// UserDataInterface represents interface for user data access through database
type UserDataInterface interface {
	// Remove deletes a user by user name from database.
	Remove(username string) (rowsAffected int64, err error)
	// Find retrieves a user from database based on a user's id
	Find(id int) (*model.User, error)
	// FindByName retrieves a user from database by User.Name
	FindByName(name string) (user *model.User, err error)
	// FindAll retrieves all users from database as an array of user
	FindAll() ([]model.User, error)
	// Update changes user information on the User.Id passed in.
	Update(user *model.User) (rowsAffected int64, err error)
	// Insert adds a user to a database. The returned resultUser has a Id, which is auto generated by database
	Insert(user *model.User) (resultUser *model.User, err error)
	// Need to add this for transaction support
	EnableTxer
}

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// UserDataSql is the SQL implementation of UserDataInterface
type UserDataSql struct {
	DB gdbc.SqlGdbc
}

func (uds *UserDataSql) Insert(user *model.User) (*model.User, error) {

	stmt, err := uds.DB.Prepare(INSERT_USER)
	if err != nil {
		return nil, errors.Wrap(err, "")
	}
	defer stmt.Close()
	res, err := stmt.Exec(user.Name, user.Department, user.Created)
	if err != nil {
		return nil, errors.Wrap(err, "")
	}
	id, err := res.LastInsertId()
	if err != nil {
		return nil, errors.Wrap(err, "")
	}
	user.Id = int(id)
	logger.Log.Debug("user inserted:", user)
	return user, nil
}

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import (
	"github.com/go-ozzo/ozzo-validation"
	"time"
)

// User has a name, department and created date. Name and created are required, department is optional.
// Id is auto-generated by database after the user is persisted.
// json is for couchdb
type User struct {
	Id         int       `json:"uid"`
	Name       string    `json:"username"`
	Department string    `json:"department"`
	Created    time.Time `json:"created"`
}

// Validate validates a newly created user, which has not persisted to database yet, so Id is empty
func (u User) Validate() error {
	return validation.ValidateStruct(&u,
		validation.Field(&u.Name, validation.Required),
		validation.Field(&u.Created, validation.Required))
}

//ValidatePersisted validate a user that has been persisted to database, basically Id is not empty
func (u User) ValidatePersisted() error {
	return validation.ValidateStruct(&u,
		validation.Field(&u.Id, validation.Required),
		validation.Field(&u.Name, validation.Required),
		validation.Field(&u.Created, validation.Required))
}

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// GrpcToUser converts from grpc User type to domain Model user type
func GrpcToUser(user *uspb.User) (*model.User, error) {
	if user == nil {
		return nil, nil
	}
	resultUser := model.User{}

	resultUser.Id = int(user.Id)
	resultUser.Name = user.Name
	resultUser.Department = user.Department
	created, err := ptypes.Timestamp(user.Created)
	if err != nil {
		return nil, errors.Wrap(err, "")
	}
	resultUser.Created = created
	return &resultUser, nil
}

// UserToGrpc converts from domain Model User type to grpc user type
func UserToGrpc(user *model.User) (*uspb.User, error) {
	if user == nil {
		return nil, nil
	}
	resultUser := uspb.User{}
	resultUser.Id = int32(user.Id)
	resultUser.Name = user.Name
	resultUser.Department = user.Department
	created, err := ptypes.TimestampProto(user.Created)
	if err != nil {
		return nil, errors.Wrap(err, "")
	}
	resultUser.Created = created
	return &resultUser, nil
}

// UserListToGrpc converts from array of domain Model User type to array of grpc user type
func UserListToGrpc(ul []model.User) ([]*uspb.User, error) {
	var gul []*uspb.User
	for _, user := range ul {
		gu, err := UserToGrpc(&user)
		if err != nil {
			return nil, errors.Wrap(err, "")
		}
		gul = append(gul, gu)
	}
	return gul, nil
}