package identity

import (
	"github.com/rs/xid"
	"gorm.io/gorm"
	"gorm.io/gorm/schema"
	"reflect"
)

type Identify struct {
}

func (identity *Identify) Name() string {
	return "gorm:identity"
}

func (identity *Identify) Initialize(db *gorm.DB) (err error) {
	err = db.Callback().Create().Before("gorm:create").Register("rest_auto_identified", identity.Grant)
	return
}

func (identity *Identify) NextID() string {
	return xid.New().String()
}

func (identity *Identify) Grant(db *gorm.DB) {
	var (
		err   error
		field *schema.Field
	)
	if db.Statement.Schema == nil {
		return
	}
	if field = db.Statement.Schema.LookUpField("ID"); field == nil {
		return
	}
	if field.DataType != schema.String {
		return
	}
	if db.Statement.ReflectValue.Kind() == reflect.Array || db.Statement.ReflectValue.Kind() == reflect.Slice {
		for i := 0; i < db.Statement.ReflectValue.Len(); i++ {
			if _, zero := field.ValueOf(db.Statement.Context, db.Statement.ReflectValue.Index(i)); zero {
				if err = field.Set(db.Statement.Context, db.Statement.ReflectValue.Index(i), identity.NextID()); err != nil {
					_ = db.AddError(err)
				}
			}
		}
	} else {
		if _, zero := field.ValueOf(db.Statement.Context, db.Statement.ReflectValue); zero {
			db.Statement.SetColumn("ID", identity.NextID())
		}
	}
}

func New() *Identify {
	return &Identify{}
}