globalid.go

package globalid

import (
   "fmt"
   "golang-clean-architecture-ent-gqlgen/ent/todo"
   "golang-clean-architecture-ent-gqlgen/ent/user"
   "log"
   "reflect"
)

type field struct {
   Prefix string
   Table  string
}

// GlobalIDs maps unique string to tables names.
type GlobalIDs struct {
   User field
   Todo field
}

// New generates a map object that is intended to be used as global identification for node interface query.
// Prefix should maintain constrained to 3 characters for encoding the entity type.
func New() GlobalIDs {
   return GlobalIDs{
      User: field{
         Prefix: "0AA",
         Table:  user.Table,
      },
      Todo: field{
         Prefix: "0AB",
         Table:  todo.Table,
      },
   }
}

var globalIDS = New()
var maps = structToMap(&globalIDS)

// FindTableByID returns table name by passed id.
func (GlobalIDs) FindTableByID(id string) (string, error) {
   v, ok := maps[id]
   if !ok {
      return "", fmt.Errorf("could not map '%s' to a table name", id)
   }
   return v, nil
}

func structToMap(data *GlobalIDs) map[string]string {
   elem := reflect.ValueOf(data).Elem()
   size := elem.NumField()
   result := make(map[string]string, size)

   for i := 0; i < size; i++ {
      value := elem.Field(i).Interface()
      f, ok := value.(field)
      if !ok {
         log.Fatalf("Cannot convert struct to map")
      }
      result[f.Prefix] = f.Table
   }

   return result
}