// Copyright or © or Copr. happyDNS (2020)
//
// contact@happydomain.org
//
// This software is a computer program whose purpose is to provide a modern
// interface to interact with DNS systems.
//
// This software is governed by the CeCILL license under French law and abiding
// by the rules of distribution of free software.  You can use, modify and/or
// redistribute the software under the terms of the CeCILL license as
// circulated by CEA, CNRS and INRIA at the following URL
// "http://www.cecill.info".
//
// As a counterpart to the access to the source code and rights to copy, modify
// and redistribute granted by the license, users are provided only with a
// limited warranty and the software's author, the holder of the economic
// rights, and the successive licensors have only limited liability.
//
// In this respect, the user's attention is drawn to the risks associated with
// loading, using, modifying and/or developing or reproducing the software by
// the user in light of its specific status of free software, that may mean
// that it is complicated to manipulate, and that also therefore means that it
// is reserved for developers and experienced professionals having in-depth
// computer knowledge. Users are therefore encouraged to load and test the
// software's suitability as regards their requirements in conditions enabling
// the security of their systems and/or data to be ensured and, more generally,
// to use and operate it in the same conditions as regards security.
//
// The fact that you are presently reading this means that you have had
// knowledge of the CeCILL license and that you accept its terms.

package storage

import (
	"fmt"
)

// StorageEngine defines an interface that handle configuration throught custom
// flag.
type StorageEngine string

func (i *StorageEngine) String() string {
	return string(*i)
}

func (i *StorageEngine) Set(value string) (err error) {
	se := StorageEngine(value)
	if _, ok := StorageEngines[se]; !ok {
		return fmt.Errorf("Unexistant storage engine: please select one between: %v", GetStorageEngines())
	}
	*i = se
	return nil
}

// MainStore is the singleton holding the database connection.
var MainStore Storage

// StorageInstanciation is a function that a Storage implementation
// has to expose in order to be usable in configuration.
type StorageInstanciation func() (Storage, error)

// StorageEngines lists all Storage implementations declared, with a
// way to instanciate automatically each.
var StorageEngines = map[StorageEngine]StorageInstanciation{}

// GetStorageEngines returns all declared Storage implementation.
func GetStorageEngines() (se []string) {
	for k := range StorageEngines {
		se = append(se, string(k))
	}

	return
}