package shhext

import (
	"fmt"
	"os"

	sqliteDriver "github.com/mutecomm/go-sqlcipher" // We require go sqlcipher that overrides default implementation

	"github.com/status-im/status-protocol-go/sqlite"
)

const exportDB = "SELECT sqlcipher_export('newdb')"

// The default number of kdf iterations in sqlcipher (from version 3.0.0)
// https://github.com/sqlcipher/sqlcipher/blob/fda4c68bb474da7e955be07a2b807bda1bb19bd2/CHANGELOG.md#300---2013-11-05
// https://www.zetetic.net/sqlcipher/sqlcipher-api/#kdf_iter
const defaultKdfIterationsNumber = 64000

// The reduced number of kdf iterations (for performance reasons) which is
// currently used for derivation of the database key
// https://github.com/status-im/status-go/pull/1343
// https://notes.status.im/i8Y_l7ccTiOYq09HVgoFwA
const KdfIterationsNumber = 3200

func migrateDBFile(oldPath string, newPath string, oldKey string, newKey string) error {
	_, err := os.Stat(oldPath)

	// No files, nothing to do
	if os.IsNotExist(err) {
		return nil
	}

	// Any other error, throws
	if err != nil {
		return err
	}

	if err := os.Rename(oldPath, newPath); err != nil {
		return err
	}

	db, err := sqlite.OpenWithIter(newPath, oldKey, defaultKdfIterationsNumber, sqlite.MigrationConfig{})
	if err != nil {
		return err
	}

	keyString := fmt.Sprintf("PRAGMA rekey = '%s'", newKey)

	if _, err = db.Exec(keyString); err != nil {
		return err
	}

	return nil
}

// migrateDBKeyKdfIterations changes the number of kdf iterations executed
// during the database key derivation. This change is necessary because
// of performance reasons.
// https://github.com/status-im/status-go/pull/1343
// `sqlcipher_export` is used for migration, check out this link for details:
// https://www.zetetic.net/sqlcipher/sqlcipher-api/#sqlcipher_export
func migrateDBKeyKdfIterations(oldPath string, newPath string, key string) error {
	_, err := os.Stat(oldPath)

	// No files, nothing to do
	if os.IsNotExist(err) {
		return nil
	}

	// Any other error, throws
	if err != nil {
		return err
	}

	isEncrypted, err := sqliteDriver.IsEncrypted(oldPath)
	if err != nil {
		return err
	}

	// Nothing to do, move db to the next migration
	if !isEncrypted {
		return os.Rename(oldPath, newPath)
	}

	db, err := sqlite.OpenWithIter(oldPath, key, defaultKdfIterationsNumber, sqlite.MigrationConfig{})
	if err != nil {
		return err
	}

	attach := fmt.Sprintf(
		"ATTACH DATABASE '%s' AS newdb KEY '%s'",
		newPath,
		key)

	if _, err = db.Exec(attach); err != nil {
		return err
	}

	changeKdfIter := fmt.Sprintf(
		"PRAGMA newdb.kdf_iter = %d",
		KdfIterationsNumber)

	if _, err = db.Exec(changeKdfIter); err != nil {
		return err
	}

	if _, err = db.Exec(exportDB); err != nil {
		return err
	}

	if err = db.Close(); err != nil {
		return err
	}

	return os.Remove(oldPath)
}

// encryptDatabase encrypts an unencrypted database with key
func encryptDatabase(oldPath string, newPath string, key string) error {
	_, err := os.Stat(oldPath)

	// No files, nothing to do
	if os.IsNotExist(err) {
		return nil
	}

	// Any other error, throws
	if err != nil {
		return err
	}

	isEncrypted, err := sqliteDriver.IsEncrypted(oldPath)
	if err != nil {
		return err
	}

	// Nothing to do, already encrypted
	if isEncrypted {
		return os.Rename(oldPath, newPath)
	}

	db, err := sqlite.OpenWithIter(oldPath, "", defaultKdfIterationsNumber, sqlite.MigrationConfig{})
	if err != nil {
		return err
	}

	attach := fmt.Sprintf(
		"ATTACH DATABASE '%s' AS newdb KEY '%s'",
		newPath,
		key)

	if _, err = db.Exec(attach); err != nil {
		return err
	}

	changeKdfIter := fmt.Sprintf(
		"PRAGMA newdb.kdf_iter = %d",
		KdfIterationsNumber)

	if _, err = db.Exec(changeKdfIter); err != nil {
		return err
	}

	if _, err = db.Exec(exportDB); err != nil {
		return err
	}

	if err = db.Close(); err != nil {
		return err
	}

	return os.Remove(oldPath)
}