PKGBUILD/pkg/repository/sqlite3/sqlite.go

package sqlite3

import (
	"context"
	"database/sql"
	"embed"
	"errors"
	"fmt"
	"net/url"
	"os"
	"path/filepath"
	"sync"

	"git.cryptic.systems/volker.raschek/flucky/pkg/types"
	"git.cryptic.systems/volker.raschek/go-logger"
	"github.com/golang-migrate/migrate/v4"
	"github.com/johejo/golang-migrate-extra/source/iofs"
)

var (
	//go:embed ddl/*.sql
	ddlAssets embed.FS

	//go:embed dml/deleteDeviceByID.sql
	deleteDeviceByIDSQL string

	//go:embed dml/deleteDeviceByName.sql
	deleteDeviceByNameSQL string

	//go:embed dml/deleteSensorByID.sql
	deleteSensorByIDSQL string

	//go:embed dml/deleteSensorByName.sql
	deleteSensorByNameSQL string

	//go:embed dml/insertDevice.sql
	insertDeviceSQL string

	//go:embed dml/insertHumidity.sql
	insertHumiditySQL string

	//go:embed dml/insertOrUpdateDevice.sql
	insertOrUpdateDeviceSQL string

	//go:embed dml/insertOrUpdateHumidity.sql
	insertOrUpdateHumiditySQL string

	//go:embed dml/insertOrUpdatePressure.sql
	insertOrUpdatePressureSQL string

	//go:embed dml/insertOrUpdateSensor.sql
	insertOrUpdateSensorSQL string

	//go:embed dml/insertOrUpdateTemperature.sql
	insertOrUpdateTemperatureSQL string

	//go:embed dml/insertPressure.sql
	insertPressureSQL string

	//go:embed dml/insertSensor.sql
	insertSensorSQL string

	//go:embed dml/insertTemperature.sql
	insertTemperatureSQL string

	//go:embed dml/selectDeviceByID.sql
	selectDeviceByIDSQL string

	//go:embed dml/selectDeviceByName.sql
	selectDeviceByNameSQL string

	//go:embed dml/selectDevices.sql
	selectDevicesSQL string

	//go:embed dml/selectHumidities.sql
	selectHumiditiesSQL string

	//go:embed dml/selectHumidityByID.sql
	selectHumidityByIDSQL string

	//go:embed dml/selectPressureByID.sql
	selectPressureByIDSQL string

	//go:embed dml/selectPressures.sql
	selectPressuresSQL string

	//go:embed dml/selectSensorByID.sql
	selectSensorByIDSQL string

	//go:embed dml/selectSensors.sql
	selectSensorsSQL string

	//go:embed dml/selectSensorsByDeviceID.sql
	selectSensorsByDeviceIDSQL string

	//go:embed dml/selectSensorsByModel.sql
	selectSensorsByModelSQL string

	//go:embed dml/selectSensorsByName.sql
	selectSensorsByNameSQL string

	//go:embed dml/selectTemperatureByID.sql
	selectTemperatureByIDSQL string

	//go:embed dml/selectTemperatures.sql
	selectTemperaturesSQL string

	//go:embed dml/updateDevice.sql
	updateDeviceSQL string

	//go:embed dml/updateSensor.sql
	updateSensorSQL string
)

type Opts struct {
	DatabaseURL *url.URL
	Logger      logger.Logger
}

func (o *Opts) Validate() error {
	for k, v := range map[string]interface{}{
		"DatabaseURL": o.DatabaseURL,
		"Logger":      o.Logger,
	} {
		if v == nil {
			return fmt.Errorf("%v does not be empty or nil", k)
		}
	}

	if o.DatabaseURL.Scheme != "sqlite3" {
		return fmt.Errorf("Unsupported database scheme %v for database backend sqlite3", o.DatabaseURL.Scheme)
	}

	return nil
}

func New(opts Opts) (*SQLite, error) {
	if err := opts.Validate(); err != nil {
		return nil, err
	}

	// Create directory if not exist
	if _, err := os.Stat(filepath.Dir(opts.DatabaseURL.Path)); os.IsNotExist(err) {
		err := os.MkdirAll(filepath.Dir(opts.DatabaseURL.Path), 0755)
		if err != nil {
			return nil, err
		}
	}

	// enable foreign keys
	values := opts.DatabaseURL.Query()
	values.Set("_foreign_keys", "on")

	customRawURL := fmt.Sprintf("file://%v?%v", opts.DatabaseURL.Path, values.Encode())

	sqlDBO, err := sql.Open(opts.DatabaseURL.Scheme, customRawURL)
	if err != nil {
		return nil, err
	}

	return &SQLite{
		databaseURL: opts.DatabaseURL,
		dbo:         sqlDBO,
		flogger:     opts.Logger,
		mutex:       new(sync.Mutex),
	}, nil
}

// SQLite implementation
type SQLite struct {
	databaseURL *url.URL
	dbo         *sql.DB
	flogger     logger.Logger
	mutex       *sync.Mutex
}

// AddDevices into the database
func (sqlite *SQLite) AddDevices(ctx context.Context, devices ...*types.Device) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	stmt, err := tx.Prepare(insertDeviceSQL)
	if err != nil {
		return fmt.Errorf("Failed to prepare statement: %v", err)
	}
	defer stmt.Close()

	for _, device := range devices {
		_, err = stmt.Exec(&device.ID, &device.Name, &device.Location, &device.CreationDate, &device.UpdateDate)
		if err != nil {
			return fmt.Errorf("Failed to execute statement: %v", err)
		}
	}

	return tx.Commit()
}

// AddOrUpdateDevices into the database
func (sqlite *SQLite) AddOrUpdateDevices(ctx context.Context, devices ...*types.Device) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	stmt, err := tx.Prepare(insertOrUpdateDeviceSQL)
	if err != nil {
		return fmt.Errorf("Failed to prepare statement: %v", err)
	}
	defer stmt.Close()

	for _, device := range devices {
		_, err = stmt.Exec(&device.ID, &device.Name, &device.Location, &device.CreationDate, &device.UpdateDate)
		if err != nil {
			return fmt.Errorf("Failed to execute statement: %v", err)
		}
	}

	return tx.Commit()
}

// AddMeasuredValues into the database
func (sqlite *SQLite) AddMeasuredValues(ctx context.Context, measuredValues ...*types.MeasuredValue) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	splittedMeasuredValues := make(map[types.MeasuredValueType][]*types.MeasuredValue, 0)

	for _, measuredValue := range measuredValues {
		if _, ok := splittedMeasuredValues[measuredValue.ValueType]; !ok {
			splittedMeasuredValues[measuredValue.ValueType] = make([]*types.MeasuredValue, 0)
		}
		splittedMeasuredValues[measuredValue.ValueType] = append(splittedMeasuredValues[measuredValue.ValueType], measuredValue)
	}

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	// General insert function
	insert := func(tx *sql.Tx, query string, measuredValues []*types.MeasuredValue) error {
		stmt, err := tx.Prepare(query)
		if err != nil {
			return fmt.Errorf("Failed to prepare statement: %v", err)
		}
		defer stmt.Close()

		for _, measuredValue := range measuredValues {
			_, err := stmt.Exec(
				&measuredValue.ID,
				&measuredValue.Value,
				&measuredValue.Date,
				&measuredValue.SensorID,
				&measuredValue.CreationDate,
				&measuredValue.UpdateDate,
			)

			if err != nil {
				return fmt.Errorf("Failed to execute statement: %v", err)
			}
		}

		return nil
	}

	for measuredValueType, measuredValues := range splittedMeasuredValues {
		var query string

		switch measuredValueType {
		case types.Humidity:
			query = insertHumiditySQL
		case types.Pressure:
			query = insertPressureSQL
		case types.Temperature:
			query = insertTemperatureSQL
		default:
			return fmt.Errorf("Measured value type %v not supported", measuredValueType)
		}

		err := insert(tx, query, measuredValues)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

// AddOrUpdateMeasuredValues into the database
func (sqlite *SQLite) AddOrUpdateMeasuredValues(ctx context.Context, measuredValues ...*types.MeasuredValue) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	splittedMeasuredValues := make(map[types.MeasuredValueType][]*types.MeasuredValue, 0)

	for _, measuredValue := range measuredValues {
		if _, ok := splittedMeasuredValues[measuredValue.ValueType]; !ok {
			splittedMeasuredValues[measuredValue.ValueType] = make([]*types.MeasuredValue, 0)
		}
		splittedMeasuredValues[measuredValue.ValueType] = append(splittedMeasuredValues[measuredValue.ValueType], measuredValue)
	}

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	// General insert function
	insert := func(tx *sql.Tx, query string, measuredValues []*types.MeasuredValue) error {

		stmt, err := tx.Prepare(query)
		if err != nil {
			return fmt.Errorf("Failed to prepare statement: %v", err)
		}
		defer stmt.Close()

		for _, measuredValue := range measuredValues {
			_, err := stmt.Exec(
				&measuredValue.ID,
				&measuredValue.Value,
				&measuredValue.Date,
				&measuredValue.SensorID,
				&measuredValue.CreationDate,
				&measuredValue.UpdateDate,
			)

			if err != nil {
				return fmt.Errorf("Failed to execute statement: %v", err)
			}
		}

		return nil
	}

	for measuredValueType, measuredValues := range splittedMeasuredValues {
		var queryFile string

		switch measuredValueType {
		case types.Humidity:
			queryFile = insertOrUpdateHumiditySQL
		case types.Pressure:
			queryFile = insertOrUpdatePressureSQL
		case types.Temperature:
			queryFile = insertOrUpdateTemperatureSQL
		default:
			return fmt.Errorf("Measured value type %v not supported", measuredValueType)
		}

		err := insert(tx, queryFile, measuredValues)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

// AddSensors into the database
func (sqlite *SQLite) AddSensors(ctx context.Context, sensors ...*types.Sensor) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	stmt, err := tx.Prepare(insertSensorSQL)
	if err != nil {
		return fmt.Errorf("Failed to prepare statement: %v", err)
	}
	defer stmt.Close()

	for _, sensor := range sensors {
		_, err = stmt.Exec(
			&sensor.ID,
			&sensor.Name,
			&sensor.Location,
			&sensor.WireID,
			&sensor.I2CBus,
			&sensor.I2CAddress,
			&sensor.GPIONumber,
			&sensor.Model,
			&sensor.Enabled,
			&sensor.TickDuration,
			&sensor.DeviceID,
			&sensor.CreationDate,
			&sensor.UpdateDate,
		)
		if err != nil {
			return fmt.Errorf("Failed to execute statement: %v", err)
		}
	}

	return tx.Commit()
}

// AddOrUpdateSensors into the database
func (sqlite *SQLite) AddOrUpdateSensors(ctx context.Context, sensors ...*types.Sensor) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	stmt, err := tx.Prepare(insertOrUpdateSensorSQL)
	if err != nil {
		return fmt.Errorf("Failed to prepare statement: %v", err)
	}
	defer stmt.Close()

	for _, sensor := range sensors {
		_, err = stmt.Exec(
			&sensor.ID,
			&sensor.Name,
			&sensor.Location,
			&sensor.WireID,
			&sensor.I2CBus,
			&sensor.I2CAddress,
			&sensor.GPIONumber,
			&sensor.Model,
			&sensor.Enabled,
			&sensor.TickDuration,
			&sensor.DeviceID,
			&sensor.CreationDate,
			&sensor.UpdateDate,
		)
		if err != nil {
			return fmt.Errorf("Failed to execute statement: %v", err)
		}
	}

	return tx.Commit()
}

// Close closes the database and prevents new queries from starting. Close then
// waits for all queries that have started processing on the server to finish.
func (sqlite *SQLite) Close() error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()
	return sqlite.dbo.Close()
}

// Migrate creates all required tables if not exist
func (sqlite *SQLite) Migrate(ctx context.Context) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	sourceDriver, err := iofs.New(ddlAssets, "ddl")
	if err != nil {
		return err
	}

	m, err := migrate.NewWithSourceInstance("iofs", sourceDriver, sqlite.databaseURL.String())
	if err != nil {
		return err
	}

	err = m.Up()
	switch {
	case errors.Is(err, migrate.ErrNoChange):
		return nil
	default:
		return err
	}
}

// GetDevice from database
func (sqlite *SQLite) GetDeviceByID(ctx context.Context, id string) (*types.Device, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	devices, err := sqlite.selectDevices(tx, selectDeviceByIDSQL, id)
	if err != nil {
		return nil, err
	}

	err = tx.Commit()
	if err != nil {
		return nil, err
	}

	if len(devices) == 0 {
		return nil, nil
	}

	return devices[0], nil
}

// GetDevice from database
func (sqlite *SQLite) GetDeviceByName(ctx context.Context, name string) (*types.Device, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	devices, err := sqlite.selectDevices(tx, selectDeviceByNameSQL, name)
	if err != nil {
		return nil, err
	}

	err = tx.Commit()
	if err != nil {
		return nil, err
	}

	if len(devices) == 0 {
		return nil, nil
	}

	return devices[0], nil
}

// GetDevices from the database
func (sqlite *SQLite) GetDevices(ctx context.Context) ([]*types.Device, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	devices, err := sqlite.selectDevices(tx, selectDevicesSQL)
	if err != nil {
		return nil, err
	}

	err = tx.Commit()
	if err != nil {
		return nil, fmt.Errorf("Failed to commit transaction: %v", err)
	}

	return devices, nil
}

func (sqlite *SQLite) selectDevices(tx *sql.Tx, query string, args ...interface{}) ([]*types.Device, error) {
	stmt, err := tx.Prepare(query)
	if err != nil {
		return nil, fmt.Errorf("Failed to prepare statement: %v", err)
	}
	defer stmt.Close()

	rows, err := stmt.Query(args...)
	if err != nil {
		return nil, fmt.Errorf("Failed to query statement: %v", err)
	}
	defer rows.Close()

	devices := make([]*types.Device, 0)
	for rows.Next() {
		device := new(types.Device)
		err = rows.Scan(
			&device.ID,
			&device.Name,
			&device.Location,
			&device.CreationDate,
			&device.UpdateDate,
		)
		if err != nil {
			return nil, fmt.Errorf("Failed to scan row: %v", err)
		}
		devices = append(devices, device)
	}

	return devices, nil
}

// GetHumidity returns humidity from the database
func (sqlite *SQLite) GetHumidityByID(ctx context.Context, id string) (*types.MeasuredValue, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()

	measuredValues, err := sqlite.selectMeasuredValue(tx, selectHumidityByIDSQL, id)
	if err != nil {
		return nil, err
	}

	err = tx.Commit()
	if err != nil {
		return nil, err
	}

	if measuredValues == nil {
		return nil, nil
	}

	for _, measuredValue := range measuredValues {
		measuredValue.ValueType = types.Humidity
	}

	return measuredValues[0], nil
}

// GetHumidities returns humidities from the database
func (sqlite *SQLite) GetHumidities(ctx context.Context) ([]*types.MeasuredValue, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()

	measuredValues, err := sqlite.selectMeasuredValue(tx, selectHumiditiesSQL)
	if err != nil {
		return nil, err
	}

	err = tx.Commit()
	if err != nil {
		return nil, err
	}

	for _, measuredValue := range measuredValues {
		measuredValue.ValueType = types.Humidity
	}

	return measuredValues, nil
}

func (sqlite *SQLite) selectMeasuredValue(tx *sql.Tx, query string, args ...interface{}) ([]*types.MeasuredValue, error) {
	stmt, err := tx.Prepare(query)
	if err != nil {
		return nil, err
	}
	defer stmt.Close()

	rows, err := stmt.Query(args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	measuredValues := make([]*types.MeasuredValue, 0)
	for rows.Next() {
		measuredValue := new(types.MeasuredValue)
		err := rows.Scan(
			&measuredValue.ID,
			&measuredValue.Value,
			&measuredValue.Date,
			&measuredValue.SensorID,
			&measuredValue.CreationDate,
			&measuredValue.UpdateDate,
		)

		if err != nil {
			return nil, err
		}

		measuredValues = append(measuredValues, measuredValue)
	}

	return measuredValues, nil
}

// GetPressure returns pressure from the database
func (sqlite *SQLite) GetPressureByID(ctx context.Context, id string) (*types.MeasuredValue, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()

	measuredValues, err := sqlite.selectMeasuredValue(tx, selectPressureByIDSQL, id)
	if err != nil {
		return nil, err
	}

	err = tx.Commit()
	if err != nil {
		return nil, err
	}

	if measuredValues == nil {
		return nil, nil
	}

	for _, measuredValue := range measuredValues {
		measuredValue.ValueType = types.Pressure
	}

	return measuredValues[0], nil
}

// GetPressures returns pressure from the database
func (sqlite *SQLite) GetPressures(ctx context.Context) ([]*types.MeasuredValue, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()

	measuredValues, err := sqlite.selectMeasuredValue(tx, selectPressuresSQL)
	if err != nil {
		return nil, err
	}

	err = tx.Commit()
	if err != nil {
		return nil, err
	}

	for _, measuredValue := range measuredValues {
		measuredValue.ValueType = types.Pressure
	}

	return measuredValues, nil
}

// GetSensor from database
func (sqlite *SQLite) GetSensorByID(ctx context.Context, id string) (*types.Sensor, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	sensors, err := sqlite.selectSensors(tx, selectSensorByIDSQL, id)
	if err != nil {
		return nil, err
	}

	err = tx.Commit()
	if err != nil {
		return nil, fmt.Errorf("Failed to commit transaction: %v", err)
	}

	if len(sensors) == 0 {
		return nil, nil
	}

	return sensors[0], nil
}

// GetSensors from the database
func (sqlite *SQLite) GetSensors(ctx context.Context) ([]*types.Sensor, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	sensors, err := sqlite.selectSensors(tx, selectSensorsSQL)
	if err != nil {
		return nil, err
	}

	err = tx.Commit()
	if err != nil {
		return nil, fmt.Errorf("Failed to commit transaction: %v", err)
	}

	return sensors, nil
}

// GetSensorsByModels from the database
func (sqlite *SQLite) GetSensorsByDeviceIDs(ctx context.Context, deviceIDs ...string) ([]*types.Sensor, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	cachedSensors := make([]*types.Sensor, 0)
	for i := range deviceIDs {
		sensors, err := sqlite.selectSensors(tx, selectSensorsByDeviceIDSQL, deviceIDs[i])
		if err != nil {
			return nil, err
		}

		cachedSensors = append(cachedSensors, sensors...)
	}

	err = tx.Commit()
	if err != nil {
		return nil, fmt.Errorf("Failed to commit transaction: %v", err)
	}

	return cachedSensors, nil
}

// GetSensorsByModels from the database
func (sqlite *SQLite) GetSensorsByModels(ctx context.Context, sensorModels ...string) ([]*types.Sensor, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	cachedSensors := make([]*types.Sensor, 0)
	for i := range sensorModels {
		sensors, err := sqlite.selectSensors(tx, selectSensorsByModelSQL, sensorModels[i])
		if err != nil {
			return nil, err
		}

		cachedSensors = append(cachedSensors, sensors...)
	}

	err = tx.Commit()
	if err != nil {
		return nil, fmt.Errorf("Failed to commit transaction: %v", err)
	}

	return cachedSensors, nil
}

// GetSensorsByModels from the database
func (sqlite *SQLite) GetSensorsByNames(ctx context.Context, sensorNames ...string) ([]*types.Sensor, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	cachedSensors := make([]*types.Sensor, 0)
	for i := range sensorNames {
		sensors, err := sqlite.selectSensors(tx, selectSensorsByNameSQL, sensorNames[i])
		if err != nil {
			return nil, err
		}

		cachedSensors = append(cachedSensors, sensors...)
	}

	err = tx.Commit()
	if err != nil {
		return nil, fmt.Errorf("Failed to commit transaction: %v", err)
	}

	return cachedSensors, nil
}

func (sqlite *SQLite) selectSensors(tx *sql.Tx, query string, args ...interface{}) ([]*types.Sensor, error) {
	stmt, err := tx.Prepare(query)
	if err != nil {
		return nil, fmt.Errorf("Failed to prepare statement: %v", err)
	}
	defer stmt.Close()

	rows, err := stmt.Query(args...)
	if err != nil {
		return nil, fmt.Errorf("Failed to query statement: %v", err)
	}
	defer rows.Close()

	sensors := make([]*types.Sensor, 0)
	for rows.Next() {
		sensor := new(types.Sensor)
		err = rows.Scan(
			&sensor.ID,
			&sensor.Name,
			&sensor.Location,
			&sensor.WireID,
			&sensor.I2CBus,
			&sensor.I2CAddress,
			&sensor.GPIONumber,
			&sensor.Model,
			&sensor.Enabled,
			&sensor.TickDuration,
			&sensor.DeviceID,
			&sensor.CreationDate,
			&sensor.UpdateDate,
		)

		if err != nil {
			return nil, fmt.Errorf("Failed to scan row: %v", err)
		}
		sensors = append(sensors, sensor)
	}

	return sensors, nil
}

// GetTemperature returns temperatures from the database
func (sqlite *SQLite) GetTemperatureByID(ctx context.Context, id string) (*types.MeasuredValue, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()

	measuredValues, err := sqlite.selectMeasuredValue(tx, selectTemperatureByIDSQL, id)
	if err != nil {
		return nil, err
	}

	err = tx.Commit()
	if err != nil {
		return nil, err
	}

	if measuredValues == nil {
		return nil, nil
	}

	for _, measuredValue := range measuredValues {
		measuredValue.ValueType = types.Temperature
	}

	return measuredValues[0], nil
}

// GetTemperatures returns temperatures from the database
func (sqlite *SQLite) GetTemperatures(ctx context.Context) ([]*types.MeasuredValue, error) {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()

	measuredValues, err := sqlite.selectMeasuredValue(tx, selectTemperaturesSQL)
	if err != nil {
		return nil, err
	}

	err = tx.Commit()
	if err != nil {
		return nil, err
	}

	for _, measuredValue := range measuredValues {
		measuredValue.ValueType = types.Temperature
	}

	return measuredValues, nil
}

// RemoveDevices from the database
func (sqlite *SQLite) RemoveDevicesByIDs(ctx context.Context, deviceIDs ...string) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	stmt, err := tx.Prepare(deleteDeviceByIDSQL)
	if err != nil {
		return fmt.Errorf("Failed to prepare statement: %v", err)
	}
	defer stmt.Close()

	for _, deviceID := range deviceIDs {
		_, err = stmt.Exec(deviceID)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

// RemoveDevices from the database
func (sqlite *SQLite) RemoveDevicesByNames(ctx context.Context, names ...string) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	stmt, err := tx.Prepare(deleteDeviceByNameSQL)
	if err != nil {
		return fmt.Errorf("Failed to prepare statement: %v", err)
	}
	defer stmt.Close()

	for _, deviceID := range names {
		_, err = stmt.Exec(deviceID)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

// RemoveSensors from the database
func (sqlite *SQLite) RemoveSensorsByIDs(ctx context.Context, sensorIDs ...string) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	stmt, err := tx.Prepare(deleteSensorByIDSQL)
	if err != nil {
		return fmt.Errorf("Failed to prepare statement: %v", err)
	}
	defer stmt.Close()

	for _, sensorID := range sensorIDs {
		_, err = stmt.Exec(sensorID)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

// RemoveSensors from the database
func (sqlite *SQLite) RemoveSensorsByNames(ctx context.Context, names ...string) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer tx.Rollback()

	stmt, err := tx.Prepare(deleteSensorByNameSQL)
	if err != nil {
		return fmt.Errorf("Failed to prepare statement: %v", err)
	}
	defer stmt.Close()

	for _, sensorID := range names {
		_, err = stmt.Exec(sensorID)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

// UpdateDevices updates a device in the database
func (sqlite *SQLite) UpdateDevices(ctx context.Context, devices ...*types.Device) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return err
	}
	defer tx.Rollback()

	stmt, err := tx.Prepare(updateDeviceSQL)
	if err != nil {
		return err
	}
	defer stmt.Close()

	for _, device := range devices {
		_, err := stmt.Exec(
			&device.Name,
			&device.Location,
			&device.CreationDate,
			&device.UpdateDate,
			&device.ID,
		)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

// UpdateSensors updates a sensor in the database
func (sqlite *SQLite) UpdateSensors(ctx context.Context, sensors ...*types.Sensor) error {
	sqlite.mutex.Lock()
	defer sqlite.mutex.Unlock()

	tx, err := sqlite.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return err
	}
	defer tx.Rollback()

	stmt, err := tx.Prepare(updateSensorSQL)
	if err != nil {
		return err
	}
	defer stmt.Close()

	for _, sensor := range sensors {
		_, err := stmt.Exec(
			&sensor.Name,
			&sensor.Location,
			&sensor.WireID,
			&sensor.I2CBus,
			&sensor.I2CAddress,
			&sensor.GPIONumber,
			&sensor.Model,
			&sensor.Enabled,
			&sensor.TickDuration,
			&sensor.DeviceID,
			&sensor.CreationDate,
			&sensor.UpdateDate,
			&sensor.ID,
		)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}