PKGBUILD/pkg/repository/postgres.go

package repository

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"net/url"
	"time"

	"git.cryptic.systems/volker.raschek/flucky/pkg/repository/postgres"
	"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"
)

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

func (o *PostgresOpts) 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 != "postgres" {
		return fmt.Errorf("Unsupported database scheme %v for database backend postgres", o.DatabaseURL.Scheme)
	}

	return nil
}

func NewPostgres(opts PostgresOpts) (Repository, error) {
	if err := opts.Validate(); err != nil {
		return nil, err
	}

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

	return &Postgres{
		databaseURL: opts.DatabaseURL,
		dbo:         sqlDBO,
		flogger:     opts.Logger,
	}, nil
}

// Postgres implementation
type Postgres struct {
	databaseURL *url.URL
	dbo         *sql.DB
	flogger     logger.Logger
}

// AddDevices into the database
func (d *Postgres) AddDevices(ctx context.Context, devices ...*types.Device) error {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

	err = d.insertDevices(tx, devices...)
	if err != nil {
		return err
	}

	return tx.Commit()
}

func (d *Postgres) insertDevices(tx *sql.Tx, devices ...*types.Device) error {
	stmt, err := tx.Prepare(postgres.InsertDeviceSQL)
	if err != nil {
		return fmt.Errorf("Failed to prepare statement: %v", err)
	}
	defer func() { _ = stmt.Close() }()

	for _, device := range devices {
		if device.CreationDate.Equal(time.Time{}) {
			device.CreationDate = time.Now()
		}

		_, 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 nil
}

func (d *Postgres) AddOrUpdateDevices(ctx context.Context, devices ...*types.Device) error {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

	err = d.insertOrUpdateDevices(tx, devices...)
	if err != nil {
		return err
	}

	return tx.Commit()
}

func (d *Postgres) insertOrUpdateDevices(tx *sql.Tx, devices ...*types.Device) error {
	stmt, err := tx.Prepare(postgres.InsertOrUpdateDeviceSQL)
	if err != nil {
		return fmt.Errorf("Failed to prepare statement: %w", err)
	}
	defer func() { _ = stmt.Close() }()

	for _, device := range devices {
		if device.CreationDate.Equal(time.Time{}) {
			device.CreationDate = time.Now()
		}

		_, 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 nil
}

// AddMeasuredValues into the database
func (d *Postgres) AddMeasuredValues(ctx context.Context, measuredValues ...*types.MeasuredValue) error {
	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 := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

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

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

		err := d.insertMeasuredValues(tx, queryFile, measuredValues...)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

func (d *Postgres) insertMeasuredValues(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 func() { _ = stmt.Close() }()

	for _, measuredValue := range measuredValues {
		if measuredValue.CreationDate.Equal(time.Time{}) {
			measuredValue.CreationDate = time.Now()
		}

		_, 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
}

// AddOrUpdateMeasuredValues into the database
func (d *Postgres) AddOrUpdateMeasuredValues(ctx context.Context, measuredValues ...*types.MeasuredValue) error {
	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 := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

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

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

		err := d.insertOrUpdateMeasuredValues(tx, queryFile, measuredValues...)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

func (d *Postgres) insertOrUpdateMeasuredValues(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 func() { _ = stmt.Close() }()

	for _, measuredValue := range measuredValues {
		if measuredValue.CreationDate.Equal(time.Time{}) {
			measuredValue.CreationDate = time.Now()
		}

		_, 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
}

// AddSensors into the database
func (d *Postgres) AddSensors(ctx context.Context, sensors ...*types.Sensor) error {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

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

	for _, sensor := range sensors {
		if sensor.CreationDate.Equal(time.Time{}) {
			sensor.CreationDate = time.Now()
		}

		_, 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 (d *Postgres) AddOrUpdateSensors(ctx context.Context, sensors ...*types.Sensor) error {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

	err = d.insertOrUpdateSensors(tx, sensors...)
	if err != nil {
		return err
	}

	return tx.Commit()
}

func (d *Postgres) insertOrUpdateSensors(tx *sql.Tx, sensors ...*types.Sensor) error {
	stmt, err := tx.Prepare(postgres.InsertOrUpdateSensorSQL)
	if err != nil {
		return fmt.Errorf("Failed to prepare statement: %v", err)
	}
	defer func() { _ = stmt.Close() }()

	for _, sensor := range sensors {
		if sensor.CreationDate.Equal(time.Time{}) {
			sensor.CreationDate = time.Now()
		}

		_, 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 nil
}

// 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 (postgres *Postgres) Close() error {
	return postgres.dbo.Close()
}

// Migrate creates all required tables if not exist
func (d *Postgres) Migrate(ctx context.Context) error {
	sourceDriver, err := iofs.New(postgres.DDLAssets, postgres.DDLAssetPath)
	if err != nil {
		return err
	}

	m, err := migrate.NewWithSourceInstance("iofs", sourceDriver, d.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 (d *Postgres) GetDeviceByID(ctx context.Context, id string) (*types.Device, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

	devices, err := d.selectDevices(tx, postgres.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 (d *Postgres) GetDeviceByName(ctx context.Context, name string) (*types.Device, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

	devices, err := d.selectDevices(tx, postgres.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 (d *Postgres) GetDevices(ctx context.Context) ([]*types.Device, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

	devices, err := d.selectDevices(tx, postgres.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 (d *Postgres) 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 func() { _ = stmt.Close() }()

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

	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("failed to scan rows: %v", err)
	}

	return devices, nil
}

// GetHumidity returns humidity from the database
func (d *Postgres) GetHumidityByID(ctx context.Context, id string) (*types.MeasuredValue, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, err
	}
	defer func() { _ = tx.Rollback() }()

	measuredValues, err := d.selectMeasuredValue(tx, postgres.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 (d *Postgres) GetHumidities(ctx context.Context) ([]*types.MeasuredValue, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, err
	}
	defer func() { _ = tx.Rollback() }()

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

	rows, err := stmt.Query(args...)
	if err != nil {
		return nil, err
	}
	defer func() { _ = 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, fmt.Errorf("failed to scan row: %v", err)
		}

		measuredValues = append(measuredValues, measuredValue)
	}

	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("failed to scan rows: %v", err)
	}

	return measuredValues, nil
}

// GetPressure returns pressure from the database
func (d *Postgres) GetPressureByID(ctx context.Context, id string) (*types.MeasuredValue, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, err
	}
	defer func() { _ = tx.Rollback() }()

	measuredValues, err := d.selectMeasuredValue(tx, postgres.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 (d *Postgres) GetPressures(ctx context.Context) ([]*types.MeasuredValue, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, err
	}
	defer func() { _ = tx.Rollback() }()

	measuredValues, err := d.selectMeasuredValue(tx, postgres.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 (d *Postgres) GetSensorByID(ctx context.Context, id string) (*types.Sensor, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

	sensors, err := d.selectSensors(tx, postgres.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 (d *Postgres) GetSensors(ctx context.Context) ([]*types.Sensor, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

	sensors, err := d.selectSensors(tx, postgres.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 (d *Postgres) GetSensorsByDeviceIDs(ctx context.Context, deviceIDs ...string) ([]*types.Sensor, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

	cachedSensors := make([]*types.Sensor, 0)
	for i := range deviceIDs {
		sensors, err := d.selectSensors(tx, postgres.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
}

// GetSensorsByModel from the database
func (d *Postgres) GetSensorsByModels(ctx context.Context, sensorModels ...string) ([]*types.Sensor, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

	cachedSensors := make([]*types.Sensor, 0)
	for i := range sensorModels {
		sensors, err := d.selectSensors(tx, postgres.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
}

// GetSensorsByModel from the database
func (d *Postgres) GetSensorsByNames(ctx context.Context, sensorNames ...string) ([]*types.Sensor, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

	cachedSensors := make([]*types.Sensor, 0)
	for i := range sensorNames {
		sensors, err := d.selectSensors(tx, postgres.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 (d *Postgres) 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 func() { _ = stmt.Close() }()

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

	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("failed to scan rows: %v", err)
	}

	return sensors, nil
}

// GetTemperature returns temperatures from the database
func (d *Postgres) GetTemperatureByID(ctx context.Context, id string) (*types.MeasuredValue, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, err
	}
	defer func() { _ = tx.Rollback() }()

	measuredValues, err := d.selectMeasuredValue(tx, postgres.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 (d *Postgres) GetTemperatures(ctx context.Context) ([]*types.MeasuredValue, error) {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
	if err != nil {
		return nil, err
	}
	defer func() { _ = tx.Rollback() }()

	measuredValues, err := d.selectMeasuredValue(tx, postgres.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
}

// Import imports devices, sensors and all measured values from a source
// repository. Existing entries will be updated.
func (d *Postgres) Import(ctx context.Context, src Repository) error {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return err
	}
	defer func() { _ = tx.Rollback() }()

	devices, err := src.GetDevices(ctx)
	if err != nil {
		return err
	}

	err = d.insertOrUpdateDevices(tx, devices...)
	if err != nil {
		return err
	}

	sensors, err := src.GetSensors(ctx)
	if err != nil {
		return err
	}

	err = d.insertOrUpdateSensors(tx, sensors...)
	if err != nil {
		return err
	}

	for _, value := range []struct {
		f     func(ctx context.Context) ([]*types.MeasuredValue, error)
		query string
	}{
		{f: src.GetHumidities, query: postgres.InsertOrUpdateHumiditySQL},
		{f: src.GetPressures, query: postgres.InsertOrUpdatePressureSQL},
		{f: src.GetTemperatures, query: postgres.InsertOrUpdateTemperatureSQL},
	} {
		measuredValues, err := value.f(ctx)
		if err != nil {
			return err
		}

		err = d.insertOrUpdateMeasuredValues(tx, value.query, measuredValues...)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

// RemoveDevices from the database
func (d *Postgres) RemoveDevicesByIDs(ctx context.Context, deviceIDs ...string) error {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

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

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

	return tx.Commit()
}

// RemoveDevices from the database
func (d *Postgres) RemoveDevicesByNames(ctx context.Context, names ...string) error {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

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

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

	return tx.Commit()
}

// RemoveSensors from the database
func (d *Postgres) RemoveSensorsByIDs(ctx context.Context, sensorIDs ...string) error {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

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

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

	return tx.Commit()
}

// RemoveSensors from the database
func (d *Postgres) RemoveSensorsByNames(ctx context.Context, sensorIDs ...string) error {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return fmt.Errorf("Failed to begin new transaction: %v", err)
	}
	defer func() { _ = tx.Rollback() }()

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

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

	return tx.Commit()
}

// UpdateDevices updates a device in the database
func (d *Postgres) UpdateDevices(ctx context.Context, devices ...*types.Device) error {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return err
	}
	defer func() { _ = tx.Rollback() }()

	stmt, err := tx.Prepare(postgres.UpdateDeviceSQL)
	if err != nil {
		return err
	}
	defer func() { _ = stmt.Close() }()

	for _, device := range devices {
		now := time.Now()
		device.UpdateDate = &now

		_, 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 (d *Postgres) UpdateSensors(ctx context.Context, sensors ...*types.Sensor) error {
	tx, err := d.dbo.BeginTx(ctx, &sql.TxOptions{ReadOnly: false})
	if err != nil {
		return err
	}
	defer func() { _ = tx.Rollback() }()

	stmt, err := tx.Prepare(postgres.UpdateSensorSQL)
	if err != nil {
		return err
	}
	defer func() { _ = stmt.Close() }()

	for _, sensor := range sensors {
		now := time.Now()
		sensor.UpdateDate = &now
		_, 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()
}