graphicek/server/services/sensor_values_service.go

package services

import (
	"database/sql"
	"time"
)

type SensorValuesService struct {
	ctx *Context
}

type sensorValue struct {
	Timestamp int64   `json:"timestamp"`
	Value     float64 `json:"value"`
}

func (s *SensorValuesService) Push(sensorId int64, value float64) (int64, error) {
	res, err := s.ctx.DB.Exec("INSERT INTO sensor_values (timestamp, sensor_id, value) VALUES (?, ?, ?)", time.Now().Unix(), sensorId, value)

	if err != nil {
		return 0, err
	}

	return res.LastInsertId()
}

func (s *SensorValuesService) GetList(sensorId int64, from int64, to int64) ([]sensorValue, error) {
	return s.getValueItems(sensorId, from, to, getAutoSensorValuesInterval(from, to))
}

func (s *SensorValuesService) GetLatest(sensorId int64, to int64) (*sensorValue, error) {
	var value = sensorValue{}

	row := s.ctx.DB.QueryRow("SELECT timestamp, value FROM sensor_values WHERE sensor_id = ? AND timestamp < ? ORDER BY timestamp DESC LIMIT 1", sensorId, to)

	err := row.Scan(&value.Timestamp, &value.Value)
	if err != nil {
		return nil, err
	}

	return &value, nil
}

func (s *SensorValuesService) getValueListQuery(sensorId int64, from int64, to int64, divide int64) (*sql.Rows, error) {
	if divide == 1 {
		return s.ctx.DB.Query("SELECT timestamp, value FROM sensor_values WHERE sensor_id = ? AND timestamp > ? AND timestamp < ? ORDER BY timestamp ASC", sensorId, from, to)
	}

	return s.ctx.DB.Query(
		"SELECT (timestamp/?)*?, AVG(value) FROM sensor_values WHERE sensor_id = ? AND timestamp > ? AND timestamp < ? GROUP BY (timestamp/?) ORDER BY timestamp ASC",
		divide,
		divide,
		sensorId,
		from,
		to,
		divide,
	)
}

func getAutoSensorValuesInterval(from int64, to int64) int64 {
	diff := to - from

	// 360 days -> 1 day interval
	if diff > 360*24*60*60 {
		return 24 * 60 * 60
	}

	// 160 days -> 1 hour interval
	if diff > 160*24*60*60 {
		return 60 * 60
	}

	// 80 days -> 10 minutes
	if diff > 80*24*60*60 {
		return 10 * 60
	}

	return 1
}

func (s *SensorValuesService) getValueItems(sensorId int64, from int64, to int64, divide int64) ([]sensorValue, error) {
	values := make([]sensorValue, 0)

	rows, err := s.getValueListQuery(sensorId, from, to, divide)

	if err != nil {
		if err == sql.ErrNoRows {
			return values, nil
		}

		return nil, err
	}

	defer rows.Close()

	for rows.Next() {
		item := sensorValue{}

		err := rows.Scan(&item.Timestamp, &item.Value)
		if err != nil {
			return nil, err
		}

		values = append(values, item)
	}

	err = rows.Err()
	if err != nil {
		return nil, err
	}

	return values, nil
}