SQLite Initial Implementation

This is the first, most basic implementation of a SQLite database for caching.
Future commits will make it much more optimized and able to efficiently store data for periods longer than 8 days.

.gitignore

@@ -2,3 +2,4 @@ config.json
 cache.json
 go.sum
 .idea
+database.db

cache.go

@@ -1,18 +1,16 @@
 package main
 
 import (
-	"encoding/json"
 	"fmt"
-	"os"
 	"time"
 )
 
 type CacheEntry struct {
-	Date                       string  `json:"date""`
-	GreenEnergyPercentage      float32 `json:"green_energy_percentage"`
-	PolledSmartEnergySummation float32 `json:"polled_smart_energy_summation"`
+	Date                       int64
+	GreenEnergyPercentage      float32
+	PolledSmartEnergySummation float32
 }
-type CacheFile []CacheEntry
+type CacheData []CacheEntry
 
 func (config Config) updateCache() {
 
@@ -36,37 +34,41 @@ func (config Config) updateCache() {
 		return
 	}
 
-	var cacheEntries []CacheEntry
+	_, err = config.db.Exec("DELETE FROM cache")
+	if err != nil {
+		fmt.Println("Error deleting previous records to cache: -", err.Error())
+		return
+	}
+
 	for key, day := range greenEnergyPercentage {
-		cacheEntries = append(cacheEntries, CacheEntry{
-			Date:                       day.DayTime.Format("02/01"),
-			GreenEnergyPercentage:      greenEnergyPercentage[key].Value,
-			PolledSmartEnergySummation: historyPolledSmartEnergySummation[key].Value,
-		})
-	}
-
-	out, _ := json.Marshal(cacheEntries)
-
-	err = os.WriteFile("cache.json", out, 0666)
+		_, err := config.db.Exec("INSERT INTO cache(time,green_energy_percentage,energy_consumption) VALUES (?,?,?);", day.DayTime.Unix(), greenEnergyPercentage[key].Value, historyPolledSmartEnergySummation[key].Value)
 		if err != nil {
-		fmt.Println("Error saving cached data to file -" + err.Error())
+			fmt.Println("Error adding record to cache: -", err.Error())
+			return
+		}
 	}
 
 }
 
-func readCache() (CacheFile, error) {
+func (config Config) readCache() (CacheData, error) {
 
-	data, err := os.ReadFile("cache.json")
+	rows, err := config.db.Query("SELECT time, green_energy_percentage, energy_consumption FROM cache")
 	if err != nil {
-		return CacheFile{}, err
+		return CacheData{}, err
+	}
+	defer rows.Close()
+	var ret CacheData
+
+	for rows.Next() {
+		var (
+			date                         int64
+			greenEnergyPercentage        float32
+			polledSmartEnergyConsumption float32
+		)
+		err = rows.Scan(&date, &greenEnergyPercentage, &polledSmartEnergyConsumption)
+		ret = append(ret, CacheEntry{date, greenEnergyPercentage, polledSmartEnergyConsumption})
 	}
 
-	var cache CacheFile
-	err = json.Unmarshal(data, &cache)
-	if err != nil {
-		return CacheFile{}, err
-	}
-
-	return cache, nil
+	return ret, nil
 
 }

config.go

@@ -2,10 +2,12 @@ package main
 
 import (
 	"crypto/sha256"
+	"database/sql"
 	"encoding/json"
 	"errors"
 	"fmt"
 	"github.com/gofiber/fiber/v2"
+	_ "github.com/mattn/go-sqlite3"
 	"os"
 	"regexp"
 	"strings"
@@ -13,6 +15,7 @@ import (
 )
 
 type Config struct {
+	db            *sql.DB
 	HomeAssistant HomeAssistant `json:"home_assistant"`
 	Sensors       Sensors       `json:"sensors"`
 	Administrator Administrator `json:"administrator"`
@@ -94,6 +97,22 @@ func loadConfig() (config Config, err error, isFirstRun bool) {
 		return Config{}, err, false
 	}
 
+	db, err := sql.Open("sqlite3", "./database.db")
+	if err != nil {
+		return Config{}, err, false
+	}
+	conf.db = db
+
+	_, err = db.Exec(`CREATE TABLE IF NOT EXISTS "cache" (
+		"time"	NUMERIC NOT NULL,
+		"green_energy_percentage"	REAL NOT NULL,
+		"energy_consumption"	REAL NOT NULL,
+		PRIMARY KEY("time")
+	);`)
+	if err != nil {
+		return Config{}, err, false
+	}
+
 	return conf, nil, false
 
 }

go.mod

@@ -5,6 +5,7 @@ go 1.17
 require (
 	github.com/gofiber/fiber/v2 v2.37.1
 	github.com/gofiber/template v1.7.1
+	github.com/mattn/go-sqlite3 v1.14.16
 	github.com/robfig/cron/v3 v3.0.1
 )
 

http.go

@@ -181,7 +181,7 @@ func (config Config) renderIndex(c *fiber.Ctx) error {
 		}, "base")
 	}
 
-	data, err := readCache()
+	data, err := config.readCache()
 	if err != nil {
 		return err
 	}
@@ -194,7 +194,7 @@ func (config Config) renderIndex(c *fiber.Ctx) error {
 	)
 
 	for _, datum := range data {
-		labels = append(labels, datum.Date)
+		labels = append(labels, time.Unix(datum.Date, 0).Format("02/01"))
 		greenEnergyPercents = append(greenEnergyPercents, datum.GreenEnergyPercentage)
 		greenEnergyConsumptionAbsolute = append(greenEnergyConsumptionAbsolute, datum.GreenEnergyPercentage/100*datum.PolledSmartEnergySummation)
 		energyConsumptions = append(energyConsumptions, datum.PolledSmartEnergySummation)

main.go

@@ -20,7 +20,7 @@ func main() {
 		cr := cron.New()
 		_, err = cr.AddFunc("@hourly", config.updateCache)
 		if err != nil {
-			return
+			log.Fatal(err)
 		}
 		cr.Start()
 		config.updateCache()