ecodash/cache.go

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"`
}
type CacheFile []CacheEntry

func (config Config) updateCache() {

	// in order to avoid querying and storing each day's data from 0001-01-01 in future versions
	if config.HomeAssistant.InstallationDate.IsZero() {
		return
	}

	now := time.Now()
	h, m, s := now.Clock()
	start := now.AddDate(0, 0, -7).Add(-(time.Duration(h)*time.Hour + time.Duration(m)*time.Minute + time.Duration(s)*time.Second))

	greenEnergyPercentage, err := config.historyAverageAndConvertToGreen(config.Sensors.FossilPercentage, start, now)
	if err != nil {
		fmt.Println("Error updating cached data for FossilPercentage -" + err.Error())
		return
	}
	historyPolledSmartEnergySummation, err := config.historyDelta(config.Sensors.PolledSmartEnergySummation, start, now)
	if err != nil {
		fmt.Println("Error updating cached data for PolledSmartEnergySummation -" + err.Error())
		return
	}

	var cacheEntries []CacheEntry
	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)
	if err != nil {
		fmt.Println("Error saving cached data to file -" + err.Error())
	}

}

func readCache() (CacheFile, error) {

	data, err := os.ReadFile("cache.json")
	if err != nil {
		return CacheFile{}, err
	}

	var cache CacheFile
	err = json.Unmarshal(data, &cache)
	if err != nil {
		return CacheFile{}, err
	}

	return cache, nil

}