package main

import (
	"context"
	"flag"
	"log"
	"os"
	"os/signal"
	"sync"
	"syscall"
	"time"
)

var logger = log.New(os.Stderr, "", log.Ltime|log.Lshortfile)

func main() {
	cfgPath := flag.String("c", "/srv/energy/collector/config.json", "path to config file")
	flag.Parse()

	cfg, err := loadConfig(*cfgPath)
	if err != nil {
		log.Fatalf("config: %v", err)
	}

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	db, err := NewDB(ctx, cfg.DB.DSN)
	if err != nil {
		log.Fatalf("db: %v", err)
	}
	defer db.Close()

	alpha, err := NewAlphaEss(cfg.AlphaEss)
	if err != nil {
		log.Fatalf("alphaess: %v", err)
	}
	defer alpha.Close()

	meters, err := NewMeterPoller(cfg.MQTT)
	if err != nil {
		log.Fatalf("meters: %v", err)
	}
	defer meters.Close()

	interval := time.Duration(cfg.SampleRate) * time.Second
	go runPollLoop(ctx, alpha, meters, db, interval)

	sig := make(chan os.Signal, 1)
	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
	<-sig
	logger.Println("shutting down")
}

func runPollLoop(ctx context.Context, alpha *AlphaEss, meters *MeterPoller, db *DB, interval time.Duration) {
	ticker := time.NewTicker(interval)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			poll(ctx, alpha, meters, db)
		}
	}
}

func poll(ctx context.Context, alpha *AlphaEss, meters *MeterPoller, db *DB) {
	t := time.Now()

	// Poll AlphaEss and all SDM630 meters in parallel.
	var (
		inverterData *InverterData
		meterData    []MeterReading
		wg           sync.WaitGroup
	)

	wg.Add(2)
	go func() {
		defer wg.Done()
		d, err := alpha.Poll()
		if err != nil {
			logger.Printf("alphaess: %v", err)
			return
		}
		inverterData = d
	}()
	go func() {
		defer wg.Done()
		meterData = meters.PollAll()
	}()
	wg.Wait()

	// Write everything with the same timestamp t.
	if inverterData != nil {
		if err := db.WriteInverter(ctx, t, inverterData); err != nil {
			logger.Printf("write inverter: %v", err)
		}
	}
	for _, r := range meterData {
		if err := db.WriteMeter(ctx, t, r); err != nil {
			logger.Printf("write meter %s: %v", r.Device, err)
		}
	}
}