// Package main — Gebos MQTT → Postgres ingester.
//
// Skeleton. Target: < 200 lines.
//
// Subscribes to topics of the form `t/<tenant_id>/d/<device_id>/<metric>`,
// extracts tenant_id and device_id from the topic, writes rows into
// public.telemetry on db-host as the gebos_ingest role (BYPASSRLS).
package main

import (
	"context"
	"log"
	"os"
	"os/signal"
	"syscall"
)

// Defaults match the local dev stack in nix/dev/process-compose.nix so
// `go run ./ingester` works without any env setup. Prod always sets these
// explicitly via the systemd unit's EnvironmentFile.
const (
	defaultBroker     = "tcp://127.0.0.1:1883"
	defaultPgURL      = "postgres://gebos_ingest@127.0.0.1:5432/gebos?sslmode=disable"
	defaultPgPassword = "dev"
)

func envOr(key, fallback string) (string, bool) {
	if v := os.Getenv(key); v != "" {
		return v, false
	}
	return fallback, true
}

func main() {
	broker, brokerDefault := envOr("GEBOS_MQTT_BROKER", defaultBroker)
	pgURL, pgURLDefault := envOr("GEBOS_POSTGRES_URL", defaultPgURL)
	pgPassword, pgPasswordDefault := envOr("GEBOS_POSTGRES_PASSWORD", defaultPgPassword)
	_ = pgPassword

	if brokerDefault || pgURLDefault || pgPasswordDefault {
		log.Printf("gebos-ingester: using dev defaults for: %s%s%s — set env vars in prod",
			ifStr(brokerDefault, "GEBOS_MQTT_BROKER ", ""),
			ifStr(pgURLDefault, "GEBOS_POSTGRES_URL ", ""),
			ifStr(pgPasswordDefault, "GEBOS_POSTGRES_PASSWORD ", ""),
		)
	}

	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
	defer stop()

	// TODO:
	//   1. pgxpool.New with password injected into the DSN
	//   2. paho MQTT client.Connect, Subscribe("t/+/d/+/+")
	//   3. on message: parse topic → (tenant_id, device_id, metric), parse
	//      payload (JSON for now), INSERT INTO public.telemetry
	//   4. batch with a short flush interval (50–100ms) for throughput
	//   5. shutdown on ctx.Done

	log.Printf("gebos-ingester: broker=%s db=%s (stub)", broker, pgURL)
	<-ctx.Done()
	log.Println("gebos-ingester: shutting down")
}

func ifStr(cond bool, a, b string) string {
	if cond {
		return a
	}
	return b
}