// Command routerd consumes alerts from NATS JetStream, resolves
// recipients (companies → sources → allowed_targets ∪ routing_rules
// → groups → individuals ∩ subscriptions), and enqueues one
// delivery per (individual, channel) to
// deliveries.<channel>.<company_id> subjects.
//
// M0: connects to NATS, /health, /metrics. No business logic.
// M1: broadcast mode — every active fcm_token in the company.
// M2: rules engine from SPEC §6 — uses internal/routing.Resolver
//     which honors source.allowed_targets, routing_rules, and
//     subscriptions (with min_severity, quiet hours, channel_mask).
//     Hard-fails on zero recipients (no silent broadcast).
package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"os"
	"os/signal"
	"strings"
	"syscall"
	"time"

	"git3.techno-world.net/lrosales/broad-announce/internal/alert"
	"git3.techno-world.net/lrosales/broad-announce/internal/broker"
	"git3.techno-world.net/lrosales/broad-announce/internal/config"
	"git3.techno-world.net/lrosales/broad-announce/internal/dedupe"
	"git3.techno-world.net/lrosales/broad-announce/internal/httpserver"
	"git3.techno-world.net/lrosales/broad-announce/internal/observability"
	"git3.techno-world.net/lrosales/broad-announce/internal/postgres"
	"git3.techno-world.net/lrosales/broad-announce/internal/routing"
	"github.com/nats-io/nats.go/jetstream"
)

// routerdMetrics is the package-level routerd metrics instance.
// Set in main() before the consume goroutine starts.
var routerdMetrics *observability.RouterdMetrics

func main() {
	cfg, err := config.LoadRouterd()
	if err != nil {
		os.Stderr.WriteString("config: " + err.Error() + "\n")
		os.Exit(1)
	}
	logger := observability.Init(cfg.Env, cfg.LogLevel, "routerd")
	logger.Info("starting",
		"env", cfg.Env,
		"addr", cfg.HTTPAddr,
		"dedupe_flush_ms", cfg.DedupeFlushMs,
	)

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

	br, err := broker.Connect(ctx, cfg.NATSURL)
	if err != nil {
		logger.Error("nats connect", "err", err)
		os.Exit(1)
	}
	defer br.Close()

	pool, err := postgres.Connect(ctx, cfg.PostgresDSN)
	if err != nil {
		logger.Error("postgres connect", "err", err)
		os.Exit(1)
	}
	defer pool.Close()

	resolver := routing.New(pool, logger.With("subsystem", "routing"))

	// M6.5: build the router-level dedupe Collapser. It collapses
	// bursts of identical alerts into 1 delivery per (source,
	// dedupe_key) pair, with a max-wait debounce so a continuous
	// stream re-flushes every flush window.
	collapseState := newFanoutState()
	collapser := dedupe.NewCollapser(
		time.Duration(cfg.DedupeFlushMs)*time.Millisecond,
		onFlushWithKey(logger, collapseState, br),
	)

	// Subscribe to all alerts.* subjects.
	js := br.JS()
	stream, err := js.Stream(ctx, "ALERTS")
	if err != nil {
		logger.Error("nats stream ALERTS", "err", err)
		os.Exit(1)
	}
	consumer, err := stream.CreateOrUpdateConsumer(ctx, jetstream.ConsumerConfig{
		Name:          "routerd",
		Durable:       "routerd",
		FilterSubjects: []string{"alerts.>"},
		AckPolicy:     jetstream.AckExplicitPolicy,
	})
	if err != nil {
		logger.Error("nats consumer", "err", err)
		os.Exit(1)
	}

	runCtx, runCancel := context.WithCancel(ctx)
	defer runCancel()

	// M9 L1: routerd metrics. Create before the consumer starts
	// so the /metrics endpoint is valid immediately.
	reg, _ := observability.NewRegistry("routerd")
	routerdMetrics = observability.NewRouterdMetrics(reg, "routerd")

	go consume(runCtx, logger, consumer, br, resolver, collapser, collapseState)
	srv := httpserver.New(httpserver.Config{
		Addr:          cfg.HTTPAddr,
		ServiceName:   "routerd",
		ShutdownGrace: cfg.ShutdownGrace,
	}, logger, observability.MetricsHandler(reg))

	errCh := make(chan error, 1)
	go func() { errCh <- srv.Start() }()
	select {
	case <-ctx.Done():
		logger.Info("shutdown signal received")
	case err := <-errCh:
		if err != nil {
			logger.Error("http server", "err", err)
			os.Exit(1)
		}
	}
	runCancel()
	time.Sleep(500 * time.Millisecond) // let consumer drain
	// M6.5: drain any pending collapses so we don't lose
	// the last few alerts of a graceful shutdown.
	collapser.FlushAll()
	if err := srv.Shutdown(ctx); err != nil {
		logger.Warn("graceful shutdown", "err", err)
	}
	logger.Info("bye")
}

func consume(
	ctx context.Context,
	logger *slog.Logger,
	c jetstream.Consumer,
	br *broker.Client,
	r *routing.Resolver,
	collapser *dedupe.Collapser,
	state *fanoutState,
) {
	// M6.5: start the Collapser's flush loop. It exits
	// when ctx is canceled.
	collapseCtx, collapseCancel := context.WithCancel(ctx)
	defer collapseCancel()
	go collapser.Run(collapseCtx)

	for {
		if ctx.Err() != nil {
			return
		}
		batch, err := c.Fetch(16, jetstream.FetchMaxWait(2*time.Second))
		if err != nil {
			if ctx.Err() != nil {
				return
			}
			logger.Warn("nats fetch", "err", err)
			time.Sleep(500 * time.Millisecond)
			continue
		}
		for m := range batch.Messages() {
			handleOne(ctx, logger, m, br, r, collapser, state)
			if batch.Error() != nil {
				logger.Warn("batch error", "err", batch.Error())
				break
			}
		}
	}
}

func handleOne(
	ctx context.Context,
	logger *slog.Logger,
	m jetstream.Msg,
	br *broker.Client,
	r *routing.Resolver,
	collapser *dedupe.Collapser,
	state *fanoutState,
) {
	var a alert.Alert
	if err := json.Unmarshal(m.Data(), &a); err != nil {
		logger.Warn("malformed alert payload", "err", err, "subject", m.Subject())
		_ = m.Ack()
		return
	}

	// Extract company_id from subject "alerts.<company_id>".
	parts := strings.SplitN(m.Subject(), ".", 2)
	if len(parts) != 2 {
		logger.Warn("bad subject", "subject", m.Subject())
		_ = m.Ack()
		return
	}
	companyID := parts[1]
	if a.CompanyID != "" && a.CompanyID != companyID {
		logger.Warn("company_id mismatch", "subject", companyID, "body", a.CompanyID)
	}
	a.CompanyID = companyID

	// M6.5: route through the Collapser-aware handler. The
	// collapse decision is made here, the actual delivery
	// publish may happen later (on flush) — but the NATS
	// message is always Ack'd now.
	_, shouldAck, shouldNak := observeAndFanout(ctx, logger, collapser, state, r, br, companyID, a)
	switch {
	case shouldNak:
		_ = m.Nak()
	case shouldAck:
		_ = m.Ack()
	}
}

var _ = fmt.Sprintf // keep import